Manufacturing Process
2 Methods of producing of 1,2,3,6,7,11b-hexahydro-4H-pyrazino-[2,1-
a]isoquinoline:
1). 214.0 g diethyl ester of oxalic acid are mixed with a solution of 238.0 g 1-
aminomethyl-1,2,3,4-tetrahydroisoquinoline in 200 ml alcohol are boiled for 7
h. After cooling, the obtained crystals of 1,2,3,6,7,11b-hexahydro-4Hpyrazino[
2,1-a]isoquinoline-3,4-dione are vacuum-filtered and washed with
acetone and dried, melting point 220°C. Yield: 240.0 g.
55.0 g lithium aluminum hydride are dissolved in 650 ml absolute
tetrahydrofuran and mixed dropwise with a suspension of 120.0 g
1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinoline-3,4-dione in 300 ml
absolute tetrahydrofuran. After 7 h of boiling, the residual hydride is
decomposed by the addition of water, and the reaction solution is worked up.
The obtained 1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinoline is
distilled in vacuum, boiling point 98°-100°C/0.01 mm. Yield: 86.0 g.
2). 16.2 g 1-aminomethyl-1,2,3,4-tetrahydroisoquinoline and 18.7 g ethylene
dibromide are boiled for 4 h in n-butanol, with the addition of 13.8 g
potassium carbonate. After the solvent is evaporated, the residue is treated with water, mixed with sodium hydroxide solution, and shaken out with
chloroform. The chloroform solution is dried, concentrated by evaporation, and
the resulting 1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinoline is
distilled at 98°-100°C/0.01 mm. The yield amounts to 7.5 g.
