Synthesis and photoisomerization of 4,4-diphenyl-2,6-di(p-methoxyphenyl)-4H-thiopyran-1,1-dioxide, an approach to the regioselectivity in photorearrangement of 2,4,4,6-tetraaryl-4H-thiopyran-1,1-dioxides

Synthesis and photoisomerization of the new sulfone derivative 1c is descri bed. Upon photolysis at 254 nm the sulfone 1c, unlike those of the model co mpound 1b and the other 2,4,4,6-tetraarylsubstituted sulfune derivatives, u ndergoes rearrangement in high regioselectivity to the bicyclic photoproduc t 2c. The isolation of bicyclic photoproducts 2b and 2c under our experimen tal conditions led us to determine the molar ratios of these species during the transformations using HPLC.