Methyl 3-(3,4-dimethoxyphenyl)-2,2-dimethyl-3-oxopropanoate → 5-(3,4-Dimethoxyphenyl)-4,4-dimethyl-2-piperidin-4-yl-2,4-dihydro-3H-pyrazol-3-one

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Reaction Conditions

Reaction Steps

1000 g of methyl 3-(3,4-dimethoxyphenyl)-2,2-dimethyl-3-oxopropanoate (compound D1) are dissolved in 10.5 l of methanol. 2500 g piperidin-4-yl-hydrazine dihydrochloride, solved in 4 l of water are added rapidly. The mixture is heated to reflux and kept at reflux temperature for 4 days. The reaction mixture is cooled to 20° C., 10 l of water are added and then methanol is removed by distillation in vacuum. The aqueous solution is allowed to stand overnight at RT. The solution is cooled and aqueous sodium hydroxide (c=10 mol/l) (about 2 l) is added during 4 to 5 h by keeping the temperature below 20° C. and the pH should be higher than 13. The product crystallizes during adding of sodium hydroxide. The mixture is stirred 1 h at 10° C., filtered over a filter press and washed with 0.5 l of water. The product is dried at 50° C. in a circulating air dryer resulting in the title compound. (compound B1)

Provenance & Evidence