Synthesis of a Pyrazol-3-ylidene Palladium Complex, Pyrazolium Salts and Mesomeric Betaines of Pyrazole as N-Heterocyclic Carbene Precursors

Dreger, Andrij; Nieger, Martin; Drafz, Martin; Schmidt, Andreas

doi:10.1515/znb-2012-0410

Cited by 9 publications

(1 citation statement)

References 31 publications

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“…Whereas these so-called pseudo-cross-conjugated mesomeric betaines (PCCMB) [11,12,14] are valuable precursors of NHCs, their cross-conjugated isomers, for example pyrazol-4-carboxylate, are not, because their decarboxylation requires vigorous conditions. [18] Several classes of mesomeric betaines, including mesoionic compounds, can be converted into anionic Nheterocyclic carbenes by deprotonation. [14] Some mesoionic compounds have been recently nicknamed [19] mesoionic Nheterocyclic olefins (mNHO) [19,20,21] or mesoionic N-heterocyclic imines [22] when they possess exocyclic methide (À CR 2 À ) or aminide (À NR À ) substituents.…”

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confidence: 99%

Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

et al. 2023

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Sydnone methides represent an almost unknown class of mesoionic compounds which possess exocyclic carbon substituents instead of oxygen (sydnones) or nitrogen (sydnone imines) in the 5‐position of a 1,2,3‐oxadiazolium ring. Unsubstituted 4‐positions give rise to the generation of anionic N‐heterocyclic carbenes by deprotonation. Preparations of new sydnone methides are described here. They can be represented by mesomeric structures with either exocyclic carbanionic groups like −C(CN)2−, −C(CN)(COOMe)−, −C(CN)(CONH2)−, and −C(CN)(SO2Me)−, or with the corresponding exocyclic C=C double bonds as a common feature with mesoionic N‐heterocyclic olefins. An X‐ray single structure analysis revealed a length of 140.7(3) pm of the exocyclic bond in the solid state. From the coalescence temperature (55 °C) determined by a series of 13C NMR experiments (150 MHz) at various temperatures, an energy of rotation of 18.5 Kcal/mol was calculated for this bond. The 13C NMR signals of the anionic N‐heterocyclic carbenes, from which the 2‐mesityl‐substituted anionic NHC proved to be stable up to 10 °C, are highly shifted upfield (δcarbene=157.9 ppm−160.5 ppm). The carbenes can be reacted in situ with elemental selenium and chlorophosphanes to yield sydnone methide selenoethers after methylation and 4‐phosphanylsydnone methides in good to excellent yields, respectively.

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Section: Introductionmentioning

confidence: 99%

Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

et al. 2023

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Interaction of N‐Heterocyclic Carbenes and Simple Carbenes with Small Molecules (One to Three Atoms) Excluding Metals: Formation of Covalent C–X Bonds

Alkorta

Elguero

2018

Journal of Heterocyclic Chem

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Synthesis of novel photoluminescent pyridinium-betaine-type molecules

et al. 2020

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A series of pyridinium-betaine like molecules has been reported; one family of molecules is built with a benzimidazole core and a second one with a pyrimidine moiety. The title compounds were prepared by mixing 2-chlorobenzimidazole or 2-bromopyrimidine with the corresponding pyridines (pyridine, 4-tert-butylpyridine, 4-hydroxypyridine, potassium 4-trifluoroboratepyridine, 4-dimethylaminopyridine) in acetonitrile or DMSO at high temperatures. The novel compounds were characterized by spectroscopic methods. The UV-Vis. and fluorescence features are reported as well. Preliminary photoluminescence results showed broadband emissions as common feature ascribed to the compounds containing benzimidazole ring. Some of the spectra nearly span over the whole visible spectral range, which pave the way to real opportunities to design single-component panchromatic emitters.

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Synthesis of a Pyrazol-3-ylidene Palladium Complex, Pyrazolium Salts and Mesomeric Betaines of Pyrazole as N-Heterocyclic Carbene Precursors

Cited by 9 publications

References 31 publications

Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

Interaction of N‐Heterocyclic Carbenes and Simple Carbenes with Small Molecules (One to Three Atoms) Excluding Metals: Formation of Covalent C–X Bonds

Synthesis of novel photoluminescent pyridinium-betaine-type molecules

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