82755-28-0Relevant articles and documents
INVESTIGATIO OF THE MECHANISMS OF FORMATION OF HETEROCYCLES BY NMR SPECTROSCOPY. INTERMEDIATES IN THE PRODUCTION OF PYRAZOLES FROM 1,3-DIKETONES AND HYDRAZINES
Selivanov, S. I.,Bogatkin, R. A.,Ershov, B. A.
, p. 788 - 795 (2007/10/02)
The structure of the intermediates formed in the reaction of 1,3-diketones RCOCH2COCH3 (R = Me, Et, t-Bu, Ph, CF3) with hydrazines NH2NHR' (R'= H, Me) in methanol and chloroform was determined by NMR spectroscopy in the normal and flow techniques.When R' = H, the reaction takes place through the formation of dihydroxypyrazolidine and 5-hydroxy-2-pyrazolines; for R'= Me, in addition, intermediate products with ketohydroxyazine and ketoenehydrazone structures were detected.A scheme with their participation is proposed for the formation of the isomeric pyrazoles.A pre-equilibrium between the 1,3-diketone, its hydrazinium salt in the Z,Z configuration, and the anion in the E,Z configuration was detected.The reaction rate of the ketone form of the 1,3-diketone is significantly higher than the reaction rate of the enol.
