Manganese-Catalyzed Directed Methylation of C(sp2)-H Bonds at 25 °C with High Catalytic Turnover.

We report here a manganese-catalyzed C-H methylation reaction of considerable substrate scope, using MeMgBr, a catalytic amount of MnCl2·2LiCl, and an organic dihalide oxidant. The reaction features ambient temperature, low catalyst loading, typically 1%, high catalytic turnover reaching 5.9 × 103, and no need for an extraneous ligand and illustrates a unique catalytic use of simple manganese salts for C-H activation, which so far has relied on catalysis by manganese carbonyls.