Phase-transfer-catalyzed asymmetric glycolate alkylation |
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Authors: | Andrus Merritt B Hicken Erik J Stephens Jeffrey C |
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Affiliation: | Brigham Young University, Department of Chemistry and Biochemistry, C100 BNSN, Provo, Utah 84602-5700, USA. mbandrus@chem.byu.edu |
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Abstract: | [reaction: see text] 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 degrees C in high yield (80-99%) and with excellent enantioselectivities (90:10 to 95:5). Useful alpha-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. |
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