[genyphur]

So in lab, I reacted tryptamine with glyoxylic acid to form 1,2,3,4-tetrahydro-beta-carboline, but I cannot seem to figure out the rational arrow-pushing mechanism for the reaction.  So far, I've figured that CO2 and H2O are formed.  I'm not asking for any straight answers, but can anyone give hints as to at least what sort of reaction is in question?

the steps i took were:
1) heating tryptamine w/ water and then glyoxylic acid monohydrate (i assume this protonates the primary amine to an NH3+...)
2) boiled the solid from step 1 with HCl
3) added water and KOH to product from part 2

thanks.

[Mitch]

Here is what I could fine: http://pubs.acs.org/cgi-bin/archive.cgi/jmcmar/1964/7/i02/pdf/jm00332a005.pdf

View it from a campus computer or use the library proxy service.

They claim its a simple acid-catalyzed condensation, but I'm not sure of the mechanism either.

[alphahydroxy]

ok, here'e a mech i've just made up - feel free to slate me but just remember it is monday morning....!

[laotree]

The mechanism, u can check www.ecompound.com, reaction reference, and Pictet-Spengler isoquinoine synthesis. The your mechanism is similar to isoquinoline synthesis, I guess.

[movies]

Yep, looks a lot like a Pictet-Spengler reaction to me.  Alphahydroxy, your decarboxylation step goes the wrong direction; you would have to lose H^- from the acid, which is bad.

The mechanism is on the wikipedia page.

[laotree]

Movie, you have sharp eyes! I did not pay attention to decarboxylation at all.

[movies]

Movie, you have sharp eyes! I did not pay attention to decarboxylation at all.

Heh, that comes from grading lots of exams!