Copper(0) Nanoparticles in Click Chemistry: Synthesis of 3,5-Disubstituted Isoxazoles

An efficient procedure for the synthesis of 3,5-disubstituted isoxazoles via [3+2] cycloaddition reaction of in situ generated nitrile oxides with acetylenes employing readily preparable copper(0) nanoparticles is described. A variety of in situ generated nitrile oxide and acetylenic substrates were engaged in the study and found to undergo cyclization in short duration affording respective isoxazoles in excellent yield. Several amino acid-derived isoxazoles were also prepared in high yield. Consistent activity of the recovered catalyst was found to be almost same up to three cycles.