Author Topic: Birch simplification: further musings on magnesium -drone342  (Read 845 times)

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Birch simplification: further musings on magnesium -drone342
« on: April 19, 2000, 03:48:00 AM »
Author  Topic:   Birch simplification: further musings on magnesium 
drone 342
Member   posted 09-20-98 06:57 PM          
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Great boogely-moogely! This may just be something worth paying attention to!
I posted my ideas of using Mg2+ species as an alternative to alkali metals as bases for making enolates, but it just dawned on me how significant this change could be, and why (or why not) it might be useful elsewhere. By using magnesium isopropoxide as a base rather than sodium isopropoxide, you have a strong base that can be prepared at home that should do just as good a job. By this line of thinking, why not go further and use it for other reactions -- like the Birch reaction! The one downside is of course that Mg's stability is both an asset and an hindrance. While it won't blow up in your face, Mg can be difficult to get to start to react and so a catayst is required (HgI2, I2, etc.) Still, this means that the Birch-Bear reduction is within the grasp of far more clandestine chemists than ever before!

Moreover, there's still the issue of the new bromosafrole->MDMA route I described. If Mg(NHMe)2 can be made at home with a reasonable amount of ease, then this is an even more attractive method.

There seems to be so many more options now; reactions that were prohibitively expensive or dangerous are now more within reach for everybody.

comments?

-drone #342


drone 342
Member   posted 09-21-98 02:02 PM          
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Some additional thoughts. Once again, Beilstein proved to be the unabridged I hoped for. After failing to find extensive information on Mg amides, I looked in my Merck. To my dismay, it looks like Mg(NH2)2 is a rather unstable, somewhat hard-to-produce material. Still, I remain hopeful.
Additionally, since this is now my default general organomagnesium ranting area, I wanted to further discuss other Mg-based Sn2 reagents for MDMA production. As we all know, metalic amides are typically several orders of magnitude stronger as nucleophiles than their corresponding protonated counterparts. This means reactions go FAST. This means instant MDMA for anybody able to get their hands on alkali or alkali earth metal methylamides.

What my idea for today was the use of grignard reagents for this purpose. Magnesium halomethylamides are known, and they'd probobly work nicely in an Sn2 reaction.

Still, I've not given up on making Mg(NHMe)2. To date, as far as I can tell, nobody has tried using a little HgX2 in this process, and I think its time somebdy ought to. Any thoughts?

-drone #342


Optimus Prime
Member   posted 09-22-98 06:17 AM          
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Ok Drone I will take a stab in the dark... since my vocab still aint up to parr I might be a little vauge...
I am under the understanding that to make an organometal that there can be no acidic H's hangin around, sos getting to the point... could it be possible to methylate hydroxylamine, then form the Grignard reagent with Mg or your Hg.... Now for class today OP has the question of Methylation... this is addin a methyl group, correct, so in terms of electronegativity wouldnt the amine rather be attached to the methyl than the hydroxy group, thus making this reaction in my twisted understandin feasible...now I know this is stupid cause the product would be methylamine and I cannot see how one would go about forming the organometal other than bubblin the methylamine through Hg since the enemy is H+...sos point #1 hydroxylamine to methylamine prolly wont work or might be harder to get/do than P2P... point #2 the bubblin through the Hg... like I said I have little understanding and a small vocabulary sos when ya correct me on 1 and 2 I will know more sos there it is...
OP


Optimus Prime
Member   posted 09-22-98 06:34 AM          
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And also bad eyesite... OK I thought that you were wanting to make Hg(NHMe)2... sos disregard everything I typed above and I wont litter up the board anymore... BUT it is a bit clearer in that light seeing how to get setup at home to do the above reactions would be next to impossible if not deadly... sos "my fault"....
OP


drone 342
Member   posted 09-22-98 10:20 AM          
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The problem with that begins with the fact that you're trying to do a Sn2 reaction (or I think at least that's what you were trying to do), with a hydroxy as a leaving group. This is problematic for the following reasons:
1)A hydroxy is more electronegative than a methyl group.

Actually, I think there are more, but my brain isn't functioning right now. The other problem area I forsee is the choice of reagent. How would you get this reagent?

Anyways, something to keep on the back burner is the idea of aprotic solvents. Now you were worried about loose protons fucking everything up. And right you are. However, there's a much sinpler answer than resorting to playing with large quantities of liquid mercury.

Acidity is a relative term. When worrying about loose H+'s, the best way to look at it is by comparing dissociation constants, or pKa's of you reaction and potential solvents. Aprotic solvents like DMF, DMSO, MeCN, DMP, etc. are excellent when worrying about these sorts of things. Hell, even dry aliphatic hydrocarbons are a good place to start.

-drone #342


Optimus Prime
Member   posted 09-22-98 11:28 AM          
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Ahhh Drone...once again you have lit the candle in the dark...at least give me dues for not being afraid to show my ignorance... ok, the electronegativity I got and understand fully, I just offered the reagent up since it is available to OP... Is this a hot reagent to get since you asked about where one would get it..??? Shit nevermind... I wrote a long reply then at the end saw the error... sos OK... sorry, teach me more...
OP


drone 342
Member   posted 09-22-98 01:45 PM          
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I'm not sure which reagent you are refering to, but I'll explain why Hg(NHMe)2 amd Mg(NHMe)2 are a little hard to come by.
1)Hg(NhMe)2. Organomercury species are insideously toxic -- death from mere milligrams of HgMe2 takes months of absolute misery before the defunct chemist is relieved from their agony. One colleague of mine died after spilling a drop of mercuric acetate in solution on her skin -- it took three months, in which she lost here hair, mind, and other basics she was rather sentimental about. Moral of the story: Don't fuck with organomercury compounds unless you mean it.

As far as I know, this compound isn't known anyways.

1) Mg(NHMe)2. This one simply has never been made before. It would not be readily isolatable, so it would have to be generated in situ. Magnesium amide spontaneously catches fire when exposed to air. This is a considerable drawback to its use, but at least it would be cheap to make.

-drone #342