Palladium-Catalyzed Dearomatizing Alkoxyarylation Of Furan Rings Access To Spiroacetals And Polysubstituted Oxabicyclic Compounds

In recent years,numerous protocols for transition-metal-catalyzed difunctionalization of alkenes have been reported,such as dioxygenation,oxyamidation,diboration,and diamination,carbonetherification and alkoxyarylation,these step-economical protocols have provided a wide range of structurally diverse functionalized compounds that are of great importance in organic synthesis.Furan-based aromatic compounds are common in nature and readily available,which can be further transformed from biomass resources.Because of their low aromaticity,furans can serve as masked alkenes,dienes,enol ethers,and 1,4-diketones,therefore,We hope to achieve difunctionalization of furan rings to obtain the new compounds.We have developed a palladium-catalyzed the 2,5-oxyarylation of furan rings via aerobic oxidative coupling reaction of boronic acids with α-hydroxyalkylfurans to provide various unsaturated spiroacetals,which may be biologically interesting and synthetically useful.Spiroacetals are presenting in numerous biologically active natural products isolated from plants,fungi,and marine organisms,which contributes to the bioactivities of insect sex pheromones,polyketide antibiotics,and microtubule stabilizing agents,and it represents a privileged scaffold in drug discovery researches,medicines and pesticide molecular aspects.Because of the diene moiety of furan ring is chemically similar to a nonaromatic alkene or diene,we have a desire to achieve 2,3-difunctionalization of furan ring synthsis to polycyclic dihydrofuran structure.Fortunately,we have reported a protocol for Pd-catalyzed dearomatizing alkoxydiarylation of furan rings’ tri-functionalization via the oxidative coupling of arylboronic acids with 5-aryl-2-hydroxyalkylfurans providing access to two types of polysubstituted oxa-bicyclic skeletons,all kinds of hexahydrofuro[3,2-b]furans were obtained diastereospecifically by means of a one-pot protocol in moderate to good yields.Spiroacetal motif is widely distributed in many bioactive natural products of different origins and essentially contributes to various bioactivities.a series of spiroacetals were biologically evaluated as insect sex attractant towards oriental fruit flies(Bactrocera dorsalis)using methyleugenol as the standard.Biological evaluation demonstrated that a large part of the tested compounds triggered apparent electrophysiological responses from both male and female fruit flies.The stereochemistry of the spiroacetals and the substitution on their phenyl rings influenced the responses to some degree.