MANGANESE(III)-BASED ASYMMETRIC OXIDATIVE FREE-RADICAL CYCLIZATION OF UNSATURATED BETA-KETO SULFOXIDES

beta-Keto sulfoxides and beta-keto sulfones can be used as substrates for Mn(III)- and Cu(II)-based oxidative free-radical cyclizations. The sulfoxide chiral center completely controls the stereochemistry of the cyclization. Oxidative cyclization of racemic sulfoxide 8 affords 13 as a single diastereomer. Oxidative cyclization of enantiomerically pure sulfoxide 20 gives 21 as a single enantiomer. The chiral auxiliary can be removed by oxidation with potassium peroxomonosulfate to give the sulfone followed by reduction with sodium amalgam to give bicyclo[3.2.1]octanone 23. Oxidative cyclization of 26 gives indanone 29, which spontaneously loses toluenesulfenic acid to give indenone 30.