Nitrileimines as an alternative to azides in base-mediated click [3 + 2] cycloaddition with methylene active nitriles.

Nitrileimines were implemented in practical click protocols with oxopropanenitriles for the straightforward 5-amino-1-pyrazole synthesis 1,3-dipolar cycloaddition. The reaction proceeds at room temperature in a short time with base catalysis and no chromatographic purification. High purity products were isolated by simple filtration.