Diastereomer-Differentiating Radical β-Addition to 4- or 5-Methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones

Addition of alkyl radicals to a diastereomeric mixture of (4 R )- and (4 S )-4-methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones gave the diastereomerically pure addition product derived from the (4 R )-isomer, while the (4 S )-isomer remained unreacted. The tert -butyl radical addition to a diastereomeric mixture of (5 R )- and (5 S )-5-methyl-2-[(2,4,6-triisopropylphenyl)sulfinyl]-2-cyclopentenones also gave the diastereomerically pure addition product. These results show that (4 R ) and (4 S ) or (5 R ) and (5 S ) diastereomers were kinetically separated in the radical β-addition. The 1,2- and 1,3-steric interactions in the radical addition to 4- or 5-methyl-2-cyclopentenones were also examined.