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 tribromobenzenesulfonyl 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.