A series of 2-aroyl-aziridines underwent 1,3-dipolar additions in both orientations to the nitrogen–oxygen bond of 1-nitrosonaphth-2-ol; spontaneous cleavage of the intermediate oxadiazolidine to a nitrone and cyclisation of the latter afforded both 2-aryl- and 2-aroyl-naphtho[1,2-d]oxazoles in good yield: the interpretation of the reaction received confirmation by independent, unambiguous synthesis of a 2-aroyl-naphtho[1,2-d]oxazole.