A study of photochromic sydnones: structure of the sydnone ring

Nešpůrek, S.; Hašek, Jindřich; Šorm, M.; Huml, K.; Obrda, J.; Lepiński, J.; Chojnacki, Henryk

doi:10.1016/0022-2860(82)85237-x

Cited by 14 publications

(3 citation statements)

References 31 publications

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“…[26][27][28] The general structural formula of sydnone is presented by (A), (B) and (C) in Chart 5. The ring has a semi-aromatic character, the N(2)-N(3)-C(4)-C(5) portion together with the exocyclic oxygen atom, O(6), are conjugate like structure (I).…”

mentioning

confidence: 99%

Syntheses of Aromatic Substituted Hydrazino-thiazole Derivatives to Clarify Structural Characterization and Antioxidant Activity between 3-Arylsydnonyl and Aryl Substituted Hydrazino-thiazoles

Shih

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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confidence: 99%

Syntheses of Aromatic Substituted Hydrazino-thiazole Derivatives to Clarify Structural Characterization and Antioxidant Activity between 3-Arylsydnonyl and Aryl Substituted Hydrazino-thiazoles

Shih

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…We performed single crystal X-ray analyses on the isolated compounds 7a and 7b. We found, that the sydnone moiety and the aryl ring at position N3 are twisted by 104.7 ° (7a) 30 and 178.9 ° (7b) 17 from the molecular plane. In addition, single crystals of Nphenylsydnone-4-carboxylic acid 11a were grown through slow evaporation of a concentrated solution in ethanol.…”

Section: Scheme 4 Synthesis Of Sydnone-4-carboxylic Acidsmentioning

confidence: 80%

Anionic N-heterocyclic carbenes by decarboxylation of sydnone-4-carboxylates

et al. 2018

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Unstable N-heterocyclic carbenes can be masked and stabilized as pseudo-cross-conjugated hetarenium-carboxylates which decarboxylate on warming. This study deals with the decarboxylation of carboxylates of mesoionic compounds to generate anionic N-heterocyclic carbenes. Lithium sydnone-4-carboxylates were therefore prepared via 4-bromosydnones by halogen-lithium exchange with nBuLi and subsequent treatment with carbon dioxide. Protonation gave the corresponding sydnone-4-carboxylic acids. Thermogravimetric measurements in addition to temperature dependent IR spectroscopy proved the decarboxylation of lithium sydnone-4-carboxylates and formation of the corresponding sydnone anions which can be represented as anionic N-heterocyclic carbenes. In DMSO-d6 solution, water favors the decarboxylation. Calculations have been performed to elucidate the mechanism of the decarboxylation in the absence and presence of water.

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“…Nešpûrek and other researchers have characterized the sydnone skeleton. The general structural formula of sydnone is presented by (f), (g) and (h) in Scheme .…”

Section: Resultsmentioning

confidence: 99%