Ir-catalyzed hydroaminomethylation of olefins with formic acid as hydrogen source

Formic acid (FA) is a neat and safe source of hydrogen storage. In this paper, PPh3-based Ir catalyst was applied to the hydroaminomethylation of olefins with FA as the hydrogen source successfully. The conversion of 1-octene reached 99 % under the optimal reaction conditions (150 degrees C, 20 h, P/Ir = 1/1, CO 3.0 MPa, NMP as the solvent), and the product amine's selectivity was 92 %. The catalytic system was also suitable for a variety of aliphatic, aromatic alpha-olefins and cycloolefins. It was demonstrated that the reaction system underwent the following steps: the dehydrogenation of FA to release H2; the hydroformylation of olefins to aldehydes; the condensation of amines and aldehydes to enamines; and the reduction of enamines by H2 to produce amines. In situ high-pressure 1H NMR spectroscopy analyses proved that the Ir-H species were facilitated by the involving of FA, which played crucial roles in hydroaminomethylation. Additionally, mercury poisoning test indicated the homogeneous nature of the catalytic process.