Asymmetric Synthesis of Fluorinated Flavanone Derivatives by an Organocatalytic Tandem Intramolecular Oxa-Michael Addition/Electrophilic Fluorination Reaction by Using Bifunctional Cinchona Alkaloids
A bifunctional quinidine derivative, containing a trifluoromethyl group, was found to catalyze a tandem intramolecular oxa‐Michael addition/electrophilic fluorination reaction of activated α,β‐unsaturated ketones (see scheme). A series of chiral fluorinated flavanone derivatives were obtained in excellent yields and with high enantioselectivities.
One-pot synthesis of 2-aryl-3-alkoxycarbonyl chromones through a cascade Lewis acid-catalyzed aldehyde olefination/oxa-Michael addition/oxidation
作者:Ningning Wang、Shuying Cai、Chao Zhou、Ping Lu、Yanguang Wang
DOI:10.1016/j.tet.2012.11.008
日期:2013.1
were effectively constructed from aryl aldehydes and 3-(2-(methoxymethoxy)phenyl)propiolates via a cascade Lewis acid catalyzed phenol ether deprotection/aldehyde olefination/intramolecular oxa-Michael addition reaction, and a sequential oxidation. This four-step reaction could be conducted in one-pot with high atom efficiency.
The extension of racemization strategies of dynamic kineticresolution in organic synthesis is a longstanding challenge, especially racemizing two or more stereogenic centers simultaneously. Through the combination of a palladium-catalyzed asymmetric allylic alkylation and a base-promoted retro-oxa-Michael addition, a dynamic kineticresolution of 2,3-disubstituted flavonoids was achieved with up to