Selective synthesis of indazoles and indoles via triazene-alkyne cyclization switched by different metals
Yan Fang1, Chengming Wang, Shengqin Su
1Key Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University, Shenzhen Graduate School, Shenzhen, China. huangyong@pkusz.edu.cn.
Abstract:
We described two orthogonal heterocycle syntheses, where an arene bearing both an alkyne and a triazene functionality underwent two distinct cyclization pathways mediated by different transition metals. Starting from the same substrates, a synthesis of 2H-indazole was accomplished by a Cu(II) salt promoted oxidative cyclization, while 2-substituted indoles could be accessed via a Ag(I) salt mediated N-N bond cleavage. This method represents the first synthesis of indoles from alkynyl triazenes. Computational analysis was performed for both reaction pathways, supporting a Lewis acid role for Cu and a π-acid catalysis for Ag.
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