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Topic: Tetrahydro-Beta-Carboline Synthesis - Reaction Mechanism  (Read 2808 times)

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Offline riina

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Tetrahydro-Beta-Carboline Synthesis - Reaction Mechanism
« on: September 11, 2013, 11:48:42 AM »
Hi,
So I came across this forum by finding this post on google :
http://www.chemicalforums.com/index.php?topic=4207.0

I am currently setting up doing the same reaction for my undergrad research project, and I'm just having a bit of a struggle working out part of the reaction mechanism.

So basically I will be making 2-acetyl-1,2,3,4-tetrahydro-beta-carboline, and I know the full process for this, but I can't work out how the decarboxylation of the carboxylic acid after the pictet-sprengler reaction works.
I have worked out the full reaction mechanism from tryptamine to 1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid, with the use of KOH and water, but my mind is just hitting a blank as to how the decarboxylation works. If I'm right, the HCl is used to stabilise the intermediate, but I can't work out the mechanism.

I really don't want an answer as such, more of a helpful explanation as to how I can work it out myself!

Many thanks!

Offline trinitrotoluene

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Re: Tetrahydro-Beta-Carboline Synthesis - Reaction Mechanism
« Reply #1 on: September 11, 2013, 09:11:59 PM »
Hi,
So I came across this forum by finding this post on google :
http://www.chemicalforums.com/index.php?topic=4207.0

I am currently setting up doing the same reaction for my undergrad research project, and I'm just having a bit of a struggle working out part of the reaction mechanism.

So basically I will be making 2-acetyl-1,2,3,4-tetrahydro-beta-carboline, and I know the full process for this, but I can't work out how the decarboxylation of the carboxylic acid after the pictet-sprengler reaction works.
I have worked out the full reaction mechanism from tryptamine to 1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid, with the use of KOH and water, but my mind is just hitting a blank as to how the decarboxylation works. If I'm right, the HCl is used to stabilise the intermediate, but I can't work out the mechanism.

I really don't want an answer as such, more of a helpful explanation as to how I can work it out myself!

Many thanks!

Check out the Wiki page on Pictet-Sprengler. Hopefully that will prod you in the right direction.

Offline riina

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Re: Tetrahydro-Beta-Carboline Synthesis - Reaction Mechanism
« Reply #2 on: September 12, 2013, 08:28:35 AM »
Hey,
thanks or the reply. I totally understand the pictet-springler reaction. I know how the ring closes, but I don't know how the next step of the reaction removes the -COOH which is a decarboxylation not the p-s reaction.
My problem is that I can't work out the movement of protons and where electrons are moved for that step.

Offline spirochete

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Re: Tetrahydro-Beta-Carboline Synthesis - Reaction Mechanism
« Reply #3 on: September 13, 2013, 01:15:53 AM »
Could you post a picture of the mechanism you understand so far, so we can see the step you're unsure about? It's much easier to read a series of structures than it is a big wall of text.

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