Ring-expansions and ring-annulations based on 3-substituted 1, 2-benzisothiazole-1, 1- dioxides have lead to a variety of novel heterocyclic systems. The reaction of 3-substituted (1H)-1-isoindolones with 1-diethylamino-1-propyne has also resulted in new, ring-expanded molecules in good to modest yields.