Selective Cascade Reaction of Bisallenes via Palladium‐Catalyzed Aerobic Oxidative Carbocyclization–Borylation and Aldehyde Trapping

A cascade reaction, consisting of a palladium‐catalyzed regioselective aerobic oxidative carbocyclization–borylation of bisallenes and a final aldehyde trapping, afforded triene alcohols with high diastereoselectivity. The cascade reaction occurs under mild reaction conditions and proceeds via an allylboron intermediate that is trapped by the aldehyde in a stereoselective manner.     

Iron(II)-Catalyzed Biomimetic Aerobic Oxidation of Alcohols

We report the first Fe^II-catalyzed biomimetic aerobic oxidation of alcohols. The principle of this oxidation, which involves several electron-transfer steps, is reminiscent of biological oxidation in the respiratory chain. The electron transfer from the alcohol to molecular oxygen occurs with the aid of three coupled catalytic redox systems, leading to a low-energy pathway. An iron transfer-hydrogenation complex was utilized as a substrate-selective dehydrogenation catalyst, along with an electron-rich quinone and an oxygen-activating Co(salen)-type complex as electron-transfer mediators. Various primary and secondary alcohols were oxidized in air to the corresponding aldehydes or ketones with this method in good to excellent yields.     

One‐Step Multigram‐Scale Biomimetic Synthesis of Psiguadial B

A gram‐scale synthesis of psiguadial B, a purported inhibitor of human hepatoma cell growth, has been achieved in one step by a biomimetic three‐component coupling of caryophyllene, benzaldehyde, and diformylphloroglucinol. This cascade reaction is catalyzed by N,N′‐dimethylethylenediamine, and proceeds at ambient temperature to generate four stereocenters, two rings, one C−O bond, and three C−C bonds. Combined computational and experimental investigations suggest the biosynthesis of the natural product is non‐enzyme mediated, and is the result of a Michael addition between caryophyllene and a reactive ortho‐quinone methide, followed by two sequential intramolecular cationic cyclization events.