Application Of Visible-light Photoredox Catalysis Involved Cooperative Catalysis In Asymmetric Alkylation

Energy is the foundation of human survival and development.With the rapid development of human society,the energy crisis and the environmental problems caused by the unreasonable use of traditional energy have become increasingly prominent.The development and application of green energy has always been the focus of scientists’research.Solar energy is inexhaustible and an ideal green energy source.Chemists continue to explore efficient ways to convert solar energy into chemical energy,and photochemistry has become a hot spot in the field of chemical research.Visible-light photoredox catalysis can use the optical properties of photosensitizers to promote the redox process in chemical reactions.Under milder conditions,it can produce reactive intermediates such as radicals or radical ions through single-electron transfer process.In recent years.it has been widely used in organic synthesis.It is also because of the high activity of intermediates such as radicals that the selectivity of the reaction,especially stereoselectivity,becomes a difficult point in photoredox catalysis.At present,the synergistic catalysis of photosensitizers and chiral catalysts is a general strategy to realize stereochemical control of these reactions.The aim of this thesis is to develop a synergistic catalytic strategy involving photoredox catalysts to realize asymmetric alkylation.The research contents are mainly divided into three parts.The first part:Highly regio-,and enantioselective radical allylic alkylation has been achieved enabled by the merger of photoredox and palladium catalysis.In this dual catalytic process,alkyl radicals generated from 4-alkyl-1,4-dihydropyridines or amines act as the coupling partners of the the π-allyl palladium complexes.The generality of this method has been illustrated through the reaction of a variety of allyl esters with 4-alkyl-1,4-dihydropyridines or amines.This mechanistically novel strategy expands the scope of the traditional Pd-catalyzed asymmetric allylic alkylation reaction and serves as its alternative and potential complement.The second part:Radical alkylation of imines with 4-alkyl-1,4-dihydropyridines co-catalyzed by iridium complex and Br(?)nsted acid under visible light irradiation has been achieved.Both aldimines and ketimines can undergo this transformation.Common functional groups,such as hydroxyl groups,ester,amide,ether,cyanide and heterocycles,can be tolerated in this reaction.A variety of stuctrually diverse amines have been produced with up to 98%isolated yields using this method.The third part:Radical acylation of imines with a-oxo acids has been achieved via an electron-donor-acceptor(EDA)complex.This mild decarboxylative acylation can proceed without the requirement of any photocatalyst or additive and produces carbon dioxide as the sole waste.The radical-based methodology presented here allows to access structurally diverse a-amino ketones in a mild,environmentally friendly,economical and efficient way.