Transition-Metal-Free [3 + 2] Cycloaddition of Nitroolefins and Diazoacetonitrile: A Facile Access to Multisubstituted Cyanopyrazoles.

A transition-metal-free [3 + 2] cycloaddition reaction between nitroolefins and diazoacetonitrile (N2CHCN) is described. This protocol exhibits several merits including simple starting materials, mild reaction conditions, broad substrate scope, good yields, and regioselectivities. The one-pot three-component reaction of nitroolefins with diazoacetonitrile (N2CHCN) and alkyl halides is also developed, thus delivering a series of multisubstituted cyanopyrazoles in good to high yields.