TIETSE
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Methylation agents
SOMEBODY NOW ABOUT METHYL CHLORIDE OR BROMIDE , IS A GOOD METHYLATION AGENT ? , BECAUSE METHYL IODIDE OR DIMETHYL SULFATE IS THE ONLY THING I FOUND IN
MY SEARCH .
Edit by Nicodem: Changed tittle to normal letters and moved to the Beginnings section due to lack of any reference given.
[Edited on 29/4/2009 by Nicodem]
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Saber
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WHY THE CAPITALS?!
Both will work, the only reason methyl iodide is preferred is its a liquid at rtp, therfore easy to manipulate, whereas methyl chloride is a gas.
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DJF90
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Looks like someones CAPS LOCK key is broken...
Methyl halides are all fairly good methylating agents, and MeCl < MeBr < MeI in terms of methylating ability. Whether you can use MeCl or MeBr
instead of MeI will depend on your substrate and the reaction conditions. As stated by the previous poster MeI is generally preferred due to its
"ease" of handling.
There are a whole load of other methylating agents out there, for example MeOTs, MeONO2, Me2SO4... You will notice they all have one thing in common;
the methyl group is bonded to a GOOD leaving group.
[Edited on 29-4-2009 by DJF90]
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panziandi
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DJF90 i think MeNO3 is questionable  certainly I had a poor experience of this.
Methyl phosphite and methyl phosphate are good for some substrates, UTFSE.
Certainly you could likely use MeCl or MeBr in a solvent. MeBr is fairly ok to manipulate using a ice-water bath to cool it below the bp.
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Saber
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There have been posts of using dimethyl oxalate as a safe methylating agent.
I am unsure as to how effective it is however.
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DJF90
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Yes the use of a solvent is a great idea. Methanol should be fine no? And I'm sure MeNO3 will find a specialised application someday. Although MeBr
can be manipulated fairly easily I dont have much confidence in the ability of the original poster seeing as he seems to have trouble working the caps
lock button...
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panziandi
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Dimethyl oxalate would be interesting. Certainly I see potential there... Dimethyl carbonate can methylate well, usually used in a pressure reactor at
a little above the bp of the ester.
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Saber
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I am going to try some methylations in the near future.
the bonus with dimethyl oxalate is it is easy to synthesise, not to mention cheap, and relativly non toxic.
In some cases where methyl chloride must be used it is usually dissolved in diethyl ether. However it is much more simple to buy methyl iodide from
Acros.
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panziandi
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Well the obvious bonus is that dimethyl oxalate is a solid and so easily manipulated as well.
Yes methyl chloride is also very expensive because it is supplied in lecture bottles. Methyl iodide is expensive also, dimethyl sulphate is quite
cheap but has the downside of evil toxicity. There are much "nicer" methylating agents.
If dimethyl oxalate works would be very good! Do you have literature references?
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Saber
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Here is a source which states diethyl oxalate is a good alkylating agent, I will have a look at my personal library for methylations with dimethyl
oxalate.
http://books.google.com/books?id=7gPnWf4UDLsC&pg=PA9&...
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Nicodem
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Thread Moved
29-4-2009 at 12:55 |
Nicodem
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The thread containing references for methylation of phenols and other nucleophiles with methyl oxalate is here.
To the extremely original MR. ALL CAPS poster: UTFSE! Besides, methylation of what?
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