- N-Heterocyclic Olefin-Ligated Palladium(II) Complexes as Pre-Catalysts for Buchwald-Hartwig Aminations.
N-Heterocyclic Olefin-Ligated Palladium(II) Complexes as Pre-Catalysts for Buchwald-Hartwig Aminations.
Chemistry (Weinheim an der Bergstrasse, Germany) (2019-05-16)
Ian C Watson, André Schumann, Haoyang Yu, Emma C Davy, Robert McDonald, Michael J Ferguson, Christian Hering-Junghans, Eric Rivard
PMID31087575
ABSTRACT
New N-heterocyclic olefins (NHOs) are described with functionalization on the ligand heterocyclic backbone and terminal alkylidene positions. Various PdII -NHO complexes have been formed and their use as pre-catalysts in Buchwald-Hartwig aminations was explored. The most active system for catalytic C-N bond formation between hindered arylamine and arylhalide substrates was accessed by combining a backbone methylated NHO with [Pd(cinnamyl)Cl]2 in the presence of NaOtBu as a base. In these active systems evidence suggests that catalysis is mediated by colloidal palladium metal, highlighting a different coordination ability of NHOs in comparison with commonly used N-heterocyclic carbene co-ligands.