Synthesis of α-Quaternary Carboxylic Acids through Cu-Catalyzed Hydrocarboxylation of Allenes with Diisobutylaluminum Hydride and Carbon Dioxide

A regioselective method for synthesizing beta,gamma-unsaturated alpha-quaternary carboxylic acids through the copper-catalyzed hydrocarboxylation of allenes with CO2 is described. Allenes undergo hydroalumination with diisobutylaluminum hydride, followed by carboxylation of the resulting allylaluminum intermediate. The presence of an N-heterocyclic carbene ligand is essential for enhancing the reactivity of the reaction. The good functional group compatibility of the reaction allows the synthesis of a wide range of functionalized alpha-quaternary carboxylic acids with high regio- and stereoselectivities for synthetic and medicinal applications.