Helical chiral 2-aminopyridinium ions were designed as a significantly more acidic (active) dual hydrogen-bonding catalyst than commonly used (thio)urea-based systems. The helicene framework was specifically utilized to position an inherently chiral barrier on the hydrogen-bonding side of the catalyst. The catalyst reactivity and enantioselectivity were successfully demonstrated in additions of 4,7-dihydroindoles to nitroalkenes (0.5-2 mol % catalyst loadings, up to 98:2 er).

Angewandte Chemie International EditionVolume 47, Issue 50 p. 9708-9710 Communication Helical Chiral Pyridine N-Oxides: A New Family of Asymmetric Catalysts† Norito Takenaka Prof., Norito Takenaka Prof. [email protected] Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this authorRobindro Singh Sarangthem Dr., Robindro Singh Sarangthem Dr. Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this authorBurjor Captain Prof., Burjor Captain Prof. Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this author Norito Takenaka Prof., Norito Takenaka Prof. [email protected] Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this authorRobindro Singh Sarangthem Dr., Robindro Singh Sarangthem Dr. Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this authorBurjor Captain Prof., Burjor Captain Prof. Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431 (USA), Fax: (+1) 305-284-4571Search for more papers by this author First published: 26 November 2008 https://doi.org/10.1002/anie.200803338Citations: 204 † We thank the Florida Department of Health (07KN-12), the American Cancer Society (IRG-98-277-07), the Sylvester Comprehensive Cancer Center, and the University of Miami for support. We also thank Prof. Stanislaw Wnuk (Florida International University) for the use of their polarimeter, and Prof. Roger LeBlanc and Charles H. Vannoy for the CD spectral measurements. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Helical Chiral Catalysts: The gram-scale synthesis of 1-azahelicenes, structural characterization of the corresponding N-oxides, and the application of this new family of catalysts to the catalytic, enantioselective ring-opening of meso epoxides is described (see scheme). Included is the first demonstration that the appropriate structural modifications beneath the plane of the pyridine N-oxide can serve as a powerful means for tuning the catalyst enantioselectivity. Citing Literature Supporting Information Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Filename Description anie_200803338_sm_miscellaneous_information.pdf8.8 MB miscellaneous information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume47, Issue50December 1, 2008Pages 9708-9710 RelatedInformation

2-Aminopyridinium ions were found to activate nitroalkenes toward conjugate addition of heteroaromatic compounds with low catalyst loadings and the Diels-Alder reaction with the periselectivity opposite to that observed with metal Lewis acids, raising the possibility that a 2-aminopyridinium core might be a promising catalaphore for the asymmetric catalyst design.