Thio phene

Supplement (combined with Volumes XVIII and XIX) XVII, 2nd 1934 2359-3031 Hydroxy compounds Furfuryl alcohol, 112. Carbonyl compounds Butyrolactone, 234. Furfural, 272. 2-Aoetyl-thio-phene, 287. Xanfhone, 366. Succinic anhydride, 404. Phthalio anhydride, 469. 

Analogous compounds derived by fusion of a benzene ring to a pyrrole furan or thio phene nucleus are called indole benzofuran and benzothiophene... 

Halogens react with benzo[6]furan by an addition-elimination mechanism to give 2- and 3-substituted products (76JCS(P2)266). Treatment of benzo[6]thiophene with chlorine or bromine in acetic acid gives predominantly 3-substituted products (71JCS(B)79). 2,2,3,3,4,5,6,7-Octachloro-2,3-dihydrobenzothiophene is obtained when benzo[6]thio-phene is treated with chlorine in the presence of 1 mole of iodine (80JOC2l5l). 

The base-catalyzed tautomerization of 4-methyl-4//-cyclopenta[c]thio-phenes 193 to the corresponding 6-methyl derivative 194 has been investigated quantitatively. Second-order rate constants and activation parameters have been determined (75CS42). 

Thus, many polymers with different conductivity were synthesized. To cite a few, these are polythiophene [158], 3-methylthiophene [159], polymers of 3-thiophene-acetic acid and methyl 3-thiophene-acetate [160], poly(2,5-thienylenevinylene) [161], poly(benzo[h]-thiophene) [162], poly(naphto[2,3-c]thio-phene) [163], poly(dithieno[3,2-h 2, 3 -fii]-thiophene) [164], poly(3- -hexylthiophene)... 

The linear prodnct is obvionsly formed according to the seqnence 2,5-di(thiocyano)thio-phene potassinm 2-mercaptido-5-thiacyanonothiophene —> tristhiomaleic anhydride thio-phene-2,5-disulfenyl biradical (the diradical valence tantomer) —> the depicted (Scheme 2.18) linear polymer in which the thiophene rings are connected by dusulfide bridges. It was recently confirmed that tristhiomaleic anhydride is nnstable and polymerizes just at the moment of its formation (see Paulssen et al. 2000, Ref. 15 therein). 

Friedel-Crafts acylation of dibenzothiophene with succinic anhydride is known to occur in the 2-position, yielding y-oxo-2-dibenzothiophene-but3Tic acid (135a). Subsequent Wolff-Kishner reduction and internal cyclization yields 7-keto-7,8,9,10-tetrahydrobenzo[6]naphtho[2,3-d]thio-phene (136a). - This reaction has been extended to 4-methyldibenzo-... 

Witter, D.J., Belvedere, S., Chen, L., Secrist, J.P., Mosley, R.T. and Miller, T.A. (2007) Benzo[b]thio phene-based histone deacetylase inhibitors. Bioorganic el Medicinal Chemistry Letters, 17,4562-4567. 

V. P. Litvinov, I. P. Konyaeva, and Ya. L. Gol dfarb, Condensed heteroaromatic systems including the thiophene ring. 28. Metallation of selenopheno[3,2-6]thio-phene. Izv. Akad. Nauk SSSR, Ser. Khim. 1575 (1974). 

The protonation of 185 and 186 with trifluoroacetic acid (TFA) gave 4-(/i t/-butylthio)-3,6-diphenyl- 193 and 4-(ter1-butylthio)-3,6-di(2-thienyl)thieno[3,4-f]thiophene-l(3//)-thione 194 (Scheme 18). The treatment of 193 with sodium hydride and then isopropyl iodide led to 4-(/i< t/-butylthio)-3,6-diphenyl-l-(isopropylthio)thieno[3,4-f]thio-phene 195 by the regeneration of the thieno[3,4-f]thiophene ring system, thus making possible the synthesis of other alkylthio-substituted thieno[3,4-(r]thiophene derivatives. When the reaction of 185 with TFA was carried out... 

In investigations by the authors (4) and Li et al. (5), polythieno[3,2-b]thio-phenes, (II) and (III), respectively, were prepared and used as semiconductors and in electronics as organic thin-film transistors. 

Fig. 29. Correlation between relative hydrogenolysis reactivity and the electron densities on sulfur. ( ) Reaction conditions 300°C, 71 atm, sulfided CoO-Mo03/A1203 (5). (1) DBT (2) benzo[fo]naphtho[2,3-4]thiophene (3) 7,8,9,10-tetrahydrobenzo[b]naphtho[2,3-rf]thio-phene (4) 5b,6,ll,lla-tetrahydrobenzo[fc]naphtho[2,3-d]thiophene. (O) Reaction conditions 450°C, 1 atm, sulfided CoO-Mo03/A1203(6). (5) Thiophene (6) tetrahydrothiophene (7) benzothiophene (8) 2,3-dihydrobenzothiophene. ( + ) Reaction conditions 360°C, 2.9 MPa, sulfided NiO-Mo03/Al203(3). (9) 1-Methyl-DBT (10) 2- or 3-methyl-DBT (11) 4-methyl-DBT (12) 4,6-dimethyl-DBT. (A) Reaction conditions 300°C, 102 atm, sulfided CoO-Mo03/ Al203(8). (13) 2,8-Dimethyl-DBT (14) 3,7-dimethyl-DBT (15) 4-methyl-DBT (16) 4,6-di-methyl-DBT. Reprinted with permission from Ref. 38, Ma et al. (1995). Copyright 1995 American Chemical Society.

Benzofuran is prepared in semicommercial amounts. Its manufacture from o-nitroethylbenzene (as well as that of indole and benzo[fc]thio-phene) has been considered.104 Alkylbenzofurans are prepared in the pharmaceutical industry as basic products.105... 

This question, previously reviewed,1,2 still gives rise to a fair amount of research. Benzofuran (1) and some of its methylated derivatives (5-methylbenzofuran, 2-methylbenzofuran, and dimethylbenzofurans) are found in various products of coal carbonization in the gases from coke manufacture,106 in the naphthalenic107,108 (with benzo[6]thio-phene) and the phenolic109 fractions of the tar, and in the products of low-temperature17 and high-temperature110-112 carbonization. 

JOC4257). In the reaction of monobromo compounds (486) and (487) with piperidine, the major products are normal ones with 3-bromobenzo[6]thiophene (487) a small amount of the cine substituted product (489) is formed (Scheme 166). 2,3-Dibromobenzo[f>]thio-phene (488) initially gives the 2-piperidino-3-bromo derivative (490) at 106 °C, which is debrominated to (489) at 180 °C. This result suggests that the small amount of (489) from (487) might arise through a transbromination-debromination sequence (73JOC1365). 

Thiophene is known to be oxidized to 2,2 - and 2,3 -dithienyls in the presence of palladium salts (78DOK(241)148). The coupling may proceed through the 7r,o--intermediate (507). Finally, the PdCl2-assisted conversion of 3-bromobenzo[6]thiophene to 3-deuteriobenzo[6]thio-phene by NaBD4 has been reported (73TL4699). 

During thermal dimerization of thiophene dioxides, one molecule functions as the 2ir-component and the other as the 477-component (B-67MI31401, 70AHC(11)177>. The initially formed dimer (513) eliminates a molecule of S02 to form the dihydrobenzo[6]thiophene (514) when R is chlorine, aromatization occurs by loss of HC1. Pyrolysis of benzo[6]thio-phene 1,1-dioxide at 185-200 °C similarly leads to (515). 

The Michael reaction was shown to proceed rapidly to produce a dihydrobenzo[6]thio-phene-3-acetic acid derivative (81) in excellent yield when the cinnamic acid (80) was treated with dry sodium methoxide in methanol (50JA2209). 

In the cyclization of arylthioacetones under strong acid conditions a partial migration of the methyl group can occur, to produce mixtures of both the 2- and 3-methylbenzo[6 ]thio-phenes. For example, cyclization of (109 R = H) in PPA at 160-180°C gave a mixture composed of about 82-85% (110) and 15-18% of (111). Similar results were obtained when R in (109) was alkyl, but not when R was chlorine or bromine (68JCS(C)2733). 

Ring-closure techniques are more commonly used to obtain 3-alkylbenzo[6]thiophenes. Thus, acid-catalyzed cyclization of arylthio methyl ketones gives the 3-alkylbenzo[6]thio-phenes in good yield, with little rearrangement (equation 3). Formation of the 3-aryl-benzo[6]thiophenes by this approach is complicated, however, by rearrangement to the 2-isomer (Section 3.15.2.3.2). 3-Methylbenzo[f> Jthiophene is also obtained by decarboxylation of the corresponding 2-carboxylic acid (equation 4), readily available from ar-mer-captocinnamic acids (Section 3.15.2.1.1). 

Thiophenethiols, like hydroxythiophenes, are unstable and tend to polymerize. Thio-phene-3-thiol was available as a by-product of the Socony-Vacuum process (52HC(3)l), and consequently a large number of 3-alkylthiothiophenes, made by addition of the thiol to... 

The 7H NMR spectra of several benzo [6]thiophene-1,1 -dioxides show the following features (relative to the unoxidized benzo[6]thio-phenes) H-2 and H-4 are consistently shielded, H-5 and H-6 are consistently deshielded, H-3 is little affected, and the changes in H-7 are small and of variable sign.88 The loss of aromaticity of the thiophene ring on oxidation of the sulfur atom leads to a more localized... 

IR spectroscopy has been used to show that 2-aminobenzo[6]thio-phenes normally exist solely as the amino tautomer,112-114 and that 2 ii2,ii3 an(j 3-hydroxybenzo[6]thiophenes117,147 exist solely as the keto tautomers, except that compounds with an adjacent carbonyl-containing group exist mainly as the enols.109,116,147> 148 3-Hydroxy-2-nitrobenzo[6]thiophene-l,1-dioxide exists as a mixture of the keto and enol forms.149... 

The IR spectra of cis- and nms-octahydrobenzo[6]thiophene have been recorded.27 IR data have been given for several benzo[6]thio-phene sulfonic acids and their derivatives.86... 

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