Pd-Catalysed Direct Arylation of Heteroaromatics Using (Poly)halobenzenesulfonyl Chlorides as Coupling Partners: One Step Access to (Poly)halo-Substituted Bi(hetero)aryls

The reactivity of (poly)halo-substituted benzenesulfonyl chlorides for Pd-catalysed desulfitative arylation was investigated. 2-, 3- and 4-bromobenzenesulfonyl chlorides react nicely to afford arylated heteroarenes in moderate to high yields without cleavage of the C–Br bonds, allowing further transformations. A minor influence upon reaction yeilds was found to be exerted by the bromo substituent on the benzene ring. Even 4-iodobenzenesulfonyl chloride, di- and tri-bromobenzenesulfonyl chlorides were successfully coupled with a range of heteroarenes without cleavage of the C–Br or C–I bonds and very regioselective arylations were observed in all cases. The reaction was also found to tolerate bromo substituents on the heteroarene.