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

Pavel K Mykhailiuk

doi:10.3762/bjoc.11.3

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

Beilstein J Org Chem. 2015 Jan 6:11:16-24. doi: 10.3762/bjoc.11.3. eCollection 2015.

Author

Pavel K Mykhailiuk¹

Affiliation

¹ Enamine Ltd., Vul. Oleksandra Matrosova 23, 01103 Kyiv, Ukraine; and Department of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Street, 64, Kyiv 01601, Ukraine.

Abstract

A one-pot reaction between C2F5CH2NH2·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·HCl and NaNO2 react first in water to generate C2F5CHN2, that participates in a [3 + 2] cycloaddition with electron-deficient alkynes in dichloromethane.

Keywords: cycloaddition; fluorine; pentafluoroethyl group; pentafluoroethyldiazomethane; pyrazole.