|
Titre:
|
Studies on the Mechanism of Direct Arylation of Pyridine N oxides: Evidence for the Essential Involvement of Acetate from the Pd(OAc)2 Pre-Catalyst at the C-H Bond Cleaving Step |
|
Auteur:
|
Sun, Ho-Yan |
|
Résumé:
|
Detailed mechanistic studies on the palladium-catalyzed direct arylation of pyridine N-oxides are presented. The order of each reaction component is determined to provide a general mechanistic picture. The C-H bond cleaving step is examined in further detail through computational studies, and the calculated results are in support of an inner-sphere concerted metallation-deprotonation (CMD) pathway. Competition experiments were conducted using N-oxides of varying electronic characters, and results revealed an enhancement of rate when using a more electron-deficient species which is in support of a CMD transition state. The effect of base on reaction rate was also examined and it was found that a carboxylate base was required for the reaction to proceed. This led to the conclusion that Pd(OAc)2 plays a pivotal role in the reaction mechanism as more than merely a pre-catalyst, but as a source of acetate base required for the C-H bond cleavage step. |
|
Date:
|
2011 |
|
URI:
|
http://hdl.handle.net/10393/19760
|
|
Superviseur:
|
Fagnou, Keith
Barriault, Louis |
|
Faculté:
|
science |
|
Degré:
|
msc |
