From isothiazoles to new or known heterocycles via cycloaddition reactions

From isothiazoles to new or known heterocycles via cycloaddition reactionsThe synthesis and chemical reactivity of 3-amino-isothiazole S-oxides have been studied by us for many years and important transformations and uses of these compounds have been found as precursors both of N- and/or S- containing heterocycles and of open chain compounds through ring opening reactions. In particular, 3-amino-isothiazole S-oxides have been demonstrated to be a versatile system and an effective reaction partners in cycloaddition reactions all of which occurred with high regioselectivity at the C-4-C-5 double bond.1 The resulting cycloadducts are susceptible to transformation in new or known heterocycles through the cleavage of one of the rings present in the primary cycloadduct. Their cleavage depends on several factors such as the reaction conditions and the substitution pattern. The combination of the cycloaddition reactions and ring transformation represents a good strategy affording mono or bicyclic compounds of both chemical and pharmacological interest. A survey of the synthetic possibility of this combination of reactions will be shown.