Oxidation of aromatic substrates. Part 4. Action of ruthenium tetraoxide on some substituted biphenyls

Abstract

Selective cleavage of biphenyls by ruthenium tetraoxide is possible, attack being directed towards the ring carrying an activating substituent; protection is afforded by electron-attracting groups. Aminobiphenyls differ from aliphatic amines (see preceding paper) in that they undergo oxidation in acidic solution, reaction being initiated by the low concentration of free base in the equilibrium mixture. However, formation of the N-trifluoroacetyl derivative prevents participation by the N atom and this group is therefore effective in protecting aromatic amines.