[GSR]

hi,

can anybody suggest the reaction mechanism involved in this cyclization reaction. (please see the attachment).

[FeLiXe]

hey, I thought of a mechanism, it's catalyzed by a strong acid

it starts out like an acid catalyzed aldole reaction (only that one component is a carboxylic group)

then you protonate your enole (you already have that strong acid). eliminate H₂O and your carbenium ion becomes an electrophile. Do an electrophilic substitution and you have the second bond.

wmf image: http://stud4.tuwien.ac.at/~e0425252/Ringschluss.wmf
Isis Draw sketch: http://stud4.tuwien.ac.at/~e0425252/Ringschluss.skc

does that sound good? what do you need this for?

[laotree]

I agree with FeLiXe to certain degree.

But I think the reaction condition should be SOCl2 or POCl3.

The first step is the Indole ring mechanism (similar to isoquinoline mechanism), the second step is a Freidel-Crafts 2-position indole acylation mechanism. This is my best guess.

The mechanism has to built on a reaction condition. I have seen a lot of mechanism that could not explain the reaction condition and procedure.

[dexangeles]

next time, we should ask the poster to privide proof that he worked on it before we give any suggestions
we are just doing their homework for them if we don't do so
and as I remember, that's against forum rules

[FeLiXe]

if I think it's fun, then I am not allowed to think of the mechanism? Is that what you are saying?

this is not really a standard high school homework kind of question

[Mitch]

We're not here to do their homework for them. Please, guide them to the answer but don't simply give it to them.

[Arsenic]

GSR learn how to fish :

Heterocyclic Chemistry
by J. A. Joule, K. Mills


one question FeLiXe,the nitrogen atom in the starting material can act as a nucleophile/base,
in your mech. protonation of the carboxylic acid and amide oxygen  has happened while the nitrogen atom has been left intact , is this valid?
The cabonyl oxygen has a great tendency of being protonated but comparing the Nucleophilicity/basicity of nitrogen in an amine  with that of oxygen in an amide or carboxylic acid it occurs to me that the amine nitrogen is the center which gets protonated , please correct me if my argument dose not stand.