钯催化烯丙基取代反应中手性配体的“甲基效应”

The "Methyl Effect" in The Enantioselective Allylic Substitution Using Palladium/Chiral Pyridinylmethyl-oxazolines

In this paper, two types of chiral ligands 1 and 2 containing pyridinyl moiety and oxazolines bridged by a methylene group were investigated in the palladium catalyzed substitution of 1,3 diphenyl 2 propenyl acetate with dimethyl malonate. Ligands 2, which have two methyl groups at the bridged methylene, gave higher enantioselectivities than their unsubstituted analogues 1. This "methyl effect" increased while the substituent on the C 4 in the oxazoline ring was changed from benzyl to tert butyl. Despite of that the "methyl effect" was found in the palladium catalyzed enantioselective allylic substitution, it was obviously significant for assisting rational design of chiral ligands and catalysts in other asymmetric reaction.