Recent Advances in N-Heterocyclic Carbene Coinage Metal Complexes in A3-Coupling and Carboxylation Reaction

Abstract

Owing of their accessibility and wide range of reactivities, alkynes make for fascinating building blocks. Either a selective alkyne carbon-carbon triple bond reaction or activation of the terminal alkyne C-H bond may be employed to functionalize them. Monocationic coinage metal complexes with a d10 electronic configuration are effective catalysts for alkyne activation. Silver(I) and gold(I) N-heterocyclic (NHC) systems are emerging as promising catalysts in multicomponent alkyne activation reactions; this review paper focuses on A3 (aldehyde-amine-alkyne)-coupling reaction and carbon dioxide fixation, furnishing a systematic overview of the scientific advances achieved during the last two decades. This study will carefully compare the corresponding silver and gold complexes employed in the two processes. The differences in reaction routes brought about by the catalyst ligand structure will be investigated with an emphasis on evaluating the benefits provided by the easily tuneable NHC backbone, in terms of chemo- and stereo-selectivity.

Internal 2D networking of silver bromide with a bidentate N-heterocyclic carbene ligand enables the formation of an inherently heterogeneous reusable catalyst for multicomponent A3 coupling

“…1B). 19–22 However, our recent findings, 23 as well as other studies, have revealed the possibility of silver( i ) atom chelation by bidentate ligands (Fig. 1C).…”

“…1A). 18–20 The structural diversity is further expanded with the use of bidentate ligands. In most instances, each NHC moiety coordinates to a different silver( i ) atom, potentially leading to dimeric neutral or cationic monomeric species (Fig.…”

A Mechanistic Insight on CuI‐Catalyzed Synthesis of Oxazolidinones through a Four‐Component Reaction

“…The field of metal-catalyzed four-component coupling reactions towards oxazolidinone synthesis is rapidly evolving, [5] but most of the catalytic systems are based on Cu(I) [6] (few contributions involve Cu(II) catalytic precursors [7] ) or combinations thereof with engineered solvents such as ionic liquids to enhance the recyclability of the resulting catalytic systems. [8] From a mechanistic point of view, the seminal work reported by Li and coworkers proposed a mechanism for the A 3 -coupling carboxylative cyclization through the formation of the corresponding propargylamine intermediate and also pointing to a synergistic effect between the amine and CO 2 .…”

Silver and Gold Complexes with NHC-Ligands Derived from Caffeine: Catalytic and Pharmacological Activity

“…Under a chemical point of view, Au(I)/Ag(I) NHC complexes are effective catalysts for some coupling reactions, such as a three-component condensation among an aldehyde, an amine, and a terminal alkyne, named the A 3 -coupling reaction, hydroamination, or alkoxylation of alkynes to produce imine or enol, respectively. Thus, the catalytic activity of new synthesized compounds was also evaluated both in A 3 -coupling and in hydroamination reactions [ 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”