SYNTHESIS OF 2,6-DIPHENYL-3-FORMYL-4H-THIOPYRAN-4-ONE AND RELATED COMPOUNDS

The title compound 1 was prepared by an unusual selenium dioxide oxidation of 4-chloro-2, 6-diphenyl-3-formyl-2/f-thiopyran (11) which was obtained either by treating 2, 6-diphenyl-4H-dihydrothiopyran-4-one (10) with POCI3/DMF or preferably by allowing POCl3 to react with the dimethylamine derivative 15. The latter compound was prepared in good yield from 10 and the dimethyl acetal of DMF. Alternatively, 1 was synthesized by acetolysis of 15 in the presence of a catalytic amount of sulfuric acid to give a good yield of 2, 6-diphenyl-3-formyl-4H-2, 3-dihydrothiopyran-4-one (16), which was readily dehydrogenated under normal conditions with selenium dioxide. © 1979, American Chemical Society. All rights reserved.