Dual role of (-)-sparteine in the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols

J Am Chem Soc. 2002 Jul 17;124(28):8202-3. doi: 10.1021/ja026553m.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerobiosis
  • Alcohols / chemistry*
  • Alcohols / isolation & purification
  • Catalysis
  • Ketones / chemical synthesis
  • Ketones / chemistry
  • Kinetics
  • Oxidation-Reduction
  • Palladium / chemistry*
  • Sparteine / chemistry*
  • Stereoisomerism

Substances

  • Alcohols
  • Ketones
  • Sparteine
  • Palladium