Sciencemadness Discussion Board

Defluorodation(?) of substituted fuorobenzenes to benzenes.

NitreRat - 7-5-2016 at 16:48

I recently managed to cheaply obtain a liter of fluorobenzene. I bought it with the intention of converting it into benzene, which is hard to obtain where I live. Unfortunately the Ph - F bond is one of the strongest in organic chemistry. You can't just substitute the fluoro group for a hydride ion. Even hydrogenation with Pd catalyst won't work.

The two methods I have been able to find that can reduce aromatic fluoro groups include:

1. The use of various transition-metal based ligands to form complexes with the aromatic rings, thus activating the ring and making the fluorine more susceptible to nucleophilic substitution.

2. A combination of CeCl3, LiAlH4 in THF can reduce the halogen substituant via a radical mechanism.

While both of these methods might be useful in a fine-chemical synthesis, I would be doing it on a 1L scale so the reagents involved are far beyond my budget for such a simple task.
Does anyone have any experience reducing aromatic fluoro groups? Can it be done on a larger scale with a simple metal reduction such as sodium, potassium or activated zinc powder?

Thanks,
NitreRat

CuReUS - 7-5-2016 at 21:43

Raney Ni in the presence of NaOH can remove F from benzene ring.

NitreRat - 8-5-2016 at 04:49

Quote: Originally posted by CuReUS  
Raney Ni in the presence of NaOH can remove F from benzene ring.


At room temp and atmospheric pressure?

Couldn't that also hydrogenate the ring as well, or is that only significant at higher temperatures and/or pressures?

CuReUS - 8-5-2016 at 07:51

Quote: Originally posted by NitreRat  

At room temp and atmospheric pressure?

yes,see this
http://oeh.tandfonline.com/doi/abs/10.1080/15298669191364686
and this
http://link.springer.com/article/10.1007/s00706-010-0362-9#p...
Quote:
Couldn't that also hydrogenate the ring as well, or is that only significant at higher temperatures and/or pressures?

the ring would get hydrogenated at 100'C under pressure

[Edited on 9-5-2016 by CuReUS]