Lewis Acid Catalysed Selective Halogenation of Aromatics Using NXS(X=Cl, Br, I)

07 February 2006

Zirconium tetrachloride and other Lewis acids, such as FeCl_³, AlCl_³, promote the halogenation of aromatics with N-halo succinimides (Y Zhang et al, SynLett, 2005, 18, 2837-2892). The examples chosen are often electron-rich aromatics, where direct halogenation may give mixtures.

Toluene only gives benzyl bromide, or if two equivalents of NBS are used benzal dibromide.

Fluorination occurs with N-fluoro benzene sulphonamide (NFSI).