Carboxylation Reactions with Carbon Dioxide Using N‐Heterocyclic Carbene‐Copper Catalysts

Abstract

The development of versatile catalyst systems and new transformations for the utilization of carbon dioxide (CO2) is of great interest and significance. This Personal Account reviews our studies on the exploration of the reactions of CO2 with various substrates by the use of N‐heterocyclic carbene (NHC)‐copper catalysts. The carboxylation of organoboron compounds gave access to a wide range of carboxylic acids with excellent functional group tolerance. The C−H bond carboxylation with CO2 emerged as a straightforward protocol for the preparation of a series of aromatic carboxylic esters and butenoates from simple substrates. The hydrosilylation of CO2 with hydrosilanes provided an efficient method for the synthesis of silyl formate on gram scale. The hydrogenative or alkylative carboxylation of alkynes, ynamides and allenamides yielded useful α,β‐unsaturated carboxylic acids and α,β‐dehydro amino acid esters. The boracarboxylation of alkynes or aldehydes afforded the novel lithium cyclic boralactone or boracarbonate products, respectively. The NHC‐copper catalysts generally featured excellent functional group compatibility, broad substrate scope, high efficiency, and high regio‐ and stereoselectivity. The unique electronic and steric properties of the NHC‐copper units also enabled the isolation and structural characterization of some key intermediates for better understanding of the catalytic reaction mechanisms.

CO2 Activation by Lewis Pairs Generated Under Copper Catalysis Enables Difunctionalization of Imines

“…The past decades have witnessed significant progress in the use of carbon dioxide (CO 2 ) as an attractive one-carbon source for the preparation of various useful chemicals . In particular, transition-metal-catalyzed reactions of CO 2 have been intensively studied, which benefit from the well-established pathway of CO 2 insertion into metal-element bonds. − On the other hand, frustrated Lewis pairs (FLP) containing a strong Lewis acidic borane unit and a phosphine or an amine Lewis base unit have been reported to form CO 2 adducts readily (Scheme a). , Indeed, a few FLP/CO 2 adducts featuring ammonium/borate moieties have been isolated by using amine/borane Lewis pairs. − However, this interesting CO 2 fixation process has been restricted to the stoichiometric reactions of CO 2 and preprepared FLP. Moreover, further transformation of the resulting carboxylate zwitterionic molecules to other CO 2 -incorporated chemicals has not yet been achieved.…”

Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO 2

“…Carbon dioxide (CO 2 ), a well-known greenhouse gas, has gained considerable attention as an ideal one-carbon building block in chemical transformations due to its abundance, low cost, and sustainability. [14][15][16][17][18][19][20][21][22][23] Hydrocarboxylations of alkenes with CO 2 , especially transition-metalcatalyzed hydrocarboxylations, represent efficient strategies to generate bioactive and synthetically useful carboxylic acids. 24 Recently, in addition to UV-light photocatalysis, 16,[25][26][27] visible-light photocatalysis has emerged as an intriguing strategy to realize novel organic transformations with CO 2 .…”

Recent Advances in Copper‐Catalyzed Carboxylation Reactions with CO2

“…In 2016, Xi and co‐workers summarized and discussed the advances in copper‐catalyzed carboxylation reactions employing CO 2 as C1 building block [8] . Hou and co‐workers also reviewed their personal studies on the carboxylation reactions with CO 2 using N ‐heterocyclic carbene (NHC)‐copper catalysts [9] . Although the relevant reviews have been presented, recent years witnessed the rapid developments of copper‐catalyzed transformations of CO 2 into carboxylic acids and their derivatives.…”

“…[8] Hou and co-workers also reviewed their personal studies on the carboxylation reactions with CO 2 using N-heterocyclic carbene (NHC)-copper catalysts. [9] Although the relevant reviews have been presented, recent years witnessed the rapid developments of copper-catalyzed transformations of CO 2 into carboxylic acids and their derivatives. Therefore, this review will update the achievements about copper-catalyzed carboxylation reactions using CO 2 with various substrates in the past five years (Scheme 1).…”