Abstract A method was developed for the synthesis of 2-oxo-4-phenyl-2, 3-dihydro-9 H- pyrimido [4, 5-b] indole as well as of 2-chloro-and 2-nitramino-4-phenylpyrimido [4, 5-b] indoles. The replacement of the chlorine atom in 2-chloropyrimidoindole gave rise to a