Isothiazoles. Part VII. An efficient palladinm-catalyzed functionalization of 3-amino-4-aryl-isothiazole 1,1-dioxides with organostannanes

The palladium-catalyzed reaction of 5-bromo-3-diethylamino-4-(4-methoxyphenyl)-isothiazole 1,1-dioxide (3) with a variety of vinyl-, aryl-, heteroaryl- and alkynylstannanes 4 provides a general and efficient method for the synthesis of 5-substituted isothiazole 1,1-dioxides 5. Different reaction conditions (catalyst, solvent, temperature) were tested for the coupling. The best results were obtained using toluene at reflux and benzylchlorobis(triphenylphosphine)palladium as catalyst. When organostannanes appeared to be less reactive, prolonged heating resulted in the formation of variable amounts of the reduction product-3-diethyiamino-4-(4-methoxyphenyl)-isothiazole 1,1-dioxide (1).