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

A series of 12H-[1]benzo[4 '',5 '']thieno[2 '',3 '':4',5']thieno[2',3':4,5]thieno[3,2-b]indoles were efficiently prepared in three steps starting from available benzo[b]thieno[2,3-d]thiophen-3(2H)ones. These fused ketones were treated with the Vilsmeier reagent and hydroxylamine hydrochloride to give the corresponding 3-chlorobenzo[b]thieno[2,3-d]thiophene-2-carbonitriles, which then reacted with methyl sulfanylacetate 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 conversion of these fused 3-aminothiophene-2-carboxylates into the corresponding 3-aminothiophene intermediates, which acted as synthetic equivalents of thiophen3(2H)-ones, followed by their acid-promoted reaction with arylhydrazines, in accordance with the Fischer indolization procedure.

Automated summary

A series of N,S-heterohexacenes were efficiently synthesized in three steps from available starting materials, utilizing various reagents and methods, ultimately yielding the desired products.