Synthesis and Some Reactions of 2-(2-Aminoanilino)cycloheptapyrroles: Leading to 5H-Cycloheptapyrrolobenzodiazepine, a Novel 20? Antiaromatic System, and Cycloheptapyrrolobenzimidazoles

Article abstract of DOI:10.1246/bcsj.63.1617

2-Chlorocycloheptapyrroles reacted with o-phenylenediamine to give 2-(2-aminoanilino)cycloheptapyrroles (2a,b) in good yields.Treatment of 2a and 2b with polyphosphoric acid afforded cyclohepta<1',2':4,5>pyrrolo<1,2-a>benzimidazole (4a) in good yields.Treatment of 2b with acids gave 6-(ethoxycarbonyl) derivatives (4b) of 4a and 12H-5,13-dihydrocyclohepta<1',2':4,5>pyrrolo<2,3-b><1,5>benzodiazepin-12-one (5).Compound 5 was methylated with methyl iodide in the presence of DBU to give 5H-12-methoxycyclohepta<1',2':4,5>pyrrolo<2,3-b><1,5>benzodiazepine, a novel 20? antiaromatic system.Treatment of 2b with sodium ethoxide gave 4b and 2H-1-(cycloheptapyrrol-2-yl)-1,3-dihydrobenzimidazol-2-one (7a).Compound 5 rearranged to 7a in the refluxing sodium ethoxide-ethanol solution.Reactions of 2a and 2b with triethyl orthoformate gave corresponding 1-(cycloheptapyrrol-2-yl)benzimidazoles.Reactions of 2a and 2b with acetic anhydride are also mentioned.