jo991011h_si_003.pdf (355.09 kB)
Configurationally Stable Biaryl Analogues of 4-(Dimethylamino)pyridine: A Novel Class of Chiral Nucleophilic Catalysts
journal contribution
posted on 1999-12-04, 00:00 authored by Alan C. Spivey, Tomasz Fekner, Sharon E. Spey, Harry AdamsA short synthetic approach toward a novel class of chiral nucleophilic catalysts, the dissymmetry
of which stems from restricted rotation about an Ar−Ar bond, has been developed. The key steps
of the synthesis include preparation of a nucleophilic 1-methyl-2-pyrrolino[3,2-c]pyridine core 16
by ortho-lithiation and creation of the biaryl axes via Suzuki cross-coupling reactions. Comparative
HPLC studies of racemization for configurationally labile biaryls 31, 38, and 43 containing 1-methyl-2-pyrrolino[3,2-c]pyridine, 4-(dimethylamino)pyridine, and 4-(1-pyrrolidino)pyridine cores, respectively, have demonstrated that a pyrrolidino substituent ortho to the biaryl axis is optimal for
slowing Ar−Ar rotation. Biaryls containing all three cores have been shown to retain DMAP-like
catalytic activity in the acylation of a hindered alcohol. Biaryls 55 and 56, which are configurationally stable at ambient temperature, have also been prepared via modification of configurationally
labile derivatives. Compounds 55 and 56 in optically pure form should provide a useful starting
point for studies on catalytic asymmetric acyl transfer using atropisomeric analogues of DMAP.
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biaryl axesmethylDMAProtationpyridine core 16configurationallychiral nucleophilic catalystsBiaryls 55Chiral Nucleophilic Catalystsbiaryls 31Comparative HPLC studiesCompounds 55Novel Classbiaryl axisArConfigurationally Stable Biaryl Analoguesambient temperatureatropisomeric analoguesacyl transferpyrrolidino substituent orthonovel class
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