Barrier to enantiomerization of unstabilized, chelated, and dipole-stabilized 2-lithiopyrrolidines
by Ashweek, N. J.; Brandt, P.; Coldham, I.; Dufour, S.; Gawley, R. E.; Haeffner, F.; Klein, R.; Sanchez-Jimenez, G.
Kinetics experiments have been used to establish the free energy, enthalpy, and entropy of activation for the enantiomerization of three structural classes of 2-lithiopyrrolidines. We find that alpha-aminoorganolithiums chelated by a N-methoxyethyl or N-Boc group have a barrier to enantiomerization (DeltaG(double dagger)) 2-3 kcal/mol lower than that of unstabilized alpha-aminoorganolithiums at 273 K. Density functional calculations were performed to clarify possible ground state and transition structures and to identify possible pathways for inversion of these chiral organolithium species.
- Journal
- Journal of the American Chemical Society
- Volume
- 127
- Issue
- 1
- Year
- 2005
- Start Page
- 449-457
- URL
- https://dx.doi.org/10.1021/ja048090l
- ISBN/ISSN
- 1520-5126; 0002-7863
- DOI
- 10.1021/ja048090l