Preparation method of ritodrine
A hydroxyphenyl and intermediate technology is applied in the field of preparation of ritodrine to achieve the effects of good selectivity, promoting economic and technological development, and improving quality
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Embodiment 1
[0029] 4-Hydroxypropiophenone (150 g, 1 mol) and 400 mL of tetrahydrofuran were added to a 1 L three-necked flask, and dry hydrogen chloride gas was introduced under stirring until the system was saturated. Methyl nitrite gas (67.0 g, 1.1 mol) was slowly fed in at 40° C. for about 4 hours, and the reaction was continued for 1 hour after the gas flow was completed. TLC detects that the reaction is complete. The solvent was recovered under reduced pressure, and the residue was recrystallized from toluene to obtain 139.6 g of off-white solid 2-oximino-4'-hydroxypropiophenone (II), with a yield of 78.2%.
Embodiment 2
[0031] In a 1L hydrogenation reactor, the intermediate 2-oximino-4'-hydroxypropiophenone (II) (89.5g, 0.5mol), 10% palladium carbon catalyst (4.5g, 5%w / w), 36 % concentrated hydrochloric acid 80mL and methanol 400mL, start stirring, according to the operating procedures of catalytic hydrogenation, pass hydrogen to 0.5MPa, raise the temperature to 60-65°C, until no hydrogen is absorbed, continue stirring for one hour. Cool down to room temperature, discharge, and filter to recover the catalyst. Concentrate under reduced pressure to recover methanol. The residue was recrystallized from isopropanol to obtain 56.5 g of off-white solid 2-amino-1-(4-hydroxyphenyl)propanol hydrochloride (III), with a yield of 75.2%.
Embodiment 3
[0033] Add intermediate 2-amino-1-(4-hydroxyphenyl)propanol hydrochloride (III) (75.5g, 0.5mol), triethylamine (10.0g, 0.1mol) and no Add 250 mL of water and ethanol, raise the temperature to 50-55°C, and stir until the system is uniformly dissolved. P-Hydroxyphenylacetaldehyde (68.0 g, 0.5 mol) was slowly added dropwise to the reaction liquid, and the drop was completed in about 1 hour. Keep this temperature and continue to react for 3 hours, and TLC detects that the reaction is complete. Ethanol was recovered under reduced pressure, and the residue was washed with n-hexane to obtain 121.3 g of yellow solid (1-(4-hydroxyphenyl)-2-[2-(4-hydroxyphenyl)ethylimine]propanol (IV) , yield 85.3%.
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