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

Abstract

A regioselective method for synthesizing β,γ‐unsaturated α‐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 α‐quaternary carboxylic acids with high regio‐ and stereoselectivities for synthetic and medicinal applications.

Visible-light-promoted regioselective hydrocarboxylation of allenes with formate salt and CO2

“…Iwasawa and co-workers first developed the palladium-catalyzed hydrocarboxylation of allenes using AlEt 3 5 or formate salt 6 (HCOONBnMe 3 ) as the reducing agent, primarily delivering branched β,γ-unsaturated carboxylic acids with a few linear products (Scheme 1a). Besides palladium, copper catalysts have also been developed in the hydrocarboxylation of allenes with HSi(OMe) 2 Me (Tsuji's group 7 and Buchwald's group 8 ) or (i-Bu) 2 AlH (Lee's group 9 ) as the reducing agents (Scheme 1b). Notably, all these methods mainly produced the branched carboxylic acids product with few exceptions.…”