The preparation method of mirtazapine and its intermediate
A compound and group technology, which is applied in the field of preparation of mirtazapine and its intermediates, can solve the problems such as the difficulty of industrial production and harsh reaction conditions that are easy to catch fire and explode
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[0010] 1, the present invention relates to the preparation method of formula I compound:
[0011]
[0012] The compound of formula I can be prepared by the compound of formula II in the presence of dehydrating agents such as sulfuric acid and polyphosphoric acid
[0013]
[0014] 2, the present invention provides the preparation method of formula II compound:
[0015] Formula II compound can be prepared by following formula reaction:
[0016]
[0017] In the present invention, the preparation of compound II is mainly carried out in the following way, in the presence of a specific reducing agent, the carboxylate group in the compound of formula III (reaction substrate) is reduced to a hydroxymethyl group to prepare compound II
[0018] In the present invention, the compound containing carboxylate formula III is used as the substrate, wherein the -R group in the compound of formula III is an alkyl group containing 1 to 6 carbon atoms, which can be methyl, ethyl, propyl...
Embodiment 1
[0039] Example 1 1-(3-carboxyethyl-2-pyridyl)-2-phenyl-4-methylpiperazine
[0040] Put 30 grams of 1-(3-carboxy-2-pyridyl)-2-phenyl-4-methylpiperazine into a 250ml four-necked flask, 50ml ethanol, 5ml concentrated sulfuric acid, heat in an oil bath, reflux for 2 hours and evaporate Remove the solvent with low boiling point until the internal temperature is about 80°C. Add 100ml of ethanol, 5ml of concentrated sulfuric acid, and then reflux for 1 hour, TLC tracking (developing solvent: dichloromethane: methanol = 7:3) until no raw material is the end of the reaction. Ethanol was distilled off under reduced pressure to obtain a reddish-brown oil. Add 120ml of dichloromethane, wash with 60ml of water, wash with 60ml*2 of saturated sodium bicarbonate solution, then wash with 60ml*2 of water, dry with 20g of anhydrous sodium sulfate, filter off the solid, and concentrate under reduced pressure to obtain 30g of a reddish-brown oily ester compound. Yield 93%.
Embodiment 2
[0041] Example 2 1-(3-carboxylate ethyl-2-pyridyl)-2-phenyl-4-methylpiperazine
[0042] Put 20g of 1-(3-carboxy-2-pyridyl)-2-phenyl-4-methylpiperazine and 100g of triethyl orthoacetate into a 300ml reaction bottle, heat the oil bath to 100°C±3°C, and keep it warm for reaction 6 hours. The solvent was distilled off under reduced pressure. The raffinate was cooled to below 30°C, 100ml of dichloromethane was added, stirred to dissolve, and washed with 100ml of water. The organic layer was dried with 10 g of anhydrous sodium sulfate for 2 hours, filtered off, and the filtrate was concentrated under reduced pressure below 60 ° C to obtain 22 g of dark brown oil product
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