A study was made of the use of calcium oxide as a catalyst at a temperature of 400–700° for the dehy‐drocyclization of four primary arylamines: 2‐aminobiphenyl, 1‐aminotriphenylene (5c), 2‐phenoxyaniline, and N‐(2‐aminophenyl)pyrrole. Maximal yields of cyclized products isolated were 53% (carbazole), 52% (4H‐naphtho[1,4‐def]carbazole), 18% (phenoxazine), and 0%, respectively. Comparison is made with reported cyclizations of the corresponding nitro and azido starting materials. In one case, treatment of I‐nitrotriphenylene with triethyl phosphite produced mainly diethyl N‐(1‐triphenylenyl)phosphoramidate (51%). Mono‐ and hemihydrochlorides of 5c are described. A mechanism for the catalyzed dehydrocy‐clization is proposed.