Copper- or iron-catalyzed stereoselective methylation of enamides using dicumyl peroxide as the methyl source

Abstract

An efficient and versatile copper- or iron-catalyzed direct β-C(sp²)–H methylation of enamides by using dicumyl peroxide (DCP) as the methylating reagent has been developed. This methodology provides convenient access to a wide range of β-C(sp²)-methylated enamides with exclusive E-selective control in moderate to good yields. Mechanistic studies reveal that a methyl radical was involved in this transformation. Notably, this method features cheap copper or iron salts as the catalyst, a simple procedure, commercially available methylation reagents, a broad substrate scope, and excellent functional group tolerance.