Asymmetric oxidation of sulfides mediated by chiral titanium complexes : mechanistic and synthetic aspects

Abstract

Asymmetric oxidation of sulfides by hydroperoxides mediated by chiral titanium complexes was further developed.The effect of water was discussed as well as steric and electronic factors of aryl groups in aryl-S-alkyl oxidation. When aryl is replaced by 1-alkyne, the sulfoxide is still obtained with high ee. The enantioselectivity of oxidation is enhanced by using cumene hydroperoxide instead of t-butyl hydroperoxide (up to 96%). The asymmetric oxidation was also run under catalytic conditions (with respect to the titanium complex) and beneficial effects were observed in the presence of molecular sieves in the reaction medium.