A Regioselective Synthesis of 5-chloro-1-vinyl- and 3-alkenyl-5-chloro-1H-pyrazoles

The reaction of 2,2-dichlorovinyl ketones with 2-(hydroxyethyl)hydrazine led to the formation of 3-substituted 5-chloro-1-(2-hydroxyethyl)-1 Н -pyrazoles. Heating 1-(2-hydroxyethyl)-1 H -pyrazoles in CHCl3 under reflux in the presence of thionyl chloride gave rise to 5-chloro-1-(2-chloroethyl)-1 H -...

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Bibliographic Details
Published in:Chemistry of heterocyclic compounds (New York, N.Y. 1965) N.Y. 1965), 2022-11, Vol.58 (11), p.588-597
Main Authors: Kobelevskaya, Valentina А., Larina, Ludmila I., Popov, Alexandr V.
Format: Article
Language:English
Subjects:
Anti-inflammatory drugs
Chemistry
Chemistry and Materials Science
Chloroform
Hydrazines
Hydrogen chloride
Ketones
Organic Chemistry
Pharmacy
Pyrazole
Pyridines
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Summary:The reaction of 2,2-dichlorovinyl ketones with 2-(hydroxyethyl)hydrazine led to the formation of 3-substituted 5-chloro-1-(2-hydroxyethyl)-1 Н -pyrazoles. Heating 1-(2-hydroxyethyl)-1 H -pyrazoles in CHCl3 under reflux in the presence of thionyl chloride gave rise to 5-chloro-1-(2-chloroethyl)-1 H -pyrazoles. 5-Chloro-1-vinyl-1 Н -pyrazoles were obtained by elimination of hydrogen chloride from the corresponding 5-chloro-1-(2-chloroethyl)-1 Н -pyrazoles by the action of NaOH in EtOH or t -BuOK in pyridine. The synthesis of 5-chloro-3-propyl-1-vinyl-1 H -pyrazole-4-carbaldehyde was carried out by the treatment of 5-chloro-1-(2-chloroethyl)-3-propyl-1 H -pyrazole-4-carbaldehyde with t -BuOK in pyridine. 3-Alkenyl-5-chloro-1-(2-chloroethyl)-1 H -pyrazoles were formed as a result of the elimination of HCl from the corresponding 3-(α-chloroalkyl)-1 H -pyrazoles in DMF at 150°C.
ISSN:0009-3122
1573-8353
DOI:10.1007/s10593-022-03139-x