Synthesis of anthra[b]thiophenes and benzo[b]naphtho[d]thiophenes

All isomers of the parent anthra[b]thiophenes and benzo[b]naphtho[d]thiophenes, namely anthra[2,3-b]thio-phene, anthra[2,1-b]thiophene, anthra[1,2-b]thiophene, benzo[b]naphtho[2,3-d]thiophene, benzo[b]naphtho[2,1-d]thiophene and benzo[b]naphtho[1,2-d]thiophene were synthesized using a new procedure.     

Synthesis of phenanthro[b]thiophenes

All isomers of the parent phenanthro[b]thiophenes, namely, phenanthro[1,2-b]thiophene, phenanthro-[2,1-b]thiophene, phenanthro[2,3-b]thiophene, phenanthro[3,4-b]thiophene, phenanthro[3,4-b]thiophene, phenanthro[4,3-b]thiophene and phenanthro[9,10-b]thiophene have been synthesized.     

Synthesis of triphenyleno[b]thiophenes

The synthesis of all the isomers of triphenyleno[b]thiophenes namely, triphenyleno[l,2-b]thiophene, triphenyleno[2,1-b]thiophene and triphenyleno[2,3-b]thiophene is described.     

Synthesis of pyreno[b]thiophenes

The synthesis of all the isomers of pyreno[b]thiophene namely, pyreno[1,2-b]thiophene, pyreno[2,1-b]thiophene and pyreno[4,5-b]thiophene is described. Their spectral characteristics are also discussed.     

Synthesis of 2-alkylbenzo[b]thiophenes

The treatment of 3-chlorobenzo[b]thiophene-2-carbonyl chloride with diethyl- or dipropylcadmium leads to the corresponding ketones, and the treatment of the acid itself with butyl- or propyllithium leads to ketones in admixture with the tertiary alcohol. The subsequent reduction of the ketones obtained with hydrazine hydrate and hydriodic acid has given 2-alkylbenzo[b]thiophenes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 33–35, January, 1984.     

Synthesis of isomeric indolobenzo[b]thiophenes

Indolo[6,5-d]benzo[b]thiophene, indolo[4,5-d]benzo[b]thiophene, indolo[5,6-d]benzo-[b]thiophene, and indolo[5,4-d]benzo[b]thiophene were obtained from the 2- and 3-dibenzothienylhydrazones by means of the Fischer reaction. The structures of the compounds obtained were proved by their PMR, IR, UV, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 203–208, February, 1980.     

Synthesis of benzo[b]phenanthro[d]thiophenes

The synthesis of benzo[b]phenanthro[1,2-d]thiphene ( 1 ), benzo[b]phenanthro[4,3-d]thiophene ( 2 ), benzo-[b]phenanthro[2,1-d]thiophene ( 3 ) and benzo[b]phenanthro[3,4-d]thiophene ( 4 ) from appropriately substituted olefines by photochemical cyclodehydrogenation is described. The photolysis of olefin 9 gave a mixture of 4 and anthra[1,2-b]benzo[d]thiophene ( 5 ).     

Synthesis of 6-phenylthiobenzo[b]thiophenes

A method of synthesizing 2-acetylamino-7-hydroxy-6-phenylthio-3-carbethoxybenzo[b]thiophenes from 6-phenylthio-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophenes has been developed. A method is also proposed for synthesis of 7-phenylthiobenzothieno[2,3-d]pyrimidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 534–536, April, 1991.     

The synthesis of benzo[b]phenanthro[d]thiophenes and anthra[b]benzo[d]thiophenes

The synthesis of benzo[b]phenanthro[2, 3-d]thiophene ( 5 ), benzo[b]phenanthro[4, 3-d]thiophene ( 6 ), benzo-[b]phenanthro[2, 1-d]thiophene ( 9 ), benzo[b]phenanthro[3, 2-d]thiophene ( 14a ), anthra[1, 2-b]benzo[d]thiophene ( 24 ), anthra[2, 3-b]benzo[d]thiophene ( 29 ) and anthra[2, 1-b]benzo[d]thiophene ( 30 ) is described as well as the preparation of 13-methylbenzo[b]phenanthro[3, 2-d]thiophene ( 14b ).     

Synthesis of 3-hetaryl-4,5,6,7-tetrahydrobenzo[b]thiophenes

A novel efficient synthesis of 3-hetaryl-4,5,6,7-tetrahydrobenzo[b]thiophenes was achieved by the cyclocondensation of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[6]thiophene-3-carboxylate with selected o-substituted aromatic amines or with alifatic, aromatic and heterocyclic acid hydrazides in the presence of polyphosphoric acid.     

Indolobenzothiophenes. 3. Synthesis and properties of indolo[7,6-d]- and indolo[6,7-d]benzo[b]thiophenes

Precursors of a new heterocyclic system, indolo[7,6-d]- and indolo[6,7-d]benzo[b] thiophenes, have been synthesized using the Fischer reaction. Some physicochemical characteristics of the compounds are reported.Communication 2, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 236–240, February, 1985.     

Synthesis of regioselectively functionalized benzo[b]thiophenes by combined ortho-lithiation-halocyclization strategies

An efficient synthesis of 3-halo-7-oxygen-functionalized benzo[b]thiophenes bearing different substituents at C-2 has been developed from N,N-diethyl O-3-halophenylcarbamates. The key steps are an ortho-lithiation reaction, which gives rise to 3-halo-2-sulfanylphenol derivatives, and a electrophilic cyclization. The subsequent functionalization of the prepared halobenzothiophenes allows the access of a wide variety of 2,3,7-regioselectively functionalized benzo[b]thiophenes in good overall yields.     

Solid-phase synthesis of 2,3-disubstituted benzo[b]thiophenes and benzo[b]selenophenes

A concise and efficient solid-phase synthesis of benzo[b]thiophenes and benzo[b]selenophenes based on a combination of palladium-mediated coupling and iodocyclization protocols has been developed.     

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.     

Toluene dioxygenase-catalyzed cis-dihydroxylation of benzo[b]thiophenes and benzo[b]furans: synthesis of benzo[b]thiophene 2,3-oxide

Enzymatic cis-dihydroxylation of benzo[b]thiophene, benzo[b]furan and several methyl substituted derivatives was found to occur in both the carbocyclic and heterocyclic rings. Relative and absolute configurations and enantiopurities of the resulting dihydrodiols were determined. Hydrogenation of the alkene bond in carbocyclic cis-dihydrodiols and ring-opening epimerization/reduction reactions of heterocyclic cis/trans-dihydrodiols were also studied. The relatively stable heterocyclic dihydrodiols of benzo[b]thiophene and benzo[b]furan showed a strong preference for the trans configuration in aqueous solutions. The 2,3-dihydrodiol metabolite of benzo[b]thiophene was utilized as a precursor in the chemoenzymatic synthesis of the unstable arene oxide, benzo[b]thiophene 2,3-oxide.     

Synthesis of 3-iodobenzo[b]thiophenes via iodocyclization/etherification reaction sequence

An efficient method was developed for the synthesis of benzo[b]thiophene core structure using a two-step, multicomponent reaction resulting in favorable yields. This convergent reaction requires room temperature thus eliminating the harsh reaction conditions usually associated with the synthesis of benzo[b]thiophene ring structures. Used in many drugs that treat conditions such as osteoporosis, asthma, and fungal infections, the benzo[b]thiophene core structure is of extreme importance to medicinal and pharmaceutical research. The key step in this process involves the use of an iodine as a cyclizing agent that acts simultaneously as a catalyst. Alcohols such as alkyl, allyl, propargyl, and benzylic are employed to prepare a diverse library of 3-iodobenzo[b]thiophenes.     

Synthesis of substituted benzo[b]thiophenes by acid-catalyzed cyclization of thiophenylacetals and ketones

Benzo[b]thiophenes substituted at the 3 position with methyl or carboxymethyl and at the 5 position with methyl, methoxy, chloro, bromo and nitro were prepared by cyclization of thiophenyl-acetals and ketones using a suspension of polyphosphoric acid in refluxing chlorobenzene. The overall efficiency of this method is superior to literature procedures because of the lower temperature and the limited amount of PPA used.