DOB via Urushibara

[Phikshun2]

Synthesis of DOB by Phikshun2

2,5-dimethoxyphenyl-2-nitropropene

10.0g of 2,5 dimethoxybenzaldehyde was dissolved in 50mL of GAA, and 6.8g of nitroethane was added.  I dreamed I got both from a photochemical supplier with relative ease.  4.0g of ammonium acetate, that had been stored for weeks over Calcium Chloride (i.e. quite anhydrous), was added and the flask swirled until everything dissolved.  This mixture was heated over a pot of boiling water, with heavy duty foil surrounding the flask and top of pot, to keep steam in.  It was left for nearly 3 hours, upon which time it had a cherry red colour, and was allowed to cool.  After cooling, solvent was stripped off under aspirator vacuum and about 100mL of dH2O was added.  The mixture was then extracted with TCE (tetrachloroethylene, brake degreaser, don't ask), and the TCE distilled off under vacuum to afford 12.4g of impure nitropropene, which was recrystallized in 80mL methanol to ~10g, and was recrystallized again from 75mL methanol to a weight of 8.4g.  I have no idea why Shulgin only got 6.7g in his 2,5-DMA synth.

2,5-dimethoxyamphetamine

Prepared Urushibara catalyst using instructions from

https://www.thevespiary.org/rhodium/Rhodium/chemistry/tmp2np-red.html

.  Had to use a cleaned out 4L milk jug instead of a 4L beaker, and I used nuggetized generic Al foil, but otherwise the same method.  Activated 15g of the aforementioned catalyst in 580mL of 40% GAA, with 130g of NaCl dissolved, at 70 deg C for a little over 7 mins.  Rinsed with 60 deg C dH2O and washed with IPA, then placed in a 500mL erlenmeyer with 375mL of anhydrous IPA, and 6.7g of the long orange crystalline needles of nitropropene prepped in the previous step.  The yellow-orange tint completely leaves the solution in about an hour.  For stirring, SWIM used a 12V computer fan, with the blades cut off and a glass stir rod (slightly bent on the end) fastened on with a rubber stopper and some crazy glue.  This was attached with a 12V supply with a variable resistor in place to control speed. Worked famously, and totally quiet, which is good, because this dream took place in a small apt.  15g of Al foil prepped in the same fashion as used to precipitate catalyst, is added gram wise, followed by the addition of 3ml 31.45% HCl (HW store grade).  This took about 2.5 hours.  The flask got quite warm near the middle of the reaction, but never achieves reflux.  After Al stops reacting, and H2 is no longer bubbling, 150ml of IPA is added, and then the reaction is basified with 50% NaOH sol.  After bubbling subsides, nice yellowish alcoholic layer settled out on top.  This was decanted, and concentrated at aspirator vacuum.  The remaining AlO sludge is extracted with xylene, and the xylene is added to the other extracts.  This was washed once with Brine, and once with dH2O, then dH2O is added, and triturated to a pH of 4.  Aqueous extract is kept, basified with NaOH solution and extracted with DCM.  DCM is evaporated overnight to provide ~3ml of orangish brown oil.  Further A/B extractions of the xylene proved not to contain any more DMA.

4-bromo-2,5-dimethoxyamphetamine

The crude DMA, which weighed 2.1g, and 15ml GAA was placed in a 50ml RBF with a claisen adaptor attached, a condenser, then a gas inlet adaptor, which was hooked to a tube leading outside.  Upon the claisen was placed a 125ml addition funnel.  Into the funnel was added 2g elemental bromine (I chilled it first in the fridge, still reeked) in 5ml GAA.  This was dripped in over a 5 minute period with magnetic stirring, and was left for about 4 hours.  This mixture was then added to 200mL dH20, and washed with 3x50mL portions of xylene.  This was basified with a 25% NaOH solution, then extracted with 100mL and then 50mL of DCM.  Upon evaporation of the solvent, about 3-4ml of a pale brown oil was recovered, which crystallized on standing overnight.  To this was added sufficient IPA to dissolve, and it was triturated dropwise with 31% HCl until a pH of 4 was obtained.  IPA was distilled off until about 20mL remained, then cold acetone was added to crash out the crystals.  Solution was vacuum filtered, and the resulting off-white crystals where recrystallized in IPA to afford 1.25g of perfectly white, fine, powder of DOB.HCl.  This worked out to about 415 hits, at 3mg a piece.  Personally, I really don’t enjoy DOB that much, but it makes acid look like kids stuff.  My roommate loves the stuff though...

P.S.  I never claimed this was anything revolutionary, but it's my first dream.  Thanks to everyone at the hive who make dreams great

[CrystalWitch]

You only start Dreaming on the second Line?  Thank you for being so tolerant and understanding.

[Phikshun2]

Okay so my writeup could use some work...  I am not a brilliant writer nor brilliant chemist.  I just thought I should post this because I was unable to turn up anything in UingTFSE about Urushibara used to reduce this particular nitropropene.

[SPISSHAK]

He's not critiquing you, he only wants to know what is published work, and work that you have done.
This is because some literature tends to exagerrate results to get noticed.
He merely wants a real-world example.

[Phikshun2]

This isn't cited from literature if that's what your inquiring, it's results achieved from experimentation by SWIP.  SWIM was using PIKaL as a reference for most of this experimentation, aside from the reduction which was performed as per Urushibara docs on Rhodium's site.

[catastrophe]

Great work Phik! This is what pioneer work is all about, trying something no one has reported trying before. And it worked! Congradulations.

[CrystalWitch]

I really mean that as a Dry Complement - really..., well, well, well done.

[Megatherium]

So - if this is by your own experimentation - how did you, make the 2,5-dimethoxybenzaldehyde ?

[SPISSHAK]

It was purchased from a rouge chemical supplier, naughty, naughty.

[Rhodium]

Excellent! The synthesis has been added to

https://www.thevespiary.org/rhodium/Rhodium/chemistry/dob.html

[Antoncho]

This was AWESOME, dear Phikshun2! AWESOME!

What is particularly pleasant, your write-up is very detailed. Even a total newbee would'n make a mistake following this.

And - no, i don't agree - what you have done isn't unnovel at all! Firstly, noone has reported Uru-Ni reduction of this particular substance yet (well, xcept for two guys at HyperLab - who were too lazy to describe what they did in all detail even in their native language  - but i must tell you their yield was pretty consistent with yours, though). Secondly, this area is very, very little explored yet and each such report is a treasure of the future.


Shall we start a little discussion on improving this kind of reduction? In terms of yield, of course - the yield sucks.

So. What is the reason here? Well, here are some facts:

Fact 1.
Reduction of nitropropenes proceeds thru an oxime intermediate (it may pass thru nitropropane stage or get reduced directly to oxime; the 1st scheme proceeds slower), which is then reduced to N-hydroxyamine and, finally, to amine.

Fact 2.
Ketoximes are unstable in acidic environment and hydrolyze into ketones (significantly less stable than aldoximes - which, i think, is THE reason for the Zn/HCl reduction not working on NP's - given the high concentrations of acid, needed in that rxn, the ketoxime simply doesn't have a chance of surviving in the rxn mixture for but a brief moment).

Fact 3.
OTOH, acidic enviroment is needed to minimize the treacerous side reaction. Amine freebase will fondly react with the 'acidic' nitropropene, forming a - well, sorta - dimer.
On the brighter side, NP's are less susceptible to that than NS's due to steric hindrance, but i think that should not bee overlooked nevertheless.


So. Here's the deal. We need a system that is acidic, but not TOO acidic. Preferrably, devoid of Lewis acid catalysts (which inevitably form in Zn or Al reductions).

And, of course, it is advisable to add nitropropene very slowly, and in solution - so that it can get reduced bee4 it reacts with the basic products.

I imagine something like a CTH hydrogenation in formic acid/KHCOO, with a BIG qtty of Ni catalyst (activated with Cr/Mo/Co), with NP being added very-very slowly as a solution in EtOAc - so that the rxn mixtr never turns appreciably yellow.


Barium, you're a catalytic hydrogenation freak, what will you say on my idea?



Antoncho

[Barium]

One of the speculated routes for amine formation from nitropropenes is;

nitropropene --> ketoxime --> imine --> amine

I have several experiences of both CTH reductions and regular catalytic hydrogenations which started emitting ammonia at a point of the reaction. The ammonia can originate either from hydrolysis of the imine or reduction of hydroxylamine. The ammonia formation is a strong evidence that the reduction actually follows this path.

Ketoximes are not that unstable in acidic eviroment. There are several articles in which ketoximes are formed in good yields by hydrogenation of nitropropenes in aq. HCl/alcohols. The acid hydrolysis of ketoximes to ketones and hydroxylamine reach a equilibrium

ketoxime + water + acid <--> ketone + (protonated)hydroxylamine

which is pushed further to the right if the ketone is removed as it´s formed, or if the hydroxylamine is allowed to react with some other carbonyl compound with which it easier forms oximes.

The idea of a buffered HCOOH/Ni CTH is not bad at all. I would perhaps choose GAA/KCOOH.

[Phikshun2]

I'm glad you like it.  I was thinking about various other hydrogenation options like CTH and pressurized parr-shaker style.  I actually thought that it was acid hydrolysis that was killing my yields, because a lot of polymerish crud is formed out of the reduction, but I'm no expert.  Anyway, I plan on attempting further experimentation in microscale, using more active catalyst, different NP's, and a variety of hydrogenation options, as time and resources permit.  I'll keep ya posted.  One Question though... How would the use of methanol affect yield?  IPA is expensive for me and ethanol not readily OTC.

[Antibody2]

way to go Phikshun2. I wouldn't be shy about trying  Urushibara Ni in MeOH.