Computational study of solvation and stereoselectivity in deprotonation ofcyclohexene oxide by a chiral lithium amide

A detailed computational investigation of possible activated complexes in t he epoxide opening of cyclohexene oxide by a chiral lithium amide is presen ted. Transition states for the two routes giving (S)- and (R)-alkoxides wit h and without solvent have been calculated. Geometry optimizations at PM3 a nd HF/3-21G levels of theory, and single point calculations at B3LYP/6-31+G (d) level have been used. The experimentally obtained stereoselectivity is semi-quantitatively reproduced at all levels except PM3//PM3. The factors f ound to control the stereoselectivity are solvation and some non-bonded int eractions other than those previously proposed. (C) 1999 Elsevier Science L td. All rights reserved.