907604-03-9Relevant academic research and scientific papers
Translation of pseudo-cross-conjugation into chemistry: Cycloadditions of mesomeric betaines to the new ring system spiro[indazole-3,3′-pyrrole]
Schmidt, Andreas,Habeck, Tobias,Lindner, Anika Sabine,Snovydovych, Bohdan,Namyslo, Jan Christoph,Adam, Arnold,Gjikaj, Mimoza
, p. 2236 - 2239 (2007)
Indazolium-3-amidates (X-ray analysis), readily available on trapping the N-heterocyclic carbene indazol-3-ylidene with isocyanates, underwent [3 + 2]-cycloadditions with activated triple bonds to spiro[indazole-3,3′- pyrroles]. A combination of NMR techn
Pseudo-cross-conjugated mesomeric betaines and N-heterocyclic carbenes of indazole
Schmidt, Andreas,Beutler, Ariane,Habeck, Tobias,Mordhorst, Thorsten,Snovydovych, Bohdan
, p. 1882 - 1894 (2008/01/27)
1,2-Dimethylindazolium-3-carboxylates are pseudo-cross-conjugated mesomeric betaines (PCCMB) and derivatives of the indazole alkaloid Nigellicin. They decarboxylate on heating to give intermediary N-heterocyclic carbenes of indazole that can be trapped wi
Nucleophilic carbenes and pseudo-cross-conjugated mesomeric betaines of indazole starting from analogues of the alkaloid-betaine nigellicine
Schmidt, Andreas,Merkel, Lars,Eisfeld, Wolfgang
, p. 2124 - 2130 (2007/10/03)
The alkaloid Nigellicine possesses the indazolium-3-carboxylate ring system as electronically relevant partial structure which represents a member of the class of pseudo-cross-conjugated mesomeric betaines. Indazolium-3-carboxylate, prepared starting from indazole-3-carboxylic acid by an esterification- methylation-saponification sequence, can be converted into the isoconjugated phenyl- and 4-(nitrophenyl)-amidates and the thiocarboxylate as additional examples of pseudo-cross-conjugated systems. In accordance with results of ab initio calculations decarboxylation of indazolium-3-carboxylate with formation of the nucleophilic carbene indazol3-ylidene begins at approximately 40°C as evidenced by temperature-dependent NMR spectroscopy. The carbene can be trapped with protons as indazolium salts, and carbon dioxide which reconstitutes the pseudo-cross-conjugated mesomeric betaine. According to the calculations, the carbene adopts a singlet ground state. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
