An Effective Route toward Dithieno[3,2-b:2',3'-d]thiophene-based Hexaheteroacenes

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.

Metal-free and regiospecific synthesis of 3-arylindoles

A microwave-assisted acid and base co-catalyzed strategy shows high efficiency in the synthesis of 3-arylindoles through tandem nucleophilic ring-opening and Fischer indolization of aryloxiranecarbonitriles and arylhydrazine hydrochlorides.