Catalytic Asymmetric Synthesis of Chiral Allylic Esters
journal contributionposted on 03.11.2010, 00:00 authored by Jeffrey S. Cannon, Stefan F. Kirsch, Larry E. Overman
A broadly useful catalytic enantioselective synthesis of branched allylic esters from prochiral (Z)-2-alkene-1-ols has been developed. The starting allylic alcohol is converted to its trichloroacetimidate intermediate by reaction with trichloroacetonitrile, either in situ or in a separate step, and this intermediate undergoes clean enantioselective SN2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst (Rp,S)-di-μ-acetatobis[(η5-2-(2′-(4′-methylethyl)oxazolinyl)cyclopentadienyl-1-C,3′-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium, (Rp,S)-[COP-OAc]2, or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined.