[(NHC)AuCl]-catalyzed Meyer-Schuster rearrangement: scope and limitations

An efficient catalytic system allowing for the synthesis of a variety of a,P-unsaturated ketones has been developed. [(NHC)AuCl] (NHC=N-heterocyclic carbene) in the presence of a silver(I) salt was found to catalyze the Meyer-Schuster rearrangernent, leading to of alpha,beta-unsaturated ketones from easily accessible propargylic alcohols in high yields. Catalysis was performed in a 2:1 mixture of methanol and water at 60 degrees C and afforded good yields even for tertiary alcohols and sterically demanding substrates. Thorough evaluation of the present catalytic system uncovered that it was unsuitable for terminal alkynes and primary alcohols. In these cases low yields of the target molecules were obtained due to the formation of unexpected by-products. (C) 2008 Elsevier Ltd. All rights reserved.