Transition metal-catalyzed carboxylation of unsaturated substrates with CO2

The utilization of CO2 as a C1 building block for the synthesis of valuable chemicals is of great importance. The transition metal-catalyzed carboxylation of unsaturated substrates with CO2 has proved to be an effective and versatile strategy for the incorporation of CO2 in organic substrates with unsaturated bonds. Different kinds of carboxylation reactions with CO2 have provided a direct access to a myriad of functionalized carboxylic acids and derivatives. This review focuses on carboxylation of unsaturated substrates with CO2 via transition metal catalysis. Various kinds of carboxylations with different catalytic systems are discussed.