Dual role of (-)-sparteine in the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols.
The mechanistic details of the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols have been elucidated. (-)-Sparteine was found to have a dual role as a chiral ligand and an exogenous base. Saturation kinetics were observed for the dependence on (-)-sparteine concentration. A first-order dependence on [alcohol] and [catalyst] as well as inhibition by addition of (-)-sparteine HCl were observed. These results are consistent with rate-limiting deprotonation under low (-)-sparteine concentrations and rate-limiting beta-hydride elimination using saturating (-)-sparteine concentrations. This conclusion is further supported by a kinetic isotope effect of 1.31 +/- 0.04 under saturation. The enantioselectivity events are also controlled by addition of (-)-sparteine in which high concentrations afford a more selective kinetic resolution.
Mueller
Jaime A
JA
Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-8500, USA.
Jensen
David R
DR
Sigman
Matthew S
MS
D000332:Aerobiosis; D000438:Alcohols / Q000737:chemistry* / Q000302:isolation & purification; D002384:Catalysis; D007659:Ketones / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D013034:Sparteine / Q000737:chemistry*; D013237:Stereoisomerism
D000438:Alcohols; D007659:Ketones; D013034:Sparteine; D010165:Palladium