Yan Fang’s work has been published in Org. Biomol. Chem.

Selective synthesis of indazoles and indoles via triazene–alkyne cyclization switched by different metals

Yan Fang,   Chengming Wang,  Shengqin Su,  Haizhu Yu* and   Yong Huang*, Org. Biomol. Chem. 2014,12, 1061-1071

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.