Sciencemadness Discussion Board

Mg/Methanol is amazing

notoxicshit - 15-6-2016 at 01:53

I stumbled upon the nice review of the use of plain Mg in Methanol.
I was in awe about what unbelievable synthetic use can be made of such an easy combination.

I have attached it at the bottom.

Take some examples:



It reduces aromatic nitro groups to amines



It dehalogenates aromatic and aliphatic halides. Only the Fittig and Grignard are able to achieve that under considerably higher effort.

It also deoxygenates (and thus deprotects) and cleaves all kinda components and of course reduces conjugated double bonds in great selectivity. It also mediates interesting reductive cyclizations.
It also reduces oximes and Grignard imine-MgX intermediates to amines.

My head is spinning, but as I do unfortunately lack formal chemistry education, I do have a few questions.

Look at the following example:
Why is the yield so bad?



An explanation would help me out alot, especially an estimation if this would be a representative example of what Mg/MeOH would do to alpha-methylcinnamic acid?
Or is debenzylation and dehalogenation competing?

Further, I asked myself what this combo would do to aliphatic nitro groups as I don't see them mentioned in the review.

Happy posting!

Attachment: 14259790.pdf (208kB)
This file has been downloaded 6550 times


Edit: can someone access Sugden, J. K. Chem. Ind. 1969, 260. ?
I am not even sure, which journal it is, but I can not access any of the ones that could be meant.
[Edited on 15-6-2016 by notoxicshit]

[Edited on 15-6-2016 by notoxicshit]

[Edited on 15-6-2016 by notoxicshit]

Paddywhacker - 15-6-2016 at 03:44

That is very interesting, but sorry, I cannot figure what "chem. ind." is. Too many possibilities.

careysub - 15-6-2016 at 05:00

Quote: Originally posted by Paddywhacker  
That is very interesting, but sorry, I cannot figure what "chem. ind." is. Too many possibilities.


It is Chemistry and Industry (London).

The ref Paddywhacker gives is exactly what the Mg in Methanol paper gives, as poor as that is.

Unfortunately the reference seems to be too slight to bring up a usable on-line link with Google, the paper authors are assuming that everyone has access to the physical periodical and can look up the specific issue to find out what the article is.

clearly_not_atara - 15-6-2016 at 10:43

Scheme 87, the reduction of oximes with Mg/MeOH and NH4OAc, is IMO the most interesting reaction in the review. Selective oxime reductions are few and far between. In particular, oxime reduction is sufficient for nitro group reduction, since we know that reducing nitro groups to oximes is relatively easy (Pd/C/[H]).
Quote:
Look at the following example:
Why is the yield so bad?


Molecules containing a CH2=CH-EWG linkage tend to undergo polymerization reactions catalyzed by nucleophiles, including MeO-. For example, this is how superglue (cyanoacrylate) works.
Quote:
It is Chemistry and Industry (London).


A search for the author, JK Sugden, on Google Scholar around 1970 turns up a large number of "citations" published in "CHEMISTRY & INDUSTRY" around 1967-1970. However, the Wiley online website only has archives going back to 2011:

http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2047-6329/issues

It appears that the journal in which the article was published was not published online. Another interesting citation from JK Sugden in Chem. Ind. around this time is "Studies on the reduction of cyclohexanone oxime" from 1967.

Anyway, the reaction should be easy to test...

[Edited on 15-6-2016 by clearly_not_atara]

subsecret - 1-7-2016 at 17:57

If you can find 4-dichlorobenzene mothballs, this would be a good route to benzene.

PHILOU Zrealone - 2-7-2016 at 11:19

Quote: Originally posted by subsecret  
If you can find 4-dichlorobenzene mothballs, this would be a good route to benzene.

1,4-dichlorobenzene or p-dichlorobenzene is not in use anymore into the European space.

Was stil available about 15 years ago by kilograms in Di-drugstore...as man pissodrome desoudorizer...

[Edited on 2-7-2016 by PHILOU Zrealone]

Texium - 2-7-2016 at 12:06

It's still readily available in the US. I might have to put that on the ever-growing list of things I'd like to try at some point. If it works it does seem like it would be a pretty easy route to benzene.

aga - 2-7-2016 at 14:40

Absolutely no references, no evidence they did it themselves, no process, no yeilds etc etc.

It's just Words, so don't stake too many $ on it.

Anyone actually interested in Chemistry and though it Might work would have tried it and would post the process.

I would, and i guess you would too if you'd made useful yields of benzene that way.

CharlieA - 21-12-2016 at 17:25

...
Look at the following example:
Why is the yield so bad?



[/rquote]

Just as a guess, maybe steric hindrance plays a part in the relatively low yield. Of course, many would be overjoyed with a 30+% yield!

Corrosive Joeseph - 22-12-2016 at 08:23

This sounds too good to be true but I don't know enough to comment...................

For anyone interested in Mg reduction of oximes I'll drop this here -

http://www.sciencemadness.org/talk/viewthread.php?tid=8275#p...

Maybe someone else knows more or it will help somebody in the future.............

/CJ

[edit] I have just noticed this review is already linked in the thread I linked to. Maybe if notoxicshit had bothered to read the whole thread he would have realized that maybe Mg/Methanol is not so amazing after all. But like I said, I don't know enough to comment. I only linked to the thread because I had a vague recollection of Mg/ammonium salt not reducing oximes.

[Edited on 22-12-2016 by Corrosive Joeseph]

[Edited on 23-12-2016 by Corrosive Joeseph]

Meltonium - 22-12-2016 at 18:05

I tried the suggested experiment of creating benzene by dehalogenating p-dichlorobenzene. To cut it short, no product was formed.

I used 4g p-DCB, 2.6g Mg turnings, and 11g i-PrOH. They were refluxed for 2 hours and let cool. Nothing seemed to happen..

Tsjerk - 22-12-2016 at 21:44

Did you "activate" your magnesium as is usual in for example Grignards? Maybe the oxide layer is interfering. I guess a small pince of iodide could also help.

I forgot what the usual activation was for magnesium but it should be easy.

Shouldn't magnesium in alcohol at least make the alkoxide under generation of hydrogen?

[Edited on 23-12-2016 by Tsjerk]

[Edited on 23-12-2016 by Tsjerk]

Meltonium - 23-12-2016 at 06:04

Quote: Originally posted by Tsjerk  
Did you "activate" your magnesium as is usual in for example Grignards? Maybe the oxide layer is interfering. I guess a small pince of iodide could also help.

I forgot what the usual activation was for magnesium but it should be easy.

Shouldn't magnesium in alcohol at least make the alkoxide under generation of hydrogen?

[Edited on 23-12-2016 by Tsjerk]

[Edited on 23-12-2016 by Tsjerk]


No I didn't activate the magnesium, and this may be why it didn't react properly. Unfortunately, I don't have any iodide on hand at the moment, so a rerun will be in the future.

CuReUS - 23-12-2016 at 06:44

Quote: Originally posted by Meltonium  

I used 4g p-DCB, 2.6g Mg turnings

for 4g of p-DCB,you have to use a slight excess of 3.26g of Mg

[Edited on 23-12-2016 by CuReUS]

zed - 28-12-2016 at 17:21

Now, this is a good idea Meltonium. Since Benzene is fairly hard to obtain nowadays, and I can Buy p-DCB, down at my local "Dollar Tree" fer $4 bucks a pound. Yeah, that's right. Portland's "Dollar Tree"....... Lloyds Center. Last I checked, They were selling p-DCB @ $1 per 4oz.

Odd situation. Could this reduction require a little H2O, acid, or base..... to "Kick it Off".

Amalgamation?

"Wet" Isopropyl Alcohol?



[Edited on 29-12-2016 by zed]

Meltonium - 29-12-2016 at 06:13

Quote: Originally posted by zed  
Now, this is a good idea Meltonium. Since Benzene is fairly hard to obtain nowadays, and I can Buy p-DCB, down at my local "Dollar Tree" fer $4 bucks a pound. Yeah, that's right. Portland's "Dollar Tree"....... Lloyds Center. Last I checked, They were selling p-DCB @ $1 per 4oz.

Odd situation. Could this reduction require a little H2O, acid, or base..... to "Kick it Off".

Amalgamation?

"Wet" Isopropyl Alcohol?

[Edited on 29-12-2016 by zed]


My little run did use wet isopropanol and unactivated magnesium. I'll try the reaction again soon using dry isopropanol, fresh magnesium turnings, and maybe activate the magnesium with a little iodine like Tsjerk suggested.

I also planned on trying to make aniline from nitrobenzene using the Mg/MeOH method shown above. First I need to make nitrobenzene though. (Perhaps from the benzene made from p-DCB???)

AvBaeyer - 29-12-2016 at 20:24

A procedure for reducing halides to the corresponding hydrocarbon using Mg/i-PrOH can be found in Organic Syntheses, Coll. Vol. 5, p 998. The detailed example is for the reduction of monochlorobenzene to benzene. The process is relatively straightforward. No mention is made of utility for dichlorobenzene but CCl4 can be reduced to methane. Perhaps with some investigation someone can produce benzene from 1,4-dichlorobenzene. Have fun.

AvB

PHILOU Zrealone - 30-12-2016 at 05:48

Quote: Originally posted by Meltonium  
Quote: Originally posted by zed  
Now, this is a good idea Meltonium. Since Benzene is fairly hard to obtain nowadays, and I can Buy p-DCB, down at my local "Dollar Tree" fer $4 bucks a pound. Yeah, that's right. Portland's "Dollar Tree"....... Lloyds Center. Last I checked, They were selling p-DCB @ $1 per 4oz.

Odd situation. Could this reduction require a little H2O, acid, or base..... to "Kick it Off".

Amalgamation?

"Wet" Isopropyl Alcohol?

[Edited on 29-12-2016 by zed]


My little run did use wet isopropanol and unactivated magnesium. I'll try the reaction again soon using dry isopropanol, fresh magnesium turnings, and maybe activate the magnesium with a little iodine like Tsjerk suggested.

I also planned on trying to make aniline from nitrobenzene using the Mg/MeOH method shown above. First I need to make nitrobenzene though. (Perhaps from the benzene made from p-DCB???)

I wonder if the methanol is realy needed...
Mg/Water/(NH4)2SO4 (weak acid) may work just fine without the methanol...there just to help a little with the solvatation of the hydrophobic nitrocompound...

Just remember that many nitroaromatic reduction by metals involve water, metal and an acid...usually a stronger one ... but
here Mg is very reactive so to temper the reaction the use of a weaker acid might be necessary.

[Edited on 30-12-2016 by PHILOU Zrealone]

Mush - 30-12-2016 at 14:58

Sugden, J.K. Reduction of Oximes. Chem. Ind. (London),1969, 9, 260,
C.A. 71,12164v

Courtesy of someone else.I hope he/she doesn't mind if I share it with you guys.

Attachment: Sugden__J.K.__Chem._Ind.__1969__9__p_260.pdf (1016kB)
This file has been downloaded 640 times

Meltonium - 31-12-2016 at 11:34

I'm attempting the p-DCB -> Benzene reaction again this time using an excess of 91% isopropanol, 4g p-DCB, and 3.3g Mg powder/turnings.

I have been refluxing the mixture for about an hour now and nothing seems to be happening. Do I add the pinch of iodine to attempt and 'activate' the magnesium, or should I add some sort of acid to try to get the reaction going?

If this run doesn't work, then I'll try again using anhydrous i-PrOH or tert-butanol because the diagram says that may work as well (I had dried some for this run but then I spilled it and gave up)

Update:

The solution was refluxed for 3 hours and then one bead of iodine was dropped into the flask. A brown color appeared from the dissolution of the Iodine. After 2 hours, the brown color mostly disappeared and the magnesium had turned black.

[Edited on 1-1-2017 by Meltonium]

Meltonium - 2-1-2017 at 07:18

My most recent attempt, I think, was a failure. The mixture was filtered to remove the magnesium and the extra p-DCB that had crystalized and then washed with water. The water caused the rest of the p-DCB to crash out of the i-PrOH solution and make fluffy, white crystals.

If any benzene was present, it was minimal.

careysub - 2-1-2017 at 08:59

Quote: Originally posted by Meltonium  
My most recent attempt, I think, was a failure. The mixture was filtered to remove the magnesium and the extra p-DCB that had crystalized and then washed with water. The water caused the rest of the p-DCB to crash out of the i-PrOH solution and make fluffy, white crystals.

If any benzene was present, it was minimal.


Thanks for trying this, we need negative reports for sure.

No one here has posted or referenced the original paper cited in the survey paper for dehalogenation with magnesium-methanol, which is:
Reductions of Alkyl and Aryl Halides with Magnesium and Methanol;
Robert O. Hutchins , Suchismita , Robert E. Zipkin & Ira M. Taffer; Synthetic Communications, 1989, V. 19, p. 1519.

I have attached it below.

Upon reading the paper I see that it can dehalogenate aryl iodine and bromine, but it has no effect on aryl chlorine, which you have confirmed.

So no benzene from moth balls by this method.

Attachment: hutchins2001.pdf (55kB)
This file has been downloaded 628 times

zed - 20-1-2017 at 16:57

Ummm. Here is a link to the Organic Synthesis Procedure, cited previously.

It appears conditions are dry, additional reactants are required, and isopropyl alcohol or butyl alcohol, must be employed.

http://www.orgsyn.org/Content/pdfs/procedures/CV5P0998.pdf

Now, I read the experimental details, and the actual solvent employed is decalin. It is brought to a reflux at approximately 180 C., and your isopropyl alcohol and Chlorobenzene are added Slowly. In an inert atmosphere.

So..... If you are trying to get the same results by refluxing your reactants in excess isopropyl alcohol.....you are going to miss the recorded, successful, reaction conditions by a lot. Isopropyl boils at ~82 C.. About 100 C. below the experimental conditions actually employed in Org.Syn..

[Edited on 21-1-2017 by zed]

[Edited on 21-1-2017 by zed]