RSS-Feed abonnieren
DOI: 10.1055/s-0034-1379446
Novel Oligomeric Helical Chiral Catalysts for Asymmetric Dearomatization
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
Publikationsverlauf
Publikationsdatum:
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.
#
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.
#
Review
M. S. Taylor, E. N. Jacobsen Angew. Chem. Int. Ed. 2006, 45, 1520–1543.
#
#