Synlett 1991; 1991(2): 119-121
DOI: 10.1055/s-1991-20650
letter
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

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
Further Information

Publication History

Publication Date:
07 March 2002 (online)

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.