The microscopic mechanisms and essential factors governing regioselectivity in Rh-catalyzed hydroformylation of allyl acetate via DFT and microkinetic modeling

The direct hydroformylation of allyl acetate followed by hydrogenation represents a novel route for 1,4-butanediol production with significant industrial potential and market prospects. In this study, we employed Density Functional Theory (DFT) and Microkinetic Modeling (MKM) to comparatively investigate two representative Rh-based catalysts with distinct product distributions (RhH(CO)₂(Xantphos) and RhH(CO)₂(PPh₃)₂), systematically elucidate the mechanisms for improving the selectivity and regulation principles of this reaction. Theoretical calculations reveal that the regioselectivity is primarily determined by the olefin insertion step. Xantphos ligand reduces the electron density of the Rh center and provides a sterically favorable environment for the linear pathway. Additionally, the acetoxy group in allyl acetate exerts a repulsive interaction with the Rh-carbonyl, directing Rh to preferentially coordinate with the β-C, thereby significantly enhancing the formation of 4-acetoxybutyraldehyde. In contrast, the PPh₃-modified Rh catalyst exhibits lower steric hindrance along the branched pathway, thus favoring the formation of branched aldehydes. Experimental investigations demonstrate that hydrogenolysis of allyl acetate predominantly occurs at the uncoordinated Rh sites, and the elevated H₂ concentration and higher temperature will promote this side reaction. For Xantphos, MKM simulations indicate that the increased pressure and optimized syngas composition (CO/H₂ = 0.5–2) can lead to linear aldehyde selectivity exceeding 98 %. Similarly, in the PPh₃ system, high pressure and a near-equimolar syngas ratio favor the formation of branched aldehyde. These findings unveil the intrinsic relationships between ligand design, reaction conditions and selectivity, establishing a structure–activity framework for hydroformylation of acetoxy-functionalized olefins. This work provides critical theoretical guidance for the rational design of efficient catalysts and advances the development of scalable 1,4-BDO production process.