Wet unsupported and supported 1,1'-binaphthalene-2,2'-diamine (BINAM) derived prolinamides are efficient organocatalysts under solvent-free conditions at room temperature to perform the synthesis of chiral tacrine analogues in good yields (up to 93%) and excellent enantioselectivies (up to 96%). The Friedlander reaction involved in this process takes place with several cyclohexanone derivatives and 2-aminoaromatic aldehydes, and it is compatible with the presence of either electron-withdrawing or electron-donating groups at the aromatic ring of the 2-aminoaryl aldehyde derivatives used as electrophiles. The reaction can be extended to cyclopentanone derivatives, affording a regioisomeric but separable mixture of products. The use of the wet silica gel supported organocatalyst, under solvent-free conditions, for this process led to the expected product (up to 87% enantiomeric excess), with its reuse being possible at least up to five times.
Catalytic Enantioselective Friedländer Condensations: Facile Access to Quinolines with Remote Stereogenic Centers
作者:Le Li、Daniel Seidel
DOI:10.1021/ol1023932
日期:2010.11.5
Enamine catalysis enables the first catalyticenantioselective Friedländer reaction. The desymmetrization of 4-substituted cyclohexanones upon reaction with o-aminobenzaldehydes allows for the synthesis of quinolines with remote stereogeniccenters. These heterocycles, which are obtained with high levels of enantioselectivity, serve as precursors for chiral tacrine analogues.