CherrieBaby (Newbee / Eraser)
09-19-01 21:13
No 215209
      Aryl Decarboxylation ??  Bookmark   

Jerry March refers to the decarboxylation of aromatic carboxylic acid with copper and quinoline.

The target reaction is Niacin ==> pyridine.

Has anyone ever done an aromatic decarboxylation?

In the above case - am I right in thinking that quinoline can be avoided? After all the only functional group is pyridyl - which Nicotinic acid (niacin) has.

Yeh - I know what you'll all say - try it and come back here to report.

PS: psychokitty

Can you get that recent article on ether hydrolysis of aryl ethers via pyridine.HCl and microwaves - post it to me please? [] - or give it to Rhodium and ask him to host it - yes I know the URL but asking $10 per article is just cheeky.
(Hive Bee)
09-19-01 21:18
No 215210
      Re: Aryl Decarboxylation ??  Bookmark   

Well, I think it is possible with this route:

Ar-COOH =(+SOCl2 and +NH3)=> Ar-CONH2 =(Hofmann)=> Ar-NH2 =(+NaNO2 + H3PO2)=> Ar-H

but I dunno if it is possible a direct decarboxylation... perhaps with an electrochemical way (Kolbe)

(Hive Bee)
09-19-01 23:20
No 215261
      Re: Aryl Decarboxylation ??  Bookmark   

Yes electrochemical.

Benzoic acid(aq) in an electrolytic cell, with furious H2 bubbling at the anode would work.

C6H5COO- - e- __> C6H5COO. __> C6H5. + CO2

Normally, two radicals would couple together, forming a dimer. This is infant chemistry here. If you bombard the radicals with hydrogen, they have a great chance of coupling with the radicals. You will get a mix of the dimer and the desired product. The more H2 bubbled, the better.

Of COURSE we don't know what we're doing! That's why it's called research! Member: C_F Fan Club
(Hive Bee)
09-19-01 23:26
No 215263
      Re: Aryl Decarboxylation ??  Bookmark   

I don't think this will work good. For me it's better get a Pd sponge, causing the formation of H radical (but it's too expensive) or product H2 in situ via electrochemical rxn or with Zn+HCl (even if it's strange.. In an electrochemical cell? bah...)

09-20-01 06:15
No 215384
      Re: Aryl Decarboxylation ??  Bookmark   

hey would you have any refs/procedures/yeilds/picturebooks or said rxn? I am looking into the possibilities of tryptophan decarboxylation.
(Old P2P Cook)
09-20-01 09:46
No 215461
      Re: Aryl Decarboxylation ??  Bookmark   

Rhodium very recently posted a good tryptophan decarboxylation using ionic copper.
06-20-02 21:18
No 323424
      No Kolbe Electro with Aryl  Bookmark   

According to Jerry March, Advanced Organic Chemistry 4th edition, p729-780. The Kolbe electrosynth does not work when the group next to the carboxyllic is aromatic. Which does not mean there is not electrolytic decarboxyllation - only that it will not be a Kolbe mechanism.