Photochemistry of some azaphenanthrene N-oxides

Abstract

1- and 4-Azaphenanthrene N-oxides undergo solvent-dependent photoisomerization, yielding naphtho-1,3-oxazepines in aprotic solvents and benzoquinolin-1 (2H)-ones in water. No ring enlargement but only isomerization to the corresponding lactam is observed to take place in the case of 9-azaphenanthrene N-oxide. Measurements of the quantum yield of two photoprocesses (lactam formation and ring enlargement) confirm the difference between the photochemical behaviour of 9-azaphenanthrene N-oxide and that of the other two N-oxides examined