Enantioselective Reductive Coupling of 1,3-Enynes to Glyoxalates Mediated by Hydrogen: Asymmetric Synthesis of β,γ-Unsaturated α-Hydroxy Esters

Catalytic hydrogenation of 1,3-enynes 1a−8a in the presence of ethyl glyoxalate at ambient pressure and temperature using a rhodium catalyst
modified by (R)-(3,5-tBu-4-MeOPh)-MeO-BIPHEP results in highly regio- and enantioselective reductive coupling to furnish the corresponding
α-hydroxy esters 1b−8b. As demonstrated by the elaboration of α-hydroxy ester 1b, the terminal and internal olefin moieties embodied by the
diene side chain are subject to selective manipulation, one over the other.