Rhodium‐Catalyzed Hydrocarboxylation of Olefins with Carbon Dioxide

The catalytic hydrocarboxylation of styrenes derivatives and α,β‐unsaturated carbonyl compounds with CO2 (101.3 kPa) in the presence of an air‐stable rhodium catalyst was explored. The combination of [RhCl(cod)]2 (cod = cyclooctadiene) as a catalyst and diethylzinc as a hydride source allowed for effective hydrocarboxylation and provided the corresponding α‐aryl carboxylic acids in moderate to excellent yields. In this catalytic process with carbon dioxide, intervention of the RhI–H species, which could be generated from the RhI catalyst and diethylzinc, was clarified. Significantly, the catalytic asymmetric hydrocarboxylation of α,β‐unsaturated esters with carbon dioxide was also performed by employing a cationic rhodium complex possessing (S)‐(–)‐4,4′‐bi‐1,3‐benzodioxole‐5,5′‐diylbis(diphenylphosphine) [(S)‐SEGPHOS] as a chiral diphosphine ligand. A plausible model for asymmetric induction was proposed by determination of the absolute configuration of the product.