Selective Association Enforced by the Confinement Effect To Boost the Regioselectivity of Vinyl Acetate Hydroformylation

Abstract

1,3-Propanediol derived from vinyl acetate through hydroformylation/hydrogenation has always been considered the most promising strategy to substitute the current technology. So far, the linear aldehyde regioselectivity of vinyl acetate hydroformylation is still far from satisfactory. Herein, we prepare a series of single-site catalysts with a confinement effect, in which different second-shell atoms (C, O, and N) are bonded with the P atom. The Rh–P–N-POPs catalyst, in which two N and one O atoms are bonded with a P atom, delivers not only a good aldehyde yield but also attractive regioselectivity (l/b = 1.5), outperforming Rh–P–C-POPs (l/b = 0.007), Rh–P–O-POPs (l/b = 0.01), and all previously reported optimizing Rh catalysts (l/b = 0.8). Characterizations and DFT calculations suggest that the enhanced performance is mainly ascribed to selective association enforced by the confinement effect and electron-deficient properties. The confinement effect, which is imposed by the ligand, hinders the chelating effect of acetate and facilitates the selective association of Rh with the terminal carbon of olefins. Meanwhile, N as second-shell atoms in the Rh–P–N-POPs catalyst endows Rh active sites with an electron-deficient coordination environment and accelerates the linear aldehyde forming rate. This work offers an effective strategy to regulate the hydroformylation performance by the confinement effect for the modulation of a second-shell atom, which sheds light on designing heterogeneous catalysts with high regioselectivity for the hydroformylation of functional olefins.