Enantioselective Conversion of Primary Alcohols to α-Exo-Methylene γ-Butyrolactones via Iridium Catalyzed C-C Bond Forming Transfer Hydrogenation: 2-(Alkoxycarbonyl)allylation

摘要

Upon exposure of acrylic ester >1 to alcohols >2a–2i in the presence of a cyclometallated iridium catalyst modified by (−)-TMBTP, catalytic C-C coupling occurs to provide enantiomerically enriched 5-substituted α-exo-methylene γ-butyrolactones >3a–3i. 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.