Oxidation of some dibenz[b,f][1,4]oxazepines by peracetic acid

A series of variously substituted dibenz[b,f][1,4]oxazepines on treatment with hydrogen peroxide in glacial acetic acid affords the correspondingly substituted 2-(2-hydroxyphenyl)benzoxazole, 10-formylphenoxazine, and dibenz[b,f][1,4]oxazepin-11(10H)-one. An oxaziridine intermediate is implicated as the common precursor of the observed products.