Synthesis and application of the first planar chiral strong Brønsted acid organocatalysts
Dieter Enders1, Monika Ludwig, Gerhard Raabe
1Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany. enders@rwth-aachen.de
Abstract:
The synthesis of planar chiral strong Brønsted acid organocatalysts derived from [2.2]paracyclophane is described. Resolution was accomplished according to a modified protocol involving pseudo-ortho-substituted [2.2]paracyclophane-based sulfoxides for the synthesis of three new sulfonic acids. The first planar chiral phosphoric acid diester was obtained from the corresponding phenyl-substituted diol derived from enantiopure 4-bromo-12-hydroxy [2.2]paracyclophane. These new classes of catalysts were tested in an enantioselective Friedel-Crafts reaction as well as in a direct asymmetric Mannich reaction and gave yields of up to 93% and ee-values of up to 38%.
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