Intramolecular cycloaddition of 3-chloro-6-(2-allyloxyphenoxy) pyridazines yielded various hydroxyxanthenes, which were also prepared by similar cycloaddition of 3-substituted-6-(2-allylphenoxy) pyridazines containing methoxy groups on their benzene rings, followed by demethylation of the resulting methoxyxanthenes. The mechanism of the reaction is discussed.
