Reductive α-Methylation of α,β-Unsaturated Ketones Catalyzed by a Mn(I) PCNHCP Pincer Complex with Methanol as Both H2 and C1–Source

With a growing demand for sustainable and environmentally friendly chemistry, there is an increasing interest in using earth-abundant metals in catalysis, especially when it can be utilized in atom-economical reactions. Here we present such an atom-economical reaction and describe the selective reductive α-methylation of α,β-unsaturated ketones with methanol as both the hydrogen and the C₁-source. The reaction is catalyzed by our previously reported earth-abundant metal catalyst [(PC_NHCP)Mn(CO)₂H] (1) and is compatible with a variety of functional groups that include –halide, –trifluoromethyl, –alkene, –alkyne, –ester, –amide, as well as the heterocycles. Based on literature precedent and our own mechanistic investigations, a plausible mechanism for the reductive α-methylation of α, β-unsaturated ketones is presented, which is further discussed in this report.