Asymmetric Conjugate Addition of Grignard Reagents to Pyranones

An efficient enantioselective synthesis of lactones was developed based on the catalytic asymmetric conjugate addition (ACA) of alkyl Grignard reagents to pyranones. The use of 2H-pyran-2-one for the first time in the ACA with Grignard reagents allows for a variety of further transformations to access highly versatile building blocks such as beta-alkyl substituted aldehydes or beta-bromo-gamma-alkyl substituted alcohols with excellent regio- and stereoselectivity.