Sulfur, mercury, and boron adducts of sydnone imine derived anionic N-heterocyclic carbenes

Freese, Tyll; Namyslo, Jan C.; Nieger, Martin; Schmidt, Andreas

doi:10.1039/c9ra00294d

Cited by 14 publications

(4 citation statements)

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“…Our interest in mesomeric betaines [22] and their relationship to neutral [12a, b, 23, 24] as well as anionic N‐heterocyclic carbenes [25] in combination with the introduction of an energy‐based quantitative index of the ease of NHC formation from precursors by deprotonation (carbene relative energy of formation, CREF) [26] stimulated initial calculations which suggested that sydnone methides are interesting precursors for the generation of unique π‐electron‐rich anionic N‐heterocyclic carbenes. This index supplements other measures of σ‐donor and/or π‐properties of NHCs such as molecular electrostatic potentials (MESP), [27] computationally derived ligand electronic parameters (CEP), [28] Tolman parameters (TEP), [29] HOMO energies, [30, 31] calculated proton affinities, [30, 32] 1 J CH and 1 J CSe coupling constants [33] of precursor salts and Se adducts, respectively, and Huynh electronic parameters (HEP) [34] of Pd complexes (review [35] ).…”

Section: Methodsmentioning

confidence: 99%

Sydnone Methides—A Forgotten Class of Mesoionic Compounds for the Generation of Anionic N‐Heterocyclic Carbenes

et al. 2021

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Sydnone methides are described from which only one single example has been mentioned in the literature so far. Their deprotonation gave anions which can be formulated as π‐electron rich anionic N‐heterocyclic carbenes. Sulfur and selenium adducts were stabilized as their methyl ethers, and mercury, gold as well as rhodium complexes of the sydnone methide carbenes were prepared. Sydnone methide anions also undergo C−C coupling reactions with 1‐fluoro‐4‐iodobenzene under Pd(PPh3)4 and CuBr catalysis. 77Se NMR resonance frequencies and 1JC4‐Se as well as 1JC4‐H coupling constants have been determined to gain knowledge about the electronic properties of the anionic N‐heterocyclic carbenes. The carbene carbon atom of the sydnone methide anion 3 j resonates at δ=155.2 ppm in 13C NMR spectroscopy at −40 °C which is extremely shifted upfield in comparison to classical N‐heterocyclic carbenes.

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Section: Methodsmentioning

confidence: 99%

Sydnone Methides—A Forgotten Class of Mesoionic Compounds for the Generation of Anionic N‐Heterocyclic Carbenes

et al. 2021

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“…Interaction of lithio sydnone imines 22 with tetracyanoethylene afforded pyrazoles as a result of reductive 1,3-dipolar cycloaddition, while the addition of azodicarboxylate gave 4-hydrazinylsydnone imines [ 50 ]. A formation of C 4 -B and C 4 -Hg adducts from carbenoids 22 was also reported [ 51 ].…”

Section: Sydnone Iminesmentioning

confidence: 90%

Recent Advances in the Synthesis and Biomedical Applications of Heterocyclic NO-Donors

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Zhilin

2021

Molecules

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Nitric oxide (NO) is a key signaling molecule that acts in various physiological processes such as cellular metabolism, vasodilation and transmission of nerve impulses. A wide number of vascular diseases as well as various immune and neurodegenerative disorders were found to be directly associated with a disruption of NO production in living organisms. These issues justify a constant search of novel NO-donors with improved pharmacokinetic profiles and prolonged action. In a series of known structural classes capable of NO release, heterocyclic NO-donors are of special importance due to their increased hydrolytic stability and low toxicity. It is no wonder that synthetic and biochemical investigations of heterocyclic NO-donors have emerged significantly in recent years. In this review, we summarized recent advances in the synthesis, reactivity and biomedical applications of promising heterocyclic NO-donors (furoxans, sydnone imines, pyridazine dioxides, azasydnones). The synthetic potential of each heterocyclic system along with biochemical mechanisms of action are emphasized.

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“…Unser langjähriges Interesse an mesomeren Betainen [22] und ihrer Schnittmenge zur Chemie sowohl neutraler [12a, b, 23, 24] als auch anionischer N‐heterocyclischer Carbene [25] (NHC) erfuhr durch die Einführung eines Energie‐basierten quantitativen Index' zur Bildung von NHCs durch Deprotonierung aus Vorläufer‐Heterocylen, den sogenannten CREF‐Werten (carbene relative energy of formation), [26] einen zusätzlichen Impetus. Erste eigene Berechnungen ließen Sydnonmethide in der Tat als interessante Vorläufer für einzigartige π‐elektronenreiche anionische N‐heterocyclische Carbene erscheinen.…”

Section: Methodsunclassified

Sydnonmethide – fast vergessene Mesoionen als Vorläufermoleküle von anionischen N‐heterocyclischen Carbenen

et al. 2021

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Wir beschreiben Sydnonmethide, von denen bisher nur ein einziges Beispiel in der Literatur erwähnt worden war. Sydnonmethide können zu Anionen deprotoniert werden, die als π‐elektronenreiche anionische N‐heterocyclische Carbene formulierbar sind. Schwefel‐ und Selenaddukte konnten wir als ihre Methylether stabilisieren sowie Quecksilber‐, Gold‐ und Rhodiumkomplexe von Sydnonmethiden herstellen. Die Anionen von Sydnonmethiden gehen zudem C‐C‐Kupplungsreaktionen mit 1‐Fluor‐4‐iodbenzol unter Pd(PPh3)4‐ und CuBr‐Katalyse ein. Zur Abschätzung der elektronischen Eigenschaften dieser anionischen N‐heterocyclischen Carbene bestimmten wir die 77Se‐NMR‐Resonanzfrequenzen und die 1JC4‐Se‐Kopplungskonstanten der Selen‐Addukte sowie die 1JC4‐H‐Kopplungskonstanten der mesoionischen Vorläufermoleküle. Im Vergleich zu klassischen N‐heterocyclischen Carbenen erscheint das Carben‐Kohlenstoffatom des Sydnonmethid‐Anions 3 j in den bei −40 °C gemessenen 13C‐NMR‐Spektren mit δ=155.2 ppm bei extrem hohem Feld.

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Sulfur, mercury, and boron adducts of sydnone imine derived anionic N-heterocyclic carbenes

Abstract: The sydnone imines (5-benzoylimino)-3-(2-methoxyphenyl)-sydnone imine and molsidomine were deprotonated at C4 to give sydnone imine anions which can be represented as anionic N-heterocyclic carbenes, respectively.

Cited by 14 publications

References 49 publications

Sydnone Methides—A Forgotten Class of Mesoionic Compounds for the Generation of Anionic N‐Heterocyclic Carbenes

Sydnone Methides—A Forgotten Class of Mesoionic Compounds for the Generation of Anionic N‐Heterocyclic Carbenes

Recent Advances in the Synthesis and Biomedical Applications of Heterocyclic NO-Donors

Sydnonmethide – fast vergessene Mesoionen als Vorläufermoleküle von anionischen N‐heterocyclischen Carbenen

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