Diverse Chemical Applications of N-Heterocyclic Carbenes

doi:10.1021/ja908253u

Cited by 43 publications

(5 citation statements)

References 20 publications

(28 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, there has been significant progress in the rational design of effective organometallic catalysts using σ-donating N -heterocyclic carbenes (NHCs), , and a number of elegant examples of NHC ligand-promoted hydrogenation have been reported by Glorius, Stephan, Crabtree, and others . Differing from classic NHCs, cyclic (amino)(alkyl)carbenes (CAACs) show an enhanced nucleophilicity because of a σ-donating alkyl substituent, which was discovered by Bertrand and has received increasing interest recently. , However, the ligand effect of CAACs in organometallic catalysis has rarely been studied .…”

mentioning

confidence: 99%

Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes

et al. 2015

View full text Add to dashboard Cite

Air-stable Rh complexes ligated by strongly σ-donating cyclic (amino)(alkyl)carbenes (CAACs) show unique catalytic activity for the selective hydrogenation of aromatic ketones and phenols by reducing the aryl groups. The use of CAAC ligands is essential for achieving high selectivity and conversion. This method is characterized by its good compatibility with unsaturated ketones, esters, carboxylic acids, amides, and amino acids and is scalable without detriment to its efficiency.

show abstract

mentioning

confidence: 99%

Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The need for heavy-metal-free and eco-friendly ROP systems following the green chemistry concept has inspired the development of various organocatalysts allowing the ROP of epoxides to proceed in a highly efficient and controllable manner under mild conditions. However, these organocatalysts exhibit several drawbacks; for example, highly reactive and sensitive catalysts such as N -heterocyclic carbenes and N -heterocyclic olefins require careful handling to avoid the adverse effects of moisture and temperature variation. , In the case of the phosphazene base ( t -Bu-P 4 ) catalyst system, the deprotonation of protic functional groups limits the scope of epoxide monomers, and the catalyst residues are suspected to be cytotoxic . Besides, the high cost (compared to that of conventional alkoxides) of organocatalysts obstructs their applications in industrial polyether production.…”

Section: Introductionmentioning

confidence: 99%

Polyether/Polythioether Synthesis via Ring-Opening Polymerization of Epoxides and Episulfides Catalyzed by Alkali Metal Carboxylates

et al. 2022

View full text Add to dashboard Cite

Alkali metal carboxylates were evaluated as simple and green catalysts for the ring-opening polymerization (ROP) of various epoxides (e.g., alkyl-substituted epoxides and glycidyl ethers) and episulfides (alkyl-substituted episulfides and thioglycidyl ethers). The thus-produced functional polyethers (end-functionalized polyethers, block copolyethers, polyether–polyester block copolymers, topologically unique polyethers, and isotactic-enriched polyethers) and polythioethers featured well-defined structures and controlled molecular weights (M n,SEC = 1.0–32 kg mol–1). The most effective catalyst was identified as cesium pivalate, and the variation of carboxylate moieties and alkali metal cations enabled the tuning of acid/base characteristics and thus allowed one to control polymerization behavior and expand the scope of functional monomers and initiators. Kinetic analysis confirmed the controlled/living nature of the polymerization process, while mechanistic studies revealed that carboxylate moieties did not directly initiate the ring-opening of epoxide monomers via nucleophilic attack but rather activated the alcohol initiators/chain ends via H-bonding and thus rendered the corresponding OH groups sufficiently nucleophilic to attack the alkali metal cation-activated epoxides.

show abstract

“…[11][12][13] This unique acid-base property, the fact that their chemical structures can be relatively easily modified, as well as easy handling cause NHC ligands to be popular in organic synthesis, surface modification, and different fields of material sciences. [14][15][16][17][18][19][20][21][22][23][24][25][26] For example, the NHC ligands are commonly employed to synthesize cross-coupling catalysts and for chemical bond activation; this, in particular, involves CÀ H activation and functionalization. [27][28][29][30][31][32][33] The next important NHC applications are their broad utilization in various fields of metathesis.…”

Section: Introductionmentioning

confidence: 99%

NMR Crystallography Enhanced by Quantum Chemical Calculations and Liquid State NMR Spectroscopy for the Investigation of Se‐NHC Adducts**

Mames

Pietrzak

Bernatowicz

et al. 2021

Chemistry A European J

View full text Add to dashboard Cite

N-heterocyclic carbene ligands (NHC) are widely utilized in catalysis and material science. They are characterized by their steric and electronic properties. Steric properties are usually quantified on the basis of their static structure, which can be determined by X-ray diffraction. The electronic properties are estimated in the liquid state; for example, via the 77 Se liquid state NMR of Se-NHC adducts. We demonstrate that 77 Se NMR crystallography can contribute to the characterization of the structural and electronic properties of NHC in solid and liquid states. Selected Se-NHC adducts are investigated via 77 Se solid state NMR and X-ray crystallography, supported by quantum chemical calculations. This investigation reveals a correlation between the molecular structure of adducts and NMR parameters, including not only isotropic chemical shifts but also the other chemical shift tensor components. Afterwards, the liquid state 77 Se NMR data is presented and interpreted in terms of the quantum chemistry modelling. The discrepancy between the structural and electronic properties, and in particular the π-accepting abilities of adducts in the solid and liquid states is discussed. Finally, the 13 C isotropic chemical shift from the liquid state NMR and the 13 C tensor components are also discussed, and compared with their 77 Se counterparts. 77 Se NMR crystallography can deliver valuable information about NHC ligands, and together with liquid state 77 Se NMR can provide an indepth outlook on the properties of NHC ligands.

show abstract

Diverse Chemical Applications of N-Heterocyclic Carbenes

Cited by 43 publications

References 20 publications

Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes

Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes

Polyether/Polythioether Synthesis via Ring-Opening Polymerization of Epoxides and Episulfides Catalyzed by Alkali Metal Carboxylates

NMR Crystallography Enhanced by Quantum Chemical Calculations and Liquid State NMR Spectroscopy for the Investigation of Se‐NHC Adducts**

Contact Info

Product

Resources

About