The title compounds have been synthesized by a one-pot two-stage reaction of PCl3, ketone methyl-hydrazones and methyl acetoacetate. Both stages were carried out at room temperature and the corresponding 2-alkenyl-1,5-dimethylpyrazol-3(2H)-ones 5, which are an unknown series of pyrazolones, were obtained in good yields. Use of a variety of enolizable ketones has shown that the reaction always occurs with the predominance of the (E)-isomer. X-Ray structure determinations of an (E)- and a (Z)-derivative [(E)-5c·HCl and (Z)-5b] permitted the assignment of their structures. The aromaticity of these derivatives is discussed.
Synthesis of 2-Alkenylpyrazol-3(2H)-one Derivatives Under Mild Conditions / G., Baccolini; D., Evangelisti; Rizzoli, Corrado; Sgarabotto, Paolo. - In: JOURNAL OF THE CHEMICAL SOCIETY. PERKIN TRANSACTIONS. I. - ISSN 0300-922X. - (1992), pp. 1729-1733. [10.1039/P19920001729]
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