Transition Metal-Free CO2 Fixation into New Carbon-Carbon Bonds.

CO2 is the ultimate renewable carbon source on Earth and the essential C1 building block for carbohydrate biosynthesis in photosynthetic organisms. Modern synthetic chemistry is facing the key challenge of developing fundamental transformations, such as C-C bond formation, in a sustainable and efficient manner from renewable sources. In this Minireview, the most significant methods recently reported for CO2 fixation under transition metal-free conditions are summarized, organized into three different chapters according to the nature of the chemical transformation that forges the new C-C bond. The focus is on the mechanistic aspects of the different CO2 activation modes, with specific attention to those systems that operate under catalytic conditions.