N-formylation of isoquinoline derivatives with CO₂ and H₂ over a heterogeneous Ru/ZIF-8 catalyst

Chemical utilization of CO2 is one of the fundamental strategies to synthesize value-added chemicals and reduce the CO2 emission. N-formyl-1,2,3,4-tetrahydroisoquinoline derivatives (FTHIQs) are important chemicals for the synthesis of medical intermediates and alkaloids. N-formylation of isoquinoline derivatives (IQs) with CO2 is an ideal protocol to synthesize the FTHIQs and utilize the CO2 source. In the present work, we prepared a heterogeneous Ru/ZIF-8 catalyst with a Ru loading of 2 wt% by a simple impregnation method and assessed its performances in the N-formylation of IQs and CO2 with H2. The Ru/ZIF-8 catalyst offered high IQ conversion of 98% and FTHIQ selectivity of 93% in the reaction under relatively mild conditions (150 °C, 2 MPa CO2, and 6 MPa H2). The catalyst possessed good universality and reusability, showing a potential in wide application of N-formylation of highly unsaturated nitrogen-containing isoquinolines.