STEREOSELECTIVE PROTONATION OF CARBANIONS .6. ENANTIOSELECTIVE PROTONATION OF GAMMA-BUTYROLACTONE ENOLATES

The lithium enolates 3Li-7Li, produced from 3-7 by LDA or LiHMDS in TH F, are protonated with eleven chiral proton sources at -78-degrees-C i n THF which produced high enantioselectivities with 1Li and 2Li[5]. Al though the enolates (3Li, 6Li, 7Li) are not deuterated quantitatively[ 1], H-1- and C-13-NMR spectra in THF at -78-degrees-C reveal not only quantitative deprotonation (3Li, 6Li) but also aggregation (dimerisati on) and hindered rotation of the phenyl group in 3Li. From comparison of the enantioselectivities produced by five chiral proton sources wit h 1Li - 6Li (Tab. 4) definite structure/selectivity correlations can n ot be derived both for the enolates and the proton sources.