Design And Synthesis Of Azaspiro-Triazole Catalysts And Their Application In Asymmetric Aqueous Michael Reaction

Asymmetric organocatalysis has attracted much attention in the past few decades. Particularly, great efforts have also been devoted to asymmetric organocatalytic reactions performed using water as reaction medium. A number of new chiral organocatalysts with high activity and high enantioselectivity have been developed and used in catalytic asymmetric reactions in aqueous system. Recently, our group has been engaged in the development of chiral spiro catalysts and several series of catalysts were preliminarily applied to the catalytic asymmetric reactions. Merging the "privileged" spiro-backbone with 1,2,3-triazole, we developed a new class of novel Azaspiro-Triazole catalysts which were demonstrated to be effective for asymmetric Michael reaction of nitromethane to α,β-unsaturated aldehydes in water-containing system. In this thesis, the following two parts are mainly discussed.1. The design and synthesis of a series of Azaspiro-Triazole catalysts were achieved. We proposed the catalysts with tunable 1,2,3-triazole unit can be easily modified using hydrophobic group, which might be suitable in aqueous system. Therefore, we developed a general and efficient approach to Azaspiro-Triazole catalysts using diazotransfer reaction and CuAAC reaction.2. Asymmetric Michael reaction of nitromethane to α,β-unsaturated aldehydes by Azaspiro-Triazole catalysts was investigated in aqueous system. The resulting adducts with excellent enantioselectivities (83-95.5% ee) and moderate to good yields (63-88%) were obtained. This method also provided a new approach for iminium-type catalysis of enals in water-containing system.