Synthesis and Application of Imidazole Deribatives. Synthesis of Pyrrolo[1, 2-a]benzimidazoles and Azepino[1, 2-a]benzimidazoles

Abstract

4-Methyl-4H-pyrrolo[1, 2-a]benzimidazol-2(1H)-one derivatives (11a-d) were synthesized by intramolecular acylation of 1-carboxymethyl-2, 3-dimethylbenzimidazolium halides (9a and 8b-d) in good yields. Treatment of the iodide (8a) with an excess of refluxing thionyl chloride gave 1, 1, 3-trichloro-4-methyl-4H-pyrrolo[1, 2-a]benzimidazol-2(1H)-one (14). Introduction of electrophiles into the 1-position of 11d and 6-position of 5-methyl-9, 10-dihydro-5H-azepino[1, 2-a]benzimidazol-7(8H)-one (2a) was achieved by successive treatment with lithium diisopropylamide and electrophiles such as methyl iodide and ketones. The azepinone 2a was reacted with various electrophiles to give 6-substituted products in good yields.