Abstract 1, 4, 5, 8-Tetraazaphenanthrene-N 1-oxide (II) reacts with POCl 3 to give equivalent amounts of 2-chloro-tetraazaphenanthrene (V) and 9-chloro-tetraazaphenanthrene (VI). Benzo [f] quinoxaline-N 1-oxide (IV) gives with the same reagent 2-chloro-benzo [f] quinoxaline (IX, 57%) and 9-chloro-benzo [f] quinoxaline (X, 15%). This last result suggests that the chloride ion has entered position 9− of II rather than position 10−, in agreement ...