methanesulfonyl chloride; triethylamine Yield given;

1: phthalic anhydride 2: 35 percent / dimethylformamide / 312 h / Ambient temperature 3: 98 percent / sodium metaperiodate / H2O; diethyl ether / 1 h / Ambient temperature 4: 48 percent / aq. AgNO3, 1 M NaOH / 15 h / Heating View Scheme