Inversion of the Configuration of Cyanohydrins by a Mitsunobu Esterification Reaction

Abstract Optically active (R)-cyanohydrins have been transformed into cyanohydrin esters of opposite configuration under Mitsunobu conditions and subsequently solvolyzed to (S)-cyanohydrins in high chemical and optical yield. The method works well for allylic and benzylic cyanohydrins. Cyanohydrins containing strongly electron donating substituents gave extensive racemization. Saturated aliphatic cyanohydrins afforded esters in which the original configuration is retained. These results are discussed in terms of the mechanism of the Mitsunobu reaction.