Synfacts 2014; 10(12): 1321
DOI: 10.1055/s-0034-1379446
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart · New York

Novel Oligomeric Helical Chiral Catalysts for Asymmetric Dearomatization

Contributor(s):
Benjamin List
,
Gabriele Pupo
Zurro M, Asmus S, Beckendorf S, Mück-Lichtenfeld C, García Mancheño O * University of Münster, University of Regensburg, and Straubing Center of Science, Germany
Chiral Helical Oligotriazoles: New Class of Anion-Binding Catalysts for the Asymmetric Dearomatization of Electron-Deficient N-Heteroarenes.

J. Am. Chem. Soc 2014;
136: 13999-14002
Further Information

Publication History

Publication Date:
18 November 2014 (online)

 

Significance

García Mancheño and co-workers report a novel class of helical chiral tetrazole-based oligomers for anion-binding catalysis. After screening different motifs, their best catalyst (3) was successfully employed in the asymmetric dearomatization of quinolines 1 to afford products 2 in good yields and with good to excellent enantio­selectivities. NMR titration experiments suggest the presence of a cooperative H-bonding network, which binds the chloride anion, accommodated inside the helical cavity.


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Comment

The authors developed a novel class of catalysts with comparable binding properties to well-developed thiourea-based organocatalysts (see Review below). They propose a fast conformational interconversion of structure 3 in the absence of the halogen (low stereocontrol). However, upon coordination to the anion, the helical chirality is reinforced, thus enabling highly enantio­selective transformations such as the reported dearomatization of quinolines.


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Review

M. S. Taylor, E. N. Jacobsen Angew. Chem. Int. Ed. 2006, 45, 1520–1543.


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