First N‐Functionalization of 4‐Nitroso‐1H‐Pyrazoles Using Monofunctional and Bifunctional Alkylating Agents

Abstract

The direct N‐alkylation reactions of ambident 3,5‐substituted 4‐nitroso‐1H‐pyrazoles are described for the first time. An efficient method of the 4‐nitroso‐1H‐pyrazoles and their sodium alkyl‐, allyl‐ salts regioselective N‐alkylation by benzyl halides, halocarboxylic acids esters, and related bifunctional alkylating agents is established with the use of superbasic conditions or reflux in acetone. A series of new N‐functionalized nitrosopyrazoles and bis(4‐nitrosopyrazole) compounds is successfully obtained with a yield of up to 85 %. Using quantum‐chemical calculations, it is shown that in terms of kinetics and thermodynamics, the N‐alkylation of the considered pyrazoles is a more advantageous process than O‐alkylation.