Studies on the synthesis and anti-inflammatory activity of 2,6-di-tert-butylphenols with a heterocyclic group at the 4-position. II.

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Abstract
2,6-Di-tert-butylphenols with an imidazo[2,1-b]thiazole or 2,3-dihydroimidazo[2,1-b]thiazole group at the 4-position were prepared. Substituents were introduced at the 5-position of 6-(3,5-di-tert-butyl-4-hydroxyphenyl)-2,3-dihydroimidazo[2,1-b]thiazole (Ia) by means of the Vilsmeier reaction and Mannich reaction. 6-(3,5-Di-tert-butyl-4-hydroxyphenyl)-2,3-dihydroimidazo[2,1-b]thiazole 1-oxide (IVa) and the 11-dioxide (IVb) were obtained by oxidation of Ia. These compounds were examined for antiinflammatory activity in adjuvant-induced arthritis in rats, and some compounds were further tested for activity in the carrageenan-induced rat paw edema assay and in the AcOH-induced writhing assay in mice. Some of the compounds showed potent antiinflammatory and analgesic activities. The most potent compound, IVa (25 mg/kg, p.o. [orally]), had about the same antiinflammatory activity as indomethacin (2 mg/kg, p.o.), but IVa (50 mg/kg, p.o.) had weaker analgesic activity than aminopyrine (50 mg/kg, p.o.).