Three-component synthesis of C2F5-substituted pyrazoles from C2F5CH2NH2•HCl, NaNO2 and electron-deficient alkynes

A one-pot reaction between C2F5CH2NH2 center dot HCl, NaNO2 and electron-deficient alkynes gives C2F5-substituted pyrazoles in excellent yields. The transformation smoothly proceeds in dichloromethane/water, tolerates the presence of air, and requires no purification of products by column chromatography. Mechanistically, C2F5CH2NH2 center dot HCl and NaNO2 react first in water to generate C2F5CHN2, that participates in a [3 + 2] cycloaddition with electron-deficient alkynes in dichloromethane.