The reactions of 4-cloro-5-formilthiazoline-2-one (1) with nitrogen nucleophiles are studied. The approaches to the synthesis of imidazolium betaines (2), 4,5-disubstituted derivatives of thiazoline-2-one (3), of pyrido[1,2-b]thiazolo[4,5-e]-1,2,4-triazepinium derivatives (4) are developed. 2-amino-5-nitropyridine reacts with compounds (1) with regrouping and transposition of oxanione to the structure (5). The structure of compounds 1-5 is established on IR and NMR-spectroscopy data.

2: R=CH₃; CH₂C₆H₅; CH₂-CH=CH₂; 3: R2=C₆H₅; 4-CH₃-C₆H₄; 4-OCH₃-C₆H₄; 4-Br-C₆H₄; NH-C₆H₅; NH-CO-C₆H₅; R3=H; CH₃;