CONTROL OF DIASTEREOSELECTIVITY IN ALKYLATION OF CHIRAL LITHIUM ENOLATES MEDIATED BY A CHIRAL SECONDARY AMINE LIGAND

Diastereoselective alkylation of chiral lithium enolates (dl-, (R)- and (S)-9) derived from 4-t-butylcyclohexanone in the presence of a chiral secondary amine (R)-1 and lithium bromide was studied. It is shown that (R)-1 regulates the direction of the attack of electrophiles. Thus highly stereoselective axial attack was observed on (R)-9, while equatorial attack on (S)-9. The present method provides an efficient procedure for the asymmetric synthesis of 2,4-disubstituted cyclohexanones.