Inhibition of (dppf)nickel-catalysed Suzuki–Miyaura cross-coupling reactions by α-halo-N-heterocycles
Alasdair K. Cooper, Megan Greaves, William Donohoe, Paul M. Burton, Thomas O. Ronson, Alan R. Kennedy, David J. Nelson
Abstract
A nickel/dppf catalyst system was found to successfully achieve the Suzuki-Miyaura cross-coupling reactions of 3- and 4-chloropyridine and of 6-chloroquinoline but not of 2-chloropyridine or of other α-halo-N-heterocycles. Further investigations revealed that chloropyridines undergo rapid oxidative addition to [Ni(COD)(dppf)] but that α-halo-N-heterocycles lead to the formation of stable dimeric nickel species that are catalytically inactive in Suzuki-Miyaura cross-coupling reactions. However, the corresponding Kumada-Tamao-Corriu reactions all proceed readily, which is attributed to more rapid transmetalation of Grignard reagents.