The role of copper(I) complexes in the selective formation of oxazoles from unsaturated nitriles and diazoesters

The 1,3-dipolar addition of ketocarbenes (generated from diazoesters) to nitriles is promoted at room temperature by palladium acetate and even more efficiently by copper trifluoromethanesulphonate. The reduction of copper(II) to copper(I) is a key step in the catalytic process, as shown by kinetic studies, EPR and polarography. © 1975.