Application Of Magnesium-catalyzed Direct Activation Of Allyl Esters In The Construction Of Chiral Oxapolycyclic Structures

Linear unsaturated esters are broadly utilized in asymmetric synthesis due to their diverse reactivity and relatively low cost,and possess highly considerable research and application value.Nonetheless,in terms of accurate activation of such compounds,there remains a lack of efficient asymmetric catalytic activation methodologies,despite the devotion made by researchers.Chiral oxapolycyclic skeletons existing extensively in natural products and molecules with drug activity is tremendously momentous skeletons in the synthesis of natural products and the development of active drugs.Presently,the asymmetric synthesis approaches of this structure are still limited,and meanwhile its synthesis steps are lengthy.Therefore,it is of prodigious significance to make findings concerning novel asymmetric catalytic strategies regarding activation of unsaturated esters with a view to constructing oxapolycyclic structures and stretching their practicality into total synthesis of natural products and synthesis of bioactive molecules.This thesis focuses on the development of a methodology whereby the direct activation of unsaturated esters can be actualized.With reference to the previous research works,we,based on binaphthol usually regarded to be inexpensive and easily available,designed and synthesized chiral diamine ligands which reacted with dibutylmagnesium to synthesize bifunctional in-situ magnesium catalysts.Under tender circumstances,the unsaturated esters within two carbonyl groups directly activated by magnesium catalysts undergo the intramolecular addition reaction to complete the intramolecular kinetic resolution of the racemic substrates,thereafter the target product was eventually attained with high enantioselectivity and a desirable conversion rate,and eventually efficient construction of oxatricyclic and oxatetracyclic structures was achieved.This reaction can be universally applied into various substrates and give exposure to a novel catalytic pathway for the synthesis of the framework,rendering greater practice potential and realistic value to this catalytic strategy.