Synthesis and application of imidazole derivatives. Synthesis of 5-methyl-7,8,9,10-tetrahydro-5H-azepino(1,2-a)benzimidazol-4-one and related compounds

5-Methyl-7, 8, 9, 10-tetrahydro-5H-azepino[1, 2-α]benzimidazol-7-one (6) was synthesized by treating 1-(3-carboxypropyl)-2, 3-dimethylbenzimidazolium iodide (11) with 1, 1'-carbonyldiimidazole in the presence of triethylamine. Refluxing 2-(5-chloro-2-oxopentyl)-1-methylbenzimidazole (4) in ethyl acetate did not afford 6 but gave (Z)-1-methyl-2-(2, 3, 4, 5-tetrahydro-2-furylidenemethyl)benzimidazole (5), which was rearranged to the corresponding (E)-isomer (7) by heating in ethyl acetate in the presence of basic alumina. The structures of 5, 6 and 7 were determined by X-ray crystallography.