Studies on the Synthesis and Anti-inflammatory Activity of 2, 6-Di-tert-butylphenols with a Heterocyclic Group at the 4-Position. V. Elimination Reaction of the Sulfinyl Group of 2, 3-Dihydroimidazo [2, 1-b] thiazole 1-Oxide

Reaction of 6-(3, 5-di-tert-butyl-4-hydroxyphenyl)-2, 3-dihydroimidazo [2, 1-b] thiazole 1-oxide (1) with superoxide anion gave 4-(3, 5-di-tert-butyl-4-hydroxyphenyl)-1-vinylimidazole (2). Compound 2 was also obtained by treatment of 1 with potassium tert-butoxide in dimethyl sulfoxide (DMSO) in the presence of oxygen, while 4-(3, 5-di-tert-butyl-4-hydroxyphenyl)-2-thioxo-1-vinyl-4-imidazoline (3) was obtained together with 2 in the absence of oxygen. When the same reaction was carried out in N, N-dimethyl formamide, 1 gave 2 and 3 in the absence of oxygen, and 4-(3, 5-di-tert-butyl-4-hydroxyphenyl)-1-vinylimidazole-2-sulfonic acid (4) in the presence of oxygen. A possible mechanistic explanation for the formation of these products is presented. Oxygenation of 6-phenyl-2, 3-dihydroimidazo [2, 1-b] thiazole 1-oxide (6) was also examined.