The effect of the reaction conditions on the course of the reactions of hindered phenols with N-F reagents

Abstract

2,4,6-Trialkyl substituted phenols were selectively transformed in high yield to para-quinols or para-quinol ethers by reaction with the N-fluoro-1,4-diazoniabicyclo[2.2.2]octane salt analogues Selectfluor™ F-TEDA-BF4 or Accufluor™ NFTh in acetonitrile in the presence of water or alcohols. At low temperature 2,4,6-tri-tert-butylphenol in pure acetonitrile gave 2-fluoro and 4-fluoro substituted cyclohexadienone products with both reagents, while at elevated temperature 2-fluoro-4,6-di-tert- butylphenol was quantitatively formed. The mechanism postulated the SET proccess, thus forming cation-radical intermediates, as the key step of the reaction was proposed.