N-formylation of amines using methanol as a potential formyl carrier by a reusable chromium catalyst

Formamides represent an abundant class of compounds in organic synthesis. They can be made efficiently by the direct catalytic coupling of methanol with amines in the presence of metal-based catalysts. However, these catalysts require complicated organic ligands, susceptible to oxidative self-degradation, restricting their practical applications. Here, we describe an inorganic ligand-supported chromium (III) catalyst, (NH4)(3)[CrMo6O18(OH)(6)], which consists of a central chromium (III) single-atomic core supported by a cycle-shaped inorganic ligand consisting of six (MoO6)-O-VI octahedra, shows excellent activity and selectivity. Various primary amines and secondary amines are successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines is also achieved. The chromium catalyst can be reused several times with little loss of the activity. Mechanistic insight is provided based on the observation of an intermediate and control experiments.