Copper-Catalyzed Hydroamination of 2-Alkynylazobenzenes: Synthesis of 3-Alkenyl-2-Indazoles.

A copper-catalyzed intramolecular synthesis of 3-alkenyl-2-indazoles from 2-alkynylazobenzenes is described. The reaction proceeds in a single step via C-N bond formation and a subsequent 1,2-hydride shift, affording products in high yields. DFT calculations suggest the 1,2-hydride shift as the rate-determining step.

Visible Light-Mediated Heterodifunctionalization of Alkynylazobenzenes for 2-Indazole Synthesis.

We disclose the heterodifunctionalization of alkynylazobenzenes promoted exclusively by visible light in the absence of any transition metal and/or photocatalyst. This reaction features excellent regioselectivity on a broad variety of substrates with perfect atom economy. Alcohols, carboxylic acids, thiols, amides, heterocycles, and even water are suitable substrates for the promotion of the oxyamination, sulfenoamination, and diamination reactions.