Nickel-Catalyzed Hydroalumination of Oxabicyclic Alkenes. Ligand Effects on the Regio- and Enantioselectivity

摘要

We have shown that nickel catalysts offer several new opportunities for selective reductive ring opening of oxabicyclic compounds. Excellent yields with little or no overreduction of the ring-opened product can be achieved with only a slight excess of the reducing agent. Lewis acids accelerate the β-elimination in the [3.2.1] series. Higher regioselectivity and new regioisomers are possible through the addition of triphenylphosphine. Most significantly, this methodology is also appropriate for the asymmetric synthesis of cyclohexenols. Further studies are in progress to expand the scope of the enantioselective process.