On the N-oxidation of 1-alkoxyphthalazines and 1,4-dialkoxyphthalazines

Abstract

1-Alkoxyphthalazine forms only one kind of N-oxide, 1-alkoxyphthalazine 3-oxide, by the action of monoperphthalic acid in ether or hydrogen peroxide in acetic acid (Table III). Phthalazine itself also forms only one kind of N-oxide, phthalazine 2-oxide, by the same treatment. 1, 4-Dialkoxyphthalazine is inert to treatment with monoperphthalic acid in ether and only a part of the alkoxyl group undergoes hydrolysis by the action of hydrogen peroxide in acetic acid to form 4-alkoxy-1(2H)-phthalazinone, the majority of the starting material being recovered. It may be concluded that the alkoxyl groups in 1- and 4-positions of the phthalazine ring cause steric hindrance of nitrogen in 2- and 3-positions at the time of N-oxidation.