Iterative Assembly of Nitrile Oxides and Ynamides: Synthesis of Isoxazoles and Pyrroles.

Described is an iterative assembly of nitrile oxides and ynamides for the synthesis of isoxazoles and pyrroles. The nitrile oxides could undergo Cu(I)-free cyclization with terminal ynamides for accessing isoxazoles, which could engage in another cyclization with internal ynamides in the presence of Au(I) catalyst to deliver pyrroles, and the reaction could be carried out in a two-step, one-pot procedure. This process is featured with mild reaction condition and broad substrate scope for the synthesis of heterocycles.