Ruthenium-Catalyzed Reductive Methylation of Imines Using Carbon Dioxide and Molecular Hydrogen

The use of the well-defined [Ru(triphos)(tmm)] catalyst, CO2 as C-1 source, and H-2 as reducing agent enabled the reductive methylation of isolated imines, as well as the direct coupling of amines with aldehydes and the subsequent reductive methylation of the in situ formed imines. The method, which afforded the corresponding N-methyl amines in very good to excellent yields, was also used for the preparation of the antifungal agent butenafine in one step with no apparent waste, thus increasing the atom efficiency of its synthesis.