Synthesis, X‐ray crystal structure determination and antiinflammatory activity of the regioisomers: 5‐phenyl‐6‐(4‐pyridyl)‐2,3‐dihydroimidazo[2,1‐b]thiazole and 6‐phenyl‐5‐(4‐pyridyl)‐2,3‐dihydroimidazo[2,1‐b]thiazole. A structural reassignment

Abstract

A regiospecific synthesis of 6‐phenyl‐5‐(4‐pyridyl)‐2,3‐dihydroimidazo[2,1‐b]thiazole (2) was accomplished by treatment of 6‐phenyl‐2,3‐dihydroimidazo[2,1‐b]thiazole (10) with the reactive complex of pyridine and ethyl chloroformate followed by oxidation with chromium(VI) oxide. Reaction of 4‐phenyl‐5‐(4‐pyridyl)imidazole‐2‐thione (12) with 1,2‐dibromoethane in the presence of base also gave 2 together with its regioisomer 3. The structures of 2 and 3 were confirmed by X‐ray crystallography. Evaluation, on oral administration, in a one hour arachidonic acid‐induced mouse ear inflammation assay, showed the inhibition of edema by 2 (48%) and 3 (34%) to be less than that of the 6‐(4‐fluorophenyl) analog 1 (SK&/F 86002) (69%), a known antiinflammatory agent.

A Glycerol promoted, regioselective synthesis of 6‐aryl substituted Imidazo[2,1‐b]thiazole and imidazo[2,1‐b]‐1,3,4‐thiadiazole through a one‐step domino process under green conditions

“…As anticancer (I, II, and III), antimicrobial (IV), antibacterial, and antiallergic drugs, many imidazo[2,1-b]thiazoles have been utilized.. [10][11][12][13] These derivatives are also discovered to be specific kinase inhibitors and receptors (V), and they are used for PET imaging of the brains of Alzheimer patients (VI) as well as the detection of -amyloid plaques. [14][15] Imidazo[2,1-b]thiazole scaffolds also have antibacterial, antifungal, [16] anti-inflammatory, [17] and anticancer [18] action in addition to the aforementioned properties. Imidazo[2,1-b]-1,3,4-thiadiazole, on the other hand, has bioactivities such antitumor, [19] antibacterial, [20] anticancer, [21] antimicrobial, [22] anti-inflammatory, [23] antifungal, [24] anti-hyperlipidemic agents, [25] and antitubercular.…”

Identification of Regioisomers in a Series of N-Substituted Pyridin-4-yl Imidazole Derivatives by Regiospecific Synthesis, GC/MS, and 1H NMR

“…In the structurally related class of 2,3-dihydroimidazo[2,1- b ]thiazole inhibitors of cytokine release, for example, the molecular structures published for the desfluoro congeners of regioisomers SK&F 86002 and SK&F 86055 (Scheme ) had been assigned on the basis of spectroscopic data . The initial assignment, however, was later disproved when X-ray crystallographic evidence became available for these compounds . Like SK&F 86002 and SK&F 86055, methylsulfanylimidazoles ML 3375 and 1 (Figure ) can be synthesized from suitable imidazole-2-thione precursors (Scheme ).…”