Author Topic: aldoxime>amine with Zn/AcOH (Read 414 times)

overunity33 · « **on:** February 15, 2010, 06:34:32 AM »

At room temperature with stirring, Zinc dust (74 mg) was added to a solution of
the oxime (44mg, 0.185 mmol) in 2 ml glacial acetic acid. Stirring was continued
for another 15 minutes. The reaction mixture was then filtered through a sintered
glass funnel with suction. The filtrate was concentrated under vacuum to afford
the amine as an oil (37mg, 0.166 mmol, 90% yield).

http://www.erowid.org/archive/rhodium/chemistry/oxime.txt

Anyone have any input? Yields are claimed 90% but I have heard lower mentioned. Would activating the Zn in diluted HCl increase yields? Workup would involve neutralizing with ammonia or NaOH, adding DCM, and washing with brine, correct?

Sedit · « **Reply #1 on:** February 16, 2010, 05:21:13 AM »

Your workup appears that it will cause some issues...

Ammonia acetate is soluble to some extent in Dichloromethane IIRC and I wouldn't doubt at NaOAc be so slightly as well. So nutralization is going to carry a bunch of shit over that you don't want to deal with later. Better would be to go for a less polar solvent to pull the amine if you plan on neutralization. Dilution of the solution with saturated brine would be a good bet as well since solubility of NaOAc may not be up to par and there will be alot of it formed on neutralization which may precipitate if the volume of the solution is to low.

Since im pretty sure that the Zinc is consumed in this reaction and not acting catalyticly I do not feel that activating the Zinc would increase yeild enough to warrent extra work that don't need to be done. You have heard reports of lower yeilds but I sure hope people where not following the time scale to frame since they are dealing with mg quantitys in this report. I would let this run much longer for anyone willing to do such a reaction and look into rate constants before attempting it.

overunity33 · « **Reply #2 on:** February 16, 2010, 06:57:20 PM »

SEDIT: thanks for the reply, very informative. Would you recommend distilling the amine? Could you do it before neutralization?

Also, found another reference:

To a solution of the substrate (oxime) (5 mmole) in methanol (10 ml) was added ammonium formate (10-20 mmole) [or ammonium chloride (10-20 mmol)] and zinc dust (10 mmol). The mixture was stirred under reflux. After the completion of the reaction (monitored by TLC), the reaction mixture was filtered through celite. The filtrate was evaporated under vacuum and the residue was taken into chloroform or ether, washed twice with 80% saturated brine solution and finally with water. The organic layer was dried over anhydrous sodium sulphate and evaporation of the organic layer was followed by purification either by preparative TLC, or by column chromatography, to yield the desired product (amine).

http://www.erowid.org/archive/rhodium/chemistry/oxime2amine.zn-af.html

Anyone have experience with this method?
Would these two methods work for aliphatic oximes/aldoxime?

frankblank · « **Reply #3 on:** December 21, 2010, 02:28:27 AM »

there is a very similar procedure that uses magnesium instead of zinc. which costs more but has the advantage of being carried out at room temperature and with just mechanical stirring. the zinc/ammonium formate method only takes place at reflux.

http://www.erowid.org/archive/rhodium/chemistry/oxime2amine.mg-af.html

i may be able to provide some real life experience with magnesium/ammonium formate reduction here pretty soon.

someone i know is trying to make b-hydroxy a,b-diphenylethylamine via reduction of benzoin oxime.

akcom · « **Reply #4 on:** December 22, 2010, 02:12:48 AM »

The reaction will proceed much quicker if the zinc is activated before hand. Although I must say, frank's post looks much more interesting.

frankblank · « **Reply #5 on:** December 25, 2010, 05:31:35 AM »

thanks. the paper said nitro groups are reduced at room temperature too. so it could be a good route for p2np's and nitrostyrenes too. rhodium did the HTML on that paper so you know its worth looking into

letters · « **Reply #6 on:** December 28, 2010, 10:51:46 AM »

notice that the paper talks about aromatic nitro groups! In the case of p2np's and nitrostyrenes, im not sure. p2np's will undergo reductive oxidation to the ketone. nitrostyrenes might be reduced fully, but im just not sure. The unsaturation might render the whole procedure useless.
If you were to first reduce the double bond of the nitroalkenes, you'll get nitroalkanes. These can defienelty be reduced with Zn/AcOH.
A practical tip - after reduction of the nitroalkene's double bond, distill it. It will greatly enhance the yield of the later reduction.
You can also use formic acid instead of acetic

frankblank · « **Reply #7 on:** January 03, 2011, 06:25:55 PM »

well do you think the magnesium/ammonium formate reduction would work on benzoin oxime to yield b-hydroxy a,b-diphenylethylamine? I admit i dont know that much about chemistry. Ive learned what i know pretty much exclusively from clandestine documents. Thanks for the reply. I've got all the stuff to try it, but there were a few other projects i wanted to try first. any advice would be greatly appreciated

WazOne · « **Reply #8 on:** April 03, 2012, 06:13:42 AM »

Just wondering where the reports from real life experience have gone?

fishinabottle · « **Reply #9 on:** April 03, 2012, 08:28:42 AM »

You all should really first do a search on such stuff over at Sciencemadness and not just a quick one. Except thats more masturbation without serious background, but even then...

- The magnesium reduction is BS it does not work.
- The zinc reduction with acetic acid works AFAIK, good quality zinc is important as is purity of the substrate (recrystallize if necessary several times! You won´t regret it!).
- Zinc MUST be activated. Either by a wash in diluted HCl (detailed instructions elsewhere) or by amalgamation. The eco-fraction may kill me but Hg activation beats the shit out of HCl activation. Reasonable and effective is to apply the acid wash AND add a minimum amount of Hg-salt to the zinc before adding acid and substrate. The reaction will start much smoother, otherwise it has the the habit to sit around like dead and as soon you turn your head to try to jump out of the flask and damn you if your flask is a bit small or your condensor reduces outlet diameter (like most Liebigs for example). On the other hand thats an experience everybody should make as it makes me feel less stupid when I hear it from others....

Quote

rhodium did the HTML on that paper so you know its worth looking into

Thats a myth. It just says he did the HTML and qualifies it neither for good nor for actually working at all.

That was just a quickie from memory so thats by no way complete. As with all references or writeups: You have to find at least two trustworthy people who were able to reproduce it or it is still pure experimental. THere are only few exceptions from this rule, one regards "official" Hyperlab releases of procedures for example another Bandil´s writeups (albeit sometimes sloppy) and of course everything I say*.

You can always ask for a method but kindly bring something fresher then the old stuff from Rhodiums page or at least show us that you have looked more into this by linking to threads or posts on the topic here or somewhere else. Preferably where somebody has actually tried something. Yes?

This will make it much easier, much of this thread is - sorry to say - halfassed, confusing, misleading or wrong.

regards
/ORG

*one of the three is absolutely not true, guess which?

Author Topic: aldoxime>amine with Zn/AcOH (Read 414 times)

overunity33

aldoxime>amine with Zn/AcOH

Sedit

Re: aldoxime>amine with Zn/AcOH

overunity33

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frankblank

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akcom

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frankblank

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letters

Re: aldoxime>amine with Zn/AcOH

frankblank

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WazOne

Re: aldoxime>amine with Zn/AcOH

fishinabottle

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