Regioselective formation of 2,5-disubstituted oxazoles via copper(I)-catalyzed cycloaddition of acyl azides and 1-alkynes

Abstract

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. © 2010 American Chemical Society.