Environmentally friendly synthesis of secondary amines via one-pot reductive amination over a heterogeneous Co–Nx catalyst
The application of earth-abundant transition metal catalysts in the mild and selective synthesis of secondary amines via the reductive amination method is very challenging. In this regard, we have developed a new method for the reductive amination of carbonyl compounds with nitro compounds over a heterogeneous Co–nitrogen (Co–Nx) catalyst under mild conditions (110 °C and 10 bar H2). This method afforded the corresponding secondary amines with the yields of 43.7–100% at 110 °C and under 10 bar H2 pressure. Kinetic studies revealed that the hydrogenation of imines was the rate-determining step with much higher activation energy than the first step of the hydrogenation of nitro compounds. To the best of our knowledge, no such non-noble heterogeneous catalyst that shows very high catalytic activity under mild conditions (110 °C and 10 bar H2) has been reported to date. This promising cheap heterogeneous catalyst allows an efficient domino reductive amination of carbonyl compounds with nitro compounds.