A method is proposed for the alkylation of pyrazoles with dichloroethane in water in the presence of the phase-transfer catalyst benzyltriethylammonium chloride (TEBAC). It was shown that dehydrochlorination of the corresponding N-(β-chloroethyl)pyrazoles in water under conditions of phase-transfer catalysis proceeds smoothly with the formation of N-vinylpyrazoles in 80-90% yield.

Alkylation of pyrazoles with 2,2`-dichloroethyl ether under conditions of phase-transfer catalysis was studied. The monoalkylation products of 3(5)-methylpyrazoles at 1903200oC undergo intramolecular cyclization to form bicyclic salts. Conditions for dehydrochlorination of N-[2-(2`-chloroethoxy)ethyl]pyrazoles into N-(2-vinyloxyethyl)pyrazoles were found.

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