Radicals derived from heteroaromatic systems. II. Thiazolyl radicals

Abstract

2-Thiazolylhydrazine and all three thiazole carbonyl peroxides have been synthesized and examined as radical precursors in solution in benzene, bromobenzene, and cumene. Silver oxide oxidation of the hydrazine or thermal decomposition of the 2-peroxide gives good yields of 2-arylthiazoles but negligible amounts of esters; in cumene a trace of bicumyl is formed. The isomer ratios in bromobenzene and cumene fully support the involvement of 2-thiazolyl radicals (1).The 4-carbonyl peroxide gives fair yields of 4-arylthiazoles but the phenyl ester is also a major product in benzene, indicative of reactions of both 4-thiazolyl radicals (2) and thiazole-4-carbonyloxy radicals. The 5-peroxide gives no products clearly diagnostic of 5-thiazolyl radicals (3) or thiazole-5-carbonyloxy radicals. Bicumyl is a major product of the reactions of the 4- and the 5-peroxides in cumene.