Fascinating frontiers of N/O-functionalized N-heterocyclic carbene chemistry: from chemical catalysis to biomedical applications

Abstract

The in vogue N-heterocyclic carbenes (NHCs) have attracted attention largely for its new found popularity in chemical catalysis and also for displaying promising traits in biomedical applications. The current perspective provides an account of our efforts in exploring the utility of N/O-functionalized N-heterocyclic carbenes in these two areas. On the catalysis front, we have employed the N/O-functionalized N-heterocyclic carbene based precatalysts for the C-C and C-N bond forming reactions like the Suzuki-Miyaura, Sonogashira and Hiyama cross-couplings, the base-free Michael addition, the alkene and alkyne hydroamination reactions and the ring-opening polymerization (ROP) of L-lactides that produce biodegradable polylactide polymers while on the biomedical application front, the anticancer and antimicrobial properties of these N/O-functionalized N-heterocyclic carbene complexes were evaluated. Towards this objective, the N-heterocyclic carbene chemistry of a variety of transition metals like Ag, Au, Ni and Pd has been investigated.

Counterion-induced modulation in biochemical properties of nitrile functionalized silver(I)-N-heterocyclic carbene complexes

“…This binding may result in more stable complexes that can slowly release Ag ions, such that the antimicrobial effect can be retained over a long period of time. Furthermore, the control over the electronic and steric properties of ligands is of critical importance for stabilizing a variety of transition metal complexes [10,11]. Subtle variations of steric bulk and electron density at the active site may have drastic effects on the antibacterial properties [12,13].…”

Thermoregulated Aqueous Biphasic Catalysis of Sonogashira Reactions

“…[25] The nature of the strong electron-donating abilities of N-heterocyclic carbene (NHC) ligands facilitates tighter binding of the ligand to the metal, which significantly enhances the catalyst's lifetime and efficiency. [26][27][28] Hence, NHC ligands have been applied in versatile catalytic reactions due to its excellent physicochemical properties. In the present paper, we report the use of a PEG-based imidazolium salt as NHC thermoregulated ligand precursors for Sonogashira reactions, being organic solvent-free and copper-free.…”

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

“…In contrast to the individual carbenes, their metal complexes have been studied as biologically active substances for more than a decade; strong antimicrobial and antitumor properties have been found (see, e.g., the following reviews [422][423][424] ). In the present section, some of the little-known antimicrobial properties of transition metal carbene complexes are described.…”