NON-KEKULE MOLECULES DERIVED CONCEPTUALLY BY HETEROATOM-FOR-CARBON SUBSTITUTION IN ALTERNANT HYDROCARBONS; M-QUINOMETHANE AND M-NAPHTHOQUINOMETHANE

Article abstract of DOI:10.1016/0040-4020(82)80159-2

Qualitative theoretical considerations suggest that substitution of a heteroatom for a C atom in an alternant hydrocarbon might result in a non-Kekule molecule with a triplet ground state, despite the non-degeneracy of the Hueckel NBMOs of the heteroatom derivative.The syntheses of 3-methylene-1-phenoxyl and 3-methylene-1-naphthoxyl are described.These compounds, biradical valence tautomers of m-quinomethanes, are characterized by EPR spectroscopy and are assigned triplet ground states.Optical resolution of 6-methylene-bicyclo<3.1.0>hex-3-ene-2-one, the precursor of 3-methylene-1-phenoxyl, is described.Repeated irradiation of the active ketone at 20K with intermittent warming to room temperature followed by re-isolation gives ketone of undiminished activity, which suggests that re-cyclization of (presumably achiral) 3-methylene-1-phenoxyl does not occur under these conditions.