An Effective Route to Dithieno[3,2-b:2′,3′-d]thiophene-Based Hexaheteroacenes

Abstract

A series of 12H-benzo[4'',5'']thieno[2'',3'':4',5']thieno[2',3':4,5]thieno[3,2-b]indoles was efficiently prepared in three step starting from available benzo[b]thieno[2,3-d]thiophen-3(2H)-ones. To this end, these fused ketones were treated with the Vilsmeier reagent and hydroxylamine hydrochloride, thus giving 3-chlorobenzo[b]thieno[2,3-d]thiophene-2-carbonitriles, which then reacted with methyl thioglycolate to form methyl 3-aminobenzo[4',5']thieno[2',3':4,5]thieno[3,2-b]thiophene-2-carboxylates in accordance with the Fiesselmann thiophene synthesis protocol. Finally, the desired N,S-heterohexacenes were obtained by the conversion of these fused 3-aminothiophene-2-carboxylates to the corresponding 3-aminothiohene intermediates, which play role of synthetic equivalents of thiophen-3(2H)-ones, followed by their acid-promoted reaction with arylhydrazines in accordance with the Fischer indolization reaction.

A general approach to construct selenopheno[3,2-b]indole-cored molecules using Fischer indolization

“…Previously, in a series of our works, we have suggested a convenient strategy for the construction of various thieno [3,2-b] indoles and thieno [3,2-b]indole-fused molecules based on the Fischer indole synthesis. 25 In the context of this strategy, the thieno [3,2-b]indole fragment of the desired molecule was constructed by Fischer indolization of the thiophen-3(2H)-one arylhydrazone part in intermediate C, formed in situ by the reaction of thiophen-3(2H)-ones A 26-29 or 3-aminothiophenes B [30][31][32][33][34] with arylhydrazines. In turn, substrates A and B were generated respectively from 3-hydroxy-or 3-aminothiophene-2-carboxylates.…”