Objective: A convenient and effective method for the obtaining of a 4-thiazolidinone ring is theт[2+3]-cyclocondensation reaction of S,N-binucleophiles with different equivalents of the dielectrophilic synthon [C2]2+. For this purpose, we achieved the synthesis of intermediate N1- methylidenethiosemicarbazones 3a-b starting from 2-amino/allylsulfanyl-5-ethyl-1,3,4- thiadiazoles 1-b via Vilsmeier-Haak formylation reaction following by condensation with thiosemicarbazide in acetic acid medium.
Methods: Organic Synthesis, NMR Spectroscopy, Elemental analysis, Pharmacological screening.
Results: The interaction of intermediate N1-methylidenethiosemicarbazones 3a-b with αhalocarboxylic (monochloroacetic, 2-bromopropionic, 2-bromobutanoic) acids or α-bromo-γbutyrolactone in acetic acid at the presence of sodium acetate was performed. As results, a series of targeted 2-hydrazino-4-thiazolidinones containing 6-phenylimidazo[2,1-b] [1,3,4] thiadiazole moiety 4a-b and their 5-alkyl substituted derivatives 5a-d and 6a-b were obtained. The structure of the synthesized compounds was confirmed by elemental analysis and NMR spectroscopy. The synthesized compounds 3a-b, 4a-b, 5a-d, and 6a-b were evaluated for their in vitro antitrypanosomal activity against Trypanosoma brucei gambiense (Feo strain).
Conclusion: The results of in vitro screening of antitrypanosomal activity against Trypanosoma brucei gambiense (TBG) allowed us to identify three highly active compounds 4b, 5b and 5c, whichбexhibited significant trypanocidal activity with a range of IC50 values of 3.7-4.4 µM and were comparable to the reference drug nifurtimox (IC50 = 4.4 µM). 

In the present work, we report an efficient synthesis and antioxidant activity evaluation of some 4-arylimino-thiazolidin-2-ones. The structures of target substances were confirmed through 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. The antioxidant activity of the synthesized compounds was measured in vitro by the method of scavenging effect on 2,2- diphenyl-1-picrylhydrazyl (DPPH) radicals. Notably, antioxidant activity was identified for the first time among 4-arylimino-thiazolidin-2-ones.