ASYMMETRIC-SYNTHESIS USING N-SULFONYLOXAZIRIDINES

The development of reagents for the asymmetric oxidation of sulfides to sulfoxides with high stereoselectivities is problematic because these substrates are nonfunctionalized. Nevertheless N-(phenylsulfonyl)(3,3-dichlorocamphoryl)oxaziridine (4) exhibits remarkably high and predictable ee's for the asymmetric oxidation of sulfides to sulfoxides (66->95% ee), selenides to selenoxides (90->95% ee) and sulfenimines to sulfinimines (85-91% ee). While steric effects are primarily responsible for the molecular recognition, an important electronic component is operational for those sulfides having an aryl group directly attached to the sulfur atom. The high ee's associate with this reagent are a consequence of the presence of complementary vacant regions and a molecular cleft or grove on the active site surface.