A. Preparation of ethyl 3-(3-benzyloxy-4-butylaniline)-2-cyanoacrylate (III)
Add 255g (1.0mol) of 4-butyl-3-benzyloxyaniline and 186g (1.2mol) of 2-cyano-3-methoxyacrylate to the reactor. After stirring evenly, heat to 30-35℃ and continue stirring for 8 hours. After the reaction is complete, heat to 65℃ under normal pressure and distill to remove the methanol generated in the reaction. The residue contains about 337.2g of 3-(3-benzyloxy-4-butylaniline)-2-cyanoacrylate (III), with a yield of about 89.2%, which can be directly used for the next step of the reaction.
Preparation of 7-benzyloxy-6-butyl-4-cyano-3-cyanoquinoline (II) Ethyl 3-(3-benzyloxy-4-butylaniline)-2-cyanoacrylate (III) (378 g, 1.0 mol) and triethyl phosphate (3000 g) were added to a reactor. After stirring evenly at room temperature, the temperature was raised to 120 °C and the reaction was continued for 10 hours. After the reaction was completed, the mixture was cooled to room temperature. The ethanol generated in the ring-closing reaction was removed by atmospheric distillation, and the solvent triethyl phosphate was removed by vacuum distillation. The residue obtained was crude 7-benzyloxy-6-butyl-4-cyano-3-cyanoquinoline (II). Recrystallization from ethanol yielded refined 7-benzyloxy-6-butyl-4-cyano-3-cyanoquinoline (II), which was 296.7 g of grayish-white solid, with a yield of about 89.4%. C. Preparation of Trimethoprim (I) 7-Benzyloxy-6-butyl-4-cyano-3-cyanoquinoline (II) (332 g, 1.0 mol), methanol (3300 g), and 15% hydrochloric acid (3300 g) were added to a reactor. After stirring, the mixture was heated to 45°C and stirred for 5 hours. Then, the temperature was raised to reflux and the reaction was continued for 10 hours. After the reaction was completed, most of the solvent was removed by distillation, and the precipitated solid was collected by filtration. This was crude Nequinate (I). Recrystallization from methanol yielded refined Nequinate (I), a white or off-white solid, 312.5 g, with a yield of approximately 85.6% and a maximum temperature (MP) of 287.3-288.1°C.
