Thiophen Analogues of Indole and Related Compounds

Thiophen Analogues of Indole and Related Compounds.—5/f-Thieno[2,3-c]-pyrroles (528) have been prepared by dehydration of iV-oxides, autooxidation of the dihydrothieno[2,3-c]pyrroles, and by dehydrogenation of 

Thieno[2,3-6]indoles (532) have been prepared through the reaction of (533) with phosphorus pentasulphide. The system (532) underwent an interesting Diels-Alder reaction, i.e. to (534), with dimethyl acetylene-dicarboxylate.  

The compounds (535) and (536) have been prepared through the condensation of 3-bromo-3-methyl-2-butanone with 2- and 3-thienylammonium hexachlorostannates in the presence of zinc chloride. Benzo[A]thieno-[3,2- )]indoles (537) have been prepared by reductive cyclization of 2-aryl-3-nitrobenzo[6]thiophens with triethyl phosphite. The parent heterocycle was also obtained from 2-(o-nitrophenyl)benzo[6]thiophen with triethyl phosphite and by heating 3-azido-2-phenyl- or 2-(o-azidophenyl)-benzo[6]-thiophen in diglyme.  

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