Mini Review of Sulfur Heterocyclization from π-Electron Deficient Quinones via Charge-Transfer...

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MINI REVIEW OF SULFUR HETEROCYCLIZATION FROMπ-ELECTRON DEFICIENT QUINONES VIA CHARGE-TRANSFER INTERACTIONAshraf A. Aly a , N. A. A. Elkanzi b & Alan B. Brown ca Chemistry Department, Faculty of Science , El-Minia University , 61519 , El-Minia , Egyptb Chemistry Department, Faculty of Science , Aswan University , 81582 , Aswan , Egyptc Department of Chemistry , Florida Institute of Technology , Melbourne , FL , 32901 , USAAccepted author version posted online: 25 Aug 2013.

To cite this article: Phosphorus, Sulfur, and Silicon and the Related Elements (2013): MINI REVIEW OF SULFURHETEROCYCLIZATION FROM π-ELECTRON DEFICIENT QUINONES VIA CHARGE-TRANSFER INTERACTION, Phosphorus, Sulfur, andSilicon and the Related Elements, DOI: 10.1080/10426507.2013.829830

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MINI REVIEW OF SULFUR HETEROCYCLIZATION FROM -ELECTRON DEFICIENT

QUINONES VIA CHARGE-TRANSFER INTERACTION

Ashraf A. Alya* and N. A. A. Elkanzib

a Chemistry Department, Faculty of Science, El-Minia University, 61519-El-Minia, Egypt

b Chemistry Department, Faculty of Science, Aswan University, 81582-Aswan, Egypt

Corresponding Author: Prof. Ashraf A. Aly; E-mail: ashrafaly63@yahoo.com.

Abstract This survey is mainly concerned with selected reactions of 2,3-dichloro-1,4-

naphthoquinone (DHNQ), 3,4,5,6-tetrachloro-1,2-benzoquinone (o-CHL), 2,3,5,6-

tetrachloro-1,4-benzoquinone (p-CHL) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

(DDQ) as π-deficient quinones which are used or offer potential use for sulfur heterocyclic

synthesis. Reaction of various donors with the π-deficient quinones are studied, especially

those via charge-transfer complex formation.

Graphical Abstract

Heterocycles

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Keywords: π-deficient quinones, donors, charge-transfer complex, selectivity, S-heterocycles.

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INTRODUCTION

A large variety of quinones including heterocyclic derivatives, have been used as synthetic

intermediates and in the medicinal, as well as dye chemistry.1-3 Compounds containing the

quinone group represent an important class of biologically active molecules that are widespread

in nature.2-7 Charge-transfer (CT) complexes composed of donors D and acceptors A have

attracted considerable attention because of their molecular magnetism and electronic phase

transitions.8 It has been shown that the quinone (Q) redox activity is related to the ability to

accept electrons (redox potential): to yield the radical anion (Q•−) or dianion (Q2−) respectively.

The redox potential is closely related to the chemical and electronic environments provided by

the solvent and the chemical substituents (electron attractor or electron donor nature) in the

structure.9-11 The electrochemical and redox properties of Qs are important factors that modify

their biologic activity.12,13 π-Deficient quinones are also well-known as a stronger oxidant than

1,4-benzoquinone. They are used as reagents for oxidative coupling and cyclization reactions,

and dehydrogenation of hydroaromatic compounds.

Heterocyclic compounds containing the quinone group represent an important class of

biologically active molecules.14 The chemistry of quinones is of considerable interest: the class

includes many natural products and numerous important synthetic products.15,16 Organic

molecules containing electron donor and acceptor moieties constitute a very interesting topic

due to their interesting optical and electronic properties.17 Accordingly, we are aiming to shed

light on the synthesis of heterocycles containing sulfur atoms from 2,3-dichloro-1,4-

naphthoquinone (1), 3,4,5,6-tetrachloro-1,2-benzoquinone (2), 2,3,5,6-tetrachloro-1,4-

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benzoquinone (3) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (4) via the formation of

charge-transfer complexes (CTC).

1. Reaction of Acceptor 1 with Thioamides

Katritzky et al.18,19 reacted 2,3-dichloro-1,4-naphthoquinone (1) with thioacetamide or

with thiourea 5. The reaction led to 2-methyl- and 2-aminonaphtho[2,3-d]thiazole-4,9-diones 7

and 8, as well as the formation of the bis-thiazole 11 (Scheme 1). They also found that 1 could

produce, in basic medium, dibenzo[b,i]-thianthrene-5,7,12,14-tetraone (6), in addition to the

monosubstituted naphthoquinone 9 and 10 besides 11 (Scheme 1).

2. Reaction of 1H-Benzo[d]imidazole-2(3H)-thione (12) with the Acceptor 1

The UV/Vis absorption maxima obtained by mixing 1H-benzo[d]imidazole-2(3H)-thione

(12) and acceptor 1 in ethyl acetate as solvent fall in the visible region (670–475 nm). These

maxima are attributed to CT complex formation, since both donor and acceptor alone did not

absorb in this region.20 The CT complex decomposes after few hours to give the fused imidazo-

1,3-thiazole 13 (Scheme 2).20

3. Reaction of Aroylphenylthioureas 14a-c with the Acceptors 1, 3 and 4

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Thiazoles are ubiquitous building blocks in medicinal chemistry and can be found in

numerous natural products (e.g. epothilone)21-23 and biologically important compounds including

the anticancer drug dasatinib, antiviral clinical candidate TMC435350, and antidiabetic drug

candidate MB06322.24 Accordingly, the reactions of aroylphenylthioureas 14a-c with 1 were

examined. The reactions proceeded via CT-complexation to give the corresponding

benzo(naphtho)thiazoles 15a-c as shown in Scheme 3.25 In the same manner, the reactions of

14a-c with acceptor 3 were studied, which produced the the corresponding

benzo(naphtho)thiazoles 16a-c (Scheme 3).25 The same trend was observed, when

aroylphenylthioureas 14a-c were subjected to acceptor 4 and compounds 17a-c (Scheme 3).25

The reaction mechanism described the reactions of the quinone π-acceptors 1 with 14a-c,

as due to a type of tautomerism that occurs in 14a-c under the reaction conditions, between the

NH and the C=S into the N=C–SH group. Thereafter, the formed SH group adds to C-2 of the

quinone, which under elimination of hydrogen chloride produces 18. Then, another nucleophilic

attack of the aromatic NH-amine in 19 on C-3 followed by elimination of another molecule

hydrogen chloride gives the stable compounds 15a-c.

One can assumed that the attack by the SH group is faster compared with the aromatic

amine. Therefore, the reaction would proceed by the steps shown in Figure 2.25

4. Reaction of Acceptor 1 with 4-Amino-5-hydrazinyl-1(4H)-1,2,4-triazole-3-thiol

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Reaction of equimolar quantities 1 with compound 20 in refluxing ethyl acetate afforded 3-

amino-2-thioxo-2,3-dihydronaphtho[2,3-e][1,2,4]triazolo[5,1-c][1,2,4]triazine-6,11(1H,5H)-

dione (21) after chromatographic purification (Scheme 4).26

Interestingly, the reaction of a mixture of one mole of 20 with two moles of 1 produced the

fused bis-naphthotriazolotriazinothiadiazine 22 in productive yield (Scheme 4). The presence of

one chlorine atom in 22 confirmed that the other one was eliminated.26

Antibacterial Activity

Compound 21 exhibited good antibacterial activity against the Gram negative Escherichia

coli (MIC 4 µg/mL) compared with ciprofloxacin (MIC <1 µg/mL). In addition, 21 showed

excellent antibacterial activity against the Gram negative Klebsiella pneumoniae (MIC, <1

µg/mL). Its activity is equal to the activity of ciprofloxacin (MIC, <1 µg/mL). Compound 21 also

exhibited excellent antibacterial activity against the Gram negative Pseudomonas aeruginosa

(MIC, <1 µg/ml), its activity is better than the activity of ciprofloxacin (MIC, 1 µg/mL).26

Similarly, direct reaction of two moles of 20 with one mole of 3,4,5,6-tetrachloro-1,2-

benzoquinone (2) under the reaction conditions illustrated in Scheme 5 afforded the

corresponding compound 22 with 85% yield (Scheme 5).26

5. Reaction of 1 and 4 with 3-Amino-2-thioxothiazolidin-4-one (Rhodanine, 23)

The addition of a pyridine solution of 1 to a solution of 3-amino-2-thioxothiazolidin-4-one

(rhodanine, 23) in pyridine afforded the naphthoquino-thiazoloxadiazine derivative 24, rather

than the naphthoquinofurothiazole 25 (Scheme 6).27

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In a different manner, the addition of 4 to rhodanine 23 results in the formation of the

dimeric product 26, in addition to another two products 27 and 28 (Scheme 7).27

6. Synthesis of Fused Imidazothiadiazoles 31

The group of Soni28 have reported the reaction of 2-amino-[1,3,4]thiadiazoles 29 with 1 to

give 2-chloro-3-([1,3,4]thiadiazol-2-ylamino)-2,3-dihydro-[1,4]naphthoquinone intermediates

30 with 33–46% yields, which were further cyclized in acetic acid to give 2-alkylnaphtho[2,3-

d]imidazo[2,3-b]thiadiazolo-5,10-dione (31, Scheme 8).28

7. Reaction of Thiocarbohydrazides 32 with 1

Substituted naphthimidazothiadiazolediones 33 and disubstituted naphtho-bis-imidazo-

thiadiazoles 34 were obtained from the reaction of substituted thiocarbohydrazides 32 with 1

(Scheme 9).29 CT-complex formation between the reactants is postulated as the intermediate

process to give the obtained products.32

The formation of the oxathiadiazole and indazole derivatives 36 and 37 requires the

reaction between ylidene thiocarbohydrazide derivative 35 and 1 (Scheme 10).30

8. Reaction of 2-Substituted Ylidene-N-phenylhydrazinecarbothioamides with 1-4

Mixing equimolar amounts of hydrazinecarbothioamides 38 and 1 in ethyl acetate for 72

hours led to the formation of substituted benzindazole-4,9-diones (39, Scheme 11).31 3,4,5,6-

Tetrachloro-1,2-benzoquinone (3) reacted with an equimolar quantity of 38 to give the indazole

derivatives 40 (Scheme 11).31

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Moreover, the addition of ethyl acetate solutions of 2-substituted ylidene-N-

phenylhydrazine-carbothioamides 38 to an equimolar quantity of tetrachloro-p-benzoquinone (3)

in ethyl acetate gave, upon standing for 48 h at room temperature, a green color which

gradually changed to brown. The separation of the reaction mixture by preparative layer

chromatography gave the heterocycles 41 (11–16%) and 43 (69–75%); the alternative products

42 and 44 were ruled out on account of their NMR and mass spectra (Scheme 12).31

Addition of dichloromethane solutions of 38 to solutions of 4 in the same solvent resulted

in the appearance of a green color, which gradually changed into brown. 5-Substituted N-

phenyl-1,3,4-thiadiazole-2-amines 45 (6–11%), together with 3-amino-5,6-dichloro-4,7-dioxo-N-

phenyl-4H-indazole-2(7H)-carbothioamide (46, 71%) (Scheme 13) were isolated by preparative

thin layer chromatography.31

9. Reaction of Acyl-thiosemicarbohydrazides 47 with 1, 3 and 4

Hassan et al.32 reported that on mixing of two-fold molar amounts of 1 with one mole of

acyl thiosemicarbohydrazides 47 in ethyl acetate with admission of air, a blue color (λmax = 573-

591 nm) appeared.32 This behavior is explained as being due to initial formation of an unstable

CTC followed by a chemical reaction, which yields substituted thiazines 48 as major products

and bis-thiazoles 49 as minor products (Scheme 14).32

On the other hand, mixing of two-fold molar amounts of 3 with one mole of acyl-

thiosemicarbohydrazides 47 in ethyl acetate with admission of air gave a blue color (λmax = 573-

591 nm).32 That behavior is explained as being due to the initial formation of an unstable CTC

followed by formation of substituted oxadiazoles 50 and heterocycles 51 and 52 (Scheme 15).32

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The reaction of two-fold molar amounts of 47 with one mole of 4 in ethyl acetate under

admission of air gives a blue color (λmax = 573-591 nm). This is again due to the initial

formation of an unstable CTC followed by the formation of the substituted

benzimidazoxadiazoles 53 and the product 50 resulting from the reaction of the

dihydrobenzoquinone (4-H2) with 47, under elimination of hydrogen cyanide and water (Scheme

16).32 Accordingly, the reaction of 47 with 4 did not produce the expected sulfur heterocyclic

compounds.32

10. Reaction of Thiocarbohydrazides 32 and Bis(thioureas) 56 with 3

The reaction of two equivalents of thiocarbohydrazides 32 with 3 in THF afforded, after

few hours, 54 and 55 (Scheme 17).33 Whilst the reaction of two equivalents of thioureidoethyl-

thiourea derivatives 56 reacted with 3 in the same solvent at room temperature to afford

substituted 7-imino-1,3,6-thiadiazepane-2-thiones 57 as minor and trichloro-7-oxo-quinoxaline-

1-carbothioic acid substituted amides 58 as major products, in addition to the corresponding

dihydrobenzoquinone (Scheme 17).33

11. Reaction of Dithiocarbamates 59 with 1

Aly et al.34 reported that after reaction of the salt 59 with 1 in DMF, 2,2'-[ethane-1,2-diyl-

bis-(azan-1-yl-1-ylidene)]dinaphtho[2,3-d][1,3]dithiole-4,9-dione (60) was obtained with 95%

yield (Scheme 18).34

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12. Reaction of Carbamodithioates 61 with 1

The carbamodithioates 61a-e were subjected to reaction with 1, to give 2-

iminonaphtho[2,3-d][1,3]dithiole-4,9-diones 62a-e (Scheme 19).35 On the basis of the

spectroscopic data, the formation of the expected naphthothiazoles 63a-e is excluded (Scheme

19).35

13. Reaction of Thienocoumarin 64 with 1

Döpp et al36 described the formation of the condensed benzoxepin 65 from the

thienocoumarin 64 and 1 in refluxing THF in the presence of triethylamine (Scheme 20).36

14. Reaction of Donors 66a and 66b with 2 and 3

Addition of 66a,b as electron donors to the acceptor 2 in ethyl acetate at room temperature

presumably leads to initial complex formation, as indicated by CT-bands in the visible region.37

These CT-complexes gradually disappear to give the heterocycles 67a,b which precipitated with

good yields from the reaction mixture (Scheme 21).37 In the same manner, the reaction of the

acceptor 3 with the same donors 66a,b afforded the trioxa(thia)-triazatrinaphthylenes 68a,b with

60–64% yield as shown in Scheme 21.37

15. Cycloaddition Reactions

15.1. Reaction of 2 with Tetrathiafulvalene 69

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Formation of the dipolar intermediate may be preceded by a single electron transfer (SET)

step. The reaction of the tetrathiafulvalene cation radical 69 (TTF•+) with ortho-chloranil 2 is

reported to give 1,4-dioxane 70 (Scheme 23).38

15.2. Mixed [4+2]- and [4+3]-Cycloaddition Reactions

Mesoionic dithiolylium-4-olates 71 provide examples of both types of cycloadducts. All but

one of the derivatives studied react with ortho-chloranil 2 to give the [4+2]-cycloadduct 72 (14–

96% yield). The 2-methyl-5-phenyl derivative of 73 (R1 = Ph, R2 = Me) represents the exception,

which gives the [4+3]-cycloadduct 73 (59% yield). (Scheme 24).39

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609-621.

7; Y= CH38; Y = NH2

9; Y= CH310; Y = NH2

base+ 11

Scheme 1. Synthesis of fused thiazoles

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Scheme 2. Synthesis of fused imidazo-1,3-thiazole 13

R 14a-ca, R = OCH3b, = CH3c, = H

+DMF, ref lux

3, DMF, ref lux

4-10 h

4-8 hO

OR4, DMF, ref lux

10-14 h

Scheme 3. Reactions of aroylphenylthioureas 14a-c with the acceptors 1, 3 and 4

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1 (1 equiv)EtOAc, ref lux, 18-24 h

1 (2 equiv)EtOAc, ref lux, 18-24 h

21 (80%)

22 (94%)

Scheme 4. Synthesis of dihydronaphtho[2,3-e][1,2,4]triazolo[5,1-c][1,2,4]triazinedione 21 and

bis-naphthotriazolotriazinothiadiazine 22

EtOAc, ref lux 24 h

22 (85%)

H2NHN SH

Scheme 5. Reaction of triazole derivative 20 with acceptor 2

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Scheme 6. Synthesis of the naphthoquinothiazoloxadiazine derivative 24

HOCl S

27 (20%)

28 (50%)

26 (10%)

Scheme 7. Reaction of rhodanine (23) with acceptor 4

AcOH/ reflux

R = H, CH3, Et, n-Pr, i-Pr

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Scheme 8. Synthesis of fused imidazothiazdiazoles 31

32 1 3334

Scheme 9. Synthesis of fused naphthoimidazothiadiazolediones 33 and naphtho-bis-

imidazothiadiazoles 34

NHNH2 + 1

R = C6H5-CH=N-

3536 37

Scheme 10. Reaction of thiocarbohydrazide 35 with 1

PhNHCSNHN=CH-RN

Scheme 11. Reaction of 38 with the acceptors 1 and 2

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PhNHCSNHN=CHR

SRNHPh

N-N=CHR

Scheme 12. Reaction of 38 with 3

PhNHCSNHN=CHR

Scheme 13. Reaction of 38 with 4

NNHCORNH

ROCHNN

RCONHNHCSNH2 + 1

Scheme 14. Synthesis of the substituted naphthothiaziness 48 and 49

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RCONHNHCSNH2

47 3 50

Scheme 15. Reaction of acyl-thiosemicarbohydrazides 47 with 3

RCONHNHCSNH2

50 (17-22%) +

53 (65-73%)

Scheme 16. Reaction of acyl-thiosemicarbohydrazides 47 with 4

N NHR Cl

N NHRN

Cl Cl32 +

3 54 (48-54%) 55 (21-24%)

NHCSNHR

NHCSNHRS

57 (14-19%)

58 (41-49%)

Scheme 17. Reaction of thiocarbohydrazides 32 and 56 with 3

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HNNHS-

2 Et3NH+

+ 1DMF

rt, 24 h

Scheme 18. Synthesis of dinaphtho[2,3-d][1,3]dithiole-4,9-dione 60

NH2Et3N, ether

72 h, 0 oC

SS Et3NH61a-e

O62a-e1, DMF

r.t., 6-8 h

+ CS2R

61-63 R Yield of 61 (%) Yield of 62 (%)

p-CH3-C6H4-

p-Cl-C6H4-

C6H5-CH2-

C6H11-

9596808790

8285768270

Scheme 19. Synthesis of 2-iminonaphtho[2,3-d][1,3]dithiole-4,9-diones 62a-e

+ 1THF, Et3N

reflux

Scheme 20. Synthesis of benzoxepine 65

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X ClCl

OCl NH2

66a: X = O66b: X = S

267a,b (70-74%)

3 68a,b (60-64%)

Scheme 21. Reaction of donors 66a,b with acceptors 2 and 3

. + + 2

Scheme 22. Reaction of the tetrathiafulvalene cation radical 69 (TTF•+) with ortho-chloranil 2

+ 2S S+

Scheme 23. Mixed [4+3]- and [4+2]-cycloaddition reactions of dithiolylium-4-olates

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14a-c + 1- HCl

Figure 2. Mechanism describing the formation of 1,3-thiazoles

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