Author Topic: AMT in the MW oven  (Read 98026 times)

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  • Guest
AMT in the MW oven
« on: July 19, 2003, 01:25:00 PM »
500mg indole-3-aldehyde was mixed with 1g nitromethane and 50mg amm.acetate. The mixture was nuked with 150W for 2min, and then rextalised from methanol.
Yeald: >90%
TLC (40% EtOAc in Hep.) 0,41


  • Guest
« Reply #1 on: July 19, 2003, 02:37:00 PM »
now also done in 10g scale. 5min MW @ 150W. Product filtered off from the cold nitroethanesolution an rextalised from methanol (still drying)


  • Guest
Technical details
« Reply #2 on: July 19, 2003, 04:08:00 PM »
Doesn't the nitromethane boil off when being nuked for so long periods of time?

Did you use any mw energy absorber (like a beaker of water), or a mw-inert heatsink for the reaction flask (like alumina)?


  • Guest
« Reply #3 on: July 19, 2003, 04:44:00 PM »
I have made my own mw-oven. Drilled a 6cm hole at the top and mounted a 30cm long copper-pipe (soldered to the inner chamber). as long as the pipe's diam. is smaller than ½ the wave length and longer than 1 wave length nothing leaks out (the wave length of mw oven is 13,5cm). Into this pipe is a glass tube with a condenser over the oven.
No mw energy absorber


  • Guest
modified microwaves
« Reply #4 on: July 19, 2003, 05:12:00 PM »
Such modifications make the setup work great, I've heard. However, please do include such essential details the next time you are posting anything mw-related...  ::)


  • Guest
Also, indicate _where_ you've drilled the hole
« Reply #5 on: July 19, 2003, 05:29:00 PM »
Also, indicate _where_ you've drilled the hole (and give its size); plus sizes of the interior of the mw oven itself.

It's a bit similar to 'the nitrostyrene was reduced with LAH to yield the phenethylamine' vs a worked-out description on how to get the thing.


  • Guest
« Reply #6 on: July 19, 2003, 06:23:00 PM »
Sorry for the shortness guy’s, but im’ in the lab right now.
First, a modificated mw.oven is not so complicated to construct.
You need a 30cm long and 6cm wide metal pipe, a metal plate (I use a round one with a diam. off 10cm) with a 6cm hole, an mw oven and a ‘hole-drill’
First you solder the pipe to the metal plate (so it look’s like a cylinder glass), then you drill a hole in the inner shell of the oven, stick’s the pipe through the hole, and soldering the plate onto the oven. Then you drill a hole in the outer oven (or throw it away) and put the oven together. That’s it. You can now reflux in your mw oven. (look at my nice drawing, any funny comment’s wont bee accepted)


  • Guest
« Reply #7 on: July 19, 2003, 06:26:00 PM »
And by the way. The 10g reaction wasen't so violent. I'm sure I could have run it in a normal mw.oven. Just turn the power off when the mixture begin to boil. (use a bigg glass, you have to bee a bit fast)


  • Guest
Just to be sure
« Reply #8 on: July 25, 2003, 03:25:00 PM »

500mg indole-3-aldehyde was mixed with 1g nitromethane and 50mg amm.acetate...

...from the cold nitroethanesolution an rextalised from methanol ...

...Doesn't the nitromethane boil off when...

it's nitroethane, right? ;)


  • Guest
Yes it is. Silly mee (lol)
« Reply #9 on: July 26, 2003, 03:15:00 AM »
Yes it is. Silly mee (lol)


  • Guest
There is just something about modifying a...
« Reply #10 on: August 14, 2003, 12:24:00 AM »
There is just something about modifying a microwave that is just a little, well, unsettling. Just out of curiosity, how did you find the exact wavelength that your microwave operates on? They didn't randomly include that in the owners manual did they? When I think about it, every microwave I've ever owned has been 2nd hand; I've never seen an owner’s manual for one.


  • Guest
mw oven frequency
« Reply #11 on: August 14, 2003, 03:10:00 AM »
All microwave ovens operate at the approximately same frequency (~2.5 GHz, or ~12cm), as 1) they are only allowed to generate RF noise at a certain band as to not disrupt any radio traffic, and 2) Microwaves of that frequency are the most effective to heat food with.

There is tons of info on things like this on the net, try google.


  • Guest
microwave oven modifications
« Reply #12 on: February 06, 2004, 11:52:00 AM »

as long as the pipe's diam. is smaller than ½ the wave length and longer than 1 wave length nothing leaks out

The diameter must be smaller than 1/2x (one half) the wavelength - 6cm or less is correct so. If it would be 1x the wavelenfth it would make a nice waveguide.

The soldering of the tube to the inner metal cavity is essential. NEVER just stick the tube just in. This would make a nice "slit antenna" with some db win. Outch.

I was rereading this thread and without nitpicking I believe this being necessary to be added for safety.



  • Guest
> Microwaves of that frequency are the most
« Reply #13 on: February 07, 2004, 12:51:00 PM »
> Microwaves of that frequency are the most effective to heat food with

Naaah, not really. Microwave heating mostly works because of the absorbtion of mw energy by water molecules (ever wondered why you could never get dry rice warm in a mw oven?)

I've seen a graph of the absorbtion of microwave radiation of water as a function of wavelength, and that showed a broad peak with its maximum at about 18 GHz or so. So basically it doesn't matter that much which frequency you use. The only requirement is that you're able to dump lot of energy in it, and that it's pretty sturdy and cheap to build. And in that respect it makes some sense to sit on the left hand side of the absorbtion graph.


  • Guest
Possible Substitution
« Reply #14 on: September 23, 2004, 04:51:00 PM »
Does anyone know of any possible substitution for nitroethane(typo in the original post by hest) in this synth? Regardless of yeild differences.


  • Guest
theory behind the reaction
« Reply #15 on: September 23, 2004, 06:18:00 PM »
This kind of reaction is called Knoevenagel or Henry condensation, and takes place between ketones/aldehydes and deprotonated nitroalkanes, usually with the aid of a base acting as deprotonating catalyst.

The ammonium acetate acts on the nitroethane as deprotonating catalyst, which then condenses with the aldehyde under dehydration to give the following compound:

Now if you substitute nitroEthane with nitroMethane, you arrive at the following nitrostyrene compound:

When you reduce the C=C bond and the nitro group (LiAlH4, or NaBH4 and then hydrogen/Pd/C), you arrive at (alpha-alkylated) tryptamines, nitromethane giving tryptamine, nitroethane AMT, nitropropane will result in two different condensation products of which one will result in AET upon reduction, and so on.

Shulgin prepared almost all his several hundred phenethylamines/amphetamines/tryptamines in the same fashion, the only difference is the starting material: benzaldehydes for phenyl compounds, indole-aldehyde for tryptamines...

Interesting; why do so much bees get grey hair while trying to decarboxylate tryptophan when there is such an easy way to tryptamine? Is it the indole-3-aldehyde (which could be hard to get)?

(hest: if you use MeNO2 and reduce to tryptamine, you can synthesize virtually every N-alkylated tryptamine by reacting the appropriate alkylhalide with tryptamine in aequ. solvent in your microwave, according to this journal I requested recently in "wanted references"...
Aqueous N-alkylation of amines using alkyl halides: direct generation of tertiary amines under microwave irradiation
(Yuhong Ju and Rajender S. Varma; Green Chem., 2004, 6 (4), (219-221)) - unfortunately noone seems to have access to the "Green Chem." journal, but this one looks cute, don't you think? From indolealdehyde to DMT with three easy reaction steps (henry/reduction/alkylation), of which two are done in a (modified) domestic microwave - sounds good!  8)  - Can't any friendly bee perhaps check if his/her library has this journal? It would match soo good here... ::) )



  • Guest
That mechanism does not make sense.
« Reply #16 on: September 24, 2004, 12:22:00 AM »
That mechanism does not make sense. The deprotonated nitroethane should have a negative charge (ie. a minus) on the alpha carbon, otherwise it isn't deprotonated at all, but for sake of a further argument let's imagine it is. After that there is another problem. The carbanion does not attack the carbonyl oxygen, but it attacks the carbonyl carbon which is more elecropositive, that is where the arrow should point at. Now it looks like there is a C-O bond formed instead of a C-C bond. That is not the first time someone makes such a mistake, keep practising. ;)


  • Guest
« Reply #17 on: September 24, 2004, 01:06:00 AM »
Usual direkt metylation of prim to tert amiens is a bad ider, so I would'nt hope for too much. Stic to reductive ammination.


  • Guest
correct mechanism
« Reply #18 on: September 24, 2004, 09:54:00 AM »
Right, actually there are two different theories: one (the knoevenagel/henry one) saying that the nitro compound becomes deprotonated by a base, and the other (nitro aldol reaction pathway, a modification of the aldol addition rxn) telling that the carbonyl compound is attacked by a base or acid - and in this case (indole-3-aldehyde + nitroethane), the reaction proceeds via the henry/knoevenagel pathway.
According to this mechanism, the starting compound R(R')C-N+(O-)=O is deprotonated, resulting in an equilibrium between the intermediates R(R')C--N+(=O)-O- and C=N+(-O-)-O- (or something like this  :) ), of which only the latter reacts with the carbonyl which donates an electron to its oxygen beforehand; like R-CH-O+, further the result is initially an alcohol which becomes later dehydrated in the process...
(this dehydration doesn't occur with aldol additions btw!)

Actually it wasn't meant to be a mechanism but rather to show someone not familiar with this reaction how the reagents cling together. (the previous post has been edited and the wrong mechanism removed)

Now here's the (hopefully) correct reaction mechanism:

If you are interested in how the different mechanisms look like in detail, here are some "good reads" (don't understand me wrong; this is just my own rating  :) ) about the subject:

Aldol addition


The Henry reaction: recent examples
(Frederick A. Luzzio)
Tetrahedron 57 (2001), 915-945

Phosphonium Salt Catalyzed Henry Nitroaldol Reactions
(J. McNulty, J. Dyck, V. Larichev, A. Capretta, A.J. Robertson)
Letters in Organic Chemistry, 2004 (1), 137-139

Hest: Why should alkylation of primary amines to yield tertiary amines be a bad idea? I have seen it being done many times already (although not with tryptamine)...(?)



  • Guest
concurring mechanism
« Reply #19 on: September 25, 2004, 10:24:00 PM »
And now for complete confusion the mechanism according to which the carbonyl compound initially forms an imine(!) with butylamine, and then the nitroalkane carbanion (deprotonated by HOAc) condenses with the carbonyl carbon...
(taken from


A solution of benzaldehyde (7.1 mL, 70 mmol) and butylamine (26 mL, 260 mmol) in benzene was stirred at reflux for 6 h using a Dean-Stark trap to remove water. The reaction mixture was evaporated to dryness to yield the imine as a yellow oil. The oil was dissolved in glacial acetic acid (20 mL), and nitroethane (5.0 mL, 70 mmol) was added. This mixture was stirred at reflux for 1 h, then cooled to rrom temperature, poured over crushed ice (100 mL), and acidified to pH 1 (with concentrated HCl). The resulting dark green (??) precipitate was isolated by filtration, washed with water (50 mL) and recrystallized from 2-propanol to yield 1-phenyl-2-nitropropene as yellow needles (6.9 g, 61%)."

"The 1-phenyl-2-nitropropene intermediate (...) was synthesized from benzaldehyde in a two-step process, as shown in scheme 3. Initially benzaldehyde was treated with butylamine, and the resulting imine was heated at reflux with nitroethane and acetic acid to yield 1-phenyl-2-nitropropene. It is reported that 1-phenyl-2-nitropropene also may be prepared by simply mixing benzaldehyde, butylamine and nitroethane and allowing the mixture to stand at room temperature for several days. In the present study, it was found that mixtures containing equimolar amounts of benzaldehyde and nitroethane in the presence of a catalytic amount of butylamine resulted in the formation of 1-phenyl-2-nitropropene within 24h. Mixtures containing butylamine concentrations equal to or exceeding the concentration of benzaldehyde and nitroethane, however, did not yield the product. GC-MS analysis of these reactions revealed only the presence of the intermediate benzaldehyde butylimine. It is possible that higher concentrations of butylamine may either interfere with the attack of nitroethane on the intermediate imine or hinder the elimination reaction (of butylamine) following nitroethane attack (scheme 3)."

As you can see, there is no real consense about the exact mechanism, as is often the case with theoretical reaction pathways...