Reversed diastereoselectivity in the ring-opening reaction of (S)-TFPO with a chiral aminoacetonitrile Schiff base

Diastereoselective ring opening of (S)-2,3-epoxy-1,1,1-trifluoropropane [(S )-TFPO: 75% ee] with an aminoacetonitrile Schiff base bearing the (R,R,R)-h ydroxypinanone chiral auxiliary [(R)-Schiff base] are described. The reacti on of (S)-TFPO with the (R)-Schiff base selectively gave one diastereomer o ut of the four possible, while that with the (S)-Schiff base gave a complex mixture of all four possible diastereomers. The stereochemistry of the rea ction products was greatly dependent on the base used for abstracting a pro ton from the (R)-Schiff base: utilization of LDA and KO'Bu resulted in prod uction of (R,R,R,S,S)- and (R,R,R,R,S)-isomers as the major diastereomers, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.