A Novel, Highly Enantioselective Ketone Alkynylation Reaction Mediated by Chiral Zinc Aminoalkoxides.

Kilogram-scale synthesis of the HIV reverse transcriptase inhibitor efavirenz was achieved by means of a highly enantioselective alkynylation of prochiral ketones 1 with alkynyllithium or alkynylmagnesium reagents in the presence of chiral zinc aminoalkoxides as mediators. With the achiral auxiliary 2,2,2-trifluoroethanol (R =CF CH ), the efavirenz precursor 2 (R =H, R =cyclopropyl) was obtained with an ee of 99.2%.