Quinazolines and 1,4-benzodiazepines. Part XXXII. The acetic anhydride rearrangement of 1,4-benzodiazepinones to isoindoles

1,3-Dihydro-5-phenyl-2H-1,4-benzodiazepin-2-ones unsubstituted in the 1-position rearrange to 1-acetyliso-indoles in the presence of acetic anhydride and pyridine. The structure of the rearranged products has been established by alternative syntheses, and the mechanism of the rearrangement is discussed.