Phase-Transfer-Catalyzed Asymmetric Glycolate Alkylation

Asymmetric surrogate glycolate alkylation has been performed under phase-transfer conditions. Diphenylmethyloxy-2,5-dimethoxyacetophenone with trifluorobenzyl cinchonidinium catalyst and cesium hydroxide provided alkylation products at −35 °C in high yield (80−99%) and with excellent enantioselectivities (90:10 to 95:5). Useful α-hydroxy products were obtained using bis-TMS peroxide Baeyer−Villiger conditions and selective transesterification. The intermediate aryl ester can be obtained with >99% ee after a single recrystallization. A tight ion-pair model for the observed (S)-stereoinduction is proposed.