The diastereoselectivity of intermolecular β-addition of alkyl radicals to 2-(arylsulfinyl)-2- cycloalkenones depends largely upon the structure of the arylsulfinyl group. The reaction of 2-cyclopentenones or 2-cyclohexenones having a sterically bulky arylsulfinyl group such as (3, 5-di-tert-butyl-4-methoxyphenyl) sulfinyl,(2, 4, 6-triisopropylphenyl) sulfinyl or (2, 4, 6- trimethylphenyl) sulfinyl group gives 3-alkyl-2-(arylsulfinyl)-1-cyclopentanones or 3-alkyl-2 ...