Applications of Helical-Chiral Pyridines as Organocatalysts in Asymmetric Synthesis

• Published in: Chemical record Vol. 13; no. 1; pp. 28 - 42
• Main Authors: Peng, Zhili, Takenaka, Norito
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.02.2013; Wiley Subscription Services, Inc
• Subjects: asymmetric catalysis; enantioselectivity; helical structures; organocatalysis; pyridines
• ISSN: 1527-8999; 1528-0691
• DOI: 10.1002/tcr.201200010

A new family of chiral pyridines has been designed and synthesized for use in asymmetric organocatalysis. Thus, helical‐chiral pyridines induce high enantioselectivity in a range of mechanistically unrelated, synthetically significant transformations, including Friedel‐Crafts alkylation with nitroalkenes, periselective Diels‐Alder reactions with nitroalkenes, the ring‐opening of epoxides with a chloride nucleophile, and the propargylation of aldehydes. Helicene‐derived catalytic scaffolds: A new family of chiral Brønsted acid catalysts and a new family of chiral Lewis base catalysts have been developed based on the previously unexplored azahelicenes (helical‐chiral pyridines). It has been successfully demonstrated that these catalysts are highly enantioselective owing to the exceedingly large steric screening effect of the helicene framework and, thus, are particularly effective for transformations that require remote enantioselection, regardless of their reaction mechanisms.