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Applied Dienamine Catalysis
R. M. de Figueiredo, R. Fröhlich, M. Christmann*
RWTH Aachen and University of Münster, Germany
19 March 2008 (online)
Cyclization of unsaturated dialdehydes 1 in the presence of a catalytic amount of chiral diphenylprolinol silyl ether 2 and benzoic acid led to the formation of highly enantioenriched bicyclic frameworks 3 (after reduction to the corresponding alcohols). Moreover, dienals 4 could be efficiently converted into monocyclic products 5. Both transformations rely on vinylogous enamine activation of an enal as electron-rich dienamine prone to undergo a rapid intramolecular Diels-Alder (IMDA) reaction or a vinylogous aldol condensation in the case of α-methylene aldehydes 4.