Manufacturing Process
166 g (1 mol) of 3,4-dimethoxybenzaldehyde were stirred for several hours (8
to 10 hours) with 180 g (2.02 mols.) of 1-nitropropane in 300 ml of methanol,
in which 12 g of metallic sodium had previously been dissolved, the stirring
taking place while heating to 45-50°C. After usual working up of the reaction mixture, there were obtained 155 g of a white, crystalline product, which
constituted the 1-(3,4-dimethoxyphenyl)-2-nitro-1-butanol and melted after
recrystallization from isopropanol at 93-94°C (uncorrected). The composition
was confirmed by elementary analysis and an infra-red spectrogram.
204 g (0.8 mol) of the above nitro alcohol were reduced at 30-35°C in 1250 g
of 44% formic acid with 320 g of powdered zinc (about 4.9 at.). After working
up, the base 1-(3,4-dimethoxyphenyl)-2-amino-1-butanol was obtained as a
white crystalline product. After recrystallization from ethyl acetate, it melted
at 91-93°C and the yield was 168 g, i.e. 93.3% of the theoretical.
90 g (0.4 mol) of the above amino alcohol are reacted at 45-50°C in 400 ml
of chloroform in the presence of 95 g (1.2 mols) of pyridine by means of 139
g (0.9 mol) of phenylacetic acid chloride. After working up the reaction
mixture, a yellowish-crystalline product was isolated (183.5 g, theoretical:
184.6 g), which melted at 123-125°C. After recrystallization from ethyl
acetate, it yielded minute, white crystals, which melted at 129 -131°C
(uncorrected). The composition of the product was confirmed by elementary
analysis.
217 g of the above 1-(3,4-dimethoxyphenyl)-2-(phenylacetamido)-butanol-1-
phenyl acetate (0.47 mol) were stirred in 80 1300 ml of xylene with 145 g of
phosphorous oxychloride at 100-105°C. After some hours, when the evolution
of hydrochloric acid gas had ceased, the reaction mixture was poured on to
ice and stirred while cold until the crystallization was completed. After
filtering, 144 g (89%) of the formed 1-benzyl-6,7-dimethoxy-3-ethyl
isoquinoline hydrochloride were obtained in the form of yellowish crystals,
which melted at 198-202°C with decomposition. From the separated aqueous
mother liquors, the remainder of the formed isoquinoline base was obtained
after treatment with ammonia and extraction with ether, the said base being
isolated by way of the sparingly soluble and readily crystallisable acid sulfate.
The salt represented a yellowish crystal powder, which melted at 239-243°C
and weighed 21 g (11%). Thus, the yield of crude isoquinoline salt was almost
the theoretical yield. The crude hydrochloride acid salt yielded white, lustrous
prisms after recrystallisation from 96% ethanol, the said prisms melting at
208-210°C with decomposition. 1-Benzyl-6,7 -dimethoxy-3-ethyl isoquinoline
may be prepared as a base from its salt by adding of equivalent of triethyl
amine or any other base.
