Manganese(I)‐Catalyzed β‐Methylation of Alcohols Using Methanol as C 1 Source

Abstract

Highly selective β‐methylation of alcohols was achieved using an earth‐abundant first row transition metal in the air stable molecular manganese complex [Mn(CO) 2 Br[HN(C 2 H 4 P i Pr 2 ) 2 ]] 1 ([HN(C 2 H 4 P i Pr 2 ) 2 ]=MACHO‐ i Pr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β‐methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β‐position, opening a pathway to “biohybrid” molecules constructed entirely from non‐fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn‐pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C−C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules