A modified Bis-OPNN phosphorus ligand for Rh-catalyzed linear-selective hydroformylation of alkenes

The hydroformylation of olefins, known as the "oxo reaction", involves the use of syngas (CO/H₂) to produce aldehyde with an additional carbon atom. However, side reactions such as the isomerization or hydrogenation of olefins often result in unexpected products and other by-products. Recent efforts in developing efficient ligands represent the most effective approach to addressing these challenges. In this study, we described a Bis-OPNN phosphorus ligand facilitated Rh-catalyzed hydroformylation with a high degree of linear selectivity across various olefins. Under mild conditions, a broad range of olefins were efficiently converted into linear aldehydes with high yields and excellent regioselectivity. The protocol also showed impressive functional group tolerance and was successfully applied to modify drugs and natural products, including the total synthesis of (±)-crispine A. Preliminary mechanistic studies revealed that this Bis-OPNN phosphorus ligand anchoring the rhodium catalyst is crucial for controlling the linear selectivity.