title: Barrier to enantiomerization of unstabilized, chelated, and dipole-stabilized 2-lithiopyrrolidines.
abstract: 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++) 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.
authors.affiliation: Department of Chemistry, University of Exeter, UK.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Ashweek
authors.forename: Peter
authors.initials: P
authors.lastname: Brandt
authors.forename: Iain
authors.initials: I
authors.lastname: Coldham
authors.forename: Samuel
authors.initials: S
authors.lastname: Dufour
authors.forename: Robert E
authors.initials: RE
authors.lastname: Gawley
authors.forename: Fredrik
authors.initials: F
authors.lastname: Haeffner
authors.forename: Rosalyn
authors.initials: R
authors.lastname: Klein
authors.forename: Graciela
authors.initials: G
authors.lastname: Sanchez-Jimenez
mesh_terms: D007700:Kinetics; D008094:Lithium / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D009942:Organometallic Compounds; D011759:Pyrrolidines; D008094:Lithium