To a flame-dried 5-mL microwave vial with a magnetic stir bar was added E-oxime 6-12 (50 mg, 0.33 mmol, 1.0 equiv), and CH2Cl2 (320 µL, 1.0 M). The reaction vessel was moved to a 0 °C ice-water bath, and triethylamine (140 µL, 0.98 mmol, 3.0 equiv) was added dropwise over 5 minutes. After the reaction mixture had stirred at 0 °C for 5 minutes, acetic anhydride (67 µL, 0.65 mmol, 2.0 equiv) was added dropwise to the reaction mixture. Following this, 4-(dimethylamino)pyridine (4.0 mg, 0.044 mmol, 0.1 equiv) was added to the reaction mixture in one portion. The reaction vessel was removed from the ice-water bath, and the reaction mixture was allowed to stir at room temperature.