The conversion of the 4-oxo-2-benzoyl-1, 2, 3, 4-tetrahydro-(3-carbolines la and lb, respectively, into their corresponding 4-amino-(3-carbolines 2a and 2b was effected in 70% yield in refluxing hydrazine. In contrast, phenylhydrazine, when heated with the 4-oxo derivative lb, gave the pyridodiindole 18a. This compound derives its origin from an initial Fischer indole cyclization, followed by loss of the 2-benzoyl group and aromatization to ...
