A novel axial chiral benzo[g]quinoline ligand partnered with AgOTf to enantioselectively catalyse a Mannich reaction between isatin N-Boc ketimines and acetylacetone

Abstract

First example of AgOTf catalysed enantioselective Mannich reaction between isatin N-Boc ketimines and acetylacetone partnered with a novel axial chiral benzo[g]quinoline ligand B1 has been disclosed. A series of multifunctional chiral 3-substituted 3-amino quaternary oxindoles have been obtained in good enantioselectivities (up to 92:8er) with high yields (61–91 % yields). After a simple recrystallization, the enantioselectivity of almost every chiral product may be greatly improved (up to 99:1er), which provides an alternative method for easy availability of high enantiomeric purity of bioactive chiral 3-substituted 3-amino quaternary oxindoles. This work has successfully demonstrated the good performances of a new kind of axially biaryl quinoline ligands and enriched the application of silver salts in asymmetric catalysis.