C(OC(=O)C)(=O)C.[C:8]([N:11]1[CH2:16][CH2:15][C:14]2[S:17][CH:18]=[CH:19][C:13]=2[CH2:12]1)(=[O:10])[CH3:9].[N+:20]([O-])([OH:22])=[O:21]>C(O)(=O)C>[C:8]([N:11]1[CH2:16][CH2:15][C:14]2[S:17][C:18]([N+:20]([O-:22])=[O:21])=[CH:19][C:13]=2[CH2:12]1)(=[O:10])[CH3:9]20 ml of an acetic anhydride solution containing 5.43 g (30 mmole) of 5-acetyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridine [prepared as described in step (a) above] were added dropwise at 10° to 18° C. over a period of one hour to 30 ml of an acetic acid solution containing 4.2 g (60 mmole) of 90% fuming nitric acid, and the mixture was then stirred at a temperature not greater than 18° C. for 1 hour. The reaction mixture was then poured into ice-water and extracted with methylene chloride. The organic layer was separated, washed with a saturated aqueous solution of sodium hydrogencarbonate and with water, in that order, and dried over anhydrous magnesium sulfate. The solvent was then removed by distillation under reduced pressure, and the resulting residue was crystallized from a mixture of hexane and toluene, to give 4.46 g of the title compound as yellow crystals.
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