Synthesis and some transformations of benzo[b]thiophene derivatives

A number of 3-chloro-2-chlorocarbonylbenzo [b] thiophenes with alkyl substituants in various positions of the benzene ring were synthesized by arylation of acrylic acid with the corresponding alkyl-substituted iodobenzenes under the influence of catalytic amounts of palladium acetate and subsequent oxidation of the resulting arylacrylic acids with thionyl chloride. Replacement of the pyridine added in the oxidation reaction by triethylbenzylammonium chloride led to substantial increases in the yields of the desired products. The possibility of conversion of the resulting benzo [b] thiophene derivatives to thiophene ring-unsubstituted benzo[b] thiophenes was shown in the case of 3-chloro-2-chlorocarbonylbenzo [b] thiophene as a result of successive saponification of the 2-chlorocarbonyl group, decarboxylation, and dechlorination.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1618–1622, December, 1982.     

Indolobenzothiophenes. 2. Some electrophilic substitution reactions of indolo[6,5-d]benzo[b]thiophene

The behavior of indolo[6,5-d]benzo[b]thiophene in acylation, Mannich, Vilsmeier, and diazo coupling reactions was investigated. Acylation with acetic anhydride proceeds unambiguously at the pyrrole nitrogen atom to give 1-acetylindolo[6,5-d] benzo[b]thiophene. The products of formylation are 2- and 3-formylindolo-[6,5-d] benzo[b]thiophenes. In the case of the Mannich reaction and diazo coupling substitution takes place in the 3 position of the indolobenzo[b]thiophene ring. The structures of the products obtained were proved by spectroscopic methods.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 211–214, February, 1981.     

Synthesis of derivatives of 2-acylamino-7-oxybenzo[b]thiophene. Bromination and nitration

Bromination of 2-acylamino-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]-thiophenes has been studied. This reaction affords 2-acylamino-6,6-dibromo-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene, which on dehydrobro-mination gives 6-bromo-7-oxybenzo[b]thiophene derivatives. The 4,6-dibromo- and 4,6-dinitro-7-oxybenzo[b]thiophenes were also obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 460–462, April, 1987.     

An investigation of condensed heteroaromatic systems including a thiophene ring

The influence of the temperature, of the natures of the initiator and of the initial compound, and of the concentrations of the reactants on the process and nature of the transformations of 2- and 3-alkyl-, 2- and 3-formyl-, and 2- and 3-hydroxymethylbenzo[b]thiophenes under conditions of liquid-phase oxidation with oxygen in the presence of cobalt acetate in acetic acid has been studied. According to their relative ease of oxidation, the homologs and derivatives of benzo[b]thiophene, thiophene, and benzene can be arranged in the following sequence: 3-methylbenzo[b]thiophene > 2-methylbenzo[b]thiophene > 2-methylthiophene > toluene > 3-methylbenzo[b]thiophene dioxide > 2-methylbenzo[b]thiophene dioxide; benzaldehyde > benzo[b]thiophene-3-carbaldehyde > thiophene-2-carbaldehyde > benzo[b]-thiophene-2-carbaldehyde; 3-hydroxymethylbenzo[b]thiophene > 2-hydroxymethylbenzo[b]-thiophene > benzyl alcohol > 2-hydroxymethylthiophene. The liquid-phase oxidation of alkyl-substituted benzo[b]thiophenes can be used to obtain aldehydes, ketones, and acids of the benzo[b]thiophene series.For Communication XXIV, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1026–1033, August, 1973.     

Thiophene chemistry—XXII : Some reactions of benzo[b]thiophene-2(3H)one

Benzo[b]thiophene-2(3H)one has been prepared from 2-t-butoxybenzo[b]thiophene by dealkylation. Alkylation of sodium, thallium and tetrabutylammonium salts of benzo[b]thiophene-2(3H)one produces both C- and O-alkylation along with products due to ring-opening. At elevated temperatures benzo[b]thiophene-2(3H)one reacts with HMPA (hexamethylphosphorictriamide) to give 2-dimethylaminobenzo[b]thiophene. Other 2-aminobenzo[b]thiophenes are produced by refluxing benzo[b]thiophene-2(3H)one in HMPA in the presence of excess of the corresponding amine.     

2-取代苯并噻吩类化合物合成研究进展

2-取代苯并噻吩广泛的存在于天然产物中,独特的分子结构使其表现出了较高的药理和生物活性,常被用于药物化学和材料化学中。已有多种具有苯并噻吩骨架药物用于临床,故具有极高的研究价值。本文结合国内外学者对这方面的相关研究,重点对2-苯基苯并噻吩、2-酰基苯并噻吩和2-氨基苯并噻吩类化合物的合成方法进行了综述。     

Synthesis of benzo[b]thiophenes by cyclization of arylketene dithioacetal monoxides under pummerer-like conditions

Treatment of arylketene bis(methylthio)acetal monoxide with trifluoromethanesulfonic anhydride leads to ring-closure to afford 2-methylthiobenzo[b]thiophene in high yield. The reaction is useful for synthesizing multisubstituted benzo[b]thiophenes.     

A new route to annulated oligothiophenes

[reaction: see text] A new convenient method for the construction of thiophene-annulated thieno[2,3-b]thiophenes has been proposed. The key step of the method is ring closure of 10H-bisthienodithiocin-10-one by strong bases. The syntheses of two previously unknown annulated oligothiophenes, thieno[2,3-b]thieno[3',2':4,5]thieno[3,2-d]thiophene (1a) and thieno[3,2-b]thieno[2',3':4,5]thieno[3,2-d]thiophene (1b), have been described to illustrate the success of the method.     

Synthesis and structure of derivatives of 7-oxo-4,5,6,7-tetrahydrobenzo[b]-thiophene and 7-hydroxybenzo[b]thiophene

The oxidation of 2-acylamino-3-ethoxycarbonyl-4,5,6,7-tetrahydrobenzo[b]thiophenes gave the corresponding 7-oxotetrahydrobenzo[b]thiophenes and some of the transformations of these compounds were studied. These compounds were used for the synthesis of 3-ethoxycarbonyl-6-bromo-7-hydroxybenzo[b]thiophene. The structures of the compounds prepared were established by chemical and spectral methods.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1626–1629, December, 1984.     

Synthesis of 3,4-Biheterylthieno[2,3-b]-thiophenes. Part I: Synthesis of 3,4-Bi(1′,3′,4′-thiadiazolyl-, s-triazolyl-,1′,3′,4′-thiadiazinyl-, 1′,3′,4′-triazinyl-, thiazolyl-, 1′,3′-thiazinyl- and primidinyl)-thieno[2,3-b]thiophenes

3,4-Diamino-2,5-dicarbethoxythieno[2,3-b]thiophene ( 1 ) was allowed to react with NaNO 2 and active methylenes to afford the corresponding azo compounds 2a-c . Hydrazonyl chloride 2a was treated with carbon disulfide, phenyl isothiocyanate, benzonitrile, benzyl cyanide, malononitrile, benzalaniline, ethyl mercaptoacetate, and ethyl glycinate to give 1,3,4-thiadiazolyl-, s-triazolyl-, 1,3,4-thiadiazinyl-, 1,3,4-triazinylthieno[2,3-b]thiophenes 3-6 respectively. The reaction of 2b,c with urea, thiourea, and guanidine afforded pyrimidinyl- and thiazinylazothieno [2,3-b]thiophenes 7-10 respectively. Bithiazolylthieno[2,3-b]thiophenes 11 and 13 were synthesized by treating compound 1 with CS 2 along with halo compounds. The addition of S,S-, N,S-, and N,O-acetals to the Schiff base 14 afforded compounds 15-17 respectively.     

Condensed pyridine bases. A new approach to the synthesis of 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethylthieno[2,3-b]thiophene. Synthesis of new derivatives of benzothieno[2,3-c]pyrylium and thieno[2′,3′:5,4]thieno-[2,3-c]pyrylium and pyridine bases

A new method is proposed for the production of substituted 3-phenacylbenzo[b]thiophenes by the intramolecular cyclization of 1-phenyl-4-phenylthio-1,3-butanediones in polyphosphoric acid. The analogous cyclization of 1-phenyl-4-(5-ethyl-2-thienylthio)-1,3-butanedione leads to 3-phenacyl-5-ethylthieno[2,3-b]thiophene. The acylation of substituted 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethylthieno[2,3-b]thiophene by the anhydrides of aliphatic acids in the presence of perchloric acid leads to 1-alkyl-3-phenylbenzothieno[2,3-c]pyrylium perchlorates and 2-ethyl-5-phenyl-7-methylthieno[2′,3′:5,4]thieno[2,3-c]pyrylium perchlorate. The action of ammonium acetate on the obtained salts gives the corresponding pyridine bases. L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1335–1339, October, 1998.     

Palladium-catalyzed C-S coupling: access to thioethers, benzo[b]thiophenes, and thieno[3,2-b]thiophenes

The first C-S bond formation/cross-coupling/cyclization domino reaction using thiourea as a cheap and easy to handle dihydrosulfide surrogate has been developed. Structurally important biarylthioether, benzo[b]thiophenes, and thieno[3,2-b]thiophene scaffolds are provided in high yield.     

Bacterial dioxygenase- and monooxygenase-catalysed sulfoxidation of benzo[b]thiophenes

Asymmetric heteroatom oxidation of benzo[b]thiophenes to yield the corresponding sulfoxides was catalysed by toluene dioxygenase (TDO), naphthalene dioxygenase (NDO) and styrene monooxygenase (SMO) enzymes present in P. putida mutant and E. coli recombinant whole cells. TDO-catalysed oxidation yielded the relatively unstable benzo[b]thiophene sulfoxide; its dimerization, followed by dehydrogenation, resulted in the isolation of stable tetracyclic sulfoxides as minor products with cis-dihydrodiols being the dominant metabolites. SMO mainly catalysed the formation of enantioenriched benzo[b]thiophene sulfoxide and 2-methyl benzo[b]thiophene sulfoxides which racemized at ambient temperature. The barriers to pyramidal sulfur inversion of 2- and 3-methyl benzo[b]thiophene sulfoxide metabolites, obtained using TDO and NDO as biocatalysts, were found to be ca.: 25-27 kcal mol(-1). The absolute configurations of the benzo[b]thiophene sulfoxides were determined by ECD spectroscopy, X-ray crystallography and stereochemical correlation. A site-directed mutant E. coli strain containing an engineered form of NDO, was found to change the regioselectivity toward preferential oxidation of the thiophene ring rather than the benzene ring.     

两种非对称芳基二噻吩并[2,3-b:3',2'-d]噻吩的合成与光谱特性

合成了两种非对称芳基取代的并三噻吩化合物.以2-溴-5-三甲基硅-二噻吩并[2,3-b:3',2'-d]噻吩为原料,经脱除四甲基硅烷(TMS)和Suzuki偶联两步反应制备了2-噻吩基二噻吩并[2,3-b:3',2'-d]噻吩,总产率为67.4%;以2-苯基二噻吩并[2,3-b:3',2'-d]噻吩为原料,经N-溴代琥...     

Photochromic oligothienoacene derivatives with photo-switchable luminescence properties and computational studies

Photochromic thieno[3,2-b]thiophenes and dithieno[3,2-b:2',3'-d]thiophene with photo-switchable luminescence properties have been synthesized using a Suzuki cross-coupling reaction; their electronic structures, and photochromic and luminescence behaviour have also been studied.     

Synthesis of 2,3-disubstituted benzo[b]thiophenes via palladium-catalyzed coupling and electrophilic cyclization of terminal acetylenes

2,3-Disubstituted benzo[b]thiophenes have been prepared in excellent yields via coupling of terminal acetylenes with commercially available o-iodothioanisole in the presence of a palladium catalyst and subsequent electrophilic cyclization of the resulting o-(1-alkynyl)thioanisole derivatives. I(2), Br(2), NBS, p-O(2)NC(6)H(4)SCl, and PhSeCl have been utilized as electrophiles. Aryl-, vinyl-, and alkyl-substituted terminal acetylenes undergo this coupling and cyclization to produce excellent yields of benzo[b]thiophenes. (Trimethylsilyl)acetylene also undergoes this coupling/cyclization process with I(2), NBS, and the sulfur and selenium electrophiles to afford the corresponding 2-(trimethylsilyl)benzo[b]thiophenes. However, cyclization of the silyl-containing thioanisole using Br(2) affords 2,3-dibromobenzo[b]thiophene.     

Palladium-catalyzed domino C-S coupling/carbonylation reactions: an efficient synthesis of 2-carbonylbenzo[b]thiophene derivatives

A facile and selective palladium-catalyzed domino procedure has been developed for the preparation of 2-carbonylbenzo[b]thiophene derivatives from 2-gem-dihalovinylthiophenols. This protocol involves intramolecular C-S coupling/intermolecular carbonylation cascade sequences and allows access to various highly functionalized benzo[b]thiophenes in moderate yields.     

Thiophenes as traps for benzyne. 3. Diaryl sulfides and the role of dipolar intermediates

The reactions of seven thiophenes with benzyne generated from diphenyliodonium-2-carboxylate (DPIC) under a standard set of conditions led among other products to the formation of alpha- and beta-naphthyl phenyl sulfides 2a and 2b from thiophene (1a) and of 2c and 2d from 2-methylthiophene (1b). Dithienyl sulfides 4a-f were produced from the halothiophenes 1c-g. The structures of the naphthyl sulfides were proven by comparison with authentic samples of 2a-f, thus eliminating one of two possible mechanisms of formation. The remaining mechanism involves [4+2]-cycloaddition of benzyne to thiophene or to an S-phenylthiophenium ylide 10 to give the dipolar 2:1 benzyne/thiophene adduct 8 followed by ring-opening. Stevens-like rearrangements of 11, formed from 10 by proton transfer, may also explain the origin of arylated thiophenes such as 12 and 3 found in some reactions of benzynes with thiophene.     

Synthesis and structure of derivatives of 7-aminobenzo[b]thiophene

Oximes of 2-acylamino-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophenes have been prepared. A method for the synthesis of derivatives of 7-aminobenzo[b]thiophene is proposed and the hydrolysis of the compounds prepared has been studied.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1178–1180, September, 1986.     

Synthesis and Study of the Anodic Behavior of 1,3,4,6-Tetraaryl-2λ 4 δ 2 -thieno[3,4-c]thiophenes

Two heterocyclic compounds based on the thieno[3,4-c]thiophene structure with four aryl substituents were prepared and their behavior in electrooxidation studied. These tetraarylthieno[3,4-c]thiophenes were synthesized in three steps starting from 1,3-dibenzoylmethane in the case of 1,3,4,6-tetraphenyl-2 u 4 i 2 -thieno[3,4-c]thiophene 1a and from 1,3-bis(4'-methoxyphenyl)propane-1,3-dione in the case of 1,3,4,6-tetrakis(4'-methoxyphenyl)-2 u 4 i 2 -thieno[3,4-c]thiophene 1b , a new compound. Both cyclic and hydrodynamic voltamperometric analyses indicate two reversible one-electron oxidation stages for compound 1b , while for compound 1a only the first stage is reversible. The preparative electrooxidation of the two compounds results in the opening of one thiophene ring giving rise to n -keto-thioketones.