6.0 g of 1'-trifluoroacetyl-3,4-dihydro-6-methoxyspiro[naphthalene-2(1H),2'-piperidine] was dissolved in 150 ml of chloroform. After 1.5 g of ammonium nitrate was suspended in this solution, 9 ml of trifluoroacetic anhydride was added, followed by overnight stirring at room temperature. After water was added, the reaction mixture was extracted with methylene chloride. The extract was dried over anhydrous sodium sulfate and filtered, after which the solvent was distilled off. The residue was purified by silica gel column chromatography to yield 1.4 g of 1'-trifluoroacetyl-3,4-dihydro-6-methoxy-7-nitrospiro[naphthalene-2(1H),2'-piperidine] and 0.457 g of 1'-trifluoroacetyl-3,4-dihydro-6-methoxy-5-nitrospiro[naphthalene-2(1H),2'-piperidine].
