[CPC]

Hallo friends,
I am going to do some bromination of some compounds which are the derivatives of acetoacetates (please have a look at the scheme attached which is reported by literatures). I would like to understand the mechanism of the reaction and I raise a discussion here.
In the suggested scheme, I guess that the proton of the methyl group next to the carbonyl function is quite acidic and is easily removed forming an anion which will combind with polarized bromine molecule to furnish the brominated derivative.
I am still wondering the role of the p-toluensulfonic acid. Probably it is to prevent the multi-bromination so that we can get the wanted mono-brominated product (In basic media, the methyl group might be further deprotonated leading to multi brominated compounds).
Can any one give me a sound discussion on the mechanism of the reaction. Should we definitely use p-toluensulfonic acid or can we use anything else?
Thank you for your consideration.
CPC

[macman104]

It is a non-nucleophilic strong acid, that will be a good acid, but you don't have to worry about it acting as a nucleophile.

The acid is used to protonate the carbonyl and help form a better enol.  Then the carbon can attack the bromine better.

EDIT:  Enol, not enolate

[CPC]

Hallo Macman104,
I see your idea. Thank you for your suggestion.
By the way, how do you explain the polarization of the Br-Br bond so that you will have an electrophilic center to wait for the C attack?
Best regards,
CPC

[macman104]

I would view it less that the bond is so polarized, but that you create a fairly stable anion (Br^- is the conjugate base of a very strong acid) that is can exist when the Br-Br bond is attacked.

[azmanam]

form a better enolate

under acidic catalysis, I think you mean enol.