The reactions of the 6-acetyl-5-ethoxycarbonyl- or 5, 6-diethoxycarbonylimidazo-[1, 2-a] pyrimidine derivatives (7a, b), which were prepared by condensation of 2-amino-4, 5-diphenylimidazole (4) with ethyl 3-ethoxymethylene-2, 4-dioxovalerate (5a) or ethyl ethoxymethyleneoxaloacetate (5b), with diazomethane are described. Thus, reaction of 7a with diazomethane at room temperature afforded three products whose structures were assigned as ethyl 5a-acetyl-4a, 5a-dihydro-2, 3-diphenyl-5H-cyclopropa [e] imidazo [1, 2-a] pyrimidine-4a-carboxylate (9), ethyl 5a-acetyl-2, 3-diphenyl-4a, 5a, 5b, 7-tetrahydro-6H-aziridino [c]-5H-cyclopropa [e] imidazo [1, 2-a] pyrimidine-4a-carboxylate (10), and the 6-methyl analog (11) of 9. When reacted with diazomethane under ice cooling, 7a afforded only 9 in 73.0% yield. Reaction of 7b with diazomethane at room temperature gave four products whose structures were assigned as diethyl 4a, 5a-dihydro-2, 3-diphenyl-5H-cyclopropa [e] imidazo [1, 2-a] pyrimidine-4a, 5a-dicarboxylate (14), diethyl 2, 3-diphenyl-4a, 5a, 5b, 7-tetrahydro-6H-aziridino [c]-5H-cyclopropa [e] imidazo [1, 2-a] pyrimidine-4a, 5a-dicarboxylate (15), diethyl 7, 8-diphenyl-3a, 3b, 5, 9a-tetrahydro-4H-aziridino [c]-3H-pyrazolo [3, 4-e] imidazo [1, 2-a] pyrimidine-3a, 9a-dicarboxylate (16), and diethyl 3a, 9a-dihydro-7, 8-diphenyl-4-methyl-3H-pyrazolo [3, 4-e] imidazo [1, 2-a] pyrimidine-3a, 9a-dicarboxylate (17). The chemical properties of 9 were also investigated. For example, 9 reacted with hydrochloric acid to give the 5, 8-dihydro-5-chloromethylimidazo [1, 2-a] pyrimidine (19) in excellent yield. When heated with acetic acid, 9 yielded the 5, 8-dihydro-5-acetoxymethylimidazo [1, 2-a] pyrimidine (25) in 12.7% yield, in addition to 40.0% yield of the 5-acetoxy-5, 6-dihydro-9H-imidazo [1, 2-a] [1, 3] diazepine (26), which was transformed into the N-imidazolylpyridone (27) by treatment with potassium hydroxide. On catalytic hydrogenation over 5% palladium charcoal, 9 gave the 5, 6-dihydro-9H-imidazo [1, 2-a] [1, 3] diazepine (32), which was then derived to the 9H-imidazo [1, 2-a] [1, 3] diazepine (36) by bromination followed by dehydrobromination.
