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Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles.

ABSTRACT: Deprotonation of indazolium salts at low temperatures gives N-heterocyclic carbenes of indazoles (indazol-3-ylidenes) which can be trapped as rhodium complexes (X-ray analysis). In the absence of Rh, the indazol-3-ylidenes spontaneously dimerize under ring cleavage of one of the N,N-bonds and ring closure to an indazole-indole spiro compound which possesses an exocyclic imine group. The E/Z isomers of the imines can be separated by column chromatography when methanol is used as eluent. We present results of a single crystal X-ray analysis of one of the E-isomers, which equilibrate in solution as well as in the solid state. Heating of the indazole-indole spiro compounds results in the formation of quinazolines by a ring-cleavage/ring-closure sequence (X-ray analysis). Results of DFT calculations are presented.

SUBMITTER: Guan Z

PROVIDER: S-EPMC3999838 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles.

Guan Zong Z Namyslo Jan C JC Drafz Martin H H MH Nieger Martin M Schmidt Andreas A

Beilstein journal of organic chemistry 20140410

Deprotonation of indazolium salts at low temperatures gives N-heterocyclic carbenes of indazoles (indazol-3-ylidenes) which can be trapped as rhodium complexes (X-ray analysis). In the absence of Rh, the indazol-3-ylidenes spontaneously dimerize under ring cleavage of one of the N,N-bonds and ring closure to an indazole-indole spiro compound which possesses an exocyclic imine group. The E/Z isomers of the imines can be separated by column chromatography when methanol is used as eluent. We presen ...[more]

PMID: 24778738

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