Transfer hydrogenation of N-heteroarenes with 2-propanol and ethanol enabled by manganese catalysis

A convenient manganese catalyzed transfer hydrogenation of N-heteroarenes by using alcohols as hydrogen sources is presented. Ideal results are achieved by applying the 6-methyl substituted triazine based (PNPipr)-N-ipr-P-5 manganese pincer complex Mn-1, which allows the hydrogenation of various substituted N-heteroarenes in good to excellent isolated yields. More importantly, biomass derived ethanol could be realized in this transformation as well, thus highlighting the sustainability of the process. Detailed DFT calculation studies support an outer sphere hydrogenation mechanism and hydride transfer from propan-2-olate to the Mn center with regeneration of the catalyst as the rate-determining step.