Main observation and conclusionrnAsymmetric hydrogenation reaction is one of the most efficient synthetic methods to form useful chiral compounds for synthetic chemistry,medicinal chemistry and material chemistry.Generally,the enantioselectivity of many hydrogenation reactions is con-trolled by steric hindrance between the chiral ligand and substrate.Recently,Zhang group developed a highly asymmetric hydrogena-tion of 2-aryl and 2-alkyl acrylic acids catalyzed by a Rh(Ⅰ)catalyst with a chiral Wudaphos ligand.The excellent enantioselectivity of this asymmetric reaction was proposed to be controlled by ion-pair interaction between the substrate and chiral ligand.In this study,a systematic density functional theory study has been carried out to investigate the reaction mechanism and origin of the enantiose-lectivity.Our computational results suggest that this reaction follows the classic mechanism involving oxidative addition of H2,migra-tory insertion and reductive elimination.Different from the C=C coordination to the metal in the common oxidative addition step,our study found that the chelation of the carboxyl group of the substrate to the cationic Rh(Ⅰ)metal is more favorable in this oxidative ad-dition step.The high enantioselectivity is proposed to be dictated by a better catalyst/substrate geometric complementarity in the major pathway to have less distortion of the catalyst for a strong ion-pair interaction.