Anodic oxidative fluorination of 2,6-di-tert-butylphenols

In the presence of Et3N–5HF electrolyte, anodic fluorination of 2,6-di-tert-butylphenols with or without a substituent X (halogen) at its para-position (1a–c) successfully afforded 4,4-difluoro-2,6-di-tert-butylcyclohexa-2,5-diene-1-one (2), which was readily converted to 4-fluoro-2,6-di-tert-butylphenol (3) in good yields by the subsequent reduction with Zn in acidic aqueous solutions. We revealed some novel information on the electrochemical oxidative fluorination mechanism of 1a–c, which is well supported by the product distribution curve and the cyclic voltammogram of the possible oxidative products, as well as that of 1a in Et3N–5HF.