1,3-Dialkylimidazolium-2-carboxylates as versatile N-heterocyclic carbene–CO2 adducts employed in the synthesis of carboxylates and α-alkylidene cyclic carbonates

Tommasi, Immacolata; Sorrentino, Fabiana

doi:10.1016/j.tetlet.2008.10.107

Cited by 71 publications

(30 citation statements)

References 55 publications

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“…[68] A few stoichiometric reactions between NHC·CO 2 betaines and inorganic reagents have been carried out by Kuhn and co-workers (Scheme 12). Thus, protonation of 1,3-diisopropyl-4,5-dimethylimidazolium-2-carboxylate (8) with hydrogen chloride or tetrafluoroboric acid under anhydrous conditions affords the corresponding imidazoliumcarboxylic acid, whose dissociation constant was determined in aqueous solution.…”

Section: Reactivitymentioning

confidence: 99%

Betaine Adducts of N‐Heterocyclic Carbenes: Synthesis, Properties, and Reactivity

2009

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N‐Heterocyclic carbenes (NHCs) form stable zwitterionicadducts with a range of heteroallenes, ketenes, and allenes. Although the first representatives of this class of inner salts were first investigated as far back as the 1960s, they have enjoyed a sustained interest from the chemical community over the years. Depending on the nature of their anionic moiety, NHC betaines display a very broad palette of reactivities and have found applications in various fields of organic synthesis and catalysis. In this Microreview, the synthesis, properties, and reactivity of NHC betaines are surveyed. The NHCs under consideration include ylidenes derived from imidazole, benzimidazole, imidazoline, thiazole, or triazole, and the heteroallenes investigated so far are carbon dioxide, carbon disulfide, isocyanates, isothiocyanates, and their selenium analogues. A historical background is provided for each type of adduct under consideration, but emphasis is placed mainly on developments that have appeared in the literature within the past few years. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Section: Reactivitymentioning

confidence: 99%

Betaine Adducts of N‐Heterocyclic Carbenes: Synthesis, Properties, and Reactivity

2009

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“…Catalysts 2017, 7, 380 22 of 54 1,3-diaryl-imidazolium-2-carboxylates (78) have been used as CO2-transfer agents for the carboxylation of ketones and nitriles [66,106,111,112]. Reactions in which a "C-COO − " moiety behave as CO2-transfer agent towards an organic compound are not common.…”

Section: In Dmsomentioning

confidence: 99%

“…Subsequently 76-77 have been used as CO2-carriers able to transfer CO2 to acetone, acetophenone, cyclohexanone and benzyl cyanide (Scheme 34b) [66,106]. Interestingly, the reaction proceeds at room temperature requiring the presence of a metal salt as NaBF4, NaBPh4 or KPF6 in stoichiometric amount.…”

Section: In Dmsomentioning

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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“…of acetophenone to form benzoyl acetate, or methanol to form monomethyl carbonate. [94][95][96] 1,3-Di-tert-butylimidazolium-2-carboxylate was used as recyclable organocatalyst in the cycloaddition of aziridines and carbon dioxide. 97 Imidazolium-2-thiocarboxylates were also described as organocatalysts.…”

Section: Scheme 36 Formation Of Isothiocyanate Adductsmentioning

confidence: 99%

Recent advances in neutral and anionic N-heterocyclic carbene – betaine interconversions. Synthesis, characterization, and applications

Schmidt¹,

Wiechmann²,

Freese³

2013

Arkivoc

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Some mesoionic compounds, i.e. five-membered representatives of the class of conjugated mesomeric betaines (CMB), are in equilibrium with their tautomeric normal N-heterocyclic carbenes (nNHC). In addition, anionic N-heterocyclic carbenes, generated by deprotonation of mesoionic compounds, have been described. The first examples of conversions of crossconjugated mesomeric betaines (CCMB), 6-oxopyrimidinium-4-olates, into normal Nheterocyclic carbenes have been reported as well. CCMB such as imidazolium-4-carboxylate and pyrazolium-4-carboxylate can decarboxylate to form abnormal (aNHC) or remote N-heterocyclic carbenes (rNHC). Most conversions of betaines into N-heterocyclic carbenes start from pseudocross-conjugated mesomeric betaines (PCCMB) which can be regarded as heterocumulene adducts of nNHC. Thus, decarboxylations of imidazolium-2-carboxylates, 1,2,4-triazole-3-carboxylates, pyrazolium-3-carboxylates or indazolium-3-carboxylates yield N-heterocyclic carbenes which have been used in catalysis, complex chemistry, heterocyclic synthesis, and organocatalysis.

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1,3-Dialkylimidazolium-2-carboxylates as versatile N-heterocyclic carbene–CO2 adducts employed in the synthesis of carboxylates and α-alkylidene cyclic carbonates

Cited by 71 publications

References 55 publications

Betaine Adducts of N‐Heterocyclic Carbenes: Synthesis, Properties, and Reactivity

Betaine Adducts of N‐Heterocyclic Carbenes: Synthesis, Properties, and Reactivity

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

Recent advances in neutral and anionic N-heterocyclic carbene – betaine interconversions. Synthesis, characterization, and applications

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