Al/Hg/HOAc Oxime redxn

[Antibody2]

Al/Hg reduction of MDP-2-P oxime in acidic EtOH
by Antibody

For obvious reasons an alternative catalyst to sodium was sought for the reduction of the oxime of MDP-2-P to its amine
derivative. This investigation led to experimentaion with various solvent systems including THF, MeOH, EtOH [1], both aqueous and non-aqueous, acidic and neutral, with various acids being employed. Hazards and low yeild ruled out THF, and long reduction times and moderate yeilds led to the abandon of MeOH systems. Aqueous systems afforded superior yeilds with all solvents triied. Non acidic solvent-sytems failed altogather. HOAc provided higher yeilds than HCl. Different acid proprtions were triied with 10 equivalents producing the highest yeilds. The amount of Al used also impacted yeilds as well as the amount of MDOH by-product produced. With increases boosting overall yeild but lowering yeild of MDOH.

It should also be noted that the following solvent/redxn system was sucessfully employed in the manufacture of MMDA and DMMDA but in lower yeilds, 10% and 50% respectively. It failed repeatedly with DMMDA-2 altogather.

Experimental
In a 4l beaker with mag stirring, 0.75 moles of activated Al (19.5g) [2] is added to 1l 95% EtOH and 100mls dH2O, followed by 0.33 moles oxime of MDP-2-P (65g) [3],and 3 moles HOAc (180g). The Rxn is heated to 60C and heat removed. There follow three additions of 0.75 moles of activated Al at 30 minutes, 1 hour, and two hours. Temperature was maintained at 60C by placing beaker in a cold water bath as necessary. There is a vigourous evolution of hydrogen as the rxn progresses, care must be taken the rxn vessel does not overflow.  An additional 150mls 95% EtOH and 15mls dH2O is added at 2hours.  At 3 hours the rxn is a viscous gel which has stopped the stir bar. An additional 300mls 95% EtOH and 30mls dH2O is added . The rxn was allowed to stir until it has returned to room temperature, during which time 1 l of 15M NaOH was prepared and cooled. The rxn vessel was placed in a cold water bath and the basic solution was added slowly over 20 minutes, with care being taken the tempertaure did not rise above 60C. 500g of NaCl was added, much of which precipitated after stirring. 500mls toluene is added with stirring. The toluene/EtOH/amine layer is separated and decanted into 750mls of dH2O, causing the EtOH to migrate to the aqueous layer. The toluene layer is separated and the aqueous/alcoholic layer is  extracted 2 times with 250mls toluene. The pooled toluene extracts are washed once with 400mls dH20 and once with 400mls brine, then driied through MgSO4 and gassed w/ dry HCl gas.

yeild 0.267 moles MDA.HCl (54g)
81% molar yeild

1) see

Post 189985 (missing)

(Antibody2: "Re: MDA via oxime", Methods Discourse)
2) activated by refluxing in 19.5g Al in 800mls of 50/50 dH2O/MeOH, with 1g Hg2Cl2 for 15 minutes, the mercuric solution was decanted, and Al was washed once with 400mls 95% EtOH, which was also decanted. Same mercuric solution was
used for all four activations.
3) prepared according to Sonson, see

Post 54080

(Sonson: "High-yielding synthesis of MDA from MDP2P", Methods Discourse)

[Chromic]

Let me be the first to say this is an excellent writeup which deserves to go on Rhodium's webpage asap! Kudos!

I also want to add that as variations on Sonson's oxime preparation that one can:

Mix:
(1) 7.9g Na2CO3  or  20.4g NaOAc.3H2O (150mmol)
(2) 15ml H2O
(3) 10.3g (NH2OH)2.H2SO4  or  8.7g NH2OH.HCl (125mmol)
(4) stir bar

Stir, then add:
(5) 100mmol phenylacetone (22.4g 2,4,5-tmp2p 16.4g pmp2p or 17.8g mdp2p)
(6) 75ml MeOH or 75mL EtOH

Then do the 1.5hr reflux, cool in fridge, and suction filter a la Sonson. The calculations were a pain, so I thought I'd include them here so other people don't have to repeat them.

[uemura]

Hello ab2,
Good to see you back! Uemura hopes you will again continue to provide such good posts as the above one in the future   . And yes, this oxime reduction should be saved on Rhodiums site! Carpe Diem

[Chromic]

I also want to add that at the end of the oxime preparation (not the reduction), I always see a white solid sludge that settles to the bottom. This is not the oxime, but some sort of inorganic salt. I'm not sure if this is common or not (anyone else seen this?), anyways, after cooling the flask in the freezer (and adding 40ml of water! oops, sorry for the omission!) the oxime crystallizes and fills the alcohol solvent with crystals. Don't skip the cooling step...

(I forgot to mention the addition of 40ml of water at the 100mmol ketone scale before putting the flask in the freezer, if one fails to do this, one won't see the oxime form as it needs that extra water to crash it out of the alcohol... and if you just add a ton of water and skip the freezing, the oxime will just "oil out"... I've made about every mistake possible with this very simple preparation, no need for other bees to repeat my mistakes...)

[Vibrating_Lights]

Swim has also seen these salts, that chromic mentions,  form after a Nitro reduction.
Vl_

[Antibody2]

yes chromic, i've seen it in virtually every oximation i've ever done, but it disappears when you add the H2O. Its either the XS base or NaCl crashed out by the ketone or oxime i think

[psychokitty]

Here's a new one (I think) for reducing nitroalkenes to aldoximes:

General Proceedure for the Synthesis of Oximes.

The synthesis of 9-anthracenylacetaldoxime is representative of the proceedure employed.  w-(Nitrovinyl)anthracene (1.25 g, 5 mmol; is this right? I can't read this part), SnCl2-2H2O (2.25 g, 10 mmol) and ethyl acetate (25 mL) were placed in a 50 mL Erlenmeyer flask and the mixture stirred at room temperature.  A mildly exothermic reaction ensued which was accompanied by the gradual disappearance of the yellow coloration (nitroalkene).  The reaction mixture was carefully poured into ice water--

Which presumably forms an acidic aqueous solution making the water soluble amine-HCl salt.

--and the solution made slightly basic (pH 7-8) by addition of 5% aqueous sodium bicarbonate.  The product was extracted into ether, washed with brine, dried (Na2SO4) and the solvent removed under reduced pressure to yield essentially pure E/Z mixture of 9-anthracenylacetaldoxime.

For nitrostyrene and p-isopropyl nitrostyrene the length of the reaction was 6 hrs with a 94% and 92% yield.  For p-bromo nitropropene, 5 hrs and 89%.

[Rhodium]

Which presumably forms an acidic aqueous solution making the water soluble amine-HCl salt.

The oxime HCl salt you mean? What is the ref for this?

[Antoncho]

This article was 1st posted by Yellium a while ago and interested me very much at the time. Rhodium said that Ritter witnessed the fact that it worked as described at that scale, but produced only tar on larger scale - but '...it may bee simply a matter of twitching the rxn conditions.'

Also - i am very interested in the possible reduction of oximes with zinc. Any successes with it yet? On Rhodium's page there is quite a collection  of such reductions, all performed on complex, picky molecules, always with ~90% yields.


Antoncho

[psychokitty]

Rhodium:  I don't know what the hell I was thinking when I wrote that.  I guess as a result of fatigue, I mistaked the end-product as an amine rather than an oxime even when I was staring right at the paper itself.  It was late when I posted last. Sorry.

Here's the ref:

Post 70459 (missing)

(yellium: "Syn. Comm 18(7), 693-697 (1988)", Novel Discourse)

[Antibody2]

i heard the same thing from ritter, i did however see another nitro>oxime SnCl2 rdxn in acetone that looked promising, i'll see if it can be found

antoncho Zn/Ni Urishibara w/ NH3 as base should reduce the oxime to amine

[Starkas]

2) activated by refluxing in 19.5g Al in 800mls of 50/50 dH2O/MeOH, with 1g Hg2Cl2 for 15 minutes, the mercuric solution was decanted, and Al was washed once with 400mls 95% EtOH, which was also decanted. Same mercuric solution was used for all four activations.

Can I use HgCl2 instead of Hg2Cl2?  Do I reflux for the same time with the same quantity (1g)?

This question probably belongs in the Newbee forum but I didn't want to start another thread.

Cheers...

[Antibody2]

HgCl2 is in fact preferable (although more dangerous to handle), it will amalgamte much quicker, and you could get by with less, probably as little as 0.1g

[Antibody2]

A recent batch of MDOH was prepared via Al/Hg redxn of the ketoxime using 5 equivalents of Al and HOAc, 150mls H2O, 200mls IPA and 1650mls MeOH using the above proceedure. (10x produces higher yeilds with a much higher MDA ratio) In an attempt to further isolate the MDOH, its lower solubility in alcohols was exploited, and was  slowly recrystalized from  an equivalent w/w of boiling MeOH. The crop of crystals that formed when the solution had cooled to RT were vacuum filtered. The balance refridgerated to produce a second crop. Then reduced and and refridgerated to yield a third. (yeild ca. 72% w/w from oxime)

The odour of the first and to a large extent the second crop was completely dissimilar to MDA. The odor could be characterized as sweet. If you are familiar with MDA there is no mistaking the two.

trip report

Post 341465 (missing)

(Antibody2: "MDOH - strong disassociative", General Discourse)

[madprosr]

he treated 9g of wet mdp2p oxime (it had been drying 5days as a paste, and was finally 'crumbly') as if it were 9g of dry oxime using antibody's reduction in EtOH.

it took a bit more EtOH than expected, like 200ml of 85% to start with and 3x 20ml more to keep it stirring over 5h. required intermittent cooling the first 1.5h to keep it at 60C.

anyway, swim used his head and added 28.5g NaOH (still overkill as pH was 14) instead of the 80g antibody reccomends, no NaCl, and enough h2o to make 1.5x the volume of EtOH in the reaction.

extracted with 100ml, 4x 50ml toluene, washed with 3x 100ml brine, dried, and gassed out 7g of bright white mda.hcl.

if you fail to add enough water to the alcoholic mother solution, it simply is not dense enough for the toluene to separate out on top. which complicates the workup and can cause emulsions that would never have otherwise occured...

anyway, the best part is that swim measured the MP at 186-188C.

from Phikal-
hydrochloride salt [of MDOH] had a mp of 149-150 °C (and should not be confused with the hydrochloride of MDA which has a mp of 185-186 °C since the mixed mp is depressed, mp 128-138 °C)

swim expected his MP to be 1-2C high, as he was measuring the temp of an oilbath containing a test tube with ~30mg mda at the bottom. so the MP is right on, no mdoh present here!

[Antibody2]

use less Al and get more mdoh

[TheBlindGenius]

Have been studying this method, perhaps in the future would like to try it.  What kind of aluminum should be used for this?  It's not really specified anywhere Ive looked whether aluminum turnings, or sheet, or foil, or whatever are to be used.

[Chromic]

Foil--any kind will work. I preferred Reynold's Heavy Duty.