The bibliographic studz of chalcones of the type 1,3-aryl(heteryl)propen-2-one with thiosemicarbazidic 4- and 1,4-disubstituted and thisemicarbazonic groups respectively gives us the information that they have a wide spectrum of biological activity, but methods of their synthesis are less described in the literature, and they became our object of study. 4,5-Dihydro-1-H-(pyrazol-3-yl)phenylhydrazinecarbothioamides 3a and 3b were obtained according to the following scheme:Reagents and reaction conditions: i, ii) 2-Py, 25oC – 24h, 90-95oC – 3h, 77-82%; iii) DMF, CH3COOH, 70-80oC, 2-3h, 60-63%. Figure 1. Synthesis of chalcone derivatives 3a, 3b, 4a and 4b.Initially N,N-dimethylthioureas 1a and 1b with hydrazine hydrate from hydrazones in pyridine at room temperature, which without being isolated upon heating cyclize to pyrazole derivatives (Fig. 1.) as described in the literature, and in parallel, dimethylamine is substituted by the hydrazine group [1] with the formation of compounds 3a and 3b, with a yield of 77%. Compound 3a was also obtained by an alternative route from isothiocyanatophenylpropen-2one 2a and hydrazine hydrate at room temperature, then on heating in pyridine (Fig. 1.). It is possible to from the same intermediates, which turn in to the finished product 3a, the yield is 82%. Compounds 4a and 4b were obtained from products 3a and 3b by boiling in ethanol with 2-pyridinecarboxyaldehyde. The antiproliferative activity of N-(4-(5-(pyridine-2-yl)-4,5dihydro-1H-pyrazol-3-yl)phenyl)-2-(pyridine-2-ylmethylene)hydrazinecarbotioamide towards HL-60 leukemia cells were patented [2].