Recent advances in nucleophile-triggered CO₂-incorporated cyclization leading to heterocycles

Carbon dioxide (CO2) has emerged as a sustainable, feasible, abundant one-carbon synthon and displays great potential in the synthesis of heterocycles such as lactones, lactams, and 2-oxazolidinones, which are privileged motifs in pharmaceutical chemistry demonstrating bioactivities. Although the fixation of CO2 is restricted due to its thermodynamic stability and kinetic inertness, multiple breakthroughs have been realized in annulation chemistry. This review concentrates on the advances made in the last five years in CO2-incorporated cyclization triggered by N-, O-, and C-nucleophiles. Three transformation modes of CO2 including carboxylative cyclization, carbonylative cyclization, and reductive cyclization have been summarized. Moreover, typical mechanisms and significant applications of these reactions are also described.