Benzo thiophene-4,7-quinone

Naturally Occurring Thiophens.—The isolation of a terpenoid benzo[ ]-thiophen-4,7-quinone (200) from an acidophilic bacterium has been reported. New naturally occurring acetylenic thiophen derivatives have been isolated from Berkheya and Cullumia species and from Chrysanthemum macrotum. Several naturally occurring acetylenic thiophens have been synthesized. ... 

Benzo[b]thiophene-2 -indole indigo, 4, 910 Benzo[b]thiophene-2,3-quinone reactions, 4, 824... 

Benzo[b]thiophene-2,3-quinone, 5-chloro-oxidation, 4, 824 Benzothiophenes, 4, 863-934 biological activity, 4, 911-913 intramolecular acylation, 4, 761 mass spectrometry, 4, 739 metabolism, 1, 242 phosphorescence, 4, 16 reactivity, 4, 741-861 spectroscopy, 4, 713-740 structure, 4, 713-740 substituents reactivity, 4, 796-839... 

The detailed structure of caldariellaquinone (12), a unique benzo[6]thiophen-4,7-quinone from Caldariella acidophila, has been elucidated. Feeding experiments with C-labelled acetate helped to define the nature and biosynthetic origin of the C30 isoprenoid chain. 

Benzo[6]thiophene-2,3-quinones are reported to undergo several interesting transformations. Oxidation of 5-chIorobenzo[6]thiophene-2,3-quinone with H202 in the presence of ammonia gives 5-chloro-l,2-benzisothiazole-3-carboxamide (Scheme 157) (70AHC(11)177). 

The UV spectra of benzo[6]thiophene-4,7-quinone and its 5-hydroxy derivative have been compared with those of their oxygen and selenium analogs.195... 

Benzo[6]thiophene-2,3-quinone 2-oxime 3-thiosemicarbazone forms asymmetric complexes with nickel and palladium.220... 

Vinylbenzo[6]thiophene undergoes Diels-Alder reactions with benzyne,468 maleic anhydride,469 benzo[6]thiophene-1,1-dioxide,469 p-benzoquinone, and various 1,4-naphthaquinones.469,470 With quinones, the product depends on the reaction conditions. For... 

Di(phenylethynyl)-2,3-dihydrobenzo[6]thiophene-2,3-diol (165) is obtained on treating benzo[6]thiophene-2,3-quinone with lithium phenylacetylide. It is converted into 2,3-di(phenylethynyl)benzo[6]-thiophene on treatment with stannous chloride.472... 

The usual procedure for the preparation of benzo[6]thiophene- 2,3-quinones, which involves acidic hydrolysis of an anil obtained from a thioindoxyl and an aromatic nitroso compound (usually p-nitroso-iV,iV-dimethylaniline), has been used to prepare 5-methyl-,625 5-chloro-,117 and 5- and 6-nitrobenzo[h]thiophene-2,3-quinone.626... 

On treatment with base, the 3-p-tosylhydrazone of benzo[6]thio-phene-2,3-quinone affords 3 - diazobenzo[6]thiophen - 2 - one (259) which reacts with triaminophosphines to give the o-quinone triamino-phosphazines (260 NR2 = NMe2, morpholino, or piperidino),627 and with phenols to give azo dyes.628... 

The iV-methyl nitrone (270) is obtained by reaction of benzo[6]-thiophene-2,3-quinone 3-oxime with diazomethane, or by treating the parent quinone with iV-methylhydroxylamine.632 With O-methyl-hydroxylamine, benzo[6]thiophene-2,3-quinone affords 271.632... 

Carbethoxycyanomethyl)benzo[6]thiophene - 4,5 - quinone (273 R = R = H)497 and its 3-bromo152 and 2-carboxy497 derivatives may be prepared also by reduction of the corresponding 5-hydroxy-4-nitroso(or 4-nitro)benzo[6]thiophene with Raney nickel and hydrazine in ethanol, to give an unstable 4-amino-5-hydroxybenzo[fr]thiophene, which is oxidized directly in situ by ferricyanide in the presence of base and ethyl cyanoacetate. Under these conditions, condensation of the resulting quinone occurs before its decomposition. 

Carbethoxycyanomethyl)benzo[6]thiophene-4,5-quinones readily afford phenazines.497... 

Attempts to prepare 7-(cyanomethyl)benzo[6]thiophene-4,5-quin -ones by elimination of the carbethoxy group from a corresponding 7-(carbethoxycyanomethyl) compound have failed, except in one case 273 (R = H, R = Br) affords 2-bromo-7-(cyanomethyl)benzo[6]thio-phene-4,5-quinone on treatment with Triton B (benzyltrimethyl-ammonium hydroxide).497... 

On heating a solution of 3,4-dibromo-4-nitro-4,5-dihydrobenzo[6]-thiophen-5-one (Section VI, 1,4) in benzene, 3-bromobenzo[6]thio-phene-4,5-quinone is obtained.497 The unstable product readily condenses with ethyl cyanoacetate in the presence of base to give 3-bromo-7-(carbethoxy cyanomethyl)benzo[6]thiophene-4,5-quinone. The 4-bromo-4-nitro-4,5-dihydrobenzo[6]thiophen-5-ones prepared by nitration of 3,4-dibromo-,152,421 4,6-dibromo-,152 3,4,6-tri-bromo-,421 and 2,3,4,6-tetrabromo-5-hydroxybenzo[6]thiophene421 decompose similarly to the corresponding 4,5-quinones on being boiled in benzene. 

Ketones (293a),682 (293b),077 and (293c),677 prepared by interaction of benzo[6]thiophene-2,3-quinone and the appropriate oi-haloketone, are cyclized by benzoyl chloride and concentrated sulfuric acid to the... 

Vinylbenzo[6]thiophene 90 reacted with benzoquinone to give a fully aromatized 1 1 cycloadduct 151 as result of a Diels-Alder reaction followed by dehydrogenation by excess quinone. Isolation of a dihydro derivative 152 was possible using a weaker solution of 3-vinylbenzo[b] thiophene, whereas a further excess of the vinyl compound and a very short reaction time afforded the terahydro derivative 153 (79AJC145). On the other hand, primary Diels-Alder adducts are isolated from 1-(3-benzo[6]thiophene)cyclohex-1 -ene and 1 -(3-benzo[fc]thiophene)-3,4-dihydronaphthalene on reaction with MA (50JA571). 

The terpenoid benzo[fc]thiophen-4,7-quinone (3) has been isolated10 from the extremely thermophilic and acidophilic bacterium Caldariella acidophila. Desulphurization with Raney nickel gave the ethyl, C30-alkyl disubstituted 1,4-benzoquinone (4). The compound (3) may be involved in the electron-transport system of the organism. 

The preparation of benzo-l,2-dithiete (264) had been claimed by oxidation of 1,2-benzenedithiol (25JIC318). However, later work has shown that the reaction product was probably a polymeric mixture (61JOC4782). Subsequently, compound 265 was irradiated to give a mixture of CO, sulfur, and dithiin and thiophene derivatives, which could, at least in part, be explained by the formation of 266 (72JHC707). Results of the thermolysis of 267 were also rationalized in terms of the intermediacy of o-dithiobenzo-quinone (the tautomer of 264) (78JOC2084). 

A tetra- and pentacyclic quinone were prepared from thioisatin. Reaction with 2-bromoacetylthiophene yielded the benzo analog of 161, and from 2-bromoacetylbenzo[h]thiophene the dibenzo analog of 162 was obtained in very low yield (53MI2). 

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