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

作者：Guan Zong; Namyslo Jan C; Drafz Martin H H; Nieger Martin; Schmidt Andreas^*

来源：Beilstein Journal of Organic Chemistry, 2014, 10: 832-840.

DOI：10.3762/bjoc.10.79

• E/Z isomerism
• indazol-3-ylidene
• mesomeric betaine
• pyrazole
• quinazoline
• Rh complex

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.

• 出版日期2014-4-10