Thiopyranothiopyran Chemistry. 2. Synthesis of 2,4-Diphenyl-4H-benzothiopyranothiopyran-10-one

Article abstract of DOI:10.1021/jo00200a025

2,4-Diphenyl-4H-benzothiopyrano<3,4-b>thiopyran-10-one was synthesized by lithiation of 3-<2(Z)-(benzylsulfinyl)-2-phenylethenyl>-4H-thiochroman-4-one, whose absolute configuration was established by X-ray crystallography.The yellow, insoluble solid obtained from this reaction was assigned the structure 2,6-diphenyl-2H-4-(2-mercaptobenzoyl)thiopyran 1-oxide (11), which, on brief heating with AcOH, yielded the title compound in 87percent yield.Treatment of 11 with 1percent aqueous cupric acetate in methylene chloride gave a new rearranged product, which was identified as 9,11-diphenylbenzo-1,8-dithiaspiro-<4,5>deca-6,9-dien-4-one.Mechanisms that would account for the formation of both of these compounds are proposed.