Synthesis of Pyrazolo[1,5‐a][1,3,5]triazine, Pyrazolo[1,5‐a]pyrimidine, and Imidazo[1,2‐b]pyrazole Derivatives Based on Imidazo[2,1‐b]thiazole Moiety

3(5)‐Aminopyrazole derivative (6) has been synthesized by the reactions of the versatile unreported 2‐cyano‐N′‐(1‐(3‐methyl‐6‐phenylimidazo[2,1‐b]thiazol‐2‐yl)ethylidene)acetohydrazide (3) with phenyl isothiocyanate in KOH/DMF solution followed by reaction with methyl iodide and hydrazine hydrate. Reaction of compound 6 with some 1,3‐dicarbonyl compounds yielded pyrazolo[1,5‐a]pyrimidine derivatives (14–17). Alkylation of compound 6 with various halo reagents, followed by intramolecular cyclization, yielded the corresponding imidazo[1,2‐b]pyrazole derivatives 27, 29, 31, and 33. All newly synthesized compounds were elucidated by considering the data of both elemental analysis and spectral data.