Thiopyrano[1]benzothiophens. Synthesis of 1-phenyl-3H-thiopyrano-[3,4-b][1]benzothiophen-3-thione 9,9-dioxide and related compounds

Abstract

The title compound (3a) was prepared by the reaction of 2-benzoylbenzo[b]thiophen-3(2H)-one 1,1-dioxide (1) with tetraphosphorus decasulphide, acetonitrile, and sodium hydrogen carbonate. The structure was confirmed by an alternative synthesis from ethyl 3-benzo[b]thienylacetate. The isomeric 4-phenyl-2H-thiopyrano[3,2-b][1]benzothiophen-2-thione 5,5-dioxide (2a) and a number of analogues of (3a) and (2a) were prepared.