[Tessa9713]

Hi,

I am trying to figure out the mechanism of synthesis for N-acetylanthranilic acid from Anthranilic acid + Acetic anhydride(heat) > Benisoxazinone + H2o >N-acetylanthranilic acid. If I can just get the first step. I have assigned the electrophile, nucleophile, acid and base sites on the 2 molocules of anthranilic acid and acetic anhydride. I just have no idea how to proceed. Do I protonate one of the carbonyl groups on the anhydride from the proton on the carboxylic acid of the anthranilic acid? However this gives me an unstable carbocation on the anhydride which probably would not happen, at least not in 2 steps. 

Can I break up the Acetic anhydride before I react it with the anthranilic acid.

I just need somewhere to lauch this from. Any help would be appreciated.

Thanks!

[lutesium]

Wellcome to the forum

I also have a question!!! While making Antharanillic acid from o-Toluidine why do we firstly acetylate it and then oxidize it??? Can the amino group be affected by the harsh KMnO4 oxidation so that acetylating it has a "protective role" on it???


Lutesium...

[Kryolith]

Can the amino group be affected by the harsh KMnO4 oxidation so that acetylating it has a "protective role" on it???

Yes. Amines can be oxidized to nitro compounds using permanganate.

EDIT (to answer the original post)
The amino group is being acetylated. In the first step the amino group attacks the (protonated) carbonyl carbon of Ac₂O.

[Tessa9713]

I apoligize but the carbonyl carbon becomes protonated before the lone pairs on the amine group bond with it?

Where does this proton come from?

I don't think I completly follow.

Thanks again,

[macman104]

Isn't this reaction in an acid?

[oh_muffin_9]

I, too, am trying to figure out this mechanism. I have thought of some interesting ways that this might work, but they do not really seem probable. For instance, is the NH₂ group (on anthranilic acid) a strong enough base to pull the hydrogen atom away from the single bonded oxygen atom of the carboxylic acid group (also on anthranilic acid), so that the oxygen atom is free to act as a nucleophile for acetic anhydride? I know this is probably just a shot in the dark. Also, after that occurs (if it does), I have no idea in which direction to proceed.

The amino group is being acetylated. In the first step the amino group attacks the (protonated) carbonyl carbon of Ac₂O.

If, in fact, the mechanism I have proposed is far-fetched, then I come to the mechanism that has been proposed here. I do not understand how and from where the carbonyl carbon of Ac₂O is being protonated.

I am really stuck on this one, so any help would be appreciated. Thanks!