Synthesis of new pyrido[3,2-b][1,4]benzoxazines and -benzothiazines

New pyrido[3,2-b][1,4]benzoxazines and pyrido[3,2-b][1,4]benzothiazines were synthesized by the base-mediated reactions of substituted 2-chloro-3-nitropyridines with o-amino(thio)phenols. The reactions involve a sequential nucleophilic substitution of the chlorine atom and the nitro group affected by either O,N- or S,N-binucleophile. In the case of aminothiophenols, the reaction proceeded via substitution of the chlorine atom followed by the Smiles rearrangement, and an intramolecular substitution of the nitro group by S-nucleophile.