Diastereofacial control in the radical addition to chiral alpha-sulfinyl enones

The beta-addition of alkyl radicals to chiral 2-(arylsulfinyl)-2-cyclopentenones (1) under bar gives 3-alkyl-2-(arylsulfinyl)-1-cyclopentanones (2) under bar with stereoselectivities depending on the bulkiness of alkyl radicals as well as the aryl sulfoxides. The X-ray analysis of the single crystal as well as the NOE experiment of 2,4,6-triisopropylphenyl sulfoxides <(1d)under bar> showed the effective shielding at the beta position by the triisopropylphenyl group. The reaction of a diastereomeric mixture of 4-methyl-2-sulfinyl-cyclopentenones <(4(S))under bar> and <(4(R))under bar> gives the kinetically resolved addition product. Radical reaction of acyclic sulfinylpentenones gives abnormal Pummerer-type reaction products.