Enantiomeric Perturbation of Equilibria. Differential Solvation of a Chiral Lithium Amide by the Enantiomers of 2-Methyltetrahydrofuran Measured by NMR Spectroscopy

摘要

We wish to report the first direct observation of diastereo-selective solvation of a chiral organolithium compound by the enantiomers of a chiral ether, i.e. solvation by (R)- and (S)-2-methyltetrahydrofuran (2-MTHF) of the dimer of lithium (1-methoxy-(R)-1 -phenylethyl)((S)-1 -phenylethyl)amine ((LiA_2) (Scheme 1). A novel method for determination of accurate equilibrium constants (K) and their temperature dependence (AH and AS) using NMR chemical shifts is also presented. It has been used to measure the differential solvation of (LiA)_2 by the R- and S-isomers of 2-MTHF.