Catalytic Asymmetric Conjugate Addition of Carboxylic Acids via Oxa-Michael Reaction of Peroxy Hemiacetals followed by Kornblum DeLaMare Fragmentation.

ABSTRACT

Disclosed herein an overall methodology constitutes an equivalent to the long sought after enantioselective intramolecular oxa-Michael (IOM) reaction of carboxylic acids. An organocatalyzed IOM reaction of in situ formed peroxy hemiacetals followed by a Kornblum DeLaMare type rearrangement cascade provides a broad class of chiral lactones in good yields and with excellent enatioselectvities. Remarkably, the pure chiral lactones are obtained without any silica gel column chromatography, and in many cases, the enantioselectivity is further increased by a simple hexane wash of the isolated solid products.