The palladium-mediated cross-coupling of aryl electrophiles and amines
(Buchwald-Hartwig amination) has become a widely used method of constructing
arylamine frameworks. A crucial aspect of the advancement of this chemistry has been
the design of ancillary ligands that are able to promote enhanced reactivity in challenging
amination reactions. Despite significant ligand development within the field, challenges
in this chemistry remain.
Chemoselective aminations, wherein one amine substrate undergoes preferential
arylation in the presence of multiple reactive amines has remained an underexplored area
of Buchwald-Hartwig amination chemistry. This thesis describes the use of
[Pd(cinnamyl)Cl]2 and N-[2-di(1-adamantylphosphino)phenyl]morpholine (Mor-
DalPhos) in an extensive study of chemoselective Buchwald-Hartwig aminations, with 62
examples of structurally diverse di-, tri-, and tetraamines obtained in synthetically useful
yields at reasonable catalyst loadings (1-5 mol % Pd). The coordination chemistry of
[(Mor-DalPhos)Pd] species was also explored, as were complementary chemoselective
aminations with the isomeric p-Mor-DalPhos ligand, leading to divergent product formation in some instances. The same [Pd(cinnamyl)Cl]2/Mor-DalPhos catalyst system
used in the chemoselectivity study was also employed in a series of Buchwald-Hartwig
aminations conducted under aqueous and solvent-free conditions, another underexplored
area of this chemistry. A total of 52 amine products were isolated using these
methodologies, moderate catalyst loadings (3 mol % Pd), and without the use of any additional additives, co-solvents, or rigorous exclusion of air.
The synthesis of low-coordinate palladium complexes featuring both NHC and
dialkylchlorophosphine ligands is also discussed herein. These complexes are prepared via a previously unreported and straightforward methodology involving an unusual net PCl bond reductive elimination, and represent a potential new class of pre-catalysts forpalladium-mediated reactions.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/14784 |
| Date | 23 April 2012 |
| Creators | Tardiff, Bennett Joseph |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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