Nucleophilic Heterocyclic Carbene Research Articles

1-Trifluoromethyl-prop-2-yne 1-iminium salts and 1-imines: reactions with the mesoionic „Nitron“

Abstract The heterocyclic mesoionic compound (1,4-diphenyl-1H-1,2,4-triazol-4-ium-3-yl)(phenyl)amide („Nitron“) has recently been found to exist in a prototropic equilibrium with minor amounts of a nucleophilic heterocyclic carbene of the 1,2,4-triazolyl-5-ylidene type. Here we report that Nitron reacts with 1-trifluoromethyl-substituted prop-2-yne iminium salts by conjugate nucleophilic addition of the anionic PhN‒ substituent in the mesoionic tautomer, whereas the nucleophilic triazolylidene form is involved in the reaction with 1-CF3-prop-2-yne imines. 3-(2,3-Dihydro-1H-benzo[c]azepin-5-yl)-1H-1,2,4-triazol-4-ium triflate salts were obtained in the former case and (Z)-9-arylidene-1,2,4,7-tetraazaspiro[4.4]nona-2,7-dienes in the latter.

Recent advances in employing homoenolates generated by N-heterocyclic carbene (NHC) catalysis in carbon-carbon bond-forming reactions.

The use of NHCs for generating homoenolate species has gained widespread popularity in recent years. A number of highly stereoselective processes of NHC-homoenolates have emerged. Homoenolate reactions have also been employed as key steps in the total synthesis of a number of natural products. The use of compatible co-catalysts, improved NHC-catalyst design and the use of novel precursors for homoenolate generation are among the major developments in this area that were disclosed recently. This tutorial review organises and presents the advancements in this rapidly growing area of catalysis and in the process updates a previous account published in 2011 in this journal.

ChemInform Abstract: Nucleophilic, Heterocyclic, Carbene‐Catalyzed, Solvent‐Free, One‐Pot Synthesis of Polyhydroquinolines via Multicomponent Hantzsch Reaction: An Efficient and Ecofriendly Approach.

Abstract A simple, efficient, and ecofriendly one-pot method has been reported for the synthesis of polyhydroquinolines in excellent yield using nucleophilic heterocyclic carbene as catalyst. The generalized approach is the Hantzsch four-component reaction of aromatic aldehyde, ethyl acetoacetate, cyclic 1,3-diketone, and ammonium acetate.

Nucleophilic, Heterocyclic, Carbene-Catalyzed, Solvent-Free, One-Pot Synthesis of Polyhydroquinolines via Multicomponent Hantzsch Reaction: An Efficient and Ecofriendly Approach

A simple, efficient, and ecofriendly one-pot method has been reported for the synthesis of polyhydroquinolines in excellent yield using nucleophilic heterocyclic carbene as catalyst. The generalized approach is the Hantzsch four-component reaction of aromatic aldehyde, ethyl acetoacetate, cyclic 1,3-diketone, and ammonium acetate.

NHC-Catalyzed Annulation of Enals to 2,4-Dien-1-ones: Efficient Diastereoselective Synthesis of 1,3-Diaryl-4-styrenyl Cyclopentenes

Nucleophilic heterocyclic carbene (NHC)-catalyzed ­annulation strategy has been utilized for the efficient synthesis of styrenyl-substituted cyclopentenes from 2,4-dienones.

ChemInform Abstract: A Cascade Reaction Actuated by Nucleophilic Heterocyclic Carbene Catalyzed Intramolecular Addition of Enals via Homoenolate to α,β‐Unsaturated Esters: Efficient Synthesis of Coumarin Derivatives.

AbstractComparable yields of (II) are obtained regardless whether the E/Z‐mixtures of the substrates are used or pure isomers.

Nucleophilic heterocyclic carbene promoted one pot multicomponent synthesis of new 6-(1H-indol-3-yl)-2-oxo-4-aryl-1,2,3,4 tetrahydropyrimidine-5-carbonitriles: an eco-compatible approach with PEG as a biodegradable medium

A three-component, one-pot, simple, direct and highly efficient cyclocondensation method has been developed for the synthesis of fourteen 6-(1H-indol-3-yl)-2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidine-5-carbonitriles by combining an arylaldehyde with 3-(cyanoacetyl)-indoles and urea in the presence of the PEG-400 and a catalytic amount of the thiazolium anion. A short reaction time, simple reaction conditions, ease of product isolation, use of a cheap and readily available and reusable catalyst make this method very attractive from an environmental and economic perspective.

A Cascade Reaction Actuated by Nucleophilic Heterocyclic Carbene Catalyzed Intramolecular Addition of Enals via Homoenolate to α,β-Unsaturated Esters: Efficient Synthesis of Coumarin Derivatives

A nucleophilic heterocyclic carbene mediated intramolecular homoenolate reaction strategy for the efficient synthesis of 4-alkyl substituted coumarins is described.

Synthesis and characterisation of quinoline functionalised imidazolium salts

A series of quinoline based imidazolium salts were prepared and characterised as nucleophilic heterocyclic carbene (NHC) ligand precursors. The symmetrically saturated imidazolium salt prepared by ring closure of achiral tetradentate diquinolyl-diamine with triethyl orthoformate is a tridentate ligand and can function as pincer ligand while the two asymmetric imidazolium salts are bidentate and have different steric bulk which may have interesting implication in catalysis. The solubility of the symmetrical dihydroimidazolium salt was enhanced by replacing the counter ion tetraflouroborate with tetrakis (3,5-bis(triflouromethyl)phenyl)borate (Barf ) and its structure confirmed by X- ray crystallography. Keywords: Nucleophilic heterocyclic carbene (NHC), Imidazolium salt, ligand, ring closure.

Synthesis and characterisation of octahydroacidie based Imidazolium salt

This paper describes the synthesis and characterization of chiral octahydroacridine based imidazolium salt. The reaction of cyclohexanone, dimethylamine hydrochloride and formaldehyde under reflux affords 2-Dimethylaminomethylcyclohexanone which undergoes reaction with cyclohexanone to give 2, 2’-Dicyclohexanoylmethane. Reaction of 2, 2’-dicyclohexanoylmethane with hydroxylamine hydrochloride affords the synthesis of Sym-Octahydroacridine from which 4-chlorooctahydroacridine was obtained by oxidation, hydrolysis and halogenation of the resulting secondary alcohol. The desired chiral octahydroacridine based imidazolium salt was prepared by refluxing of mesityl imidazole and 4-chlorooctahydroacridine in THF at 90 oC in a pressure tube for two week allowing the synthesis of a new unreported chiral bidentate NHC ligand precursor. Keywords: Nucleophilic heterocyclic carbene (NHC), octahydroacridine, ligand, mesityl imidazole

ChemInform Abstract: Nucleophilic Heterocyclic Carbene as a Novel Catalyst for Cyclopropanation of Cyano Acrylates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Novel Nucleophilic Heterocyclic Carbene Mediated Stereoselective Conjugate Addition of Enals to Nitrostyrenes via Homoenolate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Nucleophilic heterocyclic carbene as a novel catalyst for cyclopropanation of cyano acrylates

Nucleophilic heterocyclic carbenes (NHCs) have been used for the first time as catalysts in the cyclopropanation of ethyl cyanocinnamates with phenacyl bromide by Michael-initiated ring-closure (MIRC).

Novel Nucleophilic Heterocyclic Carbene Mediated Stereoselective Conjugate Addition of Enals to Nitrostyrenes via Homoenolate

A stereoselective Michael addition of homoenolate, generated from enals by nucleophilic heterocyclic carbene (NHC) catalysis, to beta-nitrostyrenes is reported for the first time. The products of this reaction obtained in good yields are of potential value in the synthesis of a variety of acyclic and heterocyclic compounds.

ChemInform Abstract: Nucleophilic Heterocyclic Carbene Catalyzed Annulation of Enals to Chalcones in Methanol: A Stereoselective Synthesis of Highly Functionalized Cyclopentanes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Nucleophilic Heterocyclic Carbene Catalyzed Annulation of Enals to Chalcones in Methanol: A Stereoselective Synthesis of Highly Functionalized Cyclopentanes

Homoenolates generated from enals by nucleophilic heterocyclic carbene (NHC) catalysis undergo annulation with chalcones in methanol to afford methyl beta-hydroxycyclopentanecarboxylates, stereoselectively. Construction of four contiguous stereocenters in a stereoselective manner is noteworthy.

Stereoselective synthesis of spirocyclopentanones viaN-heterocyclic carbene-catalyzed reactions of enals and dienones

Homoenolates generated from enals by nucleophilic heterocyclic carbene (NHC) catalysis undergo a conjugate addition/cyclization sequence with cyclic dienones, culminating in the efficient synthesis of spirocyclopentanones.

Recent advances in carbon–carbon bond-forming reactions involving homoenolates generated by NHC catalysis

Homoenolate, a species containing anionic carbon beta to a carbonyl group or a moiety that can be transformed into a carbonyl group, is a potential three carbon synthon. Recent introduction of a protocol for the generation of homoenolate directly from enals by NHC (nucleophilic heterocyclic carbene) catalysis has made it possible to explore the synthetic utility of this unique reactive intermediate. The versatility of NHC-bound homoenolate is illustrated by its annulation with various carbonyl compounds leading to gamma-butyrolactones, spiro-gamma-butyrolactones, and delta-lactones. Interception of homoenolate with imines afforded gamma-lactams and bicyclic beta-lactams. Formation of cyclopentenes and spirocyclopentanones respectively by reaction with enones and dienones is also noteworthy. This tutorial review focuses on these and other types of reactions which attest to the synthetic potential of NHC-bound homoenolates in organic synthesis.

N-Heterocyclic Carbene Catalyzed Reaction of Enals and Diaryl-1,2 diones via Homoenolate: Synthesis of 4,5,5-Trisubstituted γ-Butyrolactones

Nucleophilic heterocyclic carbene (NHC)-catalyzed annulation of enals proceeds with variety of 1,2-dicarbonyl compounds, leading to the formation of 4,4,5-trisubstituted γ-butyrolactones.

An N‐Heterocyclic Carbene‐Catalyzed [8 + 3] Annulation of Tropone and Enals via Homoenolate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.