Me5Cu3Li2: A Reagent for Conjugate Methylation of α,β-Unsaturated Aldehydes

Article abstract of DOI:10.1021/jo00134a013

Me5Cu3Li2, in ether or ether-pentane mixtures, converts α,β-unsaturated aldehydes efficiently into β-methyl aldehydes.In many cases of synthetic interest the amount of 1,2-methylation is negligible, and the reagent is far superior to Me2CuLi for conjugate methylation of enals.The performance of Me5Cu3Li2 is poor in sterically demanding situations, however.Several cuprate species were evaluated but none works as well as Me5Cu3Li2.For example, citral undergoes conjugate methylation with Me5Cu3Li2 in 80percent yield, and the product contains less than 0.5percent of 1,2-adduct.With Me2CuLi the product contains 10percent of 1,2-adduct.