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Please login or sign up for a free trial to access the full content. Direct Carboxylations of Aromatic Compounds

DOI: 10.1055/sos-SD-118-00330

Braverman, S.; Cherkinsky, M.Science of Synthesis Knowledge Updates, (20143250.

A direct carboxylation of C—H bonds with carbon dioxide without an initial stoichiometric prefunctionalization prior to the subsequent key C—C bond-forming event would be the most attractive and atom-economic route to the synthesis of carboxylic acids. One early example of such a carboxylation is the well-known base-mediated Kolbe–Schmitt synthesis of salicylic acid from sodium phenolate, albeit under harsh reaction conditions. During recent years, transition-metal-catalyzed direct carboxylation of (het)arenes has been accomplished under remarkably mild reaction conditions with highly basic gold or copper N-heterocyclic carbene complexes in combination with a stoichiometric amount of potassium or cesium base. Because these reactions are proposed to proceed through a deprotonation mechanism, they are limited to substrates which have rather acidic protons (pKa of about 30, depending on the pKa of the applied catalyst).

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