Catalysis by Amberlyst-15 under ultrasound in water: a green synthesis of 1,2,4-benzothiadiazine-1,1-dioxides and their spiro derivatives

A green and general synthesis of 1,2,4-benzothiadiazine-1,1-dioxides possessing a spiro group or a substituent at C-3 has been achieved first time via an Amberlyst-15 mediated reaction under ultrasound in water. The reaction is operationally simple and can be performed at room temperature in an open flask to give a range of products that do not require any chromatographic purification. The catalyst is recyclable.