Selective Association\nEnforced by the Confinement\nEffect To Boost the Regioselectivity of Vinyl Acetate Hydroformylation

1,3-Propanediol derived from vinyl acetate through hydroformylation/hydrogenation\nhas always been considered the most promising strategy to substitute\nthe current technology. So far, the linear aldehyde regioselectivity\nof vinyl acetate hydroformylation is still far from satisfactory.\nHerein, we prepare a series of single-site catalysts with a confinement\neffect, in which different second-shell atoms (C, O, and N) are bonded\nwith the P atom. The Rh–P–N-POPs catalyst, in which\ntwo N and one O atoms are bonded with a P atom, delivers not only\na good aldehyde yield but also attractive regioselectivity (l/b =\n1.5), outperforming Rh–P–C-POPs (l/b = 0.007), Rh–P–O-POPs\n(l/b = 0.01), and all previously reported optimizing Rh catalysts\n(l/b = 0.8). Characterizations and DFT calculations suggest that the\nenhanced performance is mainly ascribed to selective association enforced\nby the confinement effect and electron-deficient properties. The confinement\neffect, which is imposed by the ligand, hinders the chelating effect\nof acetate and facilitates the selective association of Rh with the\nterminal carbon of olefins. Meanwhile, N as second-shell atoms in\nthe Rh–P–N-POPs catalyst endows Rh active sites with\nan electron-deficient coordination environment and accelerates the\nlinear aldehyde forming rate. This work offers an effective strategy\nto regulate the hydroformylation performance by the confinement effect\nfor the modulation of a second-shell atom, which sheds light on designing\nheterogeneous catalysts with high regioselectivity for the hydroformylation\nof functional olefins.