Expanding the Synthetic Horizon With CO ₂ : A C ₁ Synthon for Constructing Organic Functionalities and Heterocycles

ABSTRACT Carbon dioxide (CO 2 ), a nontoxic, inexpensive, and renewable C 1 feedstock, has attracted significant attention as a key component in sustainable synthetic strategies. This review provides a comprehensive overview of recent advances in the utilization of CO 2 in organic synthesis, with a focus on its role as a versatile synthon for constructing pharmaceutically and industrially relevant heterocyclic frameworks. We have highlighted the synthesis of cyclic carbonates, lactones, oxazolidinones, imidazolidinones, and quinazolines using CO 2 , emphasizing catalytic methodologies that enable efficient C–C, C–N, and C–O bond formation. The review also discusses the use of CO 2 in electrochemical and photochemical transformations, as well as its function as a reaction medium and a tunable reagent in dense and supercritical phases. Special attention is given to transition metal‐catalyzed carboxylation reactions, formation of heterocycles, and direct functionalization of sp, sp 2 , and sp 3 C–H bonds. Moreover, the carbonylative cyclization reaction has been equally emphasized. Collectively, these developments underline the emerging potential of CO 2 as a sustainable platform for molecular assembly, offering environmentally benign alternatives to traditional synthesis. This review aims to guide researchers in understanding the scope and mechanistic aspects of CO 2 chemistry while promoting its integration into greener synthetic routes.