[CH3:1][C:2]([C:4]1[CH:9]=[CH:8][C:7]2[O:10][CH2:11][O:12][C:6]=2[CH:5]=1)=[O:3].[N+:13]([O-])([OH:15])=[O:14].CCOC(C)=O>C(O)(=O)C.CCCCCC>[CH3:1][C:2]([C:4]1[C:9]([N+:13]([O-:15])=[O:14])=[CH:8][C:7]2[O:10][CH2:11][O:12][C:6]=2[CH:5]=1)=[O:3]A solution of 50 g (0.305 mole) 3,4-methylenedioxy-acetophenone (Aldrich) in 200 mL glacial acetic acid was added dropwise over 30 minutes to 700 mL of cold (2-4° C.) 70% HNO3 with stirring (NOTE: the reaction will overheat without external cooling from an ice bath, which can be dangerous and lead to side products). At temperatures below 0° C., however, the reaction can be sluggish. A temperature of 3-5° C. seems to be optimal). The mixture was left stirring for another 60 minutes at 3-5° C., and then allowed to approach ambient temperature. Analysis by TLC (25% EtOAc in hexane) indicated complete conversion of the starting material within 1-2 hr. When the reaction was complete, the mixture was poured into ˜3 liters of crushed ice, and the resulting yellow solid was filtered off, washed with water and then suction-dried. Yield ˜53 g (84%), used without further purification.
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