2,5-DMA by catalytic hydrogenation
(Rated as: excellent)
In this patent Mr Curtis teach us that phenylnitropropenes and phenylnitrobutenes are reduced to amines in two stages. In the presence of Raney-nickel and a weak organinc acid the nitroalkene is first reduced to the oxime (and some amine) which undergoes hydrolysis to te ketone. At this point many tend to declare the reaction over and start the workup to separate the ketone form amine. But this guy allows the reaction to continue, so the ketone is allowed to be aminated to more amine.
When the oxime is hydrolysed, the liberated hydroxylamine seems to be decomposed (most likely by the Raney-nickel) to ammonia. This ammonia does the same job ammonia has always done with ketones in the presence of Raney-nickel and hydrogen, it aminates it.
In the first step which is very exothermic, the temperature should not be allowed to go above 80 deg C, since a lot of crap is formed then. In the second step the teperature should be raised to 120 deg C.
A five gallon autoclave was charged the following materials
MeOH 9.5 L
Acetic acid 1.2 L
Raney-nickel 0.5 kg
The autoclave was closed and flushed several times with nitrogen. Then it was heated to 55-60 deg C, and hydrogen was introduced at a pressure of 1200 psig. A stong exotherm occured and the temperature was controlled by cooling to remain at 65-75 deg C. In about one hour the exotherm subsided and the temperature stabilized at approximately 65 deg C (thereby indicating the completion of the first stage). The temperature was then increased to 120 deg C, and maintained for 60-90 minutes. A smaller hydrogen uptake was noted, being about 5% of the total hydrogen taken up. The autoclave was then cooled, flushed with nitrogen and discharged with nitrogen pressure. The reaction product was collected and purified. 2.260 g 2,5-Dimethoxyamphetamine, representing a yield of 74% was collected.
2,5-DMA by reductive amination of the ketone
An autoclave was charged with the following materials:
2,5-Dimethoxyphenylacetone 3 kg
Ammonium acetate 1.2 kg
Acetic acid 180 ml
MeOH 9.5 L
Water 300 ml
Raney-nickel 500 g
The autoclave was closed and flushed several times with nitrogen, heated to 90 deg C, and hydrogen introduced at a pressure of 1200 psig. There waws no rise in tempertaure. No measurable hydrogen was taken up after two hours, although the reaction was permitted to continue overnight. At the end of this time, no noticable amount of ketone remained. Analysis showed a 95% yield of 2,5-dimethoxyamphetamine, 3% distillation residues and 2% acid insolubles.
|Where'd you find that?||Bookmark|
Where'd you find that? I had it listed here for about a year already.
The hardest thing to explain is the obvious
|I found it a while ago when searching the patent ...||Bookmark|
I found it a while ago when searching the patent database. It has been in my "to post"-pile and now it was its turn.