organic syntheses collective volume 6

Organic Syntheses, Coll. Vol. 6, p.1 (1988); Vol. 56, p.3 (1977).

ACYLAMIDOALKYL ACETOPHENONES FROM SUBSTITUTED PHENETHYLAMINES: 2-(2-ACETAMIDOETHYL)-4,5DIMETHOXYACETOPHENONE[Acetamide, N-[2-(2-acetyl-4,5-dimethoxyphenyl)ethyl]-]

Submitted by A. Brossi, L. A. Dolan, and S. Teitel1. Checked by Hiroshi Itazaki and Wataru Nagata.

1. ProcedureCaution! Part A should be conducted in a hood to avoid inhalation of hydrogen chloride fumes. A. 6,7-Dimethoxy-1-methyl-3,4-dihydroisoquinoline. A 2-l., three-necked, round-bottomed flask equipped with a mechanical stirrer, a reflux condenser protected by a calcium chloride tube, and a pressure-equalizing dropping funnel is charged with 54.0 g. (0.243 mole) of N-acetylhomoveratrylamine (Note 1) and 275 ml. of dry toluene (Note 2). The mixture is stirred, warmed to 40, and treated with 86.4 g. (52.5 ml., 0.572 mole) (Note 3) of phosphorus oxychloride (Note 4), which is added over 1 hour (Note 5). After addition, the reaction mixture is stirred at reflux for 2 hours, then cooled with an ice bath for 4 hours. The resulting crystals are collected by filtration and dried overnight at 50 in a vacuum oven, giving 79.079.5 g. (Note 6) of 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline dichlorophosphate, m.p. 148152 (Note 7). This material is dissolved in 150 ml. of water (Note 8), and the solution is treated with 100 ml. of aqueous 40% sodium hydroxide (Note 9). The oil which separates is drawn off, and the aqueous solution is washed with three 20-ml. portions of chloroform. These extracts and the oil are combined, washed with 15 ml. of water, and dried over anhydrous sodium sulfate. Removal of chloroform with a rotary evaporator provides 47.048.0 g. (9596%) of product, which is used without purification in Part B (Note 10). B. 2-Acetyl-6,7-dimethoxy-1-methylene-1,2,3,4-tetrahydroisoquinoline. A 1-l., three-necked, roundbottomed flask equipped with a mechanical stirrer, a reflux condenser topped with a calcium chloride

drying tube, and a thermometer is charged with 110 ml. of acetic anhydride, 110 ml. of pyridine, and 45.0 g. (0.220 mole) of the dihydroisoquinoline prepared in Part A. The reaction mixture is stirred and heated at 9095 for 30 minutes, stored at room temperature overnight, and concentrated by distillation at 50 using a rotary evaporator. The residue is diluted with 20 ml. of ethyl acetate, and another evaporation under reduced pressure gives material that can be crystallized from 75 ml. of ethyl acetate to yield 38.541.0 g. (7277%) of product m.p., 106107 (Note 11). C. 2-(2-Acetamidoethyl)-4,5-dimethoxyacetophenone. A slurry of 31.0 g. (0.125 mole) of the methylene derivative obtained in Part B and 75 ml. of 5% hydrochloric acid is stirred and warmed on a steam bath to 6065. As soon as all the solid has dissolved, the solution is cooled with an ice bath to 30 and basified by slowly adding a solution of 6.25 g. of potassium carbonate in 12.5 ml. of water (Note 12). The crystalline precipitate is collected by filtration, washed with three 12.5-ml. portions of water, and air-dried, yielding 30.532.0 g. (9193%) of the acetophenone, m.p. 123125 (Note 13).

2. Notes1. N-Acetylhomoveratrylamine2 was prepared by adding 190 ml. of acetic anhydride to a stirred solution of 300 g. (1.80 moles) of -(3,4-dimethoxyphenyl)ethylamine (Aldrich Chemical Company, Inc.) in 150 ml. of pyridine at such a rate that the temperature is maintained at 9095 (ca. 1.5 hours is required). After the solution had been stored at room temperature overnight, the volatile material was evaporated under reduced pressure, and the residue was crystallized from ethyl acetate to give 286306 g. (78 83%) of acetylated product, m.p. 99100. 2. The checkers used reagent-grade toluene dried over Linde-type 5A molecular sieves. 3. The checkers obtained an identical result when the molar ratio of phosphorous oxychloride to substrate was reduced from 2.35 to 1.5. 4. The checkers obtained phosphorus oxychloride from Wako Pure Chemical Industries, Ltd., Japan and distilled it prior to use. 5. The reaction temperature increased gradually to reflux, at which time the rate of addition was adjusted to maintain reflux. 6. This weight varies with the amount of solvent remaining. 7. Analysis calculated for C12H15O2N HOPOCl2: C, 42.37; H, 4.74; N, 4.12; Cl, 20.85; P, 9.10. Found: C, 42.30; H, 4.92; N, 4.21; Cl, 19.08; P, 8.51. IR (KBr) cm.1: 2800, 1665, 1602, 1565, 1105; 1H NMR (D2O), (multiplicity, number of protons, assignment): 3.17 (s, 3H, N=CCH3), 4.25 (s, 3H, OCH3), 4.30 (s, 3H, OCH3), 7.37 (s, 1H, aryl CH), 7.62 (s, 1H, aryl CH). The submitters, working on a kilogram scale without purification of reagent or solvent and with no precaution against moisture, obtained 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline hydrochloride,2 m.p. 202203, instead of the dichlorophosphate at this stage. The checkers obtained this hydrochloride by either treating the free base with hydrochloric acid or recrystallizing the dichlorophosphate from methanolethyl acetate. 8. The crystals dissolve gradually in water and, since dissolution is exothermic due to decomposition of the dichlorophosphoric acid, ice cooling is desirable. 9. Ice is added during neutralization to keep the temperature below 30. 10. A pure sample may be prepared by crystallization from ether: m.p. 105107; UV (C2H5OH) nm. max. (): 227 (24,000), 270 (7360), 307 (6640); UV (0.01 N hydrochloric acid) nm. max. (): 244 (17,250), 302 (8740), 352 (8440); IR (KBr) cm.1: 1650 (C=N). 11. UV (C2H5OH) nm. max. (): 220 (30,750), 267 (13,200), 304 (7080); UV (0.01 N hydrochloric acid) nm. max. (): 232 (23,500), 276 (9345), 305 (6120); IR (KBr) cm.1: 880910 (C=CH2). A dimorphic form melts at 100102. A mixture of this material and the 6,7-dimethoxy-1-methyl-3,4dihydroisoquinoline described in (Note 10) melted below 90. 12. The rate of addition is dependent on the amount of foaming. Ice is added periodically to keep the temperature below 35. 13. The product can be used without further purification. Recrystallization from water gave an analytical specimen, m.p. 126127; UV (95% C2H5OH) nm. max. (): 231 (24,100), 274 (8750), 304 (5500); infrared (KBr) cm.1: 1673, 1633; 1H NMR (CDCl3), (multiplicity, number of protons, assignment): 1.92 (s, 3H, Ha), 2.60 (s, 3H, Hb), 2.683.17 (m, 2H, Hg), 3.303.68 (m, 2H, Hh), 3.93 (s, 6H, Hc and Hd), 6.687.07 (broad, 1H, Hi), 6.80 (s, 1H, He), 7.22 (s, 1H, Hf).

SUBSTITUTED ACETAMIDOETHYL ACETOPHENONES3

TABLE I

Melting Point Ultraviolet C2H2OH nm. max ()

R1 = OCH3, R2 = R3 = H 86 221 (14,700), 269 (13,600)

R1, R2 = OCH2O, R3 = H 120 230 (36,500), 273 (5200), 307 (5460)

R1 = R2 = R3 = OCH3 58 222 (14,700), 263 (16,250)

3. DiscussionThis procedure provides a facile method for converting substituted 1-methyl-3,4dihydroisoquinolines into the corresponding 2-(2-acetamidoethyl)acetophenones, which are useful intermediates in the synthesis of 1-(substituted phenethyl)-2-methyl-1,2,3,4-tetrahydroisoquinolines.4,5 The sequence is uncomplicated and affords, in excellent yield, a product that requires no further purification. In addition to the examples in Table I, this method has been utilized for the synthesis of other substituted acetophenones,4,3,6 as well as related benzophenones and a heptanophenone.7 The latter two classes of compounds have also been obtained by ring opening of 2-ethyl-1-phenyl- or 2-ethyl-1hexyl-6,7-dialkoxy-3,4-dihydroisoquinolinium iodides with benzoyl chloride.8 This preparation is referenced from: Org. Syn. Coll. Vol. 9, 268

References and Notes1. Chemical Research Department, Hoffmann-La Roche Inc., Nutley, New Jersey 07110. 2. E. Spth and N. Polgar, Monatsh. Chem., 51, 190 (1929).

3. A. Brossi, J. Wrsch, and O. Schnider, Chimia, 12, 114 (1958). 4. A. Brossi, H. Besendorf, B. Pellmont, M. Walter, and O. Schnider, Helv. Chim. Acta, 43, 1459 (1960). 5. A. Brossi, H. Besendorf, L. A. Pirk, and A. Rheiner, Jr., in G. DeStevens, Ed., "Analgetics," Academic Press, New York, 1965, pp. 287289. 6. G. Dietz, G. Faust, and W. Fiedler, Pharmazie, 26, 586 (1971). 7. J. Gardent, C. R. Hebd. Seances Acad. Sci., 247, 2010 (1958). 8. J. Gardent, Bull. Soc. Chim. Fr., 10, 1260 (1957).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)2-(2-Acetamidoethyl)-4,5-dimethoxyacetophenone 2-(2-acetamidoethyl)acetophenones 1-(substituted phenethyl)-2-methyl-1,2,3,4-tetrahydroisoquinolines potassium carbonate (584-08-7) hydrogen chloride, hydrochloric acid, hydrochloride (7647-01-0) ethyl acetate (141-78-6) methanol (67-56-1) ether (60-29-7) acetic anhydride (108-24-7) sodium hydroxide (1310-73-2) chloroform (67-66-3) sodium sulfate (7757-82-6) Acetophenone (98-86-2) benzoyl chloride (98-88-4) Phosphorus Oxychloride (21295-50-1) pyridine (110-86-1) toluene (108-88-3) methylene (2465-56-7)

-(3,4-dimethoxyphenyl)ethylamine (120-20-7) phosphorous oxychloride 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline dichlorophosphate dihydroisoquinoline 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline hydrochloride dichlorophosphate dichlorophosphoric acid 6,7-Dimethoxy-1-methyl-3,4-dihydroisoquinoline (4721-98-6) heptanophenone (1671-75-6) Acetamide, N-[2-(2-acetyl-4,5-dimethoxyphenyl)ethyl]- (57621-03-1) N-acetylhomoveratrylamine (6275-29-2) 2-Acetyl-6,7-dimethoxy-1-methylene-1,2,3,4-tetrahydroisoquinoline (57621-04-2)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


THIOL PROTECTION WITH THE ACETAMIDOMETHYL GROUP: S-ACETAMIDOMETHYL-L-CYSTEINE HYDROCHLORIDE[L-Cysteine, S-[(acetylamino)methyl]-, monohydrochloride]

Submitted by John D. Milkowski1, Daniel F. Veber2, and Ralph Hirschmann1. Checked by A. Pearce and G. Bchi.

1. ProcedureA. N-(Hydroxymethyl)acetamide. In a 2-l., round-bottomed flask, 100 g. (1.70 moles) of acetamide (Note 1) is added to a solution of 10 g. (0.072 mole) of anhydrous potassium carbonate in 137 g. (1.7 moles) of an aqueous 3638% solution of formaldehyde (Note 2). The mixture is swirled, heated on a steam bath for 3 minutes, and allowed to stand overnight at room temperature. Several pieces of crushed dry ice are added (Note 3), after which the mixture is evaporated under reduced pressure with a heating bath kept below 40 (Note 4). A 128-g. portion of anhydrous sodium sulfate is added to the remaining colorless oil, which may have some precipitated salt suspended in it. After several hours the oil is dissolved in 1 l. of acetone, the suspended drying agent and salts are filtered, and the filtrate (Note 5) is dried further with additional anhydrous sodium sulfate. The suspension is filtered, and the clear filtrate is evaporated under reduced pressure. The yield of N-(hydroxymethyl)acetamide, a colorless hygroscopic oil at this point, is 148151 g. (98100%) (Note 6). The oily product, which may solidify (Note 7) on standing for several days, is used directly in step B. B. S-Acetamidomethyl-L-cysteine hydrochloride. A 1-l., round-bottomed flask is charged with 127 g. (1.43 moles) of N-(hydroxymethyl)acetamide, 228 g. (1.30 moles) of L-cysteine hydrochloride monohydrate (Note 8), and 350 ml. of water. The resulting solution is swirled and cooled in an ice bath as 50 ml. of concentrated hydrochloric acid is slowly added (Note 9). The flask is flushed with nitrogen, capped with a nitrogen-filled balloon, and allowed to stand for 12 days at room temperature. The progress of the reaction is monitored by TLC (Note 10). When L-cysteine hydrochloride is no longer detectable, the solution is evaporated under reduced pressure at a bath temperature of ca. 40. The remaining solid is suspended in a small amount of absolute ethanol, and the mixture is again carefully evaporated to avoid bumping. This entrainment procedure with absolute ethanol is repeated several times to remove traces of water. The dry solid is dissolved in the minimum amount of methanol (Note 11), and anhydrous diethyl ether is added until the cloud point is reached. The cloudy solution is allowed to stand in a refrigerator at ca. 45 for 1 week, during which the crystalline mass is broken up several times. The white crystalline product is collected, washed with ether, and dried under reduced pressure, yielding 152190 g. (5164%) of S-acetamidomethyl-L-cysteine hydrochloride, dec. 159 25 163, []D 30.7 (c = 1, water) (Note 12),(Note 13),(Note 14).

2. Notes

1. The submitters obtained acetamide from Merck & Company, Inc. Acetamide was purchased by the checkers from the Fisher Scientific Company. 2. A 37% solution of formaldehyde in water is available from the Aldrich Chemical Company, Inc. 3. The submitters state that the failure to add dry ice at this point may result in greatly reduced yields. The purpose of the dry ice is presumably to lower the pH of the solution by converting potassium carbonate to potassium bicarbonate. 4. When the mixture was heated above 40 by the submitters, it became discolored and an insoluble precipitate was formed. 5. The filtrate may be cloudy. 6. Apparent yields in excess of the theoretical amount may be observed, owing to the presence of a small portion of water. The oily product may be dried at high vacuum over phosphorous pentoxide for several days. 7. A melting point of 5052 is reported for N-(hydroxymethyl)acetamide.3 8. The submitters purchased L-cysteine hydrochloride monohydrate from Schwartz/Mann Division, Becton, Dickinson, and Company, Mountain View Avenue, Orangeburg, New York 10962. The checkers used material supplied by Aldrich Chemical Company, Inc. 9. The pH of the solution is ca. 0.5. 10. The balloon was removed briefly while aliquots were taken. The flask was flushed again with nitrogen and the balloon was then replaced. TLC analyses were carried out on glass plates coated with silica gel G purchased from Analtech, Newark, Delaware. With a 10:2:3 (v/v/v) solution of 1-butanol, acetic acid, and water as developing solvent, the Rf values for the product and L-cysteine hydrochloride are 0.19 and 0.25, respectively. 11. The submitters dissolved the solid in methanol at room temperature; however, the solid obtained by the checkers was not very soluble under these conditions. Consequently, the material was dissolved in approximately 23 l. of methanol by gentle warming on a steam bath. 25 12. The product obtained by the checkers had []D 28 (c = 1, water); IR (Nujol) cm.1: 1715 (C=O), 1580 (C=O); 1H NMR (DCl in D2O), (multiplicity, number of protons, assignment): 2.05 (s, 3H, CH3), 3.23.4 (m, 2H, CH2CH), 4.34.5 (m, 1H, CH2CH), 4.39 (s, 2H, NCH2S). 13. On several occasions the product isolated by the submitters was contaminated with L-cystine dihydrochloride, which was not easily removed by recrystallization. In this event the product was converted to the zwitterionic form and recrystallized in the following manner: The pH of a solution of the product in water was adjusted to 6 with aqueous 2.5 N potassium hydroxide, and the solution was evaporated to dryness under reduced pressure at ca. 40. The residue was dissolved in a minimum amount of hot water, and two volumes of 95% ethanol were added to precipitate S-acetamidomethyl-L25 cysteine monohydrate, dec. 187, []589 42.5 (c = 1, water). 14. The following unchecked procedure for liberating L-cysteine from S-acetamidomethyl-L-cysteine was provided by the submitters as a model for removing the S-acetamidomethyl group from peptides. The pH of a solution of 96.1 mg. (0.500 mmole) of S-acetamidomethyl-L-cysteine in 10.0 ml. of water is adjusted to 4.0 with aqueous 0.25 N hydrochloric acid. The solution is stirred, 159.3 mg. (0.5000 mmole) of mercury(II) acetate is added, and the pH is readjusted to 4.0 by adding more 0.25 N hydrochloric acid. The resulting suspension is stirred for 1 hour at room temperature then diluted with an equal volume of water. Hydrogen sulfide gas is introduced to complete the precipitation of mercury from solution, the mixture is filtered, and the aqueous filtrate is evaporated to dryness under reduced pressure. TLC analysis on the residue as described in (Note 10) showed the presence of L-cysteine and the absence of S-acetamidomethyl-L-cysteine.

3. DiscussionThe present procedure provides a convenient method for preparing S-acetamidomethyl-L-cysteine hydrochloride.4 The zwitterionic form may be obtained readily from the hydrochloride by the procedure described in (Note 13), by ion-exchange chromatography,5 or by precipitation from 2-propanol with pyridine.6 S-Acetamidomethyl-L-cysteine has also been prepared from N-(hydroxymethyl)acetamide under anhydrous conditions in liquid hydrogen fluoride4 and in trifluoroacetic acid.7 The preparation of N-(hydroxymethyl)acetamide described in Part A is based on the procedure of Einhorn.3 The acetamidomethyl group serves as a useful thiol-protecting group for cysteine during peptide synthesis.4,7,8,9 The protecting group is stable to the conditions generally prevailing in peptide synthesis,

including not only typical solution and solid-phase procedures but also reactions carried out in liquid hydrogen fluoride.4 Peptides containing S-acetamidomethyl-L-cysteine generally have good water solubility8 and are not prone to racemization at the -position of the cysteine residue.4 The acetamidomethyl protecting group may be easily removed by reaction with either mercury(II) acetate at pH 4, as described in (Note 14), or iodine.7,8 S-Acetamidomethylation of the cysteine residues of proteins may be accomplished in liquid hydrogen fluoride, and the group may be removed by reaction with mercury(II) ion.4 The thiol group of -mercaptopropionic acid has also been protected by formation of the S-acetamidomethyl derivative.7 This preparation is referenced from: Org. Syn. Coll. Vol. 6, 252

References and Notes1. 2. 3. 4. 5. 6. 7. 8. 9. Merck Sharp & Dohme Research Laboratories, P.O. Box 2000, Rahway, New Jersey 07065. Merck Sharp & Dohme Research Laboratories, West Point, Pennsylvania 19486. A. Einhorn, Justus Liebigs Ann. Chem., 343, 207 (1905). D. F. Veber, J. D. Milkowski, S. L. Varga, R. G. Denkewalter, and R. Hirschmann, J. Am. Chem. Soc., 94, 5456 (1972). P. Hermann and E. Schreier, in H. Hanson and H. D. Jakubke, Eds., "Peptides 1972," 12th European Symposium on Peptides, North Holland, Amsterdam, 1973, pp. 126127. H. Romovacek, S. Drabarek, K. Kawasaki, S. R. Dowd, R. Obermeier, and K. Hofmann, Int. J. Pept. Protein Res., 6, 435 (1974). P. Marbach and J. Rudinger, Helv. Chim. Acta, 57, 403 (1974). B. Kamber, Helv. Chim. Acta, 54, 927 (1971). R. Hirschmann, R. F. Nutt, D. F. Veber, R. A. Vitali, S. L. Varga, T. A. Jacob, F. W. Holly, and R. G. Denkewalter, J. Am. Chem. Soc., 91, 507 (1969).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)phosphorous pentoxide ethanol (64-17-5) potassium carbonate (584-08-7) hydrochloric acid, hydrochloride (7647-01-0) Acetamide (60-35-5) acetic acid (64-19-7) methanol (67-56-1) ether, diethyl ether (60-29-7)

formaldehyde (630-08-0) hydrogen sulfide (7783-06-4) sodium sulfate (7757-82-6) nitrogen (7727-37-9) mercury(II) acetate (1600-27-7) mercury (7439-97-6) hydrogen fluoride (7664-39-3) 1-butanol (71-36-3) iodine (7553-56-2) acetone (67-64-1) pyridine (110-86-1) potassium hydroxide (1310-58-3) 2-propanol (67-63-0) potassium bicarbonate (298-14-6) trifluoroacetic acid (76-05-1) mercury(II) ion L-cysteine hydrochloride (52-89-1) L-cysteine hydrochloride monohydrate (7048-04-6) L-cystine dihydrochloride (90350-38-2) cysteine, L-cysteine (52-90-4) -mercaptopropionic acid (107-96-0) S-acetamidomethyl-L-cysteine monohydrate S-acetamidomethyl-L-cysteine L-Cysteine, S-[(acetylamino)methyl]-, monohydrochloride (28798-28-9) N-(hydroxymethyl)acetamide (625-51-4)

S-Acetamidomethyl-L-cysteine hydrochlorideCopyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


ACETIC FORMIC ANHYDRIDE[Acetic acid, anhydride with formic acid]

Submitted by Lewis I. Krimen1 Checked by James Savage and Peter Yates.

1. ProcedureA dry, 2-l., three-necked, round-bottomed flask equipped with a stirrer, a thermometer, a reflux condenser fitted with a calcium chloride tube, and a dropping funnel is charged with 300 g. (4.41 moles) of sodium formate (Note 1) and 250 ml. of anhydrous diethyl ether (Note 2). To this stirred mixture is added 294 g. (266 ml., 3.75 moles) of acetyl chloride (Note 3) as rapidly as possible, while the temperature is maintained at 2327 (Note 4). After the addition is complete, the mixture is stirred for 5.5 hours at 2327 to ensure complete reaction. The mixture is then filtered with suction, the solid residue is rinsed with 100 ml. of ether, and the washings are added to the original filtrate (Note 5). The ether is removed by distillation at reduced pressure, and the residue is distilled, yielding 212 g. (64%) of 20 colorless acetic formic anhydride, b.p. 2728 (10 mm.), 3838.5 (39 mm.); nD 1.388 (Note 6).

2. Notes1. Reagent grade sodium formate from J. T. Baker Chemical Co. was used; it was finely ground to ensure better contact. It is imperative that extreme care be taken to ensure anhydrous conditions throughout the procedure, since hydrolysis produces formic and acetic acids, which are very difficult to remove from the product. A slight excess of sodium formate ensures a product free of acetyl chloride. 2. Mallinckrodt AR grade ether was used without further drying by the submitter. The checkers, working at half scale, found it essential to dry the ether over sodium. 3. Acetyl chloride from Matheson, Coleman and Bell was used without further purification. 4. The addition of acetyl chloride is mildly exothermic; the exotherm can be controlled by slower addition or by the use of a cooling bath (2024). The addition is completed in ca. 5 minutes. 5. The filtration and subsequent ether rinse should be carried out quickly in order to keep the filtrate dry. 6. The acetic formic anhydride may be stored at 4 in a standard-taper, round-bottomed flask fitted with a polyethylene stopper. Moisture catalyzes the decomposition of the product to acetic acid, with the evolution of carbon monoxide. The material must not be stored in sealed containers! 7. The IR spectrum of neat acetic formic anhydride shows two bands in the carbonyl region at 1765 and 1791 cm.1 and carbon-oxygen-carbon stretching absorption at 1050 cm.1 (a band at 1180 cm.1 could also be due to C-O-C). The 1H NMR spectrum (neat) shows a singlet at 2.25 (acetyl protons) and a singlet at 9.05 (formyl proton). If the product is not pure, the following peaks may also be observed: 2.05 (CH3CO2H), 2.20 [(CH3CO)2O], 2.68 (CH3COCl), 8.05 (HCOOH), 8.85 [(HCO)2O]. The spectrum of the product obtained by the checkers showed slight contamination with acetic anhydride and formic anhydride.

3. DiscussionAcetic formic anhydride has been prepared by the reaction of formic acid with acetic anhydride2,3 and ketene,4,5 and of acetyl chloride with sodium formate.6 The present procedure is essentially that of Muramatsu.6 It is simpler than others previously described, gives better yields, and is easily adapted to the preparation of large quantities, usually with an increase in yield. Acetic formic anhydride is a useful intermediate for the formylation of amines,3,7 amino acids,8,9 and alcohols,2,10 for the synthesis of aldehydes from Grignard reagents,11 and for the preparation of formyl fluoride.12

References and Notes1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Abbott Laboratories, Abbott Park, North Chicago, Illinois 60064. A. Behal, C. R. Hebd. Seances Acad. Sci., 128, 1460 (1899). C. W. Huffman, J. Org. Chem., 23, 727 (1958). R. E. Dunbar and F. C. Garven, J. Am. Chem. Soc., 77, 4161 (1955). C. D. Hurd and A. S. Roe, J. Am. Chem. Soc., 61, 3355 (1939). I. Muramatsu, M. Murakami, T. Yoneda, and A. Hagitani, Bull Chem. Soc. Jpn., 38, 244 (1965). G. R. Clemo and G. A. Swan, J. Chem. Soc., 603 (1945). S. G. Waley, Chem. Ind. (London), 107 (1953). J. C. Sheehan and D. D. H. Yang, J. Am. Chem. Soc., 80, 1154 (1958). C. D. Hurd, S. S. Drake, and O. Fancher, J. Am. Chem. Soc., 68, 789 (1946). W. R. Edwards, Jr., and K. P. Kammann, Jr., J. Org. Chem., 29, 913 (1964). G. A. Olah and S. J. Kuhn, J. Am. Chem. Soc., 82, 2380 (1960).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)Acetic formic anhydride Acetic acid, anhydride with formic acid acetic acid (64-19-7) ether, diethyl ether (60-29-7) acetic anhydride (108-24-7) carbon monoxide (630-08-0) acetyl chloride (75-36-5) formic acid (64-18-6) sodium (13966-32-0) sodium formate formyl fluoride (1493-02-3) FORMIC ANHYDRIDE carbon-oxygen-carbonCopyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


ACETONE HYDRAZONE[2-Propanone, hydrazone]

Submitted by A. C. Day1 and M. C. Whiting2. Checked by G. Swift and W. D. Emmons.

1. ProcedureCaution! Hydrazine is toxic and should be handled in a hood. Anhydrous hydrazine is extremely reactive with oxidizing agents (including air) and should always be prepared and used behind a protective screen. A. Acetone azine. A 500-ml., round-bottomed flask containing 145 g. (183 ml., 2.50 moles) of acetone (Note 1) is fitted with a mechanical stirrer (Note 2) and a dropping funnel and cooled in an ice bath. With vigorous stirring, 65.5 g. (1.31 moles) of 100% hydrazine hydrate (Note 1) is added at such a rate that the temperature is maintained below 35. The addition takes 2030 minutes. The mixture is stirred for an additional 1015 minutes before 50 g. of potassium hydroxide pellets is added with vigorous stirring and continued cooling (Note 3). The upper liquid layer is separated and allowed to stand over 25 g. of potassium hydroxide pellets for 30 minutes, with occasional swirling (Note 4). After filtration, the liquid is further dried with two successive 12.5-g. portions of potassium hydroxide. 22 Distillation gives 120126 g. (8690%) of almost colorless acetone azine, b.p. 128131, nD 1.4538 (Note 5). B. Acetone hydrazone. Anhydrous hydrazine is prepared by heating under reflux 100% hydrazine hydrate with an equal weight of sodium hydroxide pellets for 2 hours, followed by distillation in a slow stream of nitrogen introduced through a capillary leak. (Caution! Distillation in air can lead to explosion.) The distillate boils at 114116 and the yield is 9597% (Note 6). A mixture of 112 g. (1.00 mole) of acetone azine and 32 g. (1.0 mole) of anhydrous hydrazine is placed in a 300-ml. round-bottomed flask fitted with a reflux air condenser and drying tube, and kept at 100 for 1216 hours. (Caution! This reaction and the subsequent distillation should be carried out behind a protective screen.) The crude product is then distilled rapidly through a water-cooled 22 condenser, and the colorless fraction boiling at 122126 is collected, nD 1.4607 (Note 7), yielding 111127 g. (7788%, (Note 7) and (Note 8)) of essentially pure acetone hydrazone (Note 9).

2. Notes1. The acetone and hydrazine hydrate were good-quality commercial products purified before use. 2. A Hershberg stirrer made of Nichrome wire is most efficient for aiding dissolution of the potassium hydroxide added after azine formation is complete. 3. The dissolution of the potassium hydroxide is strongly exothermic. A small proportion may remain undissolved. 4. A lower, aqueous phase may form at this stage, but the product is easily decanted from it. 5. The distillation gives a small forerun, b.p. 120128, containing hydrazine and acetone hydrazone. There is virtually no distillation residue. The submitters carried out the preparation of both acetone

azine and acetone hydrazone on a fourfold scale with comparable results. 6. The purity is 9598% by this method.3 The purity is lower (8595%) by an alternative procedure4 which requires separation of the hydrazine and alkaline phases above 60; with the latter method the submitters found that a frequent problem was the solidification of the lower phase in the separating funnel, and in one case a very serious fire occurred during the transfer of the hot (ca. 100) mixture to the separating funnel. 7. The forerun contains hydrazine; material boiling above 126 contains much acetone azine. With a slow rate of distillation, disproportionation occurs and the yield of acetone hydrazone is reduced. If the forerun and material boiling above 126 are combined and reheated at 100 for 1216 hours, they give more acetone hydrazone on redistillation. With further repetitions of this procedure, the yield is almost quantitative. 8. The highest yields were obtained in cases where the anhydrous hydrazine was treated with barium oxide for several hours before use. 9. The hydrazone should be used as soon as possible. If it is stored, care must be taken to exclude moisture, which catalyzes disproportionation to hydrazine and acetone azine.5,6,7 Even in the absence of moisture it disproportionates slowly at room temperature and so should be redistilled immediately before use. Old samples can be regenerated fairly satisfactorily by reheating them for 1216 hours at 100 before redistillation, but there is always some irreversible decomposition to high-boiling products during storage.

3. DiscussionThe procedure for acetone azine is essentially that of Curtius and Thun.5 The method for acetone hydrazone is adapted from that of Staudinger and Gaule.8 The hydrazone has been prepared directly from acetone and hydrazine, but this is much less satisfactory.6 Acetone hydrazone is produced in good yield by the method described, but an inferior product is obtained without the precautions noted. The compound is used for the preparation of 2diazopropane.8,9,10 This preparation is referenced from: Org. Syn. Coll. Vol. 6, 161

References and NotesDyson Perrins Laboratory, Oxford University, England. Department of Organic Chemistry, University of Bristol, England. F. Raschig, Ber. Dtsch. Chem. Ges., 43, 1927 (1910). R. A. Pennman and L. F. Audrieth, J. Am. Chem. Soc., 71, 1644 (1949). T. Curtius and K. Thun, J. Prakt. Chem., [2] 44, 161 (1891). T. Curtius and L. Pflug, J. Prakt. Chem., [2] 44, 535 (1891). Cf. K. Heyns and A. Heins, Justus Liebigs Ann. Chem., 604, 133 (1957). H. Staudinger and A. Gaule, Ber. Dtsch. Chem. Ges., 49, 1897 (1916). A. C. Day, P. Raymond, R. M. Southam, and M. C. Whiting, J. Chem. Soc. C, 467 (1966); D. E. Applequist and H. Babad, J. Org. Chem., 27, 288 (1962). 10. S. D. Andrews, A. C. Day, P. Raymond, and M. C. Whiting, Org. Synth., Coll. Vol. 6, 392 (1988). 1. 2. 3. 4. 5. 6. 7. 8. 9.

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)

sodium hydroxide pellets (1310-73-2) barium oxide nitrogen (7727-37-9) acetone (67-64-1) potassium hydroxide, potassium hydroxide pellets (1310-58-3) hydrazine hydrate (7803-57-8) hydrazine (302-01-2) Acetone hydrazone, 2-Propanone, hydrazone (5281-20-9) Acetone azine (627-70-3) 2-Diazopropane (2684-60-8)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


PREPARATION OF HYDRAZONES: ACETOPHENONE HYDRAZONE[Ethanone, 1-phenyl-, hydrazone]

Submitted by G. R. Newkome1 and D. L. Fishel2. Checked by G. Swift and W. D. Emmons.

1. ProcedureCaution! Hydrazines are toxic and should be handled in a hood. Anhydrous hydrazine is extremely reactive with oxidizing agents (including air) and should always be used behind a protective screen. A. Acetophenone N,N-dimethylhydrazone. A mixture of acetophenone (12.0 g., 0.100 mole), anhydrous N,N-dimethylhydrazine (18.0 g., 0.300 mole) (Note 1), absolute ethanol (25 ml.), and glacial acetic acid (1 ml.) (Note 2) is heated at reflux for 24 hours. During this period the colorless solution becomes bright yellow. The volatile reactants and solvent are removed under reduced pressure and the residual oil is fractionally distilled through a 10-cm. Vigreux column, giving a small forerun of unreacted acetophenone, b.p. 3040 (0.15 mm.), followed by 14.615.2 g. (9094%) of acetophenone 25 N,N-dimethylhydrazone, b.p. 5556 (0.15 mm.), nD 1.5443 (Note 3) and (Note 4). B. Acetophenone hydrazone. A mixture of acetophenone N,N-dimethylhydrazone (8.1 g., 0.050 mole) and anhydrous hydrazine (6.4 g., 0.20 mole) (Note 5) in absolute ethanol (15 ml.) is heated at reflux until the reaction mixture turns colorless (Note 6). The volatile materials are removed on a rotary evaporator without allowing the flask temperature to rise above 20 (Note 7). The colorless residual acetophenone hydrazone, which solidifies as the last traces of solvent are removed, weighs 6.56.6 g. (9799%) and is sufficiently pure for most purposes, m.p. 2425 (Note 8) and (Note 9).

2. Notes1. Anhydrous N,N-dimethylhydrazine obtained from Matheson, Coleman and Bell is used directly. It can also be prepared by the method in Org. Synth., Coll. Vol. 2, 213 (1943). 2. It is not necessary to use glacial acetic acid as a catalyst, but without it the reaction time required for completion is prolonged. 25 3. Physical constants previously reported:3 b.p. 100.5102 (10 mm.), nD 1.5455. 4. This method has been used to prepare various N,N-dimethylhydrazones in 7099% yield.4 5. A good commercial grade of anhydrous hydrazine (Eastman Organic Chemicals) is satisfactory. 6. The reaction time for complete conversion is usually less than 24 hours. A convenient "end point" is the visual color change from bright yellow to colorless or very pale yellow. 7. It is of utmost importance that the flask temperature during the removal of the volatile materials be kept below 20 to minimize possible azine formation by decomposition of the hydrazone. 8. The reported melting points are 1620,5 22,6 2425,4,7 and 26.7 9. Acetophenone hydrazone can be stored at temperatures below 0 for indefinite periods of time.

3. DiscussionThe formation of acetophenone hydrazone has been accomplished by heating acetophenone with hydrazine or hydrazine hydrate,7,8,9,10 by heating acetophenone azine with anhydrous hydrazine,6,11 by the reaction of -dimethylaminoacetophenone with hydrazine,5 and by the present method.4 This synthetic process is applicable to the preparation of most hydrazones from aldehydes and ketones. The two-step preparation offers several distinct advantages over the one-step method:6,9 (1) The yield of both steps is high; (2) the product is not contaminated with azine; (3) the isolated product is pure enough to be used in subsequent reactions without further purification. This method excels in the preparation of unstable liquid or low-melting hydrazones over the common methods of preparation.

References and Notes1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803. Department of Chemistry, Kent State University, Kent, Ohio 44240. P. A. S. Smith and E. E. Most, Jr., J. Org. Chem., 22, 358 (1957). G. R. Newkome and D. L. Fishel, J. Org. Chem., 31, 677 (1966). R. L. Letsinger and R. Collat, J. Am. Chem. Soc., 74, 621 (1952). H. Staudinger and A. Gaule, Ber. Dtsch. Chem. Ges., 49, 1897 (1916). G. Lock and K. Stach, Ber. Dtsch. Chem. Ges., 77, 293 (1944). D. E. Pearson, K. N. Carter, and C. M. Greer, J. Am. Chem. Soc., 75, 5905 (1953). T. Curtius and L. Pflug, J. Prakt. Chem., [2] 44, 535 (1891). J. Stanek, Collect. Czech. Chem. Commun., 12, 671 (1947). H. Staudinger and L. Hammet, Helv. Chim. Acta, 4, 217 (1921).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)ethanol (64-17-5) acetic acid (64-19-7) Acetophenone (98-86-2) hydrazine hydrate (7803-57-8) hydrazine (302-01-2) N,N-dimethylhydrazine (57-14-7) Acetophenone hydrazone, Ethanone, 1-phenyl-, hydrazone (13466-30-3) acetophenone azine (729-43-1) -dimethylaminoacetophenone (3319-03-7)

Acetophenone N,N-dimethylhydrazone (13466-32-5)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


3-ACETOXY-5-CYANOCHOLESTAN-7-ONE[Cholestane-5-carbonitrile, 3-(acetyloxy)-7-oxo-, (3, 5)-]

Submitted by W. Nagata and M. Yoshioka1. Checked by Robert E. Ireland, Robert Czarny, and Conrad J. Kowalski.

1. ProcedureCaution! This preparation should be carried out in a good hood. Also, great care should be taken in handling neat triethylaluminum because it is pyrophoricthat is, it ignites spontaneously upon contact with air (Note 2). Benzene has been identified as a carcinogen; OSHA has issued emergency standards on its use. All procedures involving benzene should be carried out in a well-ventilated hood, and glove protection is required. A dry, 50-ml., three-necked, round-bottomed flask equipped with a gas-inlet tube for nitrogen, a magnetic stirring bar, and a serum stopper for the introduction of reagents is flushed with nitrogen, stoppered with a glass stopper, charged with 17 ml. of anhydrous tetrahydrofuran (Note 1), then immersed in an ice bath. Stirring is begun and 3.3 g. (3.9 ml., 0.028 mole) of triethylaluminum is introduced into the flask with a dry hypodermic syringe (Note 2), (Note 3). After 510 minutes, 4.8 ml. of a 3.57 M solution of hydrogen cyanide (0.017 mole) in anhydrous tetrahydrofuran (Note 4) is added with a dry hypodermic syringe. The stirring is continued for about 510 minutes. A dry, 100-ml., three-necked, round-bottomed flask equipped with a gas-inlet tube for nitrogen, a magnetic stirring bar, and a serum stopper, as described above, is flushed with nitrogen. While the flask is being flushed, 2.50 g. (0.00565 mole) of 3-acetoxycholest-5-en-7-one (Note 5) and 0.0521 ml. (0.00289 mole) of water (Note 6) are added to the reaction flask. The flask is stoppered with a glass stopper and charged with 17 ml. of anhydrous tetrahydrofuran. After the starting material has dissolved, the cold triethylaluminum-hydrogen cyanide solution is transferred to the reaction flask with a dry hypodermic syringe. The resulting pale yellow solution is stirred at room temperature under a positive nitrogen pressure. After 3 hours, a solution of 0.044 ml. (0.0024 mole) of water in 0.87 ml. of anhydrous tetrahydrofuran is added, and the solution is allowed to stir for an additional 4 hours. The reaction mixture is poured slowly into a vigorously stirred solution of 28 ml. (0.28 mole) of concentrated hydrochloric acid and 350 ml. of ice water in a 1-l., three-necked, round-bottomed flask fitted with an efficient stirrer and immersed in an ice bath (Note 7), (Note 8). The mixture is stirred for 20 minutes with ice cooling and extracted with three 200-ml. portions of a 3:1 (v/v) mixture of diethyl ether and dichloromethane. The extracts are washed with three 200-ml. portions of aqueous 2 M sodium hydroxide, two 200-ml. portions of water, and one 200-ml. portion of saturated aqueous sodium chloride, dried over anhydrous sodium sulfate, and evaporated under reduced pressure (Note 9) and (Note 10). The crystalline residue, weighing 2.70 g., is recrystallized by dissolving it in 7.58 ml. of hot (almost boiling) benzene and adding 25 ml. of n-pentane (distilled) to the hot solution (Note 11). 3-

Acetoxy-5-cyanocholestan-7-one is obtained as white crystals, m.p. 192.5193.5; the yield is 2.272.41 g. (8691%). A second crop (50170 mg.) can be obtained, m.p. 188.5190 (Note 12); the total yield is 9293% (Note 13) and (Note 14).

2. Notes1. Prior to use the tetrahydrofuran was distilled from lithium aluminum hydride into a dry flask flushed with nitrogen and sealed with a serum stopper. 2. Caution! Triethylaluminum is pyrophoric. Use safety glasses, gloves, and an apron. Use dry sand to extinguish fires. The submitters note that a description of the properties and handling procedures for triethylaluminum are available from the Ethyl Corporation, Louisiana. The checkers used triethylaluminum in lecture bottles from Alpha Inorganics, Inc., and suggest the handling procedure described below. Since this procedure was submitted and checked, standardized solutions of triethylaluminum in various hydrocarbon solvents, which may be substituted for pure triethylaluminum, have become available from Texas Alkyls, Inc., a division of Stauffer Chemical Company. a. Checkers handling procedure. Figures 1 and 2 suggest the equipment to be used, and how to assemble it. The hose end fitting is connected to the stopcock with a piece of Teflon-lined tubing and fastened with copper wire. The stopcock should be well greased and held secure with a taut rubber band since it does have a tendency to pop out. The triethylaluminum may now be removed from the lecture bottle by the following procedure. A dry, three-necked flask equipped with serum stopper and gas-inlet tube is flushed thoroughly with nitrogen from a nitrogen bubbler. The triethylaluminum transfer apparatus is put into the open neck of the flask, the joint being well greased (the gas-inlet tube joint should also be greased). With the stopcock of the transfer apparatus open and well secured as suggested above, the tank valve is opened (usually one or two full turns) with a wrench. The flow of triethylaluminum may now be adjusted with the stopcock. When one obtains as much triethylaluminum as desired, the tank valve is closed, the transfer apparatus is allowed to drain, and the stopcock is closed. The transfer apparatus is removed from the flask which is quickly stoppered with a glass stopper while the flask is flushed with nitrogen. This flask of triethylaluminum can be stored in this manner for many weeks since this reagent is quite stable. The transfer apparatus, which may still contain some triethylaluminum, should be carefully removed, rinsed quickly with acetone, and cleaned with dilute hydrochloric acid. Figure 1. Apparatus for collecting triethylaluminum from a lecture bottle.

Figure 2. Detailed construction of the stopcock for the apparatus shown in Figure 1.

b. Submitters handling procedure. The submitters suggest another handling procedure especially useful

for removing triethylaluminum from a lecture bottle having a clogged valve outlet. Figure 3 shows the apparatus and how to transfer the material. With the cylinder clamped in upright position, remove the valve unit so that only the bottle remains. Quickly attach the adaptor to the opening of the bottle and apply a slow stream of nitrogen. Transfer the triethylaluminum into dry, nitrogen-flushed, 50-ml. ampoules using a 100- or 200-ml. Luer-lock hypodermic syringe with a needle, 43 cm. long and 2 mm. in diameter. Sweep the opening of the ampoule with nitrogen during the transfer. The syringe should be slightly greased, and the ampoules should be strong with a long, thick stem so that they can be resealed. The ampoules are sealed as soon as possible. The use of rubber caps is effective for temporary protection of the ampoules from air. The material in a 50-ml. ampoule can be divided in smaller ampoules using the apparatus shown in Figure 4, which can be used also for transferring triethylaluminum from an ampoule to a reaction flask. Figure 3. Apparatus for removing triethylaluminum from the lecture bottle.

Figure 4. Apparatus for collecting aliquots of triethylaluminum.

This procedure was not tested by the checkers. It has the advantage that one does not have to contend with a clogged lecture bottle, which in the checkers experience is best discarded. It has the disadvantage that one must handle large syringe-fulls of triethylaluminum and make several transfers without exposing the liquid to air. Caution must be exercised with either procedure. 3. Neat triethylaluminum may be replaced with a 1025% stock solution of it in anhydrous tetrahydrofuran, decreasing the amount of solvent in the reaction flask. The stock solution is prepared using a graduated flask to measure the volume of the triethylaluminum and solvent, added appropriately. The stock solution is very stable and not pyrophoric. 4. The submitters have prepared hydrogen cyanide as directed in Org. Synth., Coll. Vol. 1, 314, (1944). The checkers used a similar procedure described by Brauer.2 The hydrogen cyanide was collected in a tared flask and diluted with anhydrous tetrahydrofuran to a previously marked volume. The flask was capped with two serum stoppers (the second put on in an inverted position) to ensure against leakage and stored in a freezer. Solutions such as these seem to be stable for several months when kept cold. 5. Checkers obtained the steroid from K & K Laboratories. 6. A small amount of water has been found to accelerate the reaction. In the absence of water, the reaction was about 80% complete after 7.5 hours. Despite the rate acceleration by water, the reaction mixture should be protected from moisture, because a larger amount of water than that specified retards the reaction, owing to decomposition of the triethylaluminum. 7. This treatment is an exothermic reaction with evolution of gaseous ethane. The reaction mixture should be added in a slow stream, with good stirring, at such a rate that the content in the flask does not overflow. When the ice has melted, additional ice should be added. 8. The reaction mixture remaining on the wall of the reaction flask is treated with a small amount of cold, dilute hydrochloric acid and combined with the extraction mixture. 9. Acid treatment followed by alkaline washing of the extracts prevents possible hydrolysis of the acetoxyl and the cyano groups.

10. The submitters have performed the extraction and washing in a countercurrent manner using three 2l. separatory funnels. 11. The recrystallization was carried out in a 40-ml. centrifuge tube. The recrystallization mixture, after cooling to room temperature, was cooled in a freezer and washed twice with 20-ml. portions of cold recrystallization solvent. 12. When the second crop is contaminated with a polar material (-cyanohydrin of the product) as evidenced by a lower melting point (m.p. 160170) and TLC (Kiesel Gel GF, benzene-ethyl acetate, 4:1, Rf = 0.2), the residue from the mother liquor must be treated again with alkali before crystallization. 13. This procedure is applicable to smaller or larger scale preparations with some modification. In a smaller scale experiment, the submitters suggest using a stock solution of triethylaluminum (Note 3). In a larger scale preparation, to avoid using large syringes, it is possible to run the triethylaluminum into a dry, graduated, pressure-equalizing dropping funnel, in which case the triethylaluminum-hydrogen cyanide solution may be added to the reaction flask through a funnel instead of using a syringe. 14. The submitters used 5.76 g. of 3-acetoxycholest-5-en-7-one and obtained 5.65 g. (92%) of the cyano ketone.

3. Discussion3-Hydroxy-5-cyanocholestan-7-one has been prepared in 43% yield by the action of potassium cyanide and ammonium chloride3 on 7-ketocholesterol at 100 for 33 hours.4 The present method was developed by the submitters.4 This process is superior to classical hydrocyanation methods using an alkali metal cyanide5 and to the improved method using potassium cyanide and ammonium chloride3 with respect to reactivity, stereospecificity, and absence of side reactions. Also, the process is applicable to conjugate hydrocyanation of various ,-unsaturated carbonyl and imino compounds,4,6 cyanohydrin formation from less-reactive ketones,4 and cleavage of epoxides to produce -cyanohydrins,7 the reaction conditions being varied depending on the substrate to be used. The present procedure is typical of hydrocyanation procedures using other organoaluminum compounds. Cyanotrimethylsilane reacts with ,-unsaturated ketones in the presence of triethylaluminum to give trimethylsilyl enol ethers of -cyano ketones.8

References and Notes1. Shionogi Research Laboratory, Shionogi & Co., Ltd., Osaka, Japan. 2. O. Glemser, in G. Brauer, Ed., "Handbook of Preparatory Inorganic Chemistry," 2nd ed., Vol. 1, Academic Press, New York, 1963, p. 658. 3. W. Nagata, S. Hirai, H. Itazaki, and K. Takeda, J. Org. Chem., 26, 2413 (1961). 4. W. Nagata, M. Yoshioka, and S. Hirai, Tetrahedron Lett., 48 (1962); W. Nagata, M. Yoshioka, and M. Murakami, J. Am. Chem. Soc., 94, 4644, 4654 (1972); W. Nagata, M. Yoshioka, and T. Terasawa, J. Am. Chem. Soc., 94, 4672 (1972); W. Nagata and M. Yoshioka, Org. React., 25, 255 (1977). 5. P. Kurtz, "Methoden der Organischen Chemie," Vol. 8, Georg Thieme Verlag, Stuttgart, 1952, p. 265. 6. W. Nagata, T. Okumura, and M. Yoshioka, J. Chem. Soc. C, 2347 (1970); W. Nagata, M. Yoshioka, T. Okumura, and M. Murakami, J. Chem. Soc. C, 2355 (1970). 7. W. Nagata, M. Yoshioka, and T. Okumura, Tetrahedron Lett., 847 (1966); J. Chem. Soc. C, 2365 (1970). 8. K. Utimoto, M. Obayashi, Y. Shishiyama, M. Inoue, and H. Nozaki, Tetrahedron Lett., 21, 3389 (1980).

Appendix Chemical Abstracts Nomenclature (Collective Index Number);

(Registry Number)hydrochloric acid (7647-01-0) Benzene (71-43-2) diethyl ether (60-29-7) ammonium chloride (12125-02-9) sodium hydroxide (1310-73-2) sodium chloride (7647-14-5) hydrogen cyanide (74-90-8) sodium sulfate (7757-82-6) nitrogen (7727-37-9) potassium cyanide (151-50-8) acetone (67-64-1) n-PENTANE (109-66-0) dichloromethane (75-09-2) ethane (74-84-0) Tetrahydrofuran (109-99-9) lithium aluminum hydride (16853-85-3) triethylaluminum (97-93-8) 3-ACETOXY-5-CYANOCHOLESTAN-7-ONE, Cholestane-5-carbonitrile, 3-(acetyloxy)-7-oxo-, (3, 5)- (2827-02-3) 3-acetoxycholest-5-en-7-one triethylaluminum-hydrogen cyanide 3-Hydroxy-5-cyanocholestan-7-one 7-ketocholesterol Cyanotrimethylsilane (7677-24-9)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


p-ACETYL--BROMOHYDROCINNAMIC ACID[Benzenepropanoic acid, 4-acetyl--bromo-]

Submitted by George H. Cleland1 Checked by Michael J. Umen and Herbert O. House.

1. ProcedureCaution! Since bromoacetone, a powerful lachrymator, is produced as a by-product in this preparation, the reaction should be performed in a hood. A tared, 500-ml., two-necked, round-bottomed flask is equipped with a magnetic stirring bar, a thermometer, and an ice-filled cooling bath. A solution of 13.5 g. (0.100 mole) of 4-aminoacetophenone (Note 1) in 200 ml. of acetone is placed in the flask and stirred while 32 ml. (about 0.3 mole) of aqueous 48% hydrobromic acid is added. After the resulting solution has been cooled to 57, it is stirred continuously while 20 ml. of an aqueous solution containing 6.90 g. (0.100 mole) of sodium nitrite is added rapidly (30 seconds) beneath the surface of the reaction solution with a hypodermic syringe or a long-stemmed dropping funnel. Stirring and cooling are continued until the exothermic reaction subsides (Note 2) and the reaction solution has cooled to 1415. After 106 g. (100 ml., 1.47 moles) of acrylic acid (Note 3) is added, the solution is again cooled to 1415, with stirring, before 0.100.11 g. (0.000690.00077 mole) of copper(I) bromide (Note 4) is added. Stirring is continued, during which time the solution darkens, and nitrogen evolution is observed; the temperature of the reaction mixture is kept below 33 by use of the external cooling bath. As soon as the evolution of nitrogen has ceased (usually 20 minutes is sufficient), the reaction solution is concentrated with a rotary evaporator, giving a mixture weighing about 120130 g. The residual brown suspension is mixed with 5 g. of decolorizing charcoal and 200 ml. of water, and the resulting mixture is boiled for 3 minutes, and filtered while hot through a Bchner funnel containing Celite filter aid. The residue on the filter is washed with 100 ml. of boiling water, and the combined filtrates are diluted with 300 ml. of water. The resulting aqueous solution, from which the product begins to crystallize, is cooled in a water bath and then allowed to stand in a refrigerator (03) for 24 hours to complete the crystallization of the crude product. The crystalline solid is collected on a filter, washed with two 100-ml. portions of cold water, and dried in the air. The crude product, a pale yellow solid (19.122.2 g.), is recrystallized from 40 ml. of a 2:3 (v/v) formic acid-water mixture. The resulting crystals are collected on a filter, washed with 20 ml. of 2:3 (v/v) cold formic acid-water, and dried in the air, yielding 16.618.2 g. (6167%) of white needles, m.p. 158160, which are sufficiently pure for most purposes. Three additional crystallizations from 20-ml. portions of 2:3 (v/v) formic acid-water give 15.216.0 g. (5659%) (Note 5) of the pure p-acetyl-bromohydrocinnamic acid, m.p. 159161 (Note 6).

2. Notes

1. Commercial grades of acetone and 4-aminoacetophenone (Matheson, Coleman and Bell or Aldrich Chemical Company, Inc.) were used without further purification. 2. The temperature of the reaction mixture rises to about 30 and then falls to 15 as stirring and cooling are continued. If this preparation were performed on a larger scale, it would probably be necessary to add the sodium nitrite solution over a longer period of time in order to control the temperature. 3. A freshly opened bottle of acrylic acid, obtained from Eastman Organic Chemicals, was used without further purification. The checkers encountered difficulty in attempting to use samples of acrylic acid that had been stored in partially filled bottles for long periods of time. 4. A reagent grade of copper(I) bromide, obtained from Fisher Scientific Company, was washed with acetone until the washings were colorless and then dried. 5. The combined filtrates from these recrystallizations can be concentrated to obtain an additional 12 g. of product. 6. The product has IR absorption (KBr) at 1735, 1645, and 1607 cm.1 with a UV maximum (95% C2H5OH solution) at 252.5 nm ( 17,000). The sample has 1H NMR peaks (CF3CO2H) at 2.78 (s, 3H, CH3CO), 3.23.9 (m, 2H, benzylic CH2), 4.60 (t, J = 7.5 Hz., 1H, CHBr), 7.47 (d, J = 9 Hz., 2H, aryl CH), and 8.10 (d, J = 9 Hz., 2H, aryl CH). The mass spectrum has weak molecular peaks at m/e 270 and 272 with the following relatively abundant fragment peaks: m/e (rel. int.), 191 (73), 175 (100), 131 (52), 103 (40), 77 (55), and 51 (43). The product gives a deep red color when treated with sodium nitroprusside and aqueous base; this color changes to dark blue upon acidification with acetic acid.

3. DiscussionThis procedure has been used to prepare a variety of substituted -bromohydrocinnamic acids;2 pacetyl--bromohydrocinnamic acid was prepared for the first time by this method. The method illustrates a typical application of the Meerwein reaction for the arylation of unsaturated substrates.3 In this reaction a catalytic amount of a copper(I) salt is used to reduce an aryl diazonium salt forming an aryl radical and a copper(II) halide. Addition of the aryl radical to an unsaturated substrate forms an alkyl radical that is reoxidized by the copper(II) halide present forming an alkyl halide and regenerating the copper(I) salt catalyst. In this preparation, the product, an -bromo acid, is formed in an acidic reaction mixture and dehydrohalogenation does not occur. However, dehydrohalogenation of the intermediate halide is often observed in analogous reactions performed under neutral or basic reaction conditions.3 The use of the Meerwein reaction to form ultimately 1-(4-nitrophenyl)-1,3-butadiene by the addition of an intermediate aryl radical to 1,3-butadiene followed by dehydrohalogenation of the initially formed alkyl halide is illustrated in Organic Syntheses.4

References and Notes1. 2. 3. 4. Department of Chemistry, Occidental College, Los Angeles, California 90041. G. H. Cleland, J. Org. Chem., 26, 3362 (1961); J. Org. Chem., 34, 744 (1969). C. S. Rondestvedt, Jr., Org. React., 11, 189 (1960); Org. React., 24, 225 (1976). G. A. Ropp and E. C. Coyner, Org. Synth., Coll. Vol. 4, 727 (1963).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)4-aminoacetophenone sodium nitroprusside acetic acid (64-19-7)

HYDROBROMIC ACID (10035-10-6) nitrogen (7727-37-9) sodium nitrite (7632-00-0) acetone (67-64-1) Acrylic acid (9003-01-4) copper(I) bromide (7787-70-4) Bromoacetone (598-31-2) 1,3-Butadiene (106-99-0) Benzenepropanoic acid, 4-acetyl--bromo-, p-Acetyl--bromohydrocinnamic acid (18910-19-5) 1-(4-nitrophenyl)-1,3-butadiene (20264-89-5)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


,-DEHYDROGENATION OF -DICARBONYL COMPOUNDS BY SELENOXIDE ELIMINATION: 2-ACETYL-2-CYCLOHEXEN-1ONE[2-Cyclohexen-1-one, 2-acetyl-]

Submitted by James M. Renga and Hans J. Reich1. Checked by Albert W. M. Lee and Robert V. Stevens.

1. ProcedureCaution! Most selenium compounds are toxic; consequently care should be exercised in handling them. The hydrogen peroxide oxidation of selenides is highly exothermic, acid-catalyzed, and autocatalytic. The procedure given for adding the hydrogen peroxide solution should be carefully followed. A. 2-Acetyl-2-phenylselenocyclohexanone. A 500-ml., three-necked, round-bottomed flask is fitted with a mechanical stirrer, a pressure-equalizing dropping funnel, and a combined inlet-outlet assembly connected to a nitrogen source and a bubbler. The flask is charged with 3.36 g. (0.140 mole) of sodium hydride (Note 1), the apparatus is flushed with nitrogen, and 100 ml. of tetrahydrofuran (Note 2) is added. The suspension is stirred and cooled in an ice bath under a static nitrogen atmosphere as a solution of 14.02 g. (0.100 mole) of 2-acetylcyclohexanone (Note 3) in 15 ml. of tetrahydrofuran is added over a 15-minute period. The formation of the sodium enolate is complete when hydrogen evolution ceases and a thick suspension has developed. Stirring and cooling are continued for 20 minutes, after which a solution of 20.1 g. (0.105 mole) of benzeneselenenyl chloride (Note 4) in 20 ml. of tetrahydrofuran is rapidly added. The contents of the flask are stirred at 0 for 15 minutes and poured into a beaker containing a magnetically stirred mixture of 200 ml. of 1:1 (v/v) diethyl ether-pentane, 50 ml. of aqueous 7% sodium hydrogen carbonate, and 50 g. of ice. The layers are separated, and the aqueous layer is extracted with 50 ml. of 1:1 (v/v) etherpentane. The combined organic extracts are washed with 50 ml. of saturated aqueous sodium chloride and dried by filtration through a cone of anhydrous sodium sulfate. Evaporation of the solvents under reduced pressure gives 29.230 g. of crude, solid 2-acetyl-2-phenylselenocyclohexanone which is used in Part B without purification (Note 5). B. 2-Acetyl-2-cyclohexen-1-one. A 500-ml., three-necked, round-bottomed flask equipped with a pressure-equalizing dropping funnel, a reflux condenser, a thermometer, and a magnetic stirring bar is charged with a solution of 29.230 g. (ca. 0.1 mole) of crude 2-acetyl-2-phenylselenocyclohexanone in 100 ml. of dichloromethane (Note 6). The solution is stirred at room temperature, and a 23 ml. portion from a solution of 23.8 g. of 30% hydrogen peroxide (7.14 g., 0.21 mole) (Note 7) in 20 ml. of water is added to initiate the oxidation (Caution! (Note 8)). After the exothermic reaction begins, the mixture is

stirred and cooled in an icesalt bath as necessary to keep the temperature between 30 and 35 while the remainder of the hydrogen peroxide solution is added. When the oxidation is complete (Note 9), the icesalt bath is removed, and vigorous stirring is continued for 15 minutes at room temperature and 15 minutes at 0. The chilled suspension of benzeneseleninic acid is filtered, and the filter cake is washed with 50 ml. of dichloromethane (Note 10). The dichloromethane layer from the filtrate is washed with 50 ml. of aqueous 7% sodium hydrogen carbonate, dried by filtration through a cone of anhydrous sodium sulfate, and evaporated, providing 12.813.7 g. of crude product (Note 11). Distillation in carefully washed glassware (Note 12) at 0.1 mm. using a Kgelrohr apparatus (Note 13) with an oven temperature of 5055 gives 11.011.9 g. (7985%) of 2-acetyl-2-cyclohexen-1-one (Note 14).

2. Notes1. A 57% dispersion of sodium hydride in mineral oil was purchased from Alfa Division, Ventron Corporation. A 5.90-g. portion of the dispersion was placed in the reaction vessel and washed free of mineral oil with three 50-ml. portions of pentane by decanting the supernatant pentane after each washing. The pentane that remains in the flask is evaporated as the assembled apparatus is purged with nitrogen prior to adding the tetrahydrofuran. 2. Tetrahydrofuran was purified by the submitters by distillation from the sodium ketyl of benzophenone. 3. 2-Acetylcyclohexanone was used as supplied by Aldrich Chemical Company, Inc. 4. Benzeneselenenyl chloride was prepared by the procedure in Org. Synth., Coll. Vol. 6, 533 (1988). A freshly prepared solution of 24.8 g. (0.105 mole) of benzeneselenenyl bromide2 in 25 ml. of tetrahydrofuran may also be used. 5. The crude selenide is contaminated by volatile impurities including some 2-acetylcyclohexanone which may be removed by sublimation at 5060 to a cold finger cooled with dry ice, or by recrystallization from etherpentane. The purified product melts at 7273; IR (CCl4) cm1: 1693 strong, 1579 weak; 1H NMR (CCl4) (multiplicity, number of protons, assignment): 1.32.3 (m, 7H, ring protons), 2.30 (s, 3H, CH3), 2.52.8 (m, 1H, CHAHBC=O), 7.28 (m, 5H, C6H5Se). The product was analyzed by the submitters. Analysis calculated for C14H16O2Se: C, 56.96; H, 5.46. Found: C, 57.12; H, 5.48. 6. Dichloromethane was used without purification. 7. A 30% solution of hydrogen peroxide in water was purchased from Mallinckrodt Chemical Works. The reaction requires 2 molar equivalents of hydrogen peroxide, the first to oxidize the selenide to the selenoxide and the second to oxidize the elimination product, benzeneselenenic acid, to benzeneseleninic acid. The submitters recommend that the hydrogen peroxide solution be taken from a recently opened bottle, or titrated to verify its concentration. 8. The oxidation is autocatalytic, being catalyzed by the product, benzeneseleninic acid.3 If the temperature drops significantly below 30, the addition of hydrogen peroxide should be stopped, and the icesalt bath should be removed to maintain the rate of oxidation and avoid an accumulation of hydrogen peroxide in the flask. 9. The yellow dichloromethane solution turns colorless, and a precipitate of benzeneseleninic acid appears. 10. The benzeneseleninic acid weighs 14.416 g. (7382%) and melts at 123124. It may be reconverted to diphenyl diselenide by reduction with sodium thiosulfate2 or sodium bisulfite.4 11. The enol content of the product at this point is less than 2%. If the unenolized enedione is desired, the following distillation should be omitted and the product used without purification to avoid further isomerization. 12. The glassware was cleaned in a sodium dichromatesulfuric acid bath, washed with aqueous 10% ammonium hydroxide, and rinsed with water. The extent of enolization apparently depends on the care taken in washing the glassware and conducting the distillation. 13. Kgelrohr distillation ovens manufactured by Bchi Glasapparatfabrik are available from Brinckmann Instruments, Inc., Westbury, New York. 14. The product is contaminated by 515% of 2-acetylcyclohexanone, which was present in the crude selenide. This impurity may be avoided by purifying the selenide as described in (Note 5). The enol content of the product obtained by the submitters varied from 5 to 50%. At equilibrium the enol content is 84%. The spectral properties of the enedione are as follows: IR (CCl4) cm.1: 1694 strong, 1602 weak; 1H NMR (CCl ), (multiplicity, coupling constant J in Hz., number of protons, assignment): 1.92.2 4

(m, 2H, CH2CH2CH2), 2.35 (s, 3H, CH3), 2.32.7 (m, 4H, CH2CH2CH2), 7.56 (t, J = 4.3, H, CH2CH=C). The enol form of the product exhibits the following 1H NMR (CCl4), (multiplicity, coupling constant J in Hz., number of protons, assignment): 2.07 (s, 3H, CH3), 2.12.7 (m, 4H, CH2CH2), 5.55 (d of t, J = 4.5 and 10, 1H, CH2CH=CH), 6.19 (d of t, J = 1.5 and 10, 1H, CH2CH=CH), 15.8 (s, 1H, OH).

3. DiscussionThe procedure described here serves to illustrate a new, general method for effecting the ,dehydrogenation of ketones,2,5,6,7,8,9 aldehydes,9 esters,2,5,6,7,9 lactones,9,10 nitriles,11 sulfones, and related compounds.2,12 The individual steps in the process are formation of an -carbanion or enol derivative, phenylselenenylation with diphenyl diselenide or benzene selenenyl halides, oxidation of the resulting -phenylseleno compound to the selenoxide, and thermal syn-elimination of benzeneselenenic acid. The advantages of this method include (a) the ease of introducing the -phenylseleno group; (b) the rapid stoichiometric oxidation of the selenide with aqueous hydrogen peroxide at 2535, sodium metaperiodate in aqueous media, or ozone in dichloromethane at 78; and (c) the fact that the elimination occurs at about room temperature under essentially neutral conditions. The mild character of the reaction conditions is exemplified effectively here by the preparation of 2acetyl-2-cyclohexen-1-one from 2-acetylcyclohexanone.2 The crude product is initially isolated entirely in the less stable enedione form which is partially converted to the more stable enol form, 2-acetyl-1,3cyclohexadien-1-ol,13,14,15 during distillation at 4555. A series of ,-unsaturated -keto esters, diketones, and a -keto sulfoxide have also been prepared in the unenolized form by this procedure (Table I).2,5,6,7 In the case of the highly sensitive ethyl 5-oxo-1-cyclopentene-1-carboxylate, the hydrogen carbonate extraction must be omitted to avoid base-catalyzed decomposition during isolation.

TABLE I ,-UNSATURATED -KETO ESTERS, -DIKETONES AND A -KETO SULFOXIDE PREPARED BY SELENOXIDE ELIMINATION,-Unsaturated Product Yield (%)a ,-UnsaturatedProduct Yield (%)a

81b

74

89

89

84

55

89

a Overall yield from -keto ester, -diketone, or -keto sulfoxide. The scale was 0.010.005 mole. b The starting -keto ester and the product were 2:1 mixtures of ethyl and methyl esters. The enolized form of 2-acetyl-2-cyclohexen-1-one has been synthesized in low yield by dehydrochlorination of 2-acetyl-2-chlorocyclohexanone in collidine at 18013,14 and by elimination of

acetamide from N-(2-acetyl-3-oxo-1-cyclohexyl)acetamide at 120140.15 The preparation of other ,-unsaturated -dicarbonyl compounds has been attempted with varying degrees of success. The dehydrogenation of 2-hydroxymethylene-3-keto steroids to 2-formyl-1-3-keto compounds with 2,3dichloro-5,6-dicyano-1,4-benzoquinone has been reported.16 Ethyl 5-oxo-1-cyclopentene-1-carboxylate has been prepared by selenium dioxide oxidation of the parent -keto ester.17 -Acetoxylation of 3methyl- and 3-isopropyl-2,4-pentanedione with lead tetraacetate followed by acetate pyrolysis provided the ,-unsaturated -diketones.18 Chlorination and dehydrochlorination of 2-acetylcycloheptanone gave an enolic tautomer of 2-acetyl-2-cyclohepten-1-one.14 Numerous failures in attempts to synthesize these and other ,-unsaturated -dicarbonyl compounds by halogenation and dehydrohalogenation have been recorded as a consequence of competing Favorskii rearrangement, migration of halogen to the 'position, and decomposition of the products from a combination of the high temperatures and basic conditions employed.13,14,16,17,18,19 A number of ,-unsaturated -keto esters and -diketones have been prepared by intermolecular aldol condensations under Knoevenagel conditions,20 aldol cyclization,19,21 and Robinson annelation.22 All these procedures lead to equilibrium mixtures of keto and enol forms.

References and Notes1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706. H. J. Reich, J. M. Renga, and I. L. Reich, J. Am. Chem. Soc., 97, 5434 (1975). H. J. Reich, F. Chow, and S. L. Peake, Synthesis, 299 (1978). K. B. Sharpless and R. F. Lauer, J. Org. Chem., 39, 429 (1974). H. J. Reich, I. L. Reich, and J. M. Renga, J. Am. Chem. Soc., 95, 5813 (1973); H. J. Reich, J. M. Renga, and I. L. Reich, J. Org. Chem., 39, 2133 (1974); H. J. Reich and J. M. Renga, J. Org. Chem., 40, 3313 (1975). D. L. J. Clive, J. Chem. Soc. Chem. Commun., 695 (1973). K. B. Sharpless, R. F. Lauer, and A. Y. Teranishi, J. Am. Chem. Soc., 95, 6137 (1973). P. A. Grieco and M. Miyashita, J. Org. Chem., 39, 120 (1974). D. N. Brattesani and C. H. Heathcock, Tetrahedron Lett., 2279 (1974). For recent reviews, see H. J. Reich, Acc. Chem. Res., 12, 22 (1979); H. J. Reich, "Organoselenium Oxidations," in W. Trahanovsky, Ed., "Oxidation in Organic Chemistry," Part C, Academic Press, New York, 1978, pp. 1130; D. L. J. Clive, Tetrahedron, 34, 1049 (1978). M. E. McEntee and A. R. Pinder, J. Chem. Soc., 4419 (1957); C. W. T. Hussey and A. R. Pinder, J. Chem. Soc., 3525 (1961). A. A. Akhrem, A. M. Moiseenkov, and F. A. Lakhvich, Izv. Akad. Nauk SSSR, 407 (1972); Bull. Acad. Sci. USSR, Div. Chem. Sci., 355 (1972). J. A. Edwards, M. C. Calzada, L. C. Ibanez, M. E. Cabezas Rivera, R. Urquiza, L. Cardona, J. C. Orr, and A. Bowers, J. Org. Chem., 29, 3481 (1964). J. N. Marx, J. H. Cox, and L. R. Norman, J. Org. Chem., 37, 4489 (1972). D. Gorenstein and F. H. Westheimer, J. Am. Chem. Soc., 92, 634 (1970); C. W. T. Hussey and A. R. Pinder, J. Chem. Soc., 1517 (1962). J. A. Brenner, J. Org. Chem., 26, 22 (1962). G. B. Payne, J. Org. Chem., 24, 1830 (1959); F. Tiemann and P. Krger, Ber. Dtsch. Chem. Ges., 28, 2121 (1895). S. N. Huckin and L. Weiler, J. Am. Chem. Soc., 96, 1082 (1974). G. Stork and R. N. Guthikonda, J. Am. Chem. Soc., 94, 5109 (1972).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)sodium ketyl

3-methyl- and 3-isopropyl-2,4-pentanedione Acetamide (60-35-5) ether (60-29-7) hydrogen (1333-74-0) sodium hydrogen carbonate (144-55-8) sodium chloride (7647-14-5) sodium sulfate (7757-82-6) sodium thiosulfate (7772-98-7) nitrogen (7727-37-9) sodium bisulfite (7631-90-5) selenium dioxide (7446-08-4) Benzophenone (119-61-9) hydrogen peroxide (7722-84-1) ammonium hydroxide (1336-21-6) Pentane (109-66-0) dichloromethane (75-09-2) ozone (10028-15-6) selenium Tetrahydrofuran (109-99-9) sodium hydride (7646-69-7) hydrogen carbonate (463-79-6) Diphenyl diselenide (1666-13-3) collidine 2,3-dichloro-5,6-dicyano-1,4-benzoquinone sodium metaperiodate (7790-28-5) sulfoxide

2-acetylcyclohexanone (874-23-7) 2-Acetyl-2-cyclohexen-1-one, 2-Cyclohexen-1-one, 2-acetyl- (52784-38-0) diethyl ether-pentane 2-acetyl-2-phenylselenocyclohexanone benzeneseleninic acid (6996-92-5) Benzeneselenenyl chloride (5707-04-0) benzeneselenenyl bromide (34837-55-3) 2-acetyl-1,3-cyclohexadien-1-ol ethyl 5-oxo-1-cyclopentene-1-carboxylate 2-acetyl-2-chlorocyclohexanone 2-acetylcycloheptanone 2-acetyl-2-cyclohepten-1-one N-(2-acetyl-3-oxo-1-cyclohexyl)acetamide lead tetraacetate (546-67-8)Copyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


2-ACETYL-1,3-CYCLOPENTANEDIONE[2-Acetyl-3-hydroxy-2-cyclopenten-1-one, (Note 1)]

Submitted by Ferenc Mernyi and Martin Nilsson1. Checked by E. J. Corey, Joel I. Shulman, and Lawrence Libit.

1. ProcedureCaution! Since hydrogen chloride is evolved in this reaction, it should be conducted in a hood. A dry, 3-l., three-necked round-bottomed flask equipped with a sealed mechanical stirrer (all-glass or glass-Teflon), a reflux condenser fitted with a calcium chloride drying tube and a 100-ml. dropping funnel is charged with 50.0 g. (0.500 mole) of finely powdered succinic anhydride (Note 2), 133.4 g. (1.000 mole) of freshly crushed anhydrous aluminum chloride (Note 3), and 500 ml. of anhydrous 1,2dichloroethane. The mixture is stirred vigorously at room temperature for about 2 hours to dissolve as much of the solid reactants as possible before 50.0 g. (0.500 mole) of isopropenyl acetate (Note 4) is added rapidly through the dropping funnel; the reaction starts immediately as indicated by a rise in temperature to about 60 to 70. The mixture is refluxed for 15 minutes with continuous stirring. The hot reaction mixture, which contains a sticky oil, is poured into a stirred mixture of 200 ml. of 12 M hydrochloric acid and 1000 g. of crushed ice, and the reaction flask is rinsed with part of the acidic aqueous phase. When the dark mass has dissolved, 200 ml. of 12 M hydrochloric acid is added, and the mixture is stirred vigorously for about 3 hours (Note 5). The dichloroethane phase is separated, and the aqueous phase is extracted with eight 600-ml. portions of dichloromethane. The extracts are combined with the dichloroethane phase (Note 6) and extracted first with 600 ml. and then twice with 200-ml. portions of aqueous saturated sodium hydrogen carbonate solution. The combined sodium hydrogen carbonate extracts are washed with 200 ml. of dichloromethane and then cautiously acidified in a 3-l. beaker with 150 ml. of 12 M hydrochloric acid, with vigorous stirring. The acidic solution (Note 7) is extracted first with 600 ml. and then with four 400-ml. portions of dichloromethane. The bulk of the dichloromethane is removed by distillation at atmospheric pressure and water bath temperatures; however, the last 150 ml. of solvent is removed below room temperature under reduced pressure (about 20 mm.), leaving 2427 g. of crude 2-acetyl-1,3-cyclopentanedione as a light brown solid, m.p. 6871 (Note 8). The crude product is purified by decolorization with charcoal and recrystallization from 100150 ml. of diisopropyl ether, giving 1921 g. (2730%) of colorless needles, m.p. 7072. This material is sufficiently pure for most purposes. Further purification may be achieved by recrystallization from diisopropyl ether and/or sublimation at 60 (0.1 mm.) onto a cold-finger condenser, giving material melting at 7374 (Note 9), (Note 10).

2. Notes1. 2-Acetyl-1,3-cyclopentanedione is completely enolized in the solid state as well as in solution.2 Indirect evidence indicates that the carbon-carbon double bond of the enol is within the ring. 2. The submitters used a practical grade of succinic anhydride obtained from Matheson, Coleman and Bell.

3. The submitters used anhydrous, sublimed aluminum chloride obtained from E. Merck AG, Darmstadt, Germany. The checkers used analytical reagent grade material obtained from Mallinckrodt Chemical Works. 4. The submitters used either a pure grade (more than 98.5%) of isopropenyl acetate or a practical grade (9598%) from Fluka AG, Buchs SG, Switzerland. Generally, it was not essential to distill the material before use. 5. This treatment increases the amount of product which can be extracted from the aqueous solution. 6. Evaporation of the solvents at this stage gives an oily product which may be decolorized with charcoal and then recrystallized from diisopropyl ether to give 2-acetyl-1,3-cyclopentanedione, m.p. 68 71. However, the extraction with sodium hydrogen carbonate is preferred. 7. Decolorization of the acidic aqueous solution with charcoal at this stage improves the quality of the product. 8. 2-Acetyl-1,3-cyclopentanedione is quite volatile and appreciable losses may occur if the evaporation of the concentrated solution is continued at elevated temperature. 9. Further amounts of 2-acetyl-1,3-cyclopentanedione can be obtained by continuous extraction of the original aqueous phase with dichloromethane. The submitters have obtained total yields of product as high as 4143%. 2-Acetyl-1,3-cyclopentanedione is sparingly soluble in diethyl ether and is not extracted very efficiently from aqueous solution with ether. 10. 2-Acetyl-1,3-cyclopentanedione can be hydrolyzed to 1,3-cyclopentanedione.3,4 The preferred method4 is to keep a 0.1 M solution of 2-acetyl-1,3-cyclopentanedione in 0.1 M aqueous acetic acid at 100 for 24 hours. The solvent is then evaporated at 40 with a water pump and the yellow solid is recrystallized from butanone (with charcoal) to give 1,3-cyclopentanedione, m.p. 148150, in 6580% yield.

3. Discussion2-Acetyl-1,3-cyclopentanedione has been obtained in small amounts from the aluminum chloridecatalyzed reactions of vinyl acetate and succinyl chloride in 1,1,2,2-tetrachloroethane.5 2-Acetyl-1,3cyclopentanediones have been prepared via Dieckmann condensation of 1,4-bis(ethoxycarbonyl)-3,5hexanediones.6 The present procedure is essentially that of Mernyi and Nilsson7 with some modifications. The diacylation of isopropenyl acetate with anhydrides of dicarboxylic acids is applicable to the synthesis of several other cyclic -triketones in moderate yield.3,7 It has been used for the synthesis of 2acetyl-1,3-cyclohexanedione (40% yield), 2-acetyl-4-methyl-1,3-cyclopentanedione (10% yield), 2acetyl-4,4-dimethyl-1,3-cyclopentanedione (10% yield), 2-acetyl-5,5-dimethyl-1,3-cyclohexanedione (10% yield), 2-acetyl-1,3-cycloheptanedione (12% yield), and 2-acety-1,3-indanedione (25% yield). Maleic anhydrides under more drastic conditions give acetyl-1,3-cyclopent-4-enediones in yields from 5 to 12%.8 The corresponding acylation of the enol acetate of 2-butanone with succinic anhydride has been used to prepare 2-methyl-1,3-cyclopentanedione, an important intermediate in steroid synthesis.9,10

References and Notes1. Department of Organic Chemistry, Chalmers University of Technology and the University of Gteborg, S-412 96 Gteborg 5, Sweden. 2. S. Forsn, F. Mernyi, and M. Nilsson, Acta Chem. Scand., 18, 1208 (1964). 3. F. Mernyi and M. Nilsson, Acta Chem. Scand., 18, 1368 (1964). 4. M. Nilsson, Acta Chem. Scand. Ser. B, 35, 667 (1981). 5. A. Sieglitz and O. Horn, Chem. Ber., 84, 607 (1951). 6. M. Vandewalle, Bull. Soc. Chim. Belg., 73, 628 (1964). 7. F. Mernyi and M. Nilsson, Acta Chem. Scand., 17, 1801 (1963). 8. M. Nilsson, Acta Chem. Scand., 18, 441 (1964). 9. H. Scheck, G. Lehman, and G. Hilgetag, J. Prakt. Chem., 35, 28 (1967); Angew. Chem., 79, 97 (1967). V. J. Grenda, G. W. Lindberg, N. L. Wendler, and S. H. Pines, J. Org. Chem., 32, 1236 (1967). 10.

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)2-acety-1,3-indanedione hydrogen chloride, hydrochloric acid (7647-01-0) acetic acid (64-19-7) ether, diethyl ether (60-29-7) sodium hydrogen carbonate (144-55-8) 1,2-dichloroethane (107-06-2) aluminum chloride (3495-54-3) dichloromethane (75-09-2) Succinic anhydride (108-30-5) butanone (78-93-3) succinyl chloride (543-20-4) diisopropyl ether (108-20-3) isopropenyl acetate (108-22-5) vinyl acetate (108-05-4) dichloroethane (75-34-3) 1,1,2,2-tetrachloroethane (79-34-5) 2-Methyl-1,3-cyclopentanedione (765-69-5) 2-Acetyl-1,3-cyclopentanedione (3859-39-0) 2-Acetyl-3-hydroxy-2-cyclopenten-1-one 1,3-cyclopentanedione (3859-41-4) 2-acetyl-1,3-cyclohexanedione (4056-73-9) 2-acetyl-4-methyl-1,3-cyclopentanedione

2-acetyl-4,4-dimethyl-1,3-cyclopentanedione 2-acetyl-5,5-dimethyl-1,3-cyclohexanedione 2-acetyl-1,3-cycloheptanedioneCopyright 1921-2005, Organic Syntheses, Inc. All Rights Reserved


3-ACETYL-2,4-DIMETHYLFURAN[Ethanone, 1-(2,4-dimethyl-3-furanyl)-]

Submitted by P. D. Howes and C. J. M. Stirling1. Checked by C. Reese, M. Uskokovic, and A. Brossi.

1. ProcedureCaution! These reactions should be performed in a hood because of the noxious odors. A. Dimethyl-2-propynylsulfonium bromide. A mixture of 6.2 g. (0.10 mole) of dimethyl sulfide (Note 1), 11.9 g. (0.100 mole) of 3-bromopropyne (Note 2), and 10 ml. of acetonitrile (Note 3) is stirred magnetically for 20 hours (Note 4) in a darkened, 100-ml., round-bottomed flask (Note 5) fitted with a calcium chloride drying tube. The resulting white, crystalline mass is filtered with suction and washed with three 50-ml. portions of dry diethyl ether (Note 6), giving 16.4 g. (90%) of the sulfonium salt, m.p. 105106. This material may be used in the next step without purification but, if desired, it may be recrystallized from ethanol-ether (Note 7) with minimal loss, m.p. 109110. B. 3-Acetyl-2,4-dimethylfuran. To a solution of 8.7 g. (0.087 mole) of acetylacetone (Note 8) in 175 ml. of 0.5 M ethanolic sodium ethoxide (0.087 mole), contained in a 500-ml., round-bottomed flask, fitted with a condenser topped with a calcium chloride drying tube, is added a solution of 15.75 g. (0.0870 mole) of dimethyl-2-propynylsulfonium bromide in 150 ml. of ethanol (Note 9). The mixture is refluxed until the odor of dimethyl sulfide is no longer appreciable (Note 10). The reaction flask is then fitted with a 30-cm., helix-packed column, and by heating the flask with a water bath, ethanol is distilled through the column (Note 11). The residue is treated with 200 ml. of ether, and the suspension is filtered. Ether is distilled from the filtrate at atmospheric pressure, and the residue is distilled, giving 9.7 24 g. (81%) of 3-acetyl-2,4-dimethylfuran (Note 12) and (Note 13), b.p. 9095 (12 mm.), nD 1.4965.

2. Notes1. Dimethyl sulfide was used as supplied by British Drug Houses. 2. 3-Bromopropyne, supplied by British Drug Houses, was distilled before use (b.p. 8486). 3. Acetonitrile (Matheson, Coleman and Bell, spectral grade) was used without further treatment. 4. The maximum yield was obtained after 20 hours. Shorter reaction times give slightly lower yields. 5. If a brown glass flask is unavailable, an ordinary flask wrapped with aluminum foil may be used. 6. The ether was dried over sodium. 7. The salt was dissolved in 10 ml. of ethanol, 75 ml. of ether was added portion-wise, and the mixture was allowed to stand overnight at room temperature. 8. Acetylacetone, supplied by British Drug Houses, was distilled before use (b.p. 137). 9. The ethanol was dried with magnesium ethoxide.2 10. About 6 hours is required on this scale. 11. Distillation through the packed column is essential to prevent loss of furan by co-distillation with ethanol.

12. The product has IR absorption (neat) at 1690 cm.1 (ketone C=O and 1H NMR peaks (CCl4) at 2.20 (s, 3H, COCH3), 2.40 (s, 3H, CH3), 3.60 (s, 3H, CH3), and 7.40 (s, 1H, furyl). 13. A convenient modification of this procedure gives the furan in 7075% yield; the sulfonium salt is preformed in acetonitrile and, without isolation, the other reagents are added.

3. DiscussionThis procedure illustrates a recently published,3 simple, general method for the synthesis of substituted furans. The scope of the reaction is shown in Table I. Many variations of this procedure are clearly possible.

TABLE I FURANS PREPARED VIA ACETYLENIC SULFONIUM SALTS

Sulfonium Salt

Addend

R1

R2

R3

Yield, %2

CH3S+CH2C CH Br CH3COCH2CO2CO2C2H5 CH3 CO2C2H5

CH3 86

CH3S+CH2C CH Br

CH3COCH2SO2C6H4-4SO2C6H4CH3 CH3 4-CH3

CH3 78

CH3S+CH2C CH Br C6H5COCH2COC6H5 C6H5 COC6H5

CH3 72

CH3S+CH2C CC6H5 Br

CH3COCH2CO2C2H5

CH3 CO2C2H5 CH2C6H5 63

CH3COCH2CO2H5

CH3 CO2C2H5

C2H5 50

The method described has some features in common with the well-known, but apparently littleused, Feist-Benary furan synthesis,4 which uses an -haloketone in place of the sulfonium salt. Acetylenic bromides suitable for preparing the sulfonium salts are readily available by well-documented procedures involving acetylenic organometallic compounds. The mechanism of furan formation by this route is determined by the structure of the sulfonium salt; the course, hence the end product, is governed by whether an -substituent is present. This must be

considered when syntheses based on this procedure are being planned. Plausible mechanisms for the reaction have been suggested.3 Direct treatment of propargyl halides with -dicarbonyl compounds and subsequent treatment of the products with zinc carbonate yields 2,3,5-trisubstituted furans.5

References and Notes1. School of Physical and Molecular Sciences, University College of North Wales, Bangor, Caernarvonshire, U.K. 2. D. D. Perrin, W. L. F. Armarego, and D. R. Perrin, "Purification of Laboratory Chemicals," 1st ed., Pergamon Press, New York, 1966, p. 157. 3. J. W. Batty, P. D. Howes, and C. J. M. Stirling, J. Chem. Soc., Perkin Trans. 1, 65 (1973). 4. A. T. Blomquist and H. B. Stevenson, J. Am. Chem. Soc., 56, 146 (1934). 5. K. E. Schulte, J. Reisch, and A. Mock, Arch. Pharm. Ber. Dtsch. Pharm. Ges., 295, 627 (1962).

Appendix Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)ethanol (64-17-5) ether, diethyl ether (60-29-7) acetonitrile (75-05-8) Salt (7647-14-5) sodium (13966-32-0) sodium ethoxide (141-52-6) sulfonium dimethyl sulfide (75-18-3) Acetylacetone (123-54-6) magnesium ethoxide (2414-98-4) 3-Acetyl-2,4-dimethylfuran, Ethanone, 1-(2,4-dimethyl-3-furanyl)- (32933-07-6) 3-bromopropyne (106-96-7) dimethyl-2-propynylsulfonium bromide (23451-62-9) zinc carbonate (3486-35-9)

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2-ACETYL-6-METHOXYNAPHTHALENE[Ethanone, 1-(6-methoxy-2-naphthalenyl)-]

Submitted by L. Arsenijevic1, V. Arsenijevic1, A. Horeau2, and J. Jacques2. Checked by David Walba and Robert E. Ireland.

1. ProcedureA 1-l., three-necked, round-bottomed flask is fitted with a mechanical stirrer and a thermometer; the third neck of the flask is fitted with a 50-ml., pressure-equalizing addition funnel, carrying a drying tube attached to a gas trap. The flask is charged with 200 ml. of dry nitrobenzene (Note 1), followed by 43 g. (0.32 mole) of anhydrous aluminum chloride. After the aluminum chloride has dissolved, 39.5 g. (0.250 mole) of finely ground 2-methoxynaphthalene (nerolin, (Note 2)) is added. An ice bath is used to cool the stirred solution to about 5 before 25 g. (23 ml., 0.32 mole) of redistilled acetyl chloride (Note 3) is added dropwise over a 1520 minute period, with stirring and at a rate which holds the temperature between 10.5 and 13 (Note 4). After addition of the acetyl chloride is complete, the flask is kept immersed in the ice water while stirring is continued for 2 hours. The mixture is then allowed to stand at room temperature for at least 12 hours. The reaction mixture is cooled in an ice bath, poured with stirring into a 600-ml. beaker containing 200 g. of crushed ice, and treated with 100 ml. of concentrated hydrochloric acid. The resulting twophase mixture and 50 ml. of chloroform are transferred to a 1-l. separatory funnel (Note 5); the chloroform-nitrobenzene layer is separated and washed with three 100-ml. portions of water. The organic layer is transferred to a 2-l., round-bottomed flask, and steam-distilled. A fairly rapid flow of steam is used, and the distillation flask is heated in an oil bath at about 120. After about 3 hours (34 l. of water) the distillation is stopped, and the residue in the flask is allowed to cool. Residual water in the flask is decanted from the solid organic material and extracted with chloroform. The solid residue in the flask is dissolved in 100 ml. of chloroform and separated from any water left in the flask, and the chloroform layers are combined and dried over anhydrous magnesium sulfate. The chloroform is removed on a rotary evaporator, and the solid residue, weighing 5065 g. (still slightly wet with chloroform), is distilled under vacuum (Note 6). The receiving flask should be immersed in ice water, and the fraction boiling about 150165 (0.02 mm.) is collected (Note 7). The yellow distillate (ca. 40 g., m.p. 8595) is recrystallized from 75 ml. of methanol, cooled in an ice bath (Note 8) and filtered, yielding 22.524 g. (4548%) of white, crystalline 2-acetyl-6methoxynaphthalene (Note 9), m.p. 106.5108 (lit. 104105).3

2. Notes1. The nitrobenzene may be dried by distilling the first 10% and using the residue directly, or standing over anhydrous calcium chloride overnight and filtering. 2. 2-Methoxynaphthalene (Matheson, Coleman and Bell), m.p. 71.573, was used without further purification. 3. Acetic anhydride may be used instead of acetyl chloride. However, it is then necessary to use two molecular equivalents of aluminum chloride per mole of anhydride and increase the amount of nitrobenzene by about 30%. About the same yield of ketone is obtained. 4. Temperature control is very important (see discussion). 5. The addition of chloroform is not always indispensable, but very useful to prevent emulsification and facilitate separation of the nitrobenzene layer. The reaction vessel and beaker are rinsed with this

chloroform before it is added to the nitrobenzene layer. If an emulsion does form and phase separation becomes inconveniently slow, as much nitrobenzene as possible is withdrawn, and the emulsion and water layers are filtered by suction through a Celite cake wet with chloroform. The phases should then separate easily. 6. The material may be distilled from a two-bulb distillation flask as described in Org. Synth., Coll. Vol. 3, 133 (1955), or from a small Claisen flask. 7. Care must be taken to prevent solidificat

organic syntheses collective volume 6

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