Bronstein - 15-1-2007 at 03:54
Hi,
I want to use acetyl chloride to acetylate an amine that also has a carboxylic acid group. Normally with acetyl chloride you use a base to take up the
liberated hydrochloric acid. But I'm afraid that using a base might make a salt out of the carboxylic acid group, and then form an anhydride with the
acetyl chloride.
Am I wrong, and you can just do the reaction using a base without anhydride formation? Or can you even just skip the base altogether?
(I guess I could use the acetyl chloride to make acetic anhydride and do it according to the litterature, but I want to avoid that trouble.)
[Edited on 15-1-2007 by Bronstein]
Sauron - 15-1-2007 at 03:58
If you do make Ac2O I'd suggest considering the use of DMAP as acetylating catalyst, prferably DMAP on a solid support for ease of cleanup.
Careful as DMAP is a super toxic Ca channel blcoker.
Furch - 15-1-2007 at 06:26
I would guess that primary amines are way better nucleophiles than -COOH, i.e. acetylation of the amine will dominate. Otherwise you might want to
consider making an ester of the acid using an alcohol and H+ (bad yield though) prior to acetylation of the amine, then hydrolyze the ester when
acetylation is done.
Anyway, it should be possible to add the base at the same rate you are adding the acetyl chloride, that way you won't have much deprotonation of the
carboxylic acid function.
Just a though 
- Furch