Manufacturing Process
Stage 1: Preparation of 2-Phenyl-2-Methoxy-Ethyl Bromide - 1.3 mols of tertbutyl hypobromite is added slowly and with agitation to a mixture of 107
grams (1 mol) of vinyl benzene (styrene) and 250 ml of methanol (99%),
kept at -10°C. When the addition of the reactant is finished, the mixture is
allowed to return to ambient temperature, it is washed in water and dried on
anhydrous Na2SO4. Rectification is effected in vacuo in order to obtain a
colorless liquid BP12= 113°C, BP2-5=84°C, nD20.6 = 1.5429, yield = 76%.
Stage 2: Preparation of 1-[2-Phenyl-2-Methoxy]-Ethyl-Piperazine - 210 grams
of 2-phenyl-2-methoxy-ethyl bromide and 260 grams of anhydrous piperazine
are heated for 5 to 6 hours to reflux in 600 ml of ethanol, 500 ml of ethanol
is then distilled off and finally the solvent is removed in vacuo. The residue is
taken up in 250 ml of benzene and the piperazine hydrobromide is filtered off.
The benzene is removed in vacuo. The oily residue is taken up by 450 ml of
water and acidification is effected up to pH = 1 by concentrated HCl. The
aqueous solution is filtered; the latter is then made alkaline by 50% aqueous
NaOH. The liberated base is decanted, the alkaline aqueous solution is washed
twice by 150 ml ether. After distillation of the ether, the previously decanted
oil is added to the residue and distillation is effected in vacuo. Thus,135
grams of a colorless viscous oil, becoming carbonated in air, is obtained.
BP14= 166°C, nD20 =1.5321, yield = 61%.
Stage 3: Preparation of 1-[2-Phenyl-2-Methoxy]-Ethyl-4-[2-Benzoyl-Ethyl]-
Piperazine Dihydrochloride -There are heated to reflux and with agitation for 6
hours, 166 grams 1-[2-phenyl-2-methoxy]-ethyl-piperazine, 400 ml ethanol
(96°), 260 ml absolute ethanol with 23% HCl gas, 112 grams acetophenone,
32 grams trioxymethylene and 0.8 ml concentrated aqueous HCl. After
cooling, the product crystallizes. Recrystallization is effected in ethanol (96°)
(1.400 liters for the quantity indicated). 246 grams of a white crystalline
powder is thus obtained, slightly soluble in water and alcohol. MP (instant) =
168°C with decomposition, yield 77%.
Stage 4: Preparation of 1-[2-Phenyl-2-Methoxy]-Ethyl-4-[3-Phenyl-3-
Hydroxypropyl]-Piperazine Dihydrochloride -In a double-neck flask equipped
with a thermometer and a mechanical stirrer, there is placed in suspension in
800 ml of methanol, 233 grams of 1-[2-phenyl-2-methoxy]-ethyl-4-[2-
benzoyl-ethyl]-piperazine dihydrochloride (0.55 mol). It is cooled to
approximately 5°C, and 46 grams of NaOH pellets dissolved in 80 ml of H2O
are added. When the temperature is about 5°C, one addition of 29.2 grams of
sodium borohydride in 40 ml H2O is made. The ice-bath is then removed and
stirring continued at ambient temperature for 6 hours.
Cooling is effected in the ice-bath while slowly adding concentrated HCl up to
a pH of 2, while maintaining the temperature around 5°C. It is filtered and an
equal volume of H2O is added. If the solution is cloudy it is washed in ether. It
is alkalized by aqueous NaOH (40%), and the oil formed is extracted withether. The ether phase is washed with water saturated with NaCl, then it is
dried over anhydrous Na2SO4.
After evaporation of the solvent, a very thick, colorless oil is obtained. This
base is dissolved by 200 ml of absolute ethanol and the quantity of HCl to
obtain the dihydrochloride is added. It is left for a few hours over ice, dried,
washed with approximately 100 ml of anhydrous ether in order to obtain 190
to 195 grams of 1-[2-phenyl-2-methoxy]-ethyl-4-[3-phenyl-3-hydroxy]-
propyl-piperazine dihydrochloride after drying at 60°C in vacuo. The yield is
80%. It is recrystallized from absolute ethanol. The product is in the form of
white crystalline powder, soluble in water, slightly soluble in alcohol, insoluble
in ethyl acetate.
