Catalytic Asymmetric Synthesis of Chiral Allylic Esters

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 S N 2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst ( R p, S )-di-μ-acetatobis[(η 5 -2-(2′-(4′-methylethyl)oxazolinyl)cyclopentadienyl-1-C,3′- N )(η 4 -tetraphenylcyclobutadiene)cobalt]dipalladium, ( R p, S )-[COP-OAc] 2, or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined.