carboxylaation

Carboxylation is the chemical process of introducing a carboxyl group (-COOH) into an organic molecule, typically by incorporating carbon dioxide (CO2) as a one-carbon unit or by transferring a carboxyl group from a donor. The term is commonly spelled carboxylation; carboxylaation is a misspelling.

In biochemistry, carboxylation reactions are catalyzed by carboxylases, many of which are biotin-dependent. Notable examples include pyruvate carboxylase, which converts pyruvate to oxaloacetate in gluconeogenesis and anaplerotic pathways; acetyl-CoA carboxylase, which carboxylates acetyl-CoA to malonyl-CoA for fatty acid synthesis; propionyl-CoA carboxylase; and RuBisCO, which fixes CO2 in the Calvin cycle to form 3-phosphoglycerate. These reactions commonly use CO2 or bicarbonate as the carboxyl donor and are central to metabolism and carbon fixation.

In chemical synthesis, carboxylation can proceed by reaction with CO2 or carbonate sources. Classical methods include the reaction of Grignard reagents or organolithium compounds with CO2 to yield carboxylic acids after acidic workup. Modern approaches involve transition-metal-catalyzed carboxylations, such as nickel- or palladium-catalyzed coupling of CO2 with aryl or vinyl halides to give aryl or vinyl carboxylic acids, as well as electrochemical or photoredox methods that enable carboxylation of various substrates under milder conditions. CO2 is valued as a renewable, abundant one-carbon building block in these processes.

Applications of carboxylation span metabolism, sustainable synthesis, and carbon capture and utilization, contributing to the production of pharmaceuticals, polymers, and agrochemicals, while enabling incorporation of CO2 into value-added chemicals.