Synthesis of substituted 1,3-oxazino[5,4,3-ij]quinolin-1,3-diones by the oxidation of various pyrrolo[3,2,1-ij]quinoline-1,2-diones with m-chloroperbenzoic acid

When various pyrrolo[3,2,1-ij]quinoline-1,2-diones were oxidized with m-chloroperbenzoic acid, 1,3-oxazino[5,4,3-ij]quinolin-1,3-diones were obtained in good yields (64-86%) and characterized by spectral methods. Recyclization/rearrangement of the pyrroldione fragment of pyrrolo[3,2,1-ij]quinoline-1,2-diones, regardless of the presence and electronic nature of the substituent in the aromatic part, the presence of a bulky phenyl group or a multiple bond in the heterocyclic fragment, proceeds selectively with the formation of a 1,3-oxazine cycle, rather than an isomeric 1,4-oxazine ring. This outcome corresponds to the data acquired from quantum mechanical calculations.