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温度

0 °C

A solution of ethyl 1-tert-butyl-6,7-difluoro-1,4-dihydro-8-methoxy-4-oxoquinoline-3-carboxylate (20.0 g, 58.9 mmol) in concentrated H2SO4 (120 mL) was treated portionwise at 0° C. with solid KNO3 (8.90 g, 88.0 mmol). After stirring at 0° C. for 1 h, the reaction mixture was poured into 500 mL of ice-water and the resulting precipitate was removed by filtration. The resulting solid washed with EtOH, dried to yield ethyl 6,7-difluoro-1,4-dihydro-8-methoxy-5-nitro-4-oxoquinoline-3-carboxylate (12.77 g, 66%) as a pale yellow solid.

1. customthe resulting precipitate was removed by filtration
2. washThe resulting solid washed with EtOH
3. customdried