The synthesis of di- and tri-arylamines through halogen displacement by base-activated arylamines: comparison with the Ullmann condensation

In dipolar aprotic solvents, nitranions derived from anilines of enhanced N-acidity displace fluorine from activated aromatic compounds at room temperature. Diarylamines thus produced are free from triarylamines, which are formed at higher temperatures when diarylamines, after N-deprotonation by potassium t-butoxide or by the heavier alkali metal carbonates, similarly displace activated fluorine. Certain diarylamines can also be prepared by chlorine displacement in the presence of alkali metal carbonates. It is confirmed that such carbonates play only an auxiliary role in the Ullmann (copperassisted) diarylamine synthesis conducted in dipolar aprotic solvents; they may indeed impede the reaction in some instances.