Reversible carboxylation of N-heterocyclic carbenesElectronic supplementary information (ESI) available: crystal structure data and ORTEP for 1,3-bis(2,6-diisopropylphenyl)imidazolylium-2-carboxylate (3). See http://www.rsc.org/suppdata/cc/b3/b311350g/

Duong, Hung A.; Tekavec, Thomas N.; Arif, Atta M.; Louie, Janis

doi:10.1039/b311350g

Cited by 305 publications

(203 citation statements)

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“…Interestingly, NHCs can activate CO 2 and form imidazolium carboxylates, which allow further reactions with various organic compounds. [42][43][44] In this regard, NHCs proved to be effective catalysts for the reaction of CO 2 with epoxides to produce cyclic carbonates.…”

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confidence: 99%

A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks

et al. 2013

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A polymer analogous reaction was carried out to generate a porous polymeric network with N-heterocyclic carbenes (NHC) in the polymer backbone. Using a stepwise approach, first a polyimine network is formed by polymerization of the tetrafunctional amine tetrakis(4-aminophenyl)methane. This polyimine network is converted in the second step into polyimidazolium chloride and finally to a polyNHC network.Furthermore a porous Cu(II)-coordinated polyNHC network can be generated. Supercritical drying generates polymer networks with high permanent surface areas and porosities which can be applied for different catalytic reactions. The catalytic properties were demonstrated for example in the activation of CO 2 or in the deoxygenation of sulfoxides to the corresponding sulfides.

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confidence: 99%

A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks

et al. 2013

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“…Later, Louie and coworkers reported a different synthesis, carried out bubbling CO2 into an imidazolium salt and potassium tert-butoxide solution [52]. The various syntheses of NHC-CO2 adducts as well as their chemistry are discussed in both classical and more recent reviews [53][54][55].…”

Section: Methodsmentioning

confidence: 99%

Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

2016

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In the last twenty years, N-heterocyclic carbenes (NHCs) have acquired considerable popularity as ligands for transition metals, organocatalysts and in metal-free polymer synthesis. NHCs are generally derived from azolium based salts NHCH+X− by deprotonation or reduction (chemical or electrochemical) of NHCH+. The extensive knowledge of the physicochemical properties of NHCH+/NHC system could help to select the conditions (scaffold of NHC, nature of the counter-ion X−, solvent, etc.) to enhance the catalytic power of NHC in a synthesis. The electrochemical behavior of NHCH+/NHC system, in the absence and in the presence of solvent, was extensively discussed. The cathodic reduction of NHCH+ to NHC and the anodic oxidation of NHC, and the related effect of the scaffold, solvent, and electrodic material were emphasized. The electrochemical investigations allow acquiring further knowledge as regards the stability of NHC, the acidic and nucleophilic properties of NHCH+/NHC system, the reactivity of NHC versus carbon dioxide and the effect of the hydrogen bond on the catalytic efficiency of NHC. The question of the spontaneous or induced formation of NHC from particular ionic liquids was reconsidered via voltammetric analysis. The results suggested by the classical and the electrochemical methodologies were compared and discussed.

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“…In Section 4.2, we have mentioned the carboxylation of 1,3-dialkyimidazolium chlorides with CO2/Na2CO3 and the use of 1,3-dialkyimidazolium-2-carboxylates as CO2-carriers in the carboxylation of C(sp 3 )-H acidic compounds. NHC-CO2 compounds can be also synthesized by carboxylation of imidazol-2-yilidene precursors as reported by Kuhn in 1999 (Scheme 55b) [134] or by carboxylation of imidazol-2-ylidenes generated in situ by deprotonation of imidazolium salts (139) with potassium tert-butoxide or KN(SiMe3)2 as reported by Louie [135] and Delaude [136] Scheme 54. (a) Reaction mechanism proposed by Skrydstrup for carboxylation/cyclization of 2-alkynyl indoles with CO 2 ; (b) Bifunctional activation mechanism proposed on the basis of DFT analysis by Wong and coworkers.…”

Section: Base-promoted Carboxylation Of Aromatic and Heteroaromatic Cmentioning

confidence: 99%

Direct Carboxylation of C(sp3)-H and C(sp2)-H Bonds with CO2 by Transition-Metal-Catalyzed and Base-Mediated Reactions

Tommasi

2017

Catalysts

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This review focuses on recent advances in the field of direct carboxylation reactions of C(sp 3 )-H and C(sp 2 )-H bonds using CO 2 encompassing both transition-metal-catalysis and base-mediated approach. The review is not intended to be comprehensive, but aims to analyze representative examples from the literature, including transition-metal catalyzed carboxylation of benzylic and allylic C(sp 3 )-H functionalities using CO 2 which is at a "nascent stage". Examples of light-driven carboxylation reactions of unactivated C(sp 3 )-H bonds are also considered. Concerning C(sp 3 )-H and C(sp 2 )-H deprotonation reactions mediated by bases with subsequent carboxylation of the carbon nucleophile, few examples of catalytic processes are reported in the literature. In spite of this, several examples of base-promoted reactions integrating "base recycling" or "base regeneration (through electrosynthesis)" steps have been reported. Representative examples of synthetically efficient, base-promoted processes are included in the review.

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Reversible carboxylation of N-heterocyclic carbenesElectronic supplementary information (ESI) available: crystal structure data and ORTEP for 1,3-bis(2,6-diisopropylphenyl)imidazolylium-2-carboxylate (3). See http://www.rsc.org/suppdata/cc/b3/b311350g/

Abstract: Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a series of imidazolium carboxylates revealed carboxylation was reversible with N-aryl substituted adducts.

Cited by 305 publications

References 14 publications

A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks

A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks

Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

Direct Carboxylation of C(sp3)-H and C(sp2)-H Bonds with CO2 by Transition-Metal-Catalyzed and Base-Mediated Reactions

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