Enantioselective Nazarov Cyclization Catalyzed by a Cinchona Alkaloid Derivative.

Nucleophilic catalysts for a 1,6 addition/Nazarov cyclization/elimination sequence were evaluated for their ability to induce enantioselectivity in the electrocyclization step. Of the tertiary amines examined, it was found that a cinchona alkaloid derivative was able to generate substituted 5-hydroxy γ-methylene cyclopentenones with excellent enantioselectivity. The study results suggest that successful cyclization depends upon the ability of the dienyl diketone substrate to readily adopt an s-cis conformation.