Selective Hydroformylation of 1,3-Butadiene to Adipic Aldehyde Enabled by a Ligand-Relay Catalysis

The hydroformylation of 1,3-butadiene for the selective synthesis of adipic aldehyde (AA) has been a long-standing challenge due to its intricate reaction network, resulting in low reaction efficiency and poor chemo- and regioselectivity. Herein, we propose a dual ligand-relay catalysis strategy for the selective hydroformylation of 1,3-butadiene to an AA. This strategy entails a one-pot and two-step process, commencing with a Rh-catalyzed 1,3-butadiene hydroformylation, followed by Rh-catalyzed isomerizing hydroformylation. The reaction is facilitated by using two distinct biphosphites as auxiliary ligands, each with a specific individual role in the process. Remarkably, an unprecedented chemo- and regioselectivity of up to 65.9% toward AA was achieved with complete conversion of 1,3-butadiene, marking the highest value compared to the previous state-of-the-art catalyst systems thus far. Furthermore, the process also produced a 26.5% selectivity for n-valeraldehyde as the major byproduct, a key compound of industrial importance. This study therefore represents a significant advancement in the hydroformylation of 1,3-butadiene, showcasing the potential of this ligand-relay catalysis strategy for improving selectivity in the reaction.