2-(Alkenyloxy)naphthalene-1-carbaldehyde oximes are oxidized with potassium iodide, iodine and sodium bicarbonate directly to novel naphthopyranoisoxazoles. Naphthopyranoisoxazoles are also prepared from 2-(3-chloroallyloxy)naphthalene-1-carbaldehyde oxime or 2-(alkynyloxy)naphthalene-1-carbaldehyde oximes by oxidation with sodium hypochlorite and triethylamine. The oxidation of 2-(alkenyloxy)naphthalene-1-carbaldehyde oximes with sodium hypochlorite and triethylamine afforded novel naphthopyranoisoxazolines. The former reaction is tentatively proposed to occur via activation of the alkene side chain by means of an iodonium intermediate and either 1,3-dipolar interaction with a nitrile oxide side-group or cyclization with a hydroximic acid iodide side-group.
cycloadditions - halogenation - heterocycles - oxidations - ring closure