Reactivity of 1-nitronaphthalene and 1,3-dinitronaphthalene with conjugated dienes. An easy access to N-naphthylpyrroles

1-Nitronaphthalene reacts at high temperature with poor and moderately reactive dienes affording N-naphthylpyrroles while, with the same dienes, 1,3-dinitronaphthalene exhibits the dienophilic character of naphthalenic C3C4 bond producing the corresponding phenanthrenes through a classical Diels–Alder process.