Enantioselective Conversion of Primary Alcohols to α-<i>exo</i>-Methylene γ-Butyrolactones via Iridium-Catalyzed C–C Bond-Forming Transfer Hydrogenation: 2-(Alkoxycarbonyl)allylation

Abstract

Upon exposure of acrylic ester 1 to alcohols 2a-i in the presence of a cyclometalated iridium catalyst modified by (-)-TMBTP, catalytic C-C coupling occurs, providing enantiomerically enriched 5-substituted α-exo-methylene γ-butyrolactones 3a-i. Bromination of the methylene butyrolactone products followed by zinc-mediated reductive aldehyde addition provides the disubstituted α-exo-methylene γ-butyrolactones 6a and 6b with good to excellent levels of diastereoselectivity.