Enhancement of enantioselectivity by THF in asymmetric mo-catalyzed olefin metathesis. Catalytic enantioselective synthesis of cyclic tertiary ethers and spirocycles

Mo-catalyzed enantioselective rearrangement of achiral cyclopentenyl tertiary ethers to chiral cyclohexenyl tertiary ethers are reported. These olefin metathesis transformations proceed efficiently and with high levels of enantioselectivity. A noteworthy feature of these reactions is that added tetrahydrofuran exerts a remarkably positive influence on the enantioselectivity of the metathesis-based rearrangement. The first examples of catalytic asymmetric synthesis of spirocyclic structures by enantioselective olefin metathesis are also disclosed.