Highly selective aromatic chlorination. Part 1. The 4-chlorination of anisole and phenol with N-chloroamines in acidic solution

Abstract

Anisole and phenol are rapidly and efficiently chlorinated by N-chlorodialkylamines and N-chloro-trialkylammonium salts in trifluoroacetic acid at room temperature. Product analyses reveal that these reactions have a very marked selectivity for monochlorination of the 4-position. The reactions can also be carried out in aqueous sulphuric acid and under these conditions the selectivity is found to decrease with decreasing acidity of the solvent. The nature of the chlorinating species is discussed and it is proposed that the selective agents in these systems are N-chloroammonium ions.