Catalytic Asymmetric Claisen Rearrangement

Significance

Due to the relatively rare synthetic protocols for xenicanes, this progress described by the authors is substantial. Although the catalyst loading is high (25 mol%), the selectivity is essentially perfect (>90% de with >99% ee), making this transformation very useful. Interestingly, the authors found that the geometrical isomer with a Z-double bond (marked blue in the scheme) remains completely unchanged. They attribute this to steric repulsion in the transition state.