An efficient and facile protocol for palladacycle-catalyzed chlorination of 2-arylbenzoxazoles was developed. The results represent the first examples involving the palladacycle as the catalyst for such chlorination. This chlori- nation was not a ligand-directed ortho-C--H activation, but an electrophilic substitution process at the para-position of the nitrogen atom in the benzo ring of benzoxazole moiety, the regiochemistry of which had been confirmed by HMBC spectral analysis. The catalytic system could tolerate various halogen atoms, such as F, Cl and Br, affording the corresponding products in moderate to excellent yields.
Cyclopalladated ferrocenylimines as a novel kind of highly efficient palladium catalyst precursors, which are air-stable and easy to handle, have been successfully applied in a wide variety of catalytic reactions ranging from classical reactions, such as Heck, Suzuki, Sonogashira and Buchwald-Hartwig couplings, to cyanation, addition reactions of arylboronic acids, and coupling reactions involving terminal alkynes. The preliminary achievements regarding their applications to homogeneous catalysis are concisely described herein.
WU YangJie YANG Fan ZHANG JinLi CUI XiuLing GONG JunFang SONG MaoPing LI TieSheng
