Computational studies on the aldol-type addition of boron enolates to imines: An ab-initio approach

The aldol-type addition of enol borinates to imines was studied with ab initio MO methods (3-21G basis set). Calculations performed on unsubstituted, mono- and di-substituted structures have shown that only two competing cyclic transition states (chair-like and boat-like) are important. Their relative energy depends on the enolate geometry and on the substitution pattern. This approach allows a qualitative rationalization of the observed stereoselectivity trends in the title reaction. (C) 1997 Elsevier Science Ltd.