A new approach to the synthesis of new heterocyclic compounds with triazine and 4-thiazolidone fragments in one molecule is developed. The synthesis methods comprise [2+3]-cyclocondensation reactions essential in the preparative synthesis of 4-thiazolidone derivatives. The reactions of S,N-nucleophiles with C2-cyclization agents for the synthesis of a number of biologically active 2-triazin-4-thiazolidones were investigated. The interaction of thiosemicarbazone of sym-triazine with derivatives of α-halogencarboxylic acids and maleic anhydride resulted in correspondent (2-[2-(4,6-dichloro-1,3,5-triazin-2-yl)hydrazino]-5-(3,4,5- R-p-phenyl-methyliden)-1,3-thiazol-4-ones obtained in the one-step synthesis. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:392–396, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20631