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The reactions of enones containing trifluoromethyl groups with semicarbazide in basic media proceed unequivocally to give pyrazolidine-l-carboxamides. The directs'on of the reactions of these enones with thiosemicarbazide depends on their structure; the reaction products are pyrazolidine-and 2-pyrazoline-1-carbothioamides. An enone containing a CF 3 group and an ethoxy group capable of replacement reacts with semicarbazide to give 2-pyrazoline-l-carboxamide and with thiosemicarbazide to give the double addition product, 5-(1-thiosemicarbazido)-2-pyrazoline-l-carbothiamide.Fluoroheterocyclic compounds have been extensively studied [1, 2] in light of their high biological activity [3]. Trifluoromethyl derivatives of enones are convenient and promising starting compounds for the synthesis of heterocycles with a CF 3 group. Methods of synthesis for such enones have been intensively developed in the past decade [4, 5].The reaction of enones with hydrazines is the classical method for the synthesis of pyrazoles and pyrazolines, but this method has not been studied sufficiently relative to enones with a trifluoromethyl group. Only the synthesis of trifluoromethylpyrazolines from fluoroacetylated vinyl ethers (/3-alkoxyvinyltrifluoromethylketones) has been described [6, 7]. We have already studied the reactions of hydrazine, phenylhydrazine, and methylhydrazine with trifluoromethyl-containing enones lacking an alkoxy substituent, and obtained pyrazolines and pyrazolidines with a CF 3 group [8]. A feature of these reactions is formation of stable pyrazolidines containing a gem-aminoalcohol fragment stabilized by the electron-withdrawing effect of the CF 3 group. Dehydration of these pyrazolidines upon heating or maintaining at room temperature leads to the corresponding pyrazolines.Semicarbazide and its derivatives are multifunctional nucleophiles. The reaction of these compounds with enones holds both theoretical and practical interest since the reaction products often display biological activity [9, 10]. Contradictory data have been reported on the structure of the products of the reactions of unsaturated ketones with semicarbazide derivatives. Structures with a five- [11, 12], six-[13], and seven-membered ring [14] have been proposed. The greatest evidence is found for the formation of five-membered heterocycles, namely, pyrazoline-l-carboxamides and pyrazoline-l-carbothiamides based on x-ray diffraction structural analysis [15].The reactions of trifluoromethyl-containing enones with semicarbazide derivatives have not yet been examined. In continuation of a study of the synthesis of trifluoromethylheterocycles, we investigated the reaction of various enones containing a CF 3 group (I-VII) with semicarbazide and thiosemicarbazide under various conditions. We have already shown that enones lacking a trifluoromethyl group react to give heterocyclic derivatives in acid media (upon heating with semicarbazide hydrochloride or thiosemicarbazide hydrochloride in ethanol at reflux) [11, 15] or close-to-neutral media (in the ...

Global electrophilicity indices and carbon-halogen bond energies of a wide series of halogen derivatives were calculated in terms of the density functional theory (DFT). The calculated values were used to estimate the reactivity of halogen derivatives under conditions of catalytic olefination. Reactions of N-unsubstituted hydrazones with polyhaloalkanes in the presence of CuCl afforded substituted alkenes. The relation between the structure of polyhaloalkanes and their reactivity was studied using the reaction with 4-chlorobenzaldehyde hydrazone as an example. It was found that increase in the global electrophilicity index and decrease in the C-Hlg bond energy are accompanied by increase in the "olefinating" power of halogen derivatives.

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