Effects of electron-withdrawing group on the photoisomerization of Tetraaryl-4H-thiopyran-1,1-dioxides

Syntheses and photoisomerization of the new sulfone derivatives, 4,4-di (ptrifluoromethylphenyl)-2,6-diphenyl-4H-thiopyran-1,1-dioxide and 4-(p-trifluoromethylphenyl)-2,4,6-triphenyl-4H-thiopyran-1,1-dioxide, have been investigated. The relative molar ratios of the photoproducts are compared with those of 2,4,4,6-tetraphenyl-4H-thiopyran-1,1-dioxide as well as electron-donating substituted 4-methyl-2,4,6-triatyl-4H-thiopyran-1,1-dioxides as model compounds under identical experimental conditions using H-1 NMR spectroscopy. The results observed are discussed on the basis of a triplet excited state di-pi-methane rearrangement. (C) 2008 Wiley Periodicals, Inc.