AMT in the MW oven

[hest]

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

[hest]

now also done in 10g scale. 5min MW @ 150W. Product filtered off from the cold nitroethanesolution an rextalised from methanol (still drying)

[Rhodium]

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)?

[hest]

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

[Rhodium]

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...  

[yellium]

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.

[hest]

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)

[hest]

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)

[kurupira]

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?

[hest]

Yes it is. Silly mee (lol)

[Teon]

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.

[Rhodium]

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.

[Organikum]

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.

regards
ORG

[indium]

> 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.

[kjb1891]

Does anyone know of any possible substitution for nitroethane(typo in the original post by hest) in this synth? Regardless of yeild differences.

[indole_amine]

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!    - Can't any friendly bee perhaps check if his/her library has this journal? It would match soo good here... )


_{indole_amine}

[moo]

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.

[hest]

Usual direkt metylation of prim to tert amiens is a bad ider, so I would'nt hope for too much. Stic to reductive ammination.

[indole_amine]

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

(http://www.organic-chemistry.org/namedreactions/aldol-addition.shtm)

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)...(?)


_{indole_amine}

[indole_amine]

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

https://www.thevespiary.org/rhodium/Rhodium/pdf/forensic/amphetamine.phenylnitropropene.pdf

)


"1-phenyl-2-nitropropene
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...





_{indole_amine}

[indole_amine]

This one isn't new at all; it is the reference from entry 5 in

this document

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/it-290.html).

Interesting about it is the fact that they reduce the indolylnitroalkane to the amino derivative with the same reducing system they use for forming the pyrrole ring: nickel boride/hydrazine hydrate. Seems like a versatile reagent couple for the topic tryptamine chemistry in general, dare I say!

As starlight recently encountered problems while trying to reduce a similar indolyl-nitroalkane with Pd/C, this seemed like a good alternative to me: condense aldehyde and nitroethane, "saturate" the C=C bond using aequous NaBH₄, and then reduce the nitro group with Ni₂B/N2H4*H2O! Sounds like easy going, don't you think?

(the talked-about thread - another knoevenagel/henry approach to alpha-alkylated tryptamines:

Post 511247

(starlight: "The preparation of AET", Tryptamine Chemistry))


Nickel boride/hydrazine hydrate reduction of aromatic and aliphatic nitro compounds. Synthesis of 4-(benzyloxy)indole and .alpha.-alkyltryptamines
(David H. Lloyd, David E. Nichols)
J. Org. Chem. 1986; 51(22); 4294-4295

"(...)In a further investigation of the general utility of these reagents, we have discovered that similar reaction conditions also effect the reduction of aliphatic nitro compounds. Several substituted 1-(indol-3-yl)-2-nitroalkanes 4a-4c were reduced to the corresponding alpha-alkyltryptamines 5a-5c as illustrative examples. Indolylnitroalkanes were prepared by the condensation of substituted indoles 3a-3c with the appropriate nitroolefin, an extension of the method of Ranganathan(6). It appears that a variety of substituted alpha-alkyltryptamines may be readily prepared by this two-step method."
(they also describe the experimental details of the condensation reaction between indole and 2-nitropropene   )



and here's one of the references their article is based upon (referred to as "the method of Ranganathan"   ):

Nitroethylene: a stable, clean, and reactive agent for organic synthesis
(Darshan Ranganathan, C. Bhushan Rao, Subramania Ranganathan, Ashok K. Mehrotra, Radha Iyengar)

J. Org. Chem. 1980; 45(7); 1185-1189

(https://www.thevespiary.org/rhodium/Rhodium/pdf/nitroethene.in.organic.synthesis.pdf)



_{indole_amine}

[indole_amine]

"55ml of the methylamine acetate in IPA solution made above was put in a 250ml erlenmeyer flask with 14.4g (100mmol) Indole-3-carboxaldehyde and 9.9ml (110mmol) 1-Nitropropane. A condenser was attached to the flask and the stirred mixture was heated on a waterbath at 55-56C for 7 hours."
(

Post 514779

(starlight: "Satisfactory condensation method", Tryptamine Chemistry)


Now that looks like the imine pathway IMO. At least it would explain why he used an amine acetate rather than free amine/ammonia as catalyst (acid moiety needed). Other reasons?


_{indole_amine}

[starlight]

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)...(?)

The problem with trying to form dimethyl tryptamines through alkylation of tryptamine is the formation of quaternary salts (over-alkylation). If you use less alkylating reagent, I believe you just end up with a mixture of quaternary salt, starting substrate and maybe tiny amounts of mono-methylated or dimethylated product. The more the amine become alkylated, the more it is receptive to further alkylation (until it is the quaternary salt of course).

Here is a post with some links to further information:

Post 208020

(Lilienthal: "You can't dimethylate tryptamines with MeI or DMS", Tryptamine Chemistry)

Other alkylations with larger alkyl groups have been made to work though.

[indole_amine]

According to the same thread you referenced to, quaternary tryptammonium salts gotten from MeI alkylation can be reconverted to N,N-dimethyltryptamines with ethanolamine.

So: condense indolylaldehyde and nitromethane, reduce the nitrostyrene double bond with aequ. NaBH₄, then aminate via nickel borate/hydrazine, triacetoxyborohydride,cyanoborohydride or other selective reducing agent to get tryptamine (or do both at once with LiAlH₄), hope for not having touched the indole nitrogen   , and do whatever you like with it (there are many alkylhalides - and what about alpha-ethyl-(N,N-dimethyl)tryptamine btw? Think I gonna consult TiHKAL...) Nice if it would work.
(or, if you want N,N-DMT: simply alkylate with HCHO/NaBH₃CN - that is, unless Lilienthal is right with his cyclization theory about tetrahydro-betacarbolines...)

_{indole_amine}

[kjb1891]

Do you think that using 1-nitropropane instead of nitroethane in hest's MW method above would yield AET?

[Lilienthal]

Sure, it will.

[kjb1891]

How good do think the yeilds would be for AET compared to how good the yeilds were for AMT in the MW method?

[Rhodium]

Important:

The microwave procedure above does not produce AMT directly, but rather the nitroalkene precursor (3-Indolyl-2-nitropropene) which can be reduced to AMT using LiAlH₄ or any other known method.

[indole_amine]

And with 1-nitropropane, the intermediate/precursor substance is called 1-(indol-3-yl)-2-nitrobut-2-ene.

But the yield with 1-nitropropane will not be even half as high as when nitroethane is used in above condensation. Reason: 1-nitropropane is too long of a molecule, it can result in two different condensation products, and only one of these is the wanted one...

Oh, and there is a thread by Starlight out there, dealing with exactly this type of compound and exactly this type of reaction, too - I quoted the procedure whole seven posts earlier (

Post 533225

(indole_amine: "hmm", Tryptamine Chemistry)...

_{indole_amine}

[indole_amine]

[Maharajah]

I realize this may be a newbee question, but is Indole-3-carboxaldehyde a suitable substitution for Indole-3-aldehyde?  Thanks

[Barium]

It is the same thing, just different names.

[Maharajah]