2-thiaisatoic anhydride 1 and 3-thiaisatoic anhydride 2 were synthesized in large scale under microwave heating conditions with 85% and 67% yields respectively. The reactivity of these two compounds was studied towards various nucleophiles and appeared to be generally different from that of isatoic anhydride: many new thiophene-2 and 3-carboxylic acids were isolated with good yields as potential new pharmacological scaffolds.