Asymmetric glycolate aldol reactions using cinchonium phase-transfer catalysts.
Cinchona phase-transfer catalysts (PTC) were developed for glycolate aldol reactions to give differentially protected 1,2-diol products. Silyl enol ether 9 reacted to generate benzhydryl-protected products. O-Allyl trifluorobenzyl cinchonium hydrofluoride CN-4 (20 mol %) catalyzed the addition of 9 to benzaldehyde to give 8 as a single syn-product in 76% yield and 80% ee. Recrystallization enriched the product to 95% ee, and a Baeyer-Villiger reaction transformed the product into useful ester intermediates. [reaction: see text]
Andrus
Merritt B
MB
Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602-5700, USA. mbandrus@chem.byu.edu
Liu
Jing
J
Ye
Zhifeng
Z
Cannon
John F
JF