Tartaric Acid Derived Chiral Guanidine-Catalyzed Asymmetric Fluorination Of 3-Substituted Oxindoles

Chiral organic small molecular catalysts play an important role in asymmetric catalytic reaction and a rapid development has been witnessed in this area during the past decade. As an important member of the chiral small organic molecular catalysts, chiral guanidines showed very good catalytic performance. Guanidines based on tartaric acid derivatives have many advantages such as cheap raw materials, easy synthesis, structural modulation, and high catalytic activity.Fluorine occupies an important position in organic chemistry because of its unique role infiltrated into polymer materials, medicine, chemistry, physics, biology and many other fields. Introducing fluorine atoms in target molecules can produce significante affect on the physical and chemical properties of molecules. And it also can make a huge change of the pharmacological activity of the drug molecules. So the asymmetric fluorination reaction attracts increasing attention in the field of organic chemistry. In this paper, based on our research work, we continued to explore the catalytic activity of tartaric acid derived chiral guanidine. We applied it to the asymmetric fluorination of 3-substituted oxindoles, and it is surprising to find that a pair of corresponding enantiomers can be obtained respectively when using guanidines with different structures. After screening of catalyst, solvent, and temperature,。the optimum reaction conditions were established. Then the substrates were explored. Generally high yields and excellent enantioselectivity were obtained (up to 99% yield and up to 95% ee).