Acetic Acid → 2-[1-(chloroacetyl)piperidin-4-yl]-5-(3,4-dimethoxyphenyl)-4,4-dimethyl-2,4-dihydro-3H-pyrazol-3-one

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Reaction Conditions

Reaction Steps

430 g 5-(3,4-dimethoxyphenyl)-4,4-dimethyl-2-piperidin-4-yl-2,4-dihydro-3H-pyrazol-3-one (compound B1; synthesis alternative 2) and 215 g potassium carbonate are suspended in 6.5 l of DCM. The mixture is heated to reflux and 162 g chloroacetylchlorid is added drop wise during 1 h. The mixture is stirred at reflux temperature for 5 h, then 30 g of potassium carbonate and further 36 g of chloroacetylchlorid are added. After 1 h additional reaction time at reflux the reaction is complete. 116 g of acetic acid is added to the mixture during 10 min, then the mixture is cooled to 20° C. and during cooling 3 l of water is added. The organic layer is separated from the aqueous layer; the organic layer is washed twice with 1.5 l of water. The combined aqueous layers are extracted twice with 0.5 l of DCM. The organic layers are combined and 6 l is distilled off in vacuum. Then 2.5 l of tert. butylmethylether is added and the solution is concentrated in vacuum until crystallization starts (about 0.8 liter is distilled off). The suspension is cooled down and stirred overnight. The suspension is filtered, the solid dried in vacuum by 50° C.

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