[princess88]

Hi! Firstly, my English is not very well. So, i’m so sorry for my errors:(

I’m a graduate student at organic chemistry and my thesis project is about hydroxy acids. But firstly, i have to get some initial products. Now, i’m trying bromination of C14 acid to get 2 (alpha) bromo-C14 acid. If i get alpha bromo C14 acid, i’ll make hydroxylation to get 2-hydroxy C14 acid. But i haven’t gotten my 2-bromo product yet. I’m using red phosporus, C14 acid and bromine. For my mechanism i’m using water bath which is at 80°C and continue to hyrolysis for 10 hours. After that i’m adding absolute methanol. But it wasn’t very succesfull. I’m really stressed for it and need some help… i’m investigating which another methods are possible for it, i need some prescriptions about the alpha bromination of carboxylic acids or acid chlorides.

I also examined the web site orgsyn.org which you have recommended but i didn’t find any information about this.

If you help me about this matter, I’ll be so glad..

[fledarmus]

Scifinder gives one set of conditions using PCl₃ and Br₂ which indicates a 100% yield...

Mesoionic 5-alkyl-1,3-dithiolium-4-thiolates: Synthesis and brine shrimp toxicity; Afonso de Almeida, Paulo et al From Heterocyclic Communications, 8(6), 593-600; 2002

They show another synthesis from the ester, but don't indicate reagents.

I suspect searching for a generic alpha-bromination of carboxylates on relatively long-chain alkyls would give a lot more examples.

[discodermolide]

Hi! Firstly, my English is not very well. So, i’m so sorry for my errors:(

I’m a graduate student at organic chemistry and my thesis project is about hydroxy acids. But firstly, i have to get some initial products. Now, i’m trying bromination of C14 acid to get 2 (alpha) bromo-C14 acid. If i get alpha bromo C14 acid, i’ll make hydroxylation to get 2-hydroxy C14 acid. But i haven’t gotten my 2-bromo product yet. I’m using red phosporus, C14 acid and bromine. For my mechanism i’m using water bath which is at 80°C and continue to hyrolysis for 10 hours. After that i’m adding absolute methanol. But it wasn’t very succesfull. I’m really stressed for it and need some help… i’m investigating which another methods are possible for it, i need some prescriptions about the alpha bromination of carboxylic acids or acid chlorides.

I also examined the web site orgsyn.org which you have recommended but i didn’t find any information about this.

If you help me about this matter, I’ll be so glad..

Why don't you make the di-anion and treat it with Mooph to get the alpha OH directly?

[Honclbrif]

I was thinking a Rubottom Oxidation from the methyl ester. However, if you use molybdenum peroxide, you get to say "MOOPH!"

[Doc Oc]

Scifinder gives one set of conditions using PCl₃ and Br₂ which indicates a 100% yield...

I suspect that yield is very inflated, but this is the classical Hell-Vollhardt-Zellinski method to synthesize amino acids.

I've never done this reaction myself, but I imagine if you do get the bromination to go properly, you will need to be careful when doing the nucleophilic substitution to avoid E2 elimination.

[nox]

http://en.wikipedia.org/wiki/Hell-Volhard-Zelinsky_halogenation

I don't see why a Hell-Volhard-Zelinsky bromination wouldn't work.

Not exactly what you're looking for, but here's and OrgSyn prep: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0616

They actually isolated the acyl bromide and use it to make an ester, but I imagine if you just quench the reaction with water it would give you back your carboxylic acid.