nightflight
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MV application to reductive amination
Hi,
I was wondering about a modification of the Leuckart reductive amination process, more over a modification, that should be like this:
The thinking behind is, that all ammoniumsalts will degrade under het to ammonium and their respective acid-salt, di-electric heating allows for a
rapid and nearly complete reductive amination, when conducted with a solid clay support.
If I were to use DMF or DMSO(<-maybe even better) and MeNH*Hcl, and heated it in DMSO with the corresponding carbonyl, given a catalytic amount of
formic acid, then hydrolize it with either acid or OH, could this result in the
coupling process with the corresponding amine in the carbonyl substitution reaction?
If one used DMF wouldn´t this yield in the N,N-disubstituted product, or would the primary amine substitution MeNH be quicker and prevalent, if so,
why? (hints to literature welcome!)
Does the clay used in mv-chemistry serves as a base, so if I´d do th isd rxn in an "open vessel" experiment, should I add some base?
regards, nightflight
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roamingnome
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i applaud your inquiry into microwaves and DMSO...
the articles kicking around here still add a reducing agent like cyanoborohydride to the clay....
but another one is using glycol and formate, and Pt/C in a microwave...
still another one forms the imine with neat reagents in a microwave...
still another reduces imine with aqueous basic zinc...
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nightflight
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The idea was to avoid the use of the catalyst, by the use of formic acid as the reducing agent under dry as possible conditions and heating with a
microwave.
Ups, the HCL of the MeNH2*hcl might form explosives with DMSO so pure MeNH2 or DMF should be used.
[Edited on 21-2-2007 by nightflight]
[Edited on 21-2-2007 by nightflight]
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chemrox
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From my reading so far, you just need a compatible source of protons. Formamide has been mentioned using MW for only a few minutes. Clay, ion
exchange resins and diatomaceous earth have all been used.
I was thinking of adapting a small MW oven by cutting a hole in the top for a reflux column (unjacketed). I don't know what they're called by I want
a flask that is like a flattened RB. Not just flat on the bottom but "squashed." I was wondering if polycarbonate would be better than glass for
this as well.
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not_important
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| Quote: | Originally posted by chemrox
...
I was thinking of adapting a small MW oven by cutting a hole in the top for a reflux column (unjacketed). I don't know what they're called by I want
a flask that is like a flattened RB. Not just flat on the bottom but "squashed." I was wondering if polycarbonate would be better than glass for
this as well. |
Remember that a "small hole" can let microwaves leak out, usually some sort of choke arrangement is made around the opening or the entire extension is
enclosed in conducting mesh.
As for polycarbonate, you might want to look at this first
http://www.polymersdirect.com/jkcm/included/PD-CR-06-Trirex1...
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Organikum
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There was a post about exactly this on the HIVE, microwave assisted Leuckart with almost quantitative yields, was called something like "Son of
Leukart returns" or such....
...no time to dig it up, sorry.
A "choke" arrangement at a opening of a microwave would be the worst one can do as this would easily resemble a "slit antenna" and then you are
heading for real trouble.
Any circular opening smaller then 6cm in diameter is ok as long you dont stare directly into it when the MW is running full power and even then
chances are miniscule that something bad happens to you.
If you want to be on the safe side then add a metal tube to it which is more then 12cm long - but take care! The connection of the metaltube to the MW
MUST be completely soldered tight or you again run into the problem of possibly creating an antenna.
So for the amateur a simple hole is the best bet.
Never apply common sense to microwaves! They are non-intuitive as it can get. Only real knowledge helps. Besides this they are great and the massive
steel compartment is one of the best and most secure reaction chambers imaginable. And cheap.
/ORG
[Edited on 22-2-2007 by Organikum]
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Misanthropy
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This MW here has of course the internal tuned cavity surrounded by some space & the external shell. Does breeching the cavity & the shell,
parallel to each other not cause this antenna effect? Doesn't interfere at all with the function of the electronics open to the space between?
I don't wish to create a $50 spark gap generator.  O3 however... other threads
for that I suppose.
[Edited on 2-22-2007 by Misanthropy]
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roamingnome
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you can just blow baby powder and see the beams allowing accsess to the vault...
oh wait this is not a movie...
but i had a truley metal soup bowl once and i could put it in a microwave with no problem... i would freak people out cuase they would say.. nooooo
dont put that in there... but for what ever reason it never arced
someone explained to me that its the geometry or the edges of the metal that make it arc... i guess charge can build up on edges....
but this bowl had a smooth geomtery and no arc...
also hook up a 8dollar microwave at a thift store... if you can...
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Misanthropy
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CD's arc nicely... Anyway, my hospital is forever throwing out LARGE units for what I'd say is due simply to blown fuses. Past experience says this is
as likely as not.
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roamingnome
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officaly off topic
a grip of treasure can be had by dumpster diving around remodeling businesses, instatutions, hospitals etc....
no joke, i grudgenly gave a ride to a friend across town becuase he had no car.... i said this is becmoing a habit man....
but at a red light i look over and my jaw drops... no it was not a miniskirt, it was a old small autoclave that a dentist was tossing....
i snaged that thing with out moral problems.... it powers up but a tube in the front has no valve. or threads and water comes out when i plug it
in....... i can only assume some lead safty plug blew...
[Edited on 22-2-2007 by roamingnome]
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nightflight
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| Quote: | Originally posted by chemrox
From my reading so far, you just need a compatible source of protons. Formamide has been mentioned using MW for only a few minutes. Clay, ion
exchange resins and diatomaceous earth have all been used.
I was thinking of adapting a small MW oven by cutting a hole in the top for a reflux column (unjacketed). I don't know what they're called by I want
a flask that is like a flattened RB. Not just flat on the bottom but "squashed." I was wondering if polycarbonate would be better than glass for
this as well. |
I was thinking about formic acid because formamid will degrade to the amine and formic acid, which is believed to catalyze the reaction.
The solvent of choice should be high boiling so while heating the desired rxn-temps can be achieved.
So with out a solid clay support, resp. clay/catalylst it should be an open vessel experiment, and I don´t see, why di-electric heating shoulnd´t
accelerate this reaction?
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