2-Trihalogenomethylbenzazoles. Part IV. Reactions with difunctional nucleophiles. Formation of heterocyclic rings on the 2-position of benzazoles
The reaction of selected 2-trihalogenomethylbenzimidazoles with 1,2-difunctional amines, amino-alcohols, and amino-thiols formed benzimidazoles substituted on the 2-position with 2-imidazolin-2-yl, 2-oxazolin-2-yl, and 2-thiazolin-2-yl rings. This high-yield method was extended to the formation of six- and seven-membered-ring analogues by the reaction of the trihalogenomethyl group with 1,3- and 1,4-difunctional nucleophiles. Similarly, aromatic ortho-disubstituted nucleophiles yielded the corresponding azole derivatives. Other heterocyclic rings on the 2-position of benzimidazole were formed in reactions with semicarbazide and mercaptoethanol. The nature and activation of the trihalogenomethyl groups in these cyclisations is discussed, and some reactions of the cyclisation products are also reported.