Recent progress in rhodium-catalyzed hydroaminomethylation

Hydroaminomethylation is a perfect reaction for converting alkenes into valuable amines with high atom economy in the presence of the syngas and amines. Significant progress has been made in the past decades; however, there still remain challenges for the control of chemo-and regioselectivity concurrently. Rhodium has proved to be a better metal in hydroaminomethylation for higher activity in hydro-formylation and hydrogenation steps. Although promising results were shown by unmodified rhodium catalysts, phosphine ligand modified rhodium complexes generally displayed better activity and regio-selectivity. Among the phosphorus ligands developed, tetraphosphorus ligands exhibited much better regioselectivity due to their stronger chelating ability. Apart from the phosphorus ligands, carbene and nitrogen-containing ligands have also been developed which showed good activity due to the promotion of the hydrogenation step. Although non-enantioselective hydroaminomethylation reactions have been intensively studied, reports on asymmetric hydroaminomethylation are rare. Direct asymmetric hydroaminomethylation is very challenging and only reaction systems with two different catalysts showed promising results.