Regioselective hydroformylation of allyl alcohol catalyzed by phosphine-stabilized single-atom Rh sites

The regioselective hydroformylation of functionalized alkenes using heterogeneous catalysts remains a challenge. In this work, we developed a reusable heterogeneous single-atom Rh catalyst for the hydroformylation of allylic alcohols. A hybrid porous organic polymer, incorporating phosphine and phosphite functionalities within its framework, was synthesized as a support and a solid ligand to anchor and stabilize Rh sites by forming Rh-P bonds. The structure of single-atom Rh catalyst was comprehensively characterized. The resulting single-atom Rh catalyst exhibited high activity and excellent regioselectivity for the linear regioselective hydroformylation of allyl alcohol, yielding an important intermediate 4-hydroxyl butyraldehyde for 1,4-butanediol production. Furthermore, this single-atom Rh catalyst showed good stability, which could be easily separated for successive reuses several times without a significant decay in both activity and regioselectivity. Remarkably, various allylic alcohols underwent efficient and regioselective hydroformylation to their corresponding diols in good to high yields. Mechanistic studies highlighted the significant influence of the hydroxyl group in allylic alcohols on catalytic activity and regioselectivity. This work represents a significant advance in the regioselective hydroformylation of functionalized alkenes over a heterogeneous catalyst.