Reductive carboxylation of aromatic esters by electron transfer from magnesium metal

Magnesium-Promoted Reductive Carboxylation of Aryl Vinyl Ketones: Synthesis of γ-Keto Carboxylic Acids

Direct reductive carboxylation of easily prepared aryl vinyl ketones under the atmosphere of carbon dioxide led to the selective formation of γ-keto carboxylic acids in 38-86% yields. The reaction is characterized by the carbon-carbon bond formation of carbon dioxide at the β-position of enone, with the use of magnesium turnings that can be easily handled as the reducing agent and the eco-friendly reaction conditions such as no pressuring, no lower or higher reaction temperature, and short reaction time. This protocol showed a wide substrate scope and provided a useful and convenient alternative to access biologically important γ-keto carboxylic acids.

Umpolung Reactivity of Aldehydes toward Carbon Dioxide

Carbon dioxide is an intrinsically stable molecule. Therefore, its activation requires extra energy input in the form of reactive reagents and/or activated catalysts and, often, harsh reaction conditions. Reported here is a direct carboxylation reaction of aromatic aldehydes with carbon dioxide to afford α-keto acids as added-value products. In situ generation of a reactive cyanohydrin was the key to the successful carboxylation reaction under operationally mild reaction conditions (25-40 °C, 1 atm CO₂ ). The resulting α-keto acids served as a platform for α-amino acid synthesis by reductive amination reactions, illustrating the chemical synthesis of essential bioactive molecules from carbon dioxide.