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!