Rhodium(I)-Catalyzed Enantioselective Ring-Opening and Isomerization of Cyclobutanols through a (Z)-Unsaturated Ketone Intermediate.

A rhodium(I)-catalyzed highly enantioselective ring-opening and isomerization of cyclobutanols has been developed. The reaction provides a mild, atom-economical, and redox-neutral approach for the synthesis of chiral acyclic ketones bearing a β-tertiary stereocenter. Excellent enantioselectivities and high yields can be achieved using cyclobutanols with alkoxy substituents at the C3 position. Mechanistic studies reveal that cyclobutanol only undergoes intramolecular hydrogen migration, and the formation of a (Z)-unsaturated ketone intermediate is crucial for achieving high enantioselectivity.