A GENERAL-ROUTE TO ENANTIOMERICALLY PURE SULFOXIDES FROM A CHIRAL SULFITE

Enantiomerically pure cyclic chiral sulfite (S)-7 (trans stereochemistry) has been easily obtained in two steps from (S)-ethyl lactate. This compound was found to react cleanly with many organometallics to give crystalline sulfinates with high regioselectivity (> 90:10). Addition of a second organometallic transforms the purified sulfinate in excellent yield into a chiral sulfoxide (100% ee) of predictable absolute configuration. The mechanism and scope of this approach are discussed. This method completes the various other methods of preparation of chiral sulfoxides and is especially convenient for the preparation of tert-butyl sulfoxides. Examples for the synthesis of many chiral tert-butyl sulfoxides are given. The case of chiral sulfites derived from a C2 diol or of a chiral monoalcohol is also proposed as a route to chiral sulfinates, and some promising preliminary results have been obtained. The general main routes to obtain chiral sulfoxides from sulfites are also discussed.