Photo-induced intermolecular radical beta-addition to chiral alpha-(arylsulfinyl) enones

The reactions of alpha-(arylsulfinyl) enones with alkyl radicals having a h ydroxy or acetal group were examined under photo-irradiation in the presenc e of benzophenone. High diastereoselectivity was observed in the photo-indu ced radical reaction of 2-(arylsulfinyl)-2-cyclopentenones having a bulky a ryl group, such as the 2,4,6-triisopropylphenyl or 2,4, 6-trimethylphenyl g roup. The photo-induced reaction of 3-[(2,4,6-triisopropylphenyl)sulfinyl]- 3-pentene-2-one in 1,3-dioxolane also gave a single diastereomer of the 1,3 -dioxolan-2-yl adduct.