Isothiazolo[5,4-d]isoxazole S,S-dioxides and pyrazolo [3,4-d]-isothiazole S,S-dioxides through cycloaddition reaction on 3-benzylaminoisothiazole S,S-dioxides

By reacting 4,5-unsubstituted isothiazole dioxides with diazoalkanes and nitrile oxides bicyclic pyrazolo[3,4-d]isothiazole and isothiazolo[5,4-d]isoxazole S,S-dioxides were obtained in good yield through a regioselective cycloaddition reaction. Through cycloaddition reaction of 3-benzylamino-4-bromo-isothiazole S,S-dioxide labile cycloadducts were formed that underwent in situ dehydrobromination affording the corresponding aromatized compounds.