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Author: Subject: Indole Synthesis
Evilblaze
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[*] posted on 31-1-2010 at 09:44


Quote: Originally posted by Waffles SS  
One funny question:
May we use kitchen microwave oven for microwave irradiation step?


Not a really good idea, the kichen microwave ovens are not designed for chemistry. It will heat it up too much and the small amount of the irradiated compound will cause some problem. Place a large cup a water next to the chemical and hope the best. If you are lucky, than the microwave oven will survive.

Read this:

http://www.cem.de/images/produkte/mikro_synthese/attsqqrb.pd...

and make a similar thing.
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Waffles SS
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[*] posted on 31-1-2010 at 11:49


There is microwave irradiation device for buy(for use in chemistry)?
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Rattata2
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[*] posted on 31-1-2010 at 12:33


IPN: Thanks for the paper :) Like I thought it pretty much says what I figured it would. The PCl5 is used to remove water from the reaction - which I'm not sure if very small amounts of water would necessarily hurt anything seeing as microwaves would likely boil it out anyways..but I'm sure that it would only increase yields.

I'm assuming from various simple experiments that a household microwave would probably suffice to do most reactions..however with something like this wherein you're using hydrazines (and coming out with potentially smelly chemicals :p), I think it would be wise not to use the same one you eat from. If you can't build a microwave specific to the purposes, at least spend the $50 on one for chemical use only. And refrain from heating your burritos in it during your lab breaks :p

And just wanted to note that this reaction would probably work just fine if done via conventional heating as well..only the decarboxylation step may have to be done separately.

I'm also thinking that if one wanted to keep that 2-carboxylic acid group for whatever reason, or wanted to maintain purity during the reaction (say when doing conventional heating, as to not obtain a mixture of indole and the 2-substituent) they could protect it with an ester. This could then de-esterified and decarboxylated at once. Prolly unnecessary for most ppl but some might find that useful.

[Edited on 31-1-2010 by Rattata2]
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Rattata2
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thumbup.gif posted on 9-2-2010 at 18:28


Another addition to this thread :) Not sure where I found this but it could be useful!
--
"Polikier (317) heated the dianilide of tartaric acid with zinc chloride to obtain indole; dianilinosuccinanilide was an intermediate."

edit: Just found this in Journal - Chemical Society, London, Volume 62, Part 1

polkier indole 1.jpg - 136kB

http://books.google.com/books?id=HsIwAAAAYAAJ&pg=PA66&am...

[Edited on 10-2-2010 by Rattata2]
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zed
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[*] posted on 26-7-2010 at 11:53


I'm going to go back and read all of the references in this thread. But I do have a number on hand.

I have inspected the system to synthesize IAA via glutamic acid. It doesn't produce a high yield, but it might work. And, it does something that many of us find very attractive.....Assuming you can obtain Phenylhydrazine, it uses common materials.

http://www.freepatentsonline.com/2701251.pdf

As for the Fischer synthesis itself, I have utilized it many times.

In the past, I have used it to produced 2-Methyl Indole, 2-Phenyl Indole, Tetrahydrocarbazole, and 2-Methyl-N.N-Diethyl-Tryptamine.

The method is slam-dunk simple, and it works.

The method being proposed for the microwave synthesis of indole from pyruvic acid is so similar to the method that I used to produce 2-methyl indole, that I would try to interchange the two. Without the use of a special microwave oven, which most of us don't have.

From memory, I did the following.....I combined Acetone with Phenylhydrazine, in a large beaker, with a modest amount of absolute alcohol, then I warmed the material on a hot-water bath for an hour or so. Next, I proceeded to raise the temperature enough to boil off the solvent. The alcohol leaves, taking H2O with it. The liquid phenylhydrazone is left behind.

Next, you melt some ZnCl2 in a big beaker, heat it until it become fluid. and with vigorous glass rod stirring, you gradually mix in the Phenylhydrazone.

That's it. You let it cool a bit, dissolve the Zn Chloride, and you have fairly impressive yield of 2-Methyl Indole.

I'll see if I can dig up the exact procedure.
-------------------------------------------------------------------

OK, I cruised the web a little. Reaction conditions....Cyclization with ZnCl at 180 C.............Decarboxylation of 2-carboxylic acid to produce indole............240C
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I'll see what else I can find.
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"Since the time of this early work a number of changes have been introduced into the method, with improvement in the yields. Thus it was found (91) that by the use of an inert solvent such as methylnaphthalene, and by keeping the
temperature below 15O0C, acetone phenylhydrazone gave a 75 per cent yield of 2-methylindole, propionaldehyde phenylhydrazone an 80 per cent yield of skatole, and the phenylhydrazone of pyruvic acid gave a 60 per cent yield of indole-2-carboxylic acid."
------------------------------------------------------------------------------
From Acetaldehyde Phenylhydrazone, sadly it appears the method requires running the phenylhydrazone through a tube-furnace type set-up. http://www.google.com/patents?id=SXM7AAAAEBAJ&printsec=a...

I very much like the one-pot microwave method yielding 88% Indole from phenylhydrazine and pyruvic acid. But, it has a few problems. PCl5 isn't easy to come by, and the synthesis produces less than 3mmoles of product. Fine for an experiment...But, can it be scaled up?

[Edited on 27-7-2010 by zed]

[Edited on 27-7-2010 by zed]
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Waffles SS
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[*] posted on 22-8-2013 at 22:11



Quote:



The Baeyer–Emmerling indole synthesis is a method for synthesizing indole from a (substituted) ortho-nitrocinnamic acid and iron powder in strongly basic solution. This reaction was discovered by Adolf von Baeyer and A. Emmerling in 1869
http://en.wikipedia.org/wiki/Baeyer-Emmerling_indole_synthes...


This is interesting method and i like to try it.

O-Nitro Benzaldehyde:
-Toluene nitrate and O isomer separate by cooling.
-O,Nitro benzyl chloride prepare by reaction of Sulfuryl chloride with ONT.
-O,Nitro Benzaldehyde prepare by reaction of Hexamine with O,Nitro benzyl chloride.

O-Nitro Cinnamic Acid(Method1):
Cinnamaldehyde can also be nitrated, e.g. in a solution of acetic anhydride in acetic acid, in high-yield to 2-nitrocinnamaldehyde.This compound is then oxidized to 2-nitrocinnamic acid
http://www.orgsyn.org/orgsyn/prep.asp?rxntypeid=181&prep...

O,Nitro Cinnamic acid(method2):
-O,Nitro Cinnamic acid prepare by Perkin reaction(Acetic Anhydrid + O,Nitro Benzaldehyde +KOAC)

Final step is "Baeyer–Emmerling indole synthesis" that i dont have detail of this reaction(i just know Iron and KOH is needed)

Indole:
Somebody has more information or instruction about this route?i didnt find any useful information.


[Edited on 23-8-2013 by Waffles SS]
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AndersHoveland
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[*] posted on 22-8-2013 at 23:17


Quote: Originally posted by Waffles SS  



How readily does the enamine to the imine step proceed?
Is it spontaneous, or does it require refluxing?
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