Cycloaddition of some arylnitriloxides with 3-methylenephthalide: electrocatalytic opening of the adducts

Some 4-substituted arylnitriloxides undergo 1,3 dipolar cycloadditions with 3-methylenephthalide with formation of spirodihydroisoxazoles. These spiro adducts can be opened to the corresponding 2-(3-arylisoxazol-5-yl)benzoic a cid by various methods, including thermal and acidic treatments, as well as electrooxidation. In the latter case, the ring-opening mechanism is shown to involve a catalytic electron exchange between the substrate and an inter mediate ArCO2. radical.