Synthesis of Densely Substituted α,β,γ, δ-Dienones via the PdII-Catalyzed Allylation, H-Migration, and Aerobic Oxidative δ-Hydride Elimination Cascade

A novel protocol for the highly stereoselective synthesis of E,E-alpha,beta,gamma,delta-unsaturated dicarbonyl compounds is presented. Starting from the readily available allylic alcohols and 1,3-cliketones, an array of E,E-alpha,beta,gamma,delta-dienones can be efficiently synthesized in high yields via Pd-catalyzed dehydrative allylation, H-migration, and aerobic oxidative 6-hydride elimination cascade. In addition to the novel reaction mechanism, the use of 1:1 allylic alcohol and 1,3-diketone as reactant, 5 mol % of PdCl2 as catalyst, and 1 atm of environmentally benign 02 as oxidant, as well as the generation of only H2O byproduct, makes this protocol rapid, simple, atom-efficient, and clean.