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.