The recent advances in the copper-catalysed azide–alkyne cycloaddition (CuAAC) reactions are reviewed.

The reaction of 1-alkynes with acyl azides in the presence of [Tpm^*,BrCu(NCMe)]BF₄ [Tpm^*,Br = tris(3,5-dimethyl-4-bromopyrazolyl)methane] as the catalyst provides 2,5-oxazoles in moderate to high yields. This is a novel transformation of the CuAAC type that constitutes a significant variation of the commonly observed [3 + 2] cycloaddition reaction to yield 1,2,3-triazoles.