A phosphine ligand, such as PPh3 or 2-(dicyclohexylphosphino)biphenyl, is essential for the Pd/C-catalyzed Suzuki-Miyaura coupling of halopyridines and haloquinolines, although it has been reported that the reaction of phenyl chlorides can be catalyzed by nonprereduced Pd/C without any additives. In the reactions of bromopyridines, bromoquinolines, 2-chloropyridines, and 2-chloroquinolines, PPh3 was effective enough to provide coupling products in good yields. However, in the reactions of 3-chloropyridine, 4-chloropyridine, and 6-chloroquinoline, sterically hindered 2-(dicyclohexylphosphino)biphenyl was indispensable as a ligand.

A new continuous-flow system for C À H borylation has been developed. An insoluble catalyst prepared from chloro(1,5-cyclooctadien)iridi-A C H T U N G T R E N N U N G um(I) dimer and 2,2'-bipyridine-4,4'-dicarboxylic acid in the presence of bis(pinacolato)diboron exhibited high reactivity under continuous-flow processing without the loss of expensive iridium metal.

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