Asymmetric domino multicatalysis for the synthesis of 3-substituted phthalides: cinchonine/NHC cooperative system

Org Lett. 2014 Feb 7;16(3):1028-31. doi: 10.1021/ol5000617. Epub 2014 Jan 24.

Abstract

It is demonstrated that two organocatalysts, achiral NHC and chiral bifunctional cinchonine, are mutually compatible and operating concurrently and effectively to promote the asymmetric domino oxidation/oxa-Michael addition reaction. This protocol allowed access to both enantiomers of a product by using two natural, inexpensive pseudoenantiomeric cinchona alkaloids, cinchonine and cinchonidine, as well as to phthalides containing a chiral quaternary carbon center in good enantioselectivities.