Racemization of (S)-profen thioesters by strong neutral bases in nonpolar organic solvents: implication for ion-pair kinetic basicity.
The racemization of (S)-profen 2,2,2-trifluoroethyl thioesters in isooctane with trioctylamine as base was carried out, in which the Hammett equation log(k(int)) = 3.584sigma - 3.745 was successfully applied to describe the electron-withdrawing effect of the substituents to the alpha-phenyl moiety of the thioesters. A combination of neutral strong organic bases with different nonpolar solvents was employed to determine the second-order interconversion constants for the racemization of (S)-naproxen 2,2,2-trifluoroethyl thioester, in which solvent hydrophobicity was found to have less effect on the racemization. Implication for ion-pair kinetic basicity scale for the neutral strong bases in isooctane was further discussed.
Chen
Chia-Yin
CY
Department of Chemical Engineering, National Cheng Kung, University, Tainan 70101, Taiwan, ROC.
Chang
Yu-Shang
YS
Lin
Shun-An
SA
Wen
Hui-I
HI
Cheng
Yu-Chi
YC
Tsai
Shau-Wei
SW