CO<sub>2</sub>‐Promoted Reactions: A Prosperous Strategy for Conversion of Functional Group in Organic Synthesis
Zeyu Zhang, Chanjuan Xi
Abstract
Abstract Due to its nontoxic nature, cost‐effectiveness, and natural abundance, carbon dioxide (CO 2 ) is increasingly recognized as a valuable C1 source in organic synthesis. In addition to the building block for molecular construction, the role of CO 2 as a promoter or catalyst to enhance reaction rates and selectivity is gaining attention. Acting as a reversible covalent Lewis acid, CO 2 can function as an activating group in the transformation of various compounds, such as alcohols and amines, facilitating the dissociation of hydroxyl or activation of amino. It can also modulate the reactivity of nucleophilic reagents, including H 2 O, N‐heterocyclic carbenes (NHCs), cyanide (CN), and nucleophilic reductants like borohydride (BH 4 − ). When CO 2 interacts with these nucleophiles, it can exhibit Brønsted acidity or hydrogen‐bond donating capabilities and can also act as a coordinating ligand to transition metals in its carboxylate form (─CO 2 − ). In this review, we mainly summarize and classify the synthetic applications and mechanistic insights of CO 2 ‐promoted reactions according to different functional groups and bonding types, which include CO 2 ‐promoted functional transformation of alcohols, CO 2 ‐promoted functional transformation of amines; CO 2 ‐promoted reactions in protic solvent; CO 2 ‐promoted reactions via adducts of CO 2 and nucleophiles, CO 2 ‐promoted reductive reaction.