Palladium-Catalyzed Regioselective C-H Alkenylation of AllylicAlcohols by Phenanthroline-Type Bidentate Auxiliary

摘要

Transition-metal-catalyzed activation of C-H bond represents one of the mostactive research fields in modern organic synthesis.Compared to the significant progress inaryl C-H functionalization reactions,the activation of C-H bonds of alkenyl alcohols stillremains underdeveloped because of the major challenge in control of regioselectivity.Recently,Loh and coworkers developed the palladium-catalyzed δ-C-H alkenylation ofhomoallylic alcohols by using the hydroxyl chelating group.However,this strategy isrestricted to 1,1-disubstituted terminal alkenes.An attractive strategy to solve this problemis the introduction of directing groups.Engle et al.and Zhong et al.disclosed thedirected C-H olefination via exo-palladacycle formation enabled by different bi-ormono-dentate auxiliaries,respectively.One common limitation is that these reactions werenot applicable to sterically hindered alkene substrates.