Reaction of Azobenzene with Dichlorocarbene in Phase-transfer-catalyzed System

Azobenzene (2) reacted with dichlorocarbene at 40 °C in the presence of several phase-transfer catalysts in a binary solvent (CHCl3–aqueous KOH), giving 2,2,3,3-tetrachloro-1-phenylaziridine (3), 1-phenyl-1,3-dihydro-2H–benzimidazol-2-one (4b), dichloroacetanilide (6), N,N′-diphenylurea (7), and trace amounts of 2-chloro-1-phenylbenzimidazole (8).