3-fluorotoluene to substituted phenylacetic acids

[Lestat]

I UTFSE, and found no mention of either 2- or 3- fluorotoluenes, found this abstract detailing preperation of substituted phenylacetic acids starting from the fluorotoluene using organometallic reagents.


Fluorine- and Trifluoromethyl-Substituted Toluenes: Site Selective Metalation of Aromatic or Benzylic Positions
 
Sadahito Takagishi*, Manfred Schlosser
*Institut de Chimie organique de l'Université, Rue de la Barre 2, CH-1005 Lausanne, Switzerland
 

If employed in tetrahydrofuran and at -75 °C, the superbasic mixture of butyllithium and potassium tert-butoxide metalates 2-, 3- and 4-fluorotoluene exclusively at an aromatic position adjacent to the halogen, as demonstrated by quenching with carbon dioxide to give the corresponding benzoic acids. In contrast, a mixture of lithium diisopropylamide and potassium tert-butoxide selectively deprotonates the benzylic positions of 2- and 3-fluorotoluene to give after quenching with carbon dioxide the corresponding phenylacetic acids. With 3-(trifluoromethyl)-toluene, metal/hydrogen exchange again occurs at the methyl group while the corresponding 2- and 4-isomers do not produce interceptable organometallic intermediates.


DOI:

10.1055/s-1991-20650