Ruthenium-Catalyzed Bis-Allylation Of Imidazopyridines

Allylarenes are prevalent in various nature products and pharmaceuticals,which could also be converted into other functionalities.Consequently,allylation reactions have attracted much attention.Traditionally,allylarenes could be assessed via crosscoupling reaction of organometallic reagents with allyl electrophiles and Friedel-Crafts allylation of electron-rich arenes in the presence of Lewis acid.However,the above methodologies either require prefunctionalized arenes or suffer from poor regioselectivity.To overcome these limitations,chelation-assisted C-H functionalization has emerged as an atom-economic and environmental benign strategy for the rapid and regioselective construction of value-added scaffolds without tedious pre-functionalization.Up to now,various allylic surrogates,including allyl carbonates,allyl ester,allyl ether,allyl acetals,allyl halides,allyl alcohols,allenes,1,3-dienes,and unactivated alkenes,have been successfully utilized to realized C-H allylation.Recently,strained rings have emerged as previliged coupling partners in chelation-assisted C-H functionalization via sequential C-H activation and ring cleavage.Following this principle,allylarenes could also be prepared using vinylcyclopropanes(VCPs)and vinyl cyclic carbonates(VCCs)as the allylation reagents.On the other hand,imidazopyridines are important heterocycles with wide applications in pharmaceuticals,optoelectronics,and catalysis fields.In this context,much attention has been paid to the synthesis and functionalization of imidazopyridine scaffold.Until now,great progress has been made in C3-functionalization of imidapyridines,including formation of C-C,C-S,C-Se,and C-N bonds.On the contrary,imidazopyridine-directed C-H functionalization is less investigated.Recently,we have also developed C-H cyanation of imidazopyridines and allylation of indolines via chelation-assisted strategy.As the continuous of our previous work,we herein reported the utilization of pharmacophore imidazopyridine as an inherent directing group to realize bis-allylation via sequential C-H activation and ring cleavage(Scheme 1).