chemistry of 4-hydroxy-2(1h)-quinolone. part 2. as

Arabian Journal of Chemistry (2014) xxx, xxx–xxx

King Saud University

Arabian Journal of Chemistry

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REVIEW

Chemistry of 4-hydroxy-2(1H)-quinolone. Part 2.

As synthons in heterocyclic synthesis

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E-mail address: [email protected].

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http://dx.doi.org/10.1016/j.arabjc.2014.11.0211878-5352 ª 2014 The Author. Production and hosting by Elsevier B.V. on behalf of King Saud University.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Please cite this article in press as: Abdou, M.M. Chemistry of 4-hydroxy-2(1H)-quinolone. Part 2. As synthons in heterocyclic synthesis. Arabian Journal of C(2014), http://dx.doi.org/10.1016/j.arabjc.2014.11.021

Moaz M. Abdou *

Egyptian Petroleum Research Institute, Nasr City, P.O. 11727, Cairo, Egypt

Received 2 June 2014; accepted 3 November 2014

KEYWORDS

4-Hydroxy-2(1H)-quinolone;

Heterocycles;

Microwave irradiation;

Ionic liquid;

Multicomponent reactions;

Electrochemical routes

Abstract This review presents a systematic and comprehensive survey of the utility of 4-hydroxy-

2(1H)-quinolone as a building block of heterocyclic compounds. The reaction mechanism is

considered as well as the scope and limitation of the most important of these approaches are

demonstrated.ª 2014 The Author. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an

open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002. Synthesis of fused heterocyclic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

2.1. [6-6-5] ring system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

2.1.1. Dihydrofuran and furoquinolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002.2. [6-6-5] ring system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002.3. Fused [6-6-6] ring system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

2.3.1. Quinolino[4,3-b]benzo[f]quinolin-6-one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002.3.2. Pyranoquinolines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002.3.3. Quinolinobenzothiazinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

2.4. [6-6-8-6] ring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 002.4.1. Oxazocines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

hemistry

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2 M.M. Abdou

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00

1 2

NH

O

OH

+ OEtNH

O

OOEt

acetonitrile/ refluxAg2CO3 / Celite

3

Scheme 1

NH

O

OH

Ag (I)

Ag (0)NH

O

O.

NH

O

OOEt.

NH

O

OOEt+

NH

O

OOEt

+Ag (I)

Ag (0)

-H+

2

1 4 5

6 7

3

Scheme 2

1. Introduction

4-Hydroxy-2(1H)-quinolone is a versatile and convenientprecursor for the synthesis of a wide variety of heterocycliccompounds (Ghandi et al., 2013; Guo et al., 2013;

Abbaspour-Gilandeh et al., 2013; Neve et al., 2014; Hoeckerand Gademann, 2013). It is of particular interest as a verypromising reagent for cascade heterocyclization, which will

undoubtedly become one of the main approaches to thetargeted synthesis of heterocycles in the near future, in therapidly-rising field of combinatorial chemistry. This newmethodology based on automatic, high-tech synthetic methods

enables synthesis of a large number of novel organiccompounds as subjects for biological screening.

The first part of this review article (Abdou, 2014) is

concerned with the progress in 4-hydroxy-2(1H)-quinolone

chemistry and deals with the synthesis, chemical reactivity

and reactions of 4-hydroxy-2(1H)-quinolone. This second part

systematizes the application of 4-hydroxy-2(1H)-quinolone in

heterocyclic synthesis. The enolic reactive center in this

compound provides ample opportunities to synthesize a great

variety of novel compounds under relatively mild conditions

and using simple laboratory equipment. Thus, the two parts

are complementary and display current trends in 4-hydroxy-

2(1H)-quinolone chemistry.

In the literature survey, the reactions involving 4-hydroxy-

2(1H)-quinolone occur with regioselectivity and its course can

easily be controlled by changing reaction conditions and

varying substituents in the molecules of initial compounds.

The heterocyclic compounds are obtained in a single step with

high yield and they are reported in order of the increase of

(i) the number of rings, (ii) the size of such rings and (iii) the

number of heteroatoms present. The sequence of heteroatoms

followed is: nitrogen, oxygen and sulfur. The site of fusion in

fused heterocycles is indicated by numbers and letters and

the numbering of the heterocyclic ring systems is that reported

by chemical abstracts.

2. Synthesis of fused heterocyclic compounds

2.1. [6-6-5] ring system

2.1.1. Dihydrofuran and furoquinolinones

Dihydrofuroquinolinone and furoquinolinone alkaloids arewidely distributed in nature (Subramanian et al., 1992;Shobana and Shanmugam, 1986; Shobana et al., 1988;

Ukrainets et al., 2006). They are primarily isolated fromRutaceae species as an angularly and linearly fused structure.They are reported to have various biological activities suchas antimicrobial, antimalarial, insecticidal, antineoplastic,

antidiuretic, antiarrhythmic and sedative (Wolters and Eilert,1981; Svoboda et al., 1966; Basco et al., 1994). This wide rangeof biological properties has stimulated interest in the synthesis

of dihydrofuroquinolinone and furoquinolinone derivatives.A number of synthetic approaches to dihydrofuroquinolinones

Please cite this article in press as: Abdou, M.M. Chemistry of 4-hydroxy-2(1H)-quino(2014), http://dx.doi.org/10.1016/j.arabjc.2014.11.021

and furoquinolinones have been well reported (Senboku et al.,

1996; Suginome et al., 1990, 1991; Rao and Darbarwar, 1989;Neville et al., 1991; Grundon and Surgenor, 1978).

2.1.1.1. Oxidative cycloaddition reaction mediated by metal

salts. The oxidative addition reaction of carbon-centeredradicals to alkenes mediated by metal salts Ag(1), Ce(IV)and Mg(II) has received considerable attention over the last

decade in organic synthesis for the construction of carbon–carbon bonds.

2.1.1.1.1. Using Ag (1). Lee et al. (2000) have reported that

a facile and simple method for the synthesis of dihydrofuran,2-ethoxy-3,5-dihydro-2H-furo[3,2-c]quinolin-4-one 3, is medi-ated by the oxidative cyclization of 4-hydroxy-2(1H)-quino-

lone 1 with ethyl vinyl ether 2 and silver(I)/Celite (Fetizonreagent) in acetonitrile under reflux (Scheme 1).

Although the exact mechanism of the reaction is not clearyet, it is best described as shown in Scheme 2. The starting

material 1 is first oxidized by one equivalent of Ag(I) to gener-ate the radical 4, which then attacks olefin 2 to give the radicaladduct 5. The adduct 5 now undergoes fast oxidation by

another one equivalent of Ag(I) to a carbocation 6. Cyclizationof the carbocation 6 furnishes intermediate 7, whose deproto-nation affords the product 3 (Scheme 2).

2.1.1.1.2. Using Ce(IV). There has been a considerableinterest in the use of CAN oxidation reactions in ionic liquids.Hence, reaction of 1 with a-methylstyrene 8 and cerium(IV)

ammonium nitrate (CAN) mediated 1-n-butyl-3-methylimida-zolium tetrafluoroborate[bmim][BF4]-dichloromethane (1:9),gave tricycles 9,10 (Bar et al., 2003) (Scheme 3).

2.1.1.1.3. Manganese(III) acetate. Mn(III)-based oxidative

radical cyclization of 4-hydroxy-2(1H)-quinolone 1 with

lone. Part 2. As synthons in heterocyclic synthesis. Arabian Journal of Chemistry


NH

O

OH

CAN-[bmim][BF4]CH2Cl2 / 40o C

+

1 8

N OH

OPh

N O

OH

Ph

9 (42%) 10 (35%)

+

Scheme 3

Chemistry of 4-hydroxy-2(1H)-quinolone 3

1,1-diphenylethene 11 in boiling glacial acetic acid afforded3,5-dihydro-2H-furo[3,2-c]quinolin-4-one 12 (Kumabe andNishino, 2004) (Scheme 4).

Despite the uncertainty related to the reaction mechanism,the authors point toward manganese(III) that could oxidizetertiary carbon radical 14 to afford the corresponding carboca-tions 15, 16 which were converted into compound 12

(Scheme 5).

1

NH

O

O

NH

O

OH

+Mn(OAc)3

AcOH/100oC

PhPh

12 (73%)

Ph Ph

11

Scheme 4

NH

O

OH

Mn(OAc)3

AcOH, reflux NH

O

OMn(III)

NH

O

OPh Ph.

NH

O

OPh Ph+

NH

O

OPh Ph

+-H+

12Mn(OAc)3

AcOH, reflux

11

1 13 14

15 16

Scheme 5

NH

O

OH

R1

R2 Mn(OAc)3, 40oC[bmim][BF4]:CH2Cl2

1 17

+

17, 18, 19 R1 R

a Ph H

b Me P

c C3H7H

d C6H13 M

Scheme

Please cite this article in press as: Abdou, M.M. Chemistry of 4-hydroxy-2(1H)-quinol(2014), http://dx.doi.org/10.1016/j.arabjc.2014.11.021

A similar, manganese(III)-mediated reaction using 4-hydroxy-2(1H)-quinolone 1 and the alkenes 17 in [bmim][BF4]–dichloromethane gave a 1:1 mixture of the angular

and linear tricycles 18 and 19, respectively (Bar et al.,2001a,b) (Scheme 6).

2.2. [6-6-5] ring system

Laccase (Agaricus bisporus)-catalyzed domino reaction of 4-hydroxy-2(1H)-quinolone 1 with catechols 20 using aerial oxy-gen as the oxidant delivers for the synthesis of 10-substituted

8,9-dihydroxybenzofuro[3,2-c]quinolin-6(5H)-ones 21 as singleregioisomers with yields ranging from 61% to 77% (Hajdoket al., 2009) (Scheme 7). Some of these compounds have been

made accessible by other methods, including tyrosinase-cata-lyzed oxidation, electrochemical oxidation or crude peroxidase

R1

N OH

OR2

R1

R2N O

OH

18 19

+

2Yield% (18/19)

41/39

h 41/34

71/8

e 41/4

6

OH

NH

O

O

R

OH

ONH

OH R

OH

OH+

pH=6.0, r.t.

1 20 21

cat. laccase, O2

20, 21 R t/h Yield %

a H 20 73

b Me 18 77

c OMe 20 61

Scheme 7

one. Part 2. As synthons in heterocyclic synthesis. Arabian Journal of Chemistry


OH

OHoxidation

-2e, -2H

O

O

ONH

OH

1

__

O

O

1,4-addition

ONH

OHOH

OH

1,4-additionoxidation

-2e, -2H ONH

OHO

O

__ OH

NH

O

O

OH

25

20a 22

22 23

24

Scheme 8

1 33 34

+

NH

O

OH

OMeO

N HN R

NH

O

O

O HN R

O

OAcOH

R= OMe, Ph

Scheme 11

4 M.M. Abdou

from onion solid waste (Pandey et al., 1989; Tabakovic et al.,1983; Angeleska et al., 2013).

The reaction is postulated to proceed through a dominoprocess involving several steps (Scheme 8). Initially, thelaccase-catalyzed oxidation of the catechol 20 with O2 to

NH

O

OH

N

1

+

26

26, 27 a b c dAr 2-Cl 4-Cl 3,4-Cl2 2,4-C

Time/ h 8 8 8 8

Yield % 94.2 90.2 93.2 97.

Scheme

NH

O

OH

1

+NPh

NH

O

OH

OH

Ph

NH

O

HN

Ph

HO

26

29

30

32

Scheme 1


benzoquinone 22, which then undergoes an intermolecular1,4-addition with the enol of 1 as a nucleophile to yield 23.

A second laccase-catalyzed oxidation to the quinone interme-diate (24) which further undergoes an intramolecular 1,4-addi-tion to produce the final tetracyclic heterocycles.

2.3. Fused [6-6-6] ring system

2.3.1. Quinolino[4,3-b]benzo[f]quinolin-6-one

A short and simple synthesis of quinolino[4,3-b]benzo[f]quino-line derivatives 27 was accomplished in high yields via the

NH

O

HNR

R27

TEBACH2Ol100 oC

e f g hl2 4-F 4-Br 4-CH3 3-Cl

8 10 12 10

0 92.5 93.5 91.6 87.8

9

NH

O

OH

NH

PhH2O

NH2

NH

O

OH2N

-H2O

NH

O

HN

Ph

28

31

27

0



NH

OH

O ONH

OHR

O

NH

O

OR

OO

HN

EtO

OEt

OEt Ac2O

1

+ + 90°C, 4 h

35 7363

35,37 R Yield %

a Ph 71

b Me 46

c 2-Pyrazinyl 9

d 3-Pyridinyl 31

Scheme 12

NH

OH

O

1

+NH

O

O

O HN Ph

O

O

NEtO

Ph

O

NEt3, pyridine

Reflux, 4h

39 (69%)38

Scheme 13

NH

O

OH

+NH

O

O

O

O

OEt

O

Pyridine, DMFHeating, 5h

OO

41 (58 %)1 40

Scheme 14

NH

O

OH

+NH

O

O

REtO

CN

OR

NaOEt, EtOH

R: CN, COOEt.

1 3424

Scheme 15

NH

O

OH

+ OEtEtO

OO

O

CH3CO2N

0.5h

1 44

Scheme 1



reaction of N-benzilidenenaphthalen-2-amines 26 and 4-hydroxy-2(1H)-quinolone 1 in aqueous media catalyzed by tri-ethylbenzylammonium chloride (TEBAC) (Wang et al., 2005)(Scheme 9).

Though the detailed mechanism of the above reaction hasnot been clarified yet, the formation of 27 can be explainedby the possible mechanism presented in Scheme 10.

2.3.2. Pyranoquinolines

Pyranoquinolines are the main constituent unit of the many ofthe alkaloids of the plant family Rutaceae (Manske and

Rodrigo, 1988; Sainsbury, 1978; Chen et al., 1997; Waboet al., 2005; Michael, 2002, 2003, 2004, 2005) and have gainedmuch importance because of their interesting pharmacological

properties and synthetic applications (Chen et al., 1994; Barret al., 1995; Nahas and Abdel-Hafez, 2005; Amin, 1993;Magesh et al., 2004; Schiemann et al., 2007).

2.3.2.1. Angular pyranoquinolines. 2.3.2.1.1. Pyrano[3,2-c]quinoline-2,5(2H,6H)-diones. Many methods for the synthe-sis of pyrano[3,2-c]quinoline-2,5(2H,6H)-dione derivatives

have been reported successively. It has been reported thatthe preparation of 3-acetyl(benzoyl)amino-5,6-dihydropyr-ano[3,2-c]quinoline-2,5(2H,6H)-dione 34 was accomplished

by the treatment of methyl 2-acetyl(benzoyl)amino-3-(N,N-dimethylamino)propenoates 33 with 1 in acetic acid (Ngadjuiet al., 1992; Kralj et al., 1997) (Scheme 11).

An elegant and efficient one-pot synthesis of acylaminoderivatives of quinoline 37 was achieved by the reaction of35, triethyl orthoformate (TOF) 36 and 4-hydroxy-2(1H)-quin-olone 1 in acetic anhydride (Kmetic et al., 1993) (Scheme 12).

Kepe et al. (1995) observed that treatment of 4-ethoxymeth-ylene-2-phenyl-5(4H)-oxazolone 38 with 1 under basicconditions in boiling mixtures of pyridine and triethylamine

NH

O

O

O

COOEtH4, nitrobenzene

, 220 °C

45

6



NH

O

OH

NH

O

O

O

R1

R2

EtO

OO

R2R1

CH3COONH4, nitrobenzene+

200 °C

1 46 47

46, 47 R1 R2 Yield %

a H CH3 73 %

b H C6H5 47 %

c CH2-C6H5 CH3 83 %

Scheme 17

NH

OH

O NH

O

OR2

NH2

R2

CNH

R1

R1

+ reflux

A : Triethylamine in ethanol, Time= 0.75h, Heating.B : Piperidine in ethanol, Time= 2h, Heating.

1 48 49

A,B

48,49 R1 R2Yield%(A/B)

a H CN 83/ 70

b 4-N(CH3)2 CN --/ 63

c 4-OCH3 CN --/ 65

d 4-Cl CN 79/ 60

e H COOEt 87 / 67

f 4-CH3 COOEt 90 / --

g 4-OCH3 COOEt 63 / --

h 4-Cl COOEt 84 / 65

Scheme 18

R_CHO +CN

CN NH4OAC CNR

CN

1

NH

O

OH

NH4OAC_H

54

NH

O

O

53

NH

NCO

R

O

CN

NH

O

R

O

CNN

NH4OAC

NH

O

R

O

CNNH

NH

O

R

O

CNNH2

50 51 53

55

565752

Scheme 20

6 M.M. Abdou

led to N-(5,6-dihydro-2,5-dioxo-2H-pyrano[3,2-clquinoline-3-yl)benzamide 39 [50] (Scheme 13).

4-Hydroxy-2(1H)-quinolone 1 when condensed with ethyl-2,3-dihydro-3-oxobenzofuran-2-carboxylate 40 afforded thecorresponding 6H,12H-benzofuropyrano[3,2-c]quinoline-6,12-

diones 41 (Kepe et al., 1992) (Scheme 14).

R : CH3CH2, CH3CH2CH2, C6H5, 4-CH3C6H4, 4- 4-NO2C6H4, 4-CNC6H4, 4-ClC6H4 , 4-BrC6H 3,4-OCH2OC6H3, 3- CH3O-4-HOC6H3, 2-Fur

501

CN

CNR-CHO +

NH

O

OH

+

51

Scheme 1


Reaction of ethoxymethylenemalononitrile and ethylethoxymethylenecyanoacetate 42, with 4-hydroxy-2(1H)-quin-

olone 1 led to the corresponding 2,5-dioxo-5,6-dihydro-pyr-ano[3.2-c]quinolines 43 exhibiting remarkable visible fluo-rescence (Mulwad et al., 1999) (Scheme 15).

Schmidt and Junek (1978) have reported the synthesis ofpyrano[3,2-c]quinoline-2,5-diones 45 via the treatment of4-hydroxy-2(1H)-quinolone 1 with 1-ethoxycarbonylethyliden

44 in nitrobenzene (Scheme 16).The Pechmann-Duisberg reaction was employed by Kappe

and Mayer (1981) to synthesize pyrano[3,2-c]quinoline-2,5-diones 47 via condensation of 1 with b-ketoesters 46 and

CH3OC6H4, 4-FC6H4, 4-HOC6H4, 2-ClC6H4,4,3-NO2C6H4 , 2,4-Cl2C6H3 , 3,4-Cl2C6H3 ,yl, 4-Pyridyl.

NH

O

R

O

CNNH2

52

EtOH

9



1 58 59

NH

O

OH

+ +NH

O

O

60 (82 %)

(CH2O)n

COOH1,4-dioxaneN2 atm, 4.5 h

Scheme 21

NH

OH

O

1

+NH

OCH3CHO

Et2NH, C6H6Heating, 5h

O

OH

62 (51%)61

Scheme 22

1

NH

NH

O

OO

OH

+

69 (67%)

PPA, xylene10h, 145 °C

68

Scheme 24

NH

O

OH

NH

O

O

H3C R

RO+

Conditions: A : Yb(OTf)3, CH3CN, 12h, Heating. B : Ethylenediaminediacetic acid in CH2Cl2, Time= 10h, T= 20 °C.

C: Water, 6h, 80 °C.

Variousconditions

1 70 71

70,71 R Condition Yield %

a H A 53

a H B 70

b CH3 A 50

b CH3 C 70

b CH3 B 94

c C2H5 B 77

d C3H7 B 82

e CH2-CH2=CH-CH(CH3)2 A 40

f CH2-CH2=CH-CH(CH3)2 C 71

Scheme 25

NH

O

OH

+O

OH

HN

O

+Cl

ClO

O

RO

RN toluene

80-95 0C

R= C6H5, CH2C6H5

1 72 73 74

Scheme 26


ammonium acetate at 200 �C in nitrobenzene (Scheme 17).

Also, this reaction can be performed in pyridine instead ofnitrobenzene.

2.3.2.1.2. 2-Aminopyrano[3,2-c]quinolin-5-ones.

Using two component condensation: A number of publications(Kumar and Rajendran, 2004; Dodia and Shah, 2001) have

been taken out for Michael reactions of 4-hydroxy-2(1H)-quinolone 1 with various substituted acrylonitriles 48 in thepresence of base (triethylamine or piperidine) as a catalyst

resulting in the corresponding 2-amino-4-aryl-1,4,5,6-tetrahy-dro-pyrano[3,2-c]quinolin-5-ones 49 (Scheme 18).

Using three component condensation: There have been severalmethods for synthesizing pyranoquinoline derivatives, includ-ing the three-component reaction of 4-hydroxy-2(1H)-quino-

lone 1, aldehydes 50, malononitrile for the synthesis of2-amino-3-cyano-1,4,5,6-tetrahydropyrano[3,2-c]quinolin-5-onederivatives 52 catalyzed by TEBA (benzyltriethylammonium

chloride), piperidine, TsOH, NH2SO3H, SiO2–NaHSO3,ZnCl2, MgCl2, Cu (ClO4)2-6H2O, Et3N, DBU, imidazole,ammonium acetate, KF–Al2O3 and Yb(OTf)3) (Sowellimet al., 1995, 1996; Wang et al., 2004a,b, 2006; Nasseri and

Sadeghzadeh, 2013; Lei et al., 2011; Peng et al., 2005;Kumar et al., 2009) (Scheme 19). Recently, Guan et al.

1

NH

O

OH

_HDEA

63

NH

O

O

CH3CHO

64NH

O

O OH

65

NH

O

O

66

NH

O

OH

NH

O

CH3 OH

-H2O

RCH=CHNEt2

NH

O

O

NEtEt

NH

O

O

OH

hydrolysis

67

H

H, 63

62

Scheme 23

Please cite this article in press as: Abdou, M.M. Chemistry of 4-hydroxy-2(1H)-quinolone. Part 2. As synthons in heterocyclic synthesis. Arabian Journal of Chemistry(2014), http://dx.doi.org/10.1016/j.arabjc.2014.11.021


NH

O

OH

+1 h

O

O

OHN

NaOHO

O

HNCH3

HN

O

OO

+

H3C

1 75 76 77

Scheme 27

1 7978

NH

O

OH

+NH2

SH

NH

O

SHN

.DMF

120 °C, 12h

Scheme 28

8 M.M. Abdou

(2013) found that 2-amino-3-cyano-1,4,5,6-tetrahydropyr-

ano[3,2-c]quinolin-5-one derivatives 52 could be preparedwithout catalyst in a mixed solvent of ethanol and water.

The condensation of 1, aldehyde 50, malononitrile 51 mayoccur by a mechanism of Knoevenagel condensation, Michaeladdition, intramolecular cyclization, and isomerization. Ini-

tially, intermediate 53 is formed by Knoevenagel condensationof aldehyde 50 and malononitrile 51 by the action ofammonium acetate. Then, the proton of 4-hydroxy-2(1H)-

quinolone 1 is abstracted by ammonium acetate to formintermediate 54. Michael addition of intermediate 54 on 53

leads to the formation of 55, followed by cyclization andisomerization, affords the corresponding 2-amino-4H-pyr-

ano[3,2-c]quinolin-5(6H)-one derivatives 52 (Wang et al.,2004a,b) (Scheme 20).

2.3.2.1.3. 3,4-Dihydrobenzopyrano[3,2-c]quinoIin-5(6H)-one.2,2-Dimethyl-3,4-dihydropyrano[3,2-c]quinoIin-5(6H)-one 60 wasprepared by refluxing a solution of l with para-formaldehyde 58

and 3,3-dimethylacrylic acid 59 in 1,4-dioxane under nitrogenatmosphere for 4.5 h (Suresh et al., 2005) (Scheme 21).

2,3,4,6-Tetrahydro-2-hydroxy-4-methylpyrano[3,2-c]quino-

lin-5-one 62 are synthesized from 4-hydroxy-2(1H)-quinolone

3

2

1

1 2

3

3

3 3

3 3

Scheme 2


1 by tandem Knoevenagel condensation with an acetaldehyde61 in the presence of diethylamine as a base in refluxingbenzene (Ye et al., 1999) (Scheme 22).

The possible mechanism could account for the formation ofproduct 62 via base-catalyzed condensation of a quinolinone 1with an acetaldehyde 61 yielding the corresponding 4-hydroxy-

3-(1-hydroxyethyl)quinolin-2-one 64, which is dehydrated onheating in the basic reaction medium to furnish the highlyelectrophilic quinone methide intermediate 65. The quinonemethide 65 then undergoes competitive Michael-type addition

of the enamine proceeds in a 1,4-fashion and results in anintramolecular cyclization to give the 2-(diethylamino)pyrano-[3,2-c]quinolin-5-one 66, which on hydrolysis during

the reaction affords the final product 62 (Scheme 23).An efficient synthesis of pyranoquinoline alkaloids is

described by Thangavel et al. (2007) via direct treatment of iso-

prene 68 with 4-hydroxy-2(1H)-quinolone 1 in the presence ofpolyphosphoric acid, furnishing dihydroflindersine 69 in goodyield (Scheme 24).

2.3.2.1.4. Miscellaneous pyrono quinolone. In water medium,

environmentally benign, facile, and efficient synthesis of pyr-ans 71 was achieved in good yields by domino Knoevenagelreaction of 1 with several a,b-unsaturated aldehydes 70 (Jung

et al., 2010) (Scheme 25). This method has been successfullyapplied to the synthesis of biologically interesting and natu-rally occurring pyranoquinolinone alkaloids in good yields.

Also, this reaction can be achieved by ytterbium(III) triflate(Lee et al., 2001) or ethylenediaminediacetic acid in dichloro-methane (Wang and Yong, 2007).

2.3.2.3. Linear pyranoquinolines. Nohammer and Kappe (1976)showed that the reaction of 4-hydroxy-2(1H)-quinolone 1 withmalonyl chlorides 72 in the presence of N,N-dimethylaniline 73

31

2

9




yielded the corresponding linear pyronoquinolones 74

(Scheme 26).Sangeetha and Prasad (2006) adopted a novel and highly

efficient methodology for synthesizing quinolino[2,3-o]carbaz-olo[6,5-a]pyran-7,8-diones 77 with interesting biological activ-ity via reaction of 1 with vinyl acetate 75 and 3,11-dihydro-2,4-

dioxopyrano[2,3-o]carbazoles 76 (Scheme 27).

2.3.3. Quinolinobenzothiazinones

One of the most successful strategies for constructing 5H-quin-

olin[3,4-b][1,4]benzothiazin-6(12H)-one 79 as a new agent withestrogenic activity mediated by estrogen receptors (ER) is thecondensation and oxidative cyclization of amino thiophenol

78 with 1 in dioxane in the presence of p-toluene sulfonic acid(Ruano et al., 1991) or N,N-dimethylformamide (Coppolaet al., 1981) (Scheme 28).

2.4. [6-6-8-6] ring system

2.4.1. Oxazocines

Basic alumina supported and solvent-free synthesis of noveloxazocines 81 has been achieved in excellent yields by tandemC-alkylation followed by intramolecular O-alkylation of 1 with

quinolinium salts 80 under microwave irradiation (Mondalet al., 2011) (Scheme 29).

3. Conclusion

The data considered in this review clearly demonstrate that 4-hydroxy-2(1H)-quinolone may be successfully used to synthe-

size a wide variety of heterocycles of academic and pharmaceu-ticals interest. Finally, all chemistry presented here along withthat already discussed in my previous review article (Abdou,

2014), clearly demonstrates the utility of 4-hydroxy-2(1H)-quinolone for countless organic transformations.

Acknowledgements

It is a pleasure to acknowledge the contributions made by myco-workers mentioned in the list of references. For financial

support, I would like to thank the Academy of ScientificResearch and Technology, ASRT, Egypt. Also, the authorregrets any omissions that may have occurred in this review.

Finally, I would like to thank Professor El-Sayed I. El-Desokyfor reading the manuscript and making useful suggestions.

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