Asymmetric Michael Reaction Of 3-Acyloxy-2-Oxindole Catalyzed By Chiral Heterobimetallic Zinc/Strontium Complex

3-Substituted-3-hydroxy-2-oxindole has potential medicinal value,while 3-hydroxy-2-oxindole is unstable under alkaline condition,3-acyloxy-2-oxindole produced by esterifying the 3-position has good stability,so we believe that 3-acetoxy-2-oxindole will to be a valuable Michael donor to construct a carbon stereocenter at the C3 position of oxindole.Hence,we have developed a new chiral heterobimetallic zinc /strontium catalyst based on binuclear aminophenol sulfonamide,which catalyzes the Michael reaction by a simple one-pot reaction.It is our first time to use this catalytic system to synthesize oxindole with high enantioselectivity and high diastereoselective using 3-acetoxy-2-oxindole as substrate by a series of optimized conditions.Chiral product has a maximum enantioselectivity greater than 99% and a diastereoselective greater than 30: 1,and a yield of 94%.The excellent results are still obtained when the reaction substrate is increased to 5mmol to reach the gram level,with an ee value of up to 97%,a dr value 20: 1 and a yield of89%.The results of control reaction show that the complex with the ratio of Zn / Sr / L1 of 1: 1: 1 is the optimal reaction activity catalyst.