α-Alkylation of Ketones Using Primary Alcohols: Unveiling the Role of Manganese-Salen Complexes.

The α-alkylation of ketones with primary alcohols has been systematically investigated using two distinct phosphine-free manganese-complexes (Mn-ph and Mn-en) bearing tetradentate Salen ligands. Remarkably, the complex Mn-ph with an aromatic imine bridge was found to be efficient in comparison to Mn-en, leading to an excellent yield of α-alkylated ketone with good selectivity under operationally convenient conditions. Interestingly, a wide range of aromatic, cyclic, and heterocyclic ketones are effectively alkylated under the optimized reaction conditions. Notably, the transformation proceeds via an environmentally benign and atom-efficient pathway, generating water as the sole byproduct. The control experiments reveal the involvement of dehydrogenation of alcohols and hydrogen autotransfer (HA) pathway. These findings highlight the potential of Mn(II)-salen complexes in catalytic HA processes, expanding their applications in sustainable C ─ C bond formation strategies.