Highly regioselective dipolar cycloadditions of nitrile oxides with α,β-acetylenic aldehydes

1,2-Oxazol derivatives 3 were prepared by a highly regioselective 1,3-dipolar cycloaddition of nitrile oxides and alpha,beta-acetylenicaldehydes 1 in good yields. Reactive nitrile oxides were generated in situ from stable chloro-oxime reagents 2 and triethyl amine. The cycloaddition reaction showed broad substrate scope and good functional group compatibility. (C) 2016 Elsevier Ltd. All rights reserved.