Azoles. Part 4. Nucleophilic substitution reactions of halogenoimidazoles

Abstract

A number of N-protected derivatives of 2,4,5-tribromoimidazole, 4(5)-bromo-5(4)-nitroimidazole, and 2,4(5)-dibromo-5(4)-nitroimidazole have been prepared by standard procedures and treated with various nucleophiles. Whereas 2,4,5-tribromo (and tri-iodo)imidazole reacted with sodium benzenethiolate to give the corresponding 4,5-dihalogenoimidazole and diphenyl disulphide, 1-protected derivatives of 2,4,5-tribromoimidazole reacted with various sodium alkane (or arene)thiolates and with sodium isopropoxide, in isopropyl alcohol, by displacement of the 2-bromine atom. 1-Benzyl-5-bromo-4-nitroimidazole (14), 2-(5-bromo-4-nitroimidazol-1-yl)acetate (25), and 5-bromo-4-nitro-1-phenacylimidazole (26) reacted by displacement of the 5-bromine atom. The product arising from reaction of the last compound with ethyl 2-mercaptoacetate in ethanol in the presence of base, cyclised to give ethyl 3-hydroxy-7-nitro-3-phenylimidazolo[5,1-b]thiazine-2-carboxylate (35).