* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
Three-necked flask was charged with 100 g of ethyl 1-cyclopropyl-6,7-difluoro-8-methoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylate,Adding 600mL of acetonitrile, stirring, adding 2-hydroxybenzylamine 37mL, heating to 120 C for 6h, cooling, pouring the reaction solution into 1mol / L dilute hydrochloric acid, stirring, adding 500mLEA extraction,The aqueous phase was extracted with EA 300 mL × 2 and the organic layers were combined, dried and evaporated to dryness to give 92.3 g of the yellow product which was used in the next step without further purification.
9. The dried solid was dissolved in 420 g of glacial acetic acid and stirred for 16-24 hours.10. To the reaction system, 932 g of methyl tert-butyl ether was added, and the mixture was stirred and crystallized at 0 to 10 C for 4 to 6 hours.11. Centrifuge the system, centrifuge the solids with 250 ml of 85% ethanol and centrifuge again.12. Centrifuge the solid at 40-50 C to dry, to obtain the final product 35.4g, white.