Polymer International Polym Int 48 :109–116 (1999)

Highly diastereoselective synthesis of novelpolymers via tandem Diels–Alder–enereactions

Shadpour E Mallakpour,*,¹ Abdol-Reza Hajipour, Ali-Reza Mahdavian andFatemeh RafiemanzelatOrganic Polymer Chemis try Res earch Laboratory , College of Chemis try , Is fahan Univers ity of Technology, Is fahan 84156, Iran

Abstract : Cis-9,10-dihydro-9,10-ethanoanthracene-11-12-dicarboxylic acid anhydride (1) was con-

verted into its amic acid derivative by reaction with L-leucine. The cyclization reaction was carried

out in situ using triethylamine to give the succinic imide-acid derivative (2). Compound (2) was con-

verted to the acid chloride (3) by reaction with thionyl chloride. The reaction of acid chloride (3) with

isoeugenol (4) was carried out in chloroform and a novel optically active isoeugenol ester derivative

(5) was obtained in high yield. 4-Phenyl-1,2,4-triazoline-3,5-dione (PhTD) (6) was allowed to react

with compound (5). The reaction is very fast and gives only one diastereoisomer of (7) via Diels–Alder

and ene pathways in quantitative yield. Compound (7) was characterized by 1H NMR, IR, speciüc

rotation and elemental analysis, and was used as a model for the polymerization reactions. The poly-

merization reactions of compound (5) with bis-triazolinediones (8), (9) were performed in N,N-

dimethylacetamide (DMAc) at room temperature. The reactions are exothermic and fast, and give

novel optically active polymers. Some physical properties and structural characterizations of these

new polymers have been studied, and are reported.

1999 Society of Chemical Industry(

Keywords: Diels–Alder polymerization; optically active polymers ; 4-phenyl-1,2,4-triazoline-3,5-dione; bis-triazolinediones ; inherent viscosity ; diastereomers ; cis-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylicacid anhydride

INTRODUCTION

The synthesis and application of optically activepolymers have received considerable attentionrecently, because polymers with chiral structures arebiologically very important. Most natural polymersare optically active and have special chemical activ-ities, such as catalytic properties that exist in genes,proteins and enzymes. Some other applications couldbe listed such as, (1) constructing chiral media forasymmetric synthesis, (2) chiral stationary phases forresolution of enantiomers in chromatographic tech-niques and (3) chiral liquid crystals in ferroelectricsand non-linear optical devices.1h4 These applicationshave initiated more research to improve syntheticprocedures for optically active polymers. Diþerentoptically active homopolymers and copolymers havebeen prepared and their syntheses reported in the lit-erature.

4-Substituted-1,2,4-triazoline-3,5-diones areextremely reactive dienophiles,5h16 enophiles10h16

and electrophiles.17h20 Styrene undergoes facile reac-tion with both triazolinediones and bis-triazolinediones ; in the latter case this leads topolymer formation via double Diels–Alder andDiels–Alder–ene sequences.20 The reaction of 1,1-diphenylethylene (DPE) with maleic anhydride hasbeen reported to give only a double Diels–Alderadduct.21h24 The reaction takes place at elevatedtemperature. During our studies with tri-azolinedione, we observed that DPE undergoesreaction with triazolinediones and withbis-triazolinediones at room temperature and gavenovel small molecules and polymers25 via Diels–Alder–ene and double Diels–Alder reactions. Poly-merization of triazolinediones with trans-stilbene andtrans-3,3-dichloro-1-phenyl-1-propene26,27 also gavepolymers via Diels–Alder–ene and double Diels–Alder reactions. We also reported the polymerizationreaction of 2-methoxy-4-propenylphenyl methyl-carbamate,14 which gives polymers by Diels–Alder–

* Corres pondence to : E Organic PolymerShadpour Mallakpour,

Chemis try Res earch Laboratory, College of Chemis try, Is fahan

Univers ity of Technology, Is fahan 84156, Iran

¹ E-mail : MALLAK=CC.IUT.AC.RI

Contract/grant s pons or : Res earch Affairs Divis ion, Is fahan

Univers ity of Technology, Is fahan, Iran.

Contract/grant number : 1CHA771.

(Received 25 February 1998; revis ed vers ion received 28 May

1998; accepted 3 September 1998)

( 1999 Society of Chemical Industry. Polym Int 0959-8103/99/$17.50 109

SE Mallakpour et al

ene reactions pathways.To our knowledge, there is no report on the prep-

aration of optically active polymers via Diels–Alderand ene reactions. In this paper, we wish to reportthe synthesis of two novel optically active polymersvia continuous Diels–Alder–ene reactions for the ürsttime.

EXPERIMENTAL

Materials and equipment

Reagents were purchased from Fluka Chemical Co,Aldrich Chemical Co and Riedel-deHaen AG. 4-Phenyl-1,2,4-triazoline-3,5-dione (PhTD) (6) andbis-triazolinediones (8) and (9) were prepared by areported procedure.5h11,14,28,29 N,N-Dimethyl-acetamide (DMAc) was dried over BaO and then dis-tilled under reduced pressure. Chloroform waswashed with water, dried over and distilled atCaCl2normal pressure. Proton nuclear magnetic resonance(1H NMR, 90 and 250MHz) spectra were recordedon Varian EM-390 and Bruker Advance DPX250MHz instruments. Multiplicities of proton reso-nances are designated as singlet (s), doublet (d),triplet (t), quarter (q), multiplet (m) and broad (br).Tetramethylsilane (TMS) was used as an internalreference. IR spectra were recorded on a Shimadzu435 IR spectrophotometer. Spectra of solids weremeasured using KBr pellets. Vibrational transitionfrequencies are reported in wavenumbers (cm~1).Band intensities are assigned as weak (w), medium(m), shoulder (sh), strong (s) and broad (br). Inher-ent viscosities were measured by a standard pro-cedure using a Cannon Fensk routine viscometer.Speciüc rotations were measured with a PerkinElmer-241 polarimeter. Mass spectra were recordedon a Shimadzu GC-MS-QP 1000PX. Thermalgravimetric analysis (TGA) data for polymers weretaken on a Stanton-650 TGA under atmosphereN2at a rate of 10¡Cmin~1 and diþerential scanningcalorimetry (DSC) data were recorded on aDSC-PL-1200 instrument under atmosphere at aN2rate of 10¡Cmin~1 at the Iranian Polymer Institute.

Preparation of cis-9,10-dihydro-9,10-

ethanoanthracene-11,12-dicarboxylic acid anhydride

(1)

This compound was synthesized according to thereported procedure.30h32

Preparation of (2S)-(9,10-dihydro-9,10-

ethanoanthracene-11,12-dicarboximido)-4-methyl

pentanoic acid (2)

Into a 500ml round-bottomed ýask 2.69g(9.75] 10~3 mol) of cis-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid anhydride(1), 1.28g (9.75] 10~3 mol) of L-leucine, 200ml oftoluene and 1.00ml (7.17] 10~3 mol) of tri-ethylamine were added. The stirrer was started andthe mixture was reýuxed under a Dean–Stark system

for 72h. At the end of the reýuxing period, thesolvent was removed under reduced pressure and20ml of aqueous acidic solution (13ml of water and7ml of HCl 30.5%) was added to the residue, whichproduced a white gummy-like precipitate. To thisprecipitate which was triturated and ültered oþ, 5mlof concentrated HCl (30.5%) was added and the pre-cipitate triturated more, until it was well powdered.Then 10ml of distilled water was added and themixture stirred vigorously for 15min. The whitepowder was ültered and dried to give 3.25g (85.6%)of (2). Recrystallization from hot acetic acid gaveneedle-like crystals, m.p. 246–248¡C. [a]D25\

(0.305g in 100ml IR (KBr):[ 0.20¡ CHCl3),3450(m), 3000–2500(s,br), 1780–1640(s,br), 1460–1340(s,br), 1280–1110(s,br), 1040(m), 1010(m), 940–900(s,br), 870(w), 850(w), 830(w), 760–720(s,br),660(w), 620–600(s,br) cm~1.

Analysis. Calcd for C 74.02% ; HC24H23NO4 :5.95% ; N 3.60%. Found: C 73.70% ; H 6.00% ; N3.90%.

Preparation of (2S)-(9,10-dihydro-9,10-

ethanoanthracene-11,12-dicarboximido)-4-methyl

pentanoyl chloride (3)

2.00g (5.14] 10~3 mol) of (2) was placed in a 25mlround-bottomed ýask equipped with a condenserand 1.8ml (2.48] 10~2 mol) of freshly distilledthionyl chloride (excess amount) was added. Themixture was heated on a water bath up to 50¡C, untilthe suspension mixture was converted to a clear solu-tion. After dissolution was completed, the solutionwas stirred for 1.5h. The thionyl chloride wasremoved under reduced pressure to leave a viscousliquid which was crystallized in (as solvent)CCl4and n-hexane (as non-solvent) to give 1.90g (90.9%)of white crystal, m.p. 123–125¡C. [a]D25\ ] 3.77¡(0.32g in 100ml IR (KBr): 3060(w),CHCl3).3020(w), 2950(m), 2900(m), 2850(w), 1790(s),1710(s), 1460(s), 1370(s,br), 1260(m), 1250(w),1190(m), 1130(m), 1090(m), 1040(w), 1010(m),970(m), 910(w), 860(w), 830(m), 790(s), 760–740(s,br), 620–600(s,br), 530(s) cm~1, 1H NMR

TMS, 90MHz): d 0.50–0.70(q,(CCl4/CDCl3 ,J \ 4.5Hz); 1.30(s); 150–1.70(t, J \ 6.0Hz) (thesethree peaks show totally 9H); 3.30–3.40(s,2H); 4.50–4.70(q,1H, J \ 6.0Hz); 4.80–4.90(s,2H); 7.20–7.60(m,8H).

Analysis. Calcd for C 70.67%, HC24H22ClNO3 :5.44% ; N 3.43%. Found: C 70.60% ; H 5.30% ; N3.20%.

Preparation of 2-methoxy-4-(1-propenyl)phenyl-(2S)-

(9,10-dihydro-9,10-ethanoanthracene-11,12-

dicarboximido)-4- methyl pentanoate (5) (chiral

monomer)

0.08g (4.60] 10~4 mol) of isoeugenol (4) and 1ml ofdry chloroform were placed in a two necked round-bottomed ýask, after which a solution of 0.13g(3.19] 10~4 mol) of (3) in 1.5ml of dry chloroform

110 Polym Int 48 :109–116 (1999)

Diastereoselective synthesis of novel polymers

was added dropwise at 0¡C over a period of 30min.At the end of the addition the reaction mixture wasstirred at 0¡C for 1h and then 0.2ml(1.43] 10~3 mol) of triethylamine in 1ml of drychloroform was added at 0¡C over a period of 30min.The reaction was stirred at room temperature for20h. Finally it was reýuxed for 2h. After addition of10ml of chloroform to the reaction mixture, extrac-tion was carried out according to the followingregime: (i) 2] 10ml distilled water, (ii) 4] 10ml of1% KOH solution (w/v), (iii) washing of the organicphase with distilled water until the extracted aqueousphase became neutral. The organic phase was driedover sodium sulphate, and chloroform was evapo-rated with a rotary evaporator to leave 0.16g (93.7%)of white solid. Recrystallization from hot ethanol assolvent, and water as non-solvent gave white crystals,m.p. 165–166¡C. (0.42g in 100ml[a]D25\ [ 12.56¡

IR (KBr): 3080(w), 3040(w), 3010(w),CHCl3).2950(m), 2900(m), 2850(w), 1760(s), 1710(s),1600(m), 1510(s), 1460(s), 1450(m), 1390(s),1300(m), 1260(s), 1200(s), 1150(s), 1120(s), 1040(m),960(m), 940(w), 930(w), 910(w), 860(m), 820–800(w,br), 780(m), 750(s), 630–610(m,br), 520(m,br) cm~1.1H NMR TMS, 250MHz): d 0.53–0.59(q,(CCl4 ,6H, J \ 6.0Hz); 1.15–1.19(m,1H); 1.50–1.54(q,2H,J \ 6.0Hz); 1.79–1.81(d,3H, J \ 6.2Hz); 3.10–3.20(m,2H); 3.70–3.71(s,3H); 4.47–4.53(q,1H,J \ 6.7Hz); 4.67–4.68(d,2H, J \ 2.5Hz); 6.00–6.39(m,2H); 6.71–6.73(m,13H); 7.02–7.26(m,8H).Mass for m/e (rel. intensity): 536C34H33NO5 :(M ] 1, 1.1); 535 (M`, 1.1); 373 (13.3); 372 (49.0);345 (25.7); 344 (100.0); 180 (10.7); 179 (72.8); 178(59.8); 166 (84.0); 164 (27.0); 124 (30.8); 110 (38.9);98 (11.6); 69 (37.6); 55 (10.5); 43 (32.3); 41 (24.8).

Analysis. Calcd for C 76.24% ; HC34H33NO5 :6.21% ; N 2.61%. Found: C 75.50% ; H 6.30% ; N2.61%.

Preparation of model compound (7)

A solution of 0.20g (3.79] 10~4 mol) of (5) in 2mlof methylene chloride was placed in a 25ml round-bottomed ýask and 0.13g (7.58] 10~4 mol) ofPhTD (6) in 8ml of dry chloroform was added drop-wise at room temperature. As the solution of PhTDwas added, the red solution quickly turned pale-yellow. The reaction mixture was stirred overnight atroom temperature. The solvent was removed underreduced pressure and the residue was dried to give0.33g (98.0%) of white solid. Recrystallization fromhot methanol gave white crystals, with a decomposi-tion temperature of 270¡C; (0.49g[a]D25\ [ 5.57¡in 100ml DMF). IR (KBr): 3450(w,br) 3300(m),3050(w), 2950(m), 2850(w), 1790–1770(s,br), 1730–1700(s,br), 1600(w), 1500(s), 1460–1450(s,br),1420(s), 1380(s), 1320(m), 1270(m), 1220(w,br),1180–1150(m,br), 1120(m), 1040(m), 1020(m),910(m,br), 760(s), 720(w), 690(m), 640–610(m,br),580(m), 550–540(w,br) cm~1. 1H NMR (DMSO-d6 ,TMS, 250MHz): d 0.56 (two d, 6H); 1.21–1.23(d,

J \ 6.3Hz); 1.30–1.47(m,br) (these two peaks showtotally 6H); 3.47(d, overlapped with the peak ofwater, 2H); 3.70(s,3H); 4.63(q,1H), 4.81(m,br,3H);5.41(s,1H); 7.02–7.54(m,19H); 7.97(s,1H); 10.71(s,br,1H).

Analysis. Calcd for C 67.79% ; HC50H43N7O9 :4.89% ; N 11.07%. Found: C 66.50% ; H 5.00% ; N10.50%.

Polymerization of bis(p-3,5-dioxo-1,2,4-triazoline-

4-ylphenyl) methane (8) with (5)

In a 25ml round-bottomed ýask, 0.12g(2.27] 10~4 mol) of (5) and 0.08g (2.27] 10~4 mol)of bis-(p-3,5-dioxo-1,2,4-triazoline-4-ylphenyl)methane (BPMTD) (8) were mixed and 0.8ml of dryDMAc was added. After about 10min, the twomonomers had dissolved and the red colour ofBPMTD had completely faded. The solution becamepale brown, viscous and was stirred at room tem-perature overnight. The resulting viscous solutionwas precipitated in 50ml of distilled water. Theyellow precipitate was ültered and dried, leaving0.19g (93.1%) of yellow solid. [a]D25\ [ 11.73¡(0.50g in 100ml DMF); [ginh]25\ 0.16dl g~1(0.50g dl~1 in DMF). IR (KBr): 3450(m), 3250–3050(w,br), 2950(m), 2910(m), 1780–1770(s,br),1720–1700(s,br), 1620(w,br), 1510(s), 1460(m,sh),1420–1380(s,br), 1260(m), 1190–1120(s,br), 1040(m),1020(m), 910(w,br), 850(w,br), 760(m), 630(w,br),610(w,br), 580(w,br), 540–500(w,br) cm~1. 1HNMR (DMSO- TMS, 90MHz): d 0.4–0.7(m,br),d6 ,1.1–1.6(m,br); 1.8–2.0(m,br); 3.7–3.9(s); 4.5–5.0(m,br); 5.4–5.6(s,br); 7.0–7.7(m,br); 8.0–8.1(s); 10.2–10.7(s,br).

Analysis. Calcd for as repeatingC51H43N7O9unit : C 68.22% ; H 4.83% ; N 10.92%. Found: C66.80% ; H 5.10% ; N 10.20%.

Polymerization of 1,6-bis-(3,5-dioxo-1,2,4-triazoline-

4-yl)hexane (9) with (5)

In a 25ml round-bottomed ýask, 0.15g(2.84] 10~4 mol) of (5) and 0.08g (2.84] 10~4 mol)of 1,6-bis-(3,5-dioxo-1,2,4-triazoline-4-yl)hexane(HMTD) (9) were mixed and 0.6ml of dry DMAcwas added. In about 20min, the two monomers weredissolved and the pink colour of HMTD had fadedcompletely. The solution became pale orange,viscous and was stirred at room temperature over-night. The resulting polymer was precipitated in50ml of distilled water. The white precipitate wasültered, dried to give 0.22g (94.5%) of white solid.

(0.43g in 100ml DMF);[a]D25\ [ 14.35¡(0.43g dl in DMF). IR (KBr):[ginh]25 \ 0.13dl g~1

3450(w), 3350–3150(w,br), 3100–3000(w), 2950(s),2850(s), 1780–1760(s,br), 1720–1680(s,br), 1510(s),1460–1450(s,br), 1420(s), 1380(s), 1260(s,br), 1200–1190(m,br), 1160–1150(w,br), 1120(w,br), 1040–1030(w,br), 960(w,br), 940–930(w,br), 910(w,br),860(w), 760(s), 630–580(m,br), 540–520(w,br) cm~1.1H NMR (DMSO- TMS, 90MHz): d 0.5–0.7(m,d6 ,

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SE Mallakpour et al

br); 1.0–1.7(m,br); 1.8–2.0(m,br); 3.0–4.0(m,br);4.5–5.0(m,br); 5.3(s,br); 6.9–7.6(m,br); 8.0–8.3(s).

Analysis. Calcd for C 64.77% ; HC44H45N7O9 :5.56% ; N 12.02%. Found: C 65.00% ; H 5.80% ; N10.40%.

RESULTS AND DISCUSSION

The reactions carried out in order to synthesize aprecursor of the chiral monomer are shown inScheme 1. 2(S)-(9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboximido)-4-methyl penta-noic acid (2) was synthesized from the reaction ofL-leucine with cis-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid anhydride (1) intoluene, and in the presence of triethylamine underreýuxing conditions.

After recrystallization of the protected L-leucine(2) in acetic acid and veriücation of its purity by ele-mental analysis, it was used in the next step of thereaction for the preparation of 2(S)-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-methylpentanoyl chloride (3). This reaction was carried outin excess thionyl chloride under neat conditions. Theappearance of a peak at 1790cm~1 in the IR spec-trum shows the formation of acid chloride. Afterfurther puriücation, compound (3) was reacted withisoeugenol (4) in chloroform and 2-methoxy-4-(1-propenyl)phenyl - 2(S) - (9,10 - dihydro-9,10-ethano -anthracene-11,12-dicarboximido)-4-methyl penta-noate (5) was obtained as a novel chiral monomer inhigh yield (Scheme 2).

The disappearance of the peak at 1790cm~1 andthe appearance of the peak at 1760cm~1 in the IRspectrum of compound (5) conürm the conversion ofacid chloride to its ester derivative. The 1H NMRspectrum studies of this compound (5) are also veryinteresting (Fig 1). The isoeugenol (4) used in thisexperiment is a mixture of cis and trans isomers.There is already one chiral centre in the molecule, sowe must obtain two stereoisomers (twodiastereoisomers) of L-cis and L-trans. One of thepieces of evidence for the presence of two diastereo-isomers is the existence of two methoxy groups at3.70 and 3.71ppm the expanded form of which isshown in Fig 2. However, the bridge protons

are unequivalent according to(H5wH6 , H7wH8)the lack of plane or centre of symmetry, but the

Scheme 1

Scheme 2

expanded 1H NMR spectra (Figs 3, 4) cannot diþer-entiate them well. Therefore we expect and toH7 H8appear as two doublet groups (Fig 3) and andH5 H6as two quartet groups (Fig 4). Of course in this spec-trum more symmetrical splitting is observed becauseof the unequivalency of and It should beH5 H6 .noted that here, each group refers to the L-cis andL-trans isomers. The peaks between 0.53–0.59ppmbelong to the protons of the L-leucine moietyCH3(Fig 5). According to the diastereotopicity of thesetwo methyl groups and the presence of L-cis andL-trans isomers, we expect to have two quartetgroups. A quartet pattern is seen in Fig 1 and itsexpanded form shows these two groups as anapproximate octet-like pattern. Elemental analysisand the mass spectrum are also in agreement withthe structure of compound (5). The two isomerswere used in Diels–Alder–ene reaction without anyseparation in order to prepare model compound (7)(Scheme 3) and polymers (10) and (11) (Scheme 4).The reaction of PhTD with 2-methoxy-4-(1-pro-penyl)phenyl methyl carbamate has been shown14 toyield two products, a major adduct formed by theDiels–Alder–ene reaction in 98% yield, and a minoradduct formed by the double Diels–Alder reaction inabout 2% yield. The reaction of PhTD with chiralmonomer (5) however, gave only one adduct by theDiels–Alder–ene reaction pathways (Scheme 3).

According to the data available from the 1H NMRspectrum and expanded areas of model compound(7), only one diastereoisomer is formed (Fig 6). AnAB-quartet pattern of proton in the L-leucineH8moiety at 4.63ppm conürms the presence of only one

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Diastereoselective synthesis of novel polymers

Figure 1. 1H NMR (250MHz) s pectrum of

compound (5) in at room temperature.CCl4

diastereoisomer. Another piece of evidence is asinglet at 5.41ppm related to which proves theH3 ,presence of only one diastereoisomer (Fig 7).However, the multiplicity of shows that the angleH3

Figure 2. 1H NMR (250MHz) s pectrum of compound (5) in atCCl4

room temperature. Expanded region for proton 9.

Figure 3. 1H NMR (250MHz) s pectrum of compound (5) in atCCl4

room temperature. Expanded region for proton 4.

between and is nearly 90¡ which prevents anyH3 H1coupling between them so that only a singlet is seen.The other evidence is one doublet at 1.20–1.23ppm,which is related to the heterocyclic methyl group that

Figure 4. 1H NMR (250MHz) s pectrum of compound (5) in atCCl4

room temperature. Expanded region for protons 5 and 6.

Figure 5. 1H NMR (250MHz) s pectrum of compound (5) in atCCl4

room temperature. Expanded region for proton 1.

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Scheme 3

conürms the presence of only one diastereoisomer(Fig 8).

All the above data exhibit 100% diastereomericexcess. We believe that the reason for obtaining thispercentage of d.e. is related to the induction ofchirality from L-leucine with its bulky protectinggroup. Of course, more studies are needed to provethis claim.

Polymerization reactions

Reaction of BPMTD (8) with (5) was carried out inDMAc at room temperature (Scheme 4). The reac-tion is very fast and the resulting polymer wasobtained as a pale-yellow solid. The resulting

Scheme 4

polymer (10) was characterized by IR and 1H NMRspectra which are in agreement with structure (10).Although the 1H NMR spectrum of the polymer isbroad, it resembles the spectrum of model compound(7). The elemental analysis of polymer (10) also con-ürms this structure. This polymer shows opticalrotation. Polymer (10) is soluble in polar solvents

Figure 6. 1H NMR (250MHz) s pectrum of compound

(7) in at room temperature.DMSO-d6

Figure 7. 1H NMR (250MHz) s pectrum of compound

(7) in at room temperature.DMSO-d6

Expanded region for protons 1, 3, 6, 8, 12 and 13.

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Diastereoselective synthesis of novel polymers

Figure 8. 1H NMR (250MHz) s pectrum of compound (7) in DMSO-

at room temperature. Expanded region ford6proton 2.

such as DMSO, DMF and DMAc, and is insolublein solvents such as methanol, ethanol, ether, waterand non-polar solvents. The reaction of HMTD (9)with chiral monomer (5) was also performed inDMAc at room temperature. The resulting polymer(11) was obtained as a white solid. The IR and 1HNMR spectra of polymer (11) resemble those ofmodel compound (7); therefore structure (11) wasassigned to it (Scheme 4). The solubility character-istics of polymer (11) are similar to those of polymer(10). Polymer (11) also shows optical rotation. Reac-tion conditions and some physical properties forthese novel optically active polymers are summarizedin Table 1.

Table 1. Reaction conditions and phys ical

properties of polymers (10) and (11)

Parameter Polymer

(10 ) (11 )

Reaction s olvent DMAc DMAc

Fading timea (min) 10 20

Non-s olvent Water Water

Yield (%) 93.1 94.5

Tg(¡C) 151 112

Tw

b (¡C) 297 285

[a]D25 (deg) [11.73c [14.35d

[ginh.]25 (dl gÉ1) 0.16c 0.13d

a Time for dis appearance of triazolinedione colour.

b Temperature for 5% weight los s .c Meas ured at a concentration of 0.50 g dlÉ1 in DMF

at 25¡C.d Measured at a concentration of 0.43g dl~1 inDMF at 25¡C.

Thermal properties

The thermal behaviour of polymers (10) and (11) hasbeen studied. Their DSC thermograms (Fig 9) showthat they have almost the same diþerential scanningcalorimetric characteristics. For polymer (10), thereis an endothermic transition at 151¡C which could berelated to its glass transition temperature and an(Tg)exothermic transition with a maximum at 387¡C

Figure 9. DSC thermograms of polymers

(10) (ÈÈ) and (11) (– – –).

Figure 10. TGA thermograms of polymers

(10) (ÈÈ) and (11) (– – –).

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owing to decomposition of the polymer throughbond breakage. These transitions could be seen forpolymer (11), ürstly at 112¡C and secondly at 376¡C.TGA thermograms (Fig 10) of these polymers revealthat they are thermally stable. Polymers (10) and (11)show 5% weight loss at 297¡C and 285¡C, respec-tively. The residual weight percentages for thesepolymers at 600¡C are 23.0% and 17.0%, respec-tively.

CONCLUSIONS

The present work has shown that compound (5) is aninteresting novel chiral monomer for a tandemDiels–Alder–ene polymerization reaction. Its reac-tion with PhTD is fast and gives a cycloadditionadduct in a 2 : 1 molar ratio. This adduct is opticallyactive and only one diastereoisomer is formed.Therefore compound (5) can act as a difunctionalmonomer AA@ in which the second functionality isproduced during the course of the reaction. Thereaction of chiral monomer (5) with bis-triazolinediones gives novel optically active polymersvia Diels–Alder–ene reactions. More research intothe stereochemistry and mechanism, and towards thepreparation of other optically active polymers by thisnovel method are under investigation.

ACKNOWLEDGEMENT

One of the authors (SEM) wishes to express hisgratitude to the Research Aþairs Division, IsfahanUniversity of Technology, Isfahan, for partialsupport through Grant No. 1CHA771. We thank theAmine Pharmaceutical Center, Isfahan, Iran, forrecording optical rotations. We also thank theIranian Polymer Institute for recording TGA andDSC data.

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