Efficient C-C Bond Formation and Cleavage Reaction Promoted by Triethylborane and Late Transition Metal Catalysis

Ni catalyzes homoallylation of aldehydes with 1,3-dienes in the presence of triethylborane to provide bishomoallyl alcohols. Triethylborane serves as reducing agent and Lewis acid to promote the homoallylation via oxanickelacycles. Under similar conditions, Rh catalyzes the reductive coupling reaction of aldehydes and 1,3-dienes to provide homoallyl alcohols while Pd catalyst promotes the ene-type reaction to provide dienyl homoallyl alcohols.Triethylborane also activates allylic alcohols to form π-allylpalladium key intermediates by oxidative addition of Pd(0) toward allylic C-O bonds and achieves amphiphilic allylations. A combination of Pd catalyst and triethylborane effectively promotes 3-hydroxy-4-pentenoic acid to undergo β-decarboxylative C-C bond cleavage reaction via β-vinyloxapalladacyclopentanone to provide conjugated diene and carbon dioxide.