Ruthenium-catalyzed meta-selective C-H sulfonation of azoarenes with arylsulfonyl chlorides

We have developed meta-selective C-Ar-H bond sulfonation of azoarenes with aryl sulfonyl chloride in the presence of the [Ru(p-cymene)Cl-2](2) catalyst. Further reduction of the desired product provided a meta-sulfonated aromatic amine. Preliminary mechanistic studies indicated that the meta-sulfonation of azoarenes might involve an electrophilic aromatic substitution (SEAr) directed by the C-Ar-Ru sigma-bond.