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Utilization of Stop-flow Micro-tubing Reactors for the Development of Organic Transformations
Published on: January 4, 2018
Two unusual, competitive mechanisms for (2-ethynylphenyl)triazene cyclization: pseudocoarctate versus pericyclic
David B Kimball1, Rainer Herges, Michael M Haley
1Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, USA.
Abstract:
The cyclization of (2-ethynylphenyl)triazenes in ODCB at 200 degrees C gives exclusively cinnolines, whereas addition of CuCl to 1,2-dichloroethane solutions of the triazenes at 50 degrees C results in the sole formation of isoindazoles. DFT calculations and deuterium labeling studies suggest the intermediacy of a 3-dehydrocinnolinium ion, produced through a pericyclic transition state. Calculations and trapping studies strongly implicate a carbene intermediate in isoindazole formation, which proceeds through a pseudocoarctate transition state.
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