Enantioselective Allylic Alkylation By Cooperative Photoredox/ Palladium Catalysis

As a renewable and inexhaustible energy source,visible light is a hot topic for chemists to study how to efficiently convert this energy into chemical energy and apply it to organic synthesis.The application of light reactions is limited by the fact that most organic molecules cannot directly absorb visible light,through the development,design and use of photocatalyst,the application range of visible light catalysis is greatly expanded and the types of visible light catalysis are enriched.Visible light oxidation-reduction catalysis is the use of photocatalyst under the excitation of visible light to transition from ground state to excited state so as to have the ability of oxidation or reduction,under mild conditions,single electron transfer occurs with organic substrates to produce highly active free radical intermediates,which is widely used in organic synthesis.Visible light redox catalysis can obtain highly active free radical intermediates from abundant natural functional groups under mild conditions.These reaction intermediates are usually not easy to be produced by non-photocatalytic strategy,and coupling reactions that are difficult to achieve with a single transition metal can be achieved by co-catalyzing with the transition metal.Due to the high activity of the free radical intermediates produced in the visible light oxidation-reduction catalysis process,the control of stereoselectivity has always been the difficulty of visible light catalysis.In this paper,cheap and easily available carboxylic acids are used as precursors of alkyl radicals,the use of visible light redox and chiral palladium co-catalyzed strategy to produce alkyl radicals,under mild conditions to achieve asymmetric allyl alkylation reaction,the construction of a homoallylic alcohols compound with chiral quaternary carbon center.The reaction conditions are mild,except for the products produced during the reaction process,only carbon dioxide is discharged from the system,which is characterized by green,clean and good atomic economy,and the reaction has good yield,regional selectivity and stereoselectivity.Through the full expansion of the reaction substrate,it shows that the visible light redox and palladium co-catalyzed strategy to achieve the allyl asymmetric alkylation strategy is applicable.Moreover,it can be used as a substitute and supplement for the traditional olefin asymmetric allyl substitution reaction,and expands the synthesis strategy of chiral homoallylic alcohols compound.