Switching of Enantioselectivity in the Cu-Catalyzed Asymmetric Decarboxylative Aldol Reaction of Tryptanthrin with <i>β-</i>Keto Acids: An Unexpected Counteranion Effect
Fangfang Feng, Xueqi Wang, Long Sun, Chi Wai Cheung, Jing Nie, Jun‐An Ma
Abstract
Cu-bisoxazoline-catalyzed enantioselective decarboxylative aldol reaction of tryptanthrin with aryl-substituted β-keto acids is developed, providing a straightforward approach to deliver a series of phaitanthrin A analogues. Both enantiomers of the products can be obtained with good to high enantioselectivity in the presence of a single chiral ligand by simply changing the copper salts. Based on the X-ray crystallographic analysis of chiral Cu(II)-bisoxazoline complexes, the tentative stereochemical models are presented to account for the observed counteranion-induced switching in enantioselectivity.
Topics & Concepts
ChemistryAldol reactionEnantioselective synthesisCatalysisEnantiomerLigand (biochemistry)DecarboxylationChiral ligandCopperCombinatorial chemistryStereoisomerismEnantiomeric excessOrganic chemistryStereochemistryReceptorBiochemistryAdvanced Synthetic Organic ChemistryAsymmetric Synthesis and CatalysisQuinazolinone synthesis and applications