作者:Claudia De Fusco、Sara Meninno、Consiglia Tedesco、Alessandra Lattanzi
DOI:10.1039/c2ob27283k
日期:——
The first enantioselective α-hydroxylation reaction of α-substituted β-ketoamides has been developed by using the commercially available hydroquinine/TBHP system. The tertiary alcohols are obtained in good to high yield and up to 83% ee, which can be improved by a single crystallization.
Abstract The asymmetric α-hydroxylation of β-dicarbonylcompounds was catalyzed by C-2′-modified cinchonine-derived phase-transfer catalysts. Excellent yields (up to 95%) and good enantioselectivities (up to 89% ee) were obtained. The reaction was carried out in a flow microreactor and similar results were obtained (up to 93% yield, 84% ee), the residence time was shortened from 24 h in batch to 2 h
Development of C-6′-modified quinine-derived phase-transfer catalysts and their application in the enantioselective α-hydroxylation of β-dicarbonyl compounds
We have developed C-6'-modified quinine quaternary ammonium salts as phase transfer catalysts for alpha-hydroxylation of beta-dicarbonyl compounds. The quinine quaternary ammonium salts, which was modified at C-6' and the N atom, had good activity for alpha-hydroxylation of B-dicarbonyl compounds. By using 5 mol % of 6-hydroxyl-N-(4'-fluoro-2'-trifluoromethyl)quinine quaternary ammonium salt as the organocatalyst, cumene hydroperoxide as the oxidant, toluene as the solvent, and 50% K2HPO4 as the aqueous alkali at room, temperature, the yield and enantioselectivity of the alpha-hydroxylation of beta-keto esters were 95% and 88%, respectively. This catalytic system was also applicable for beta-keto amides (92% yield and 76% ee). (C) 2016 Elsevier Ltd. All rights reserved.