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- Title
Synthetic and Organocatalytic Studies of Quinidine Analogues with Ring-Size Modifications in the Quinuclidine Moiety.
- Authors
Breman, Arjen C.; van der Heijden, Gydo; van Maarseveen, Jan H.; Ingemann, Steen; Hiemstra, Henk
- Abstract
Six highly enantiopure analogues of [2.2.2] were synthesized with five- or seven-membered rings in the (original) quinuclidine skeleton. Five of these compounds were prepared through epoxide opening by a secondary cyclic amine, providing the nor- and homoquinuclidine moieties through five- and six-membered ring formation. This method failed in the case of seven-membered ring formation, so for that particular ring size a different synthetic route starting from 3-quinuclidone was applied. The six novel analogues were examined as organocatalysts in four asymmetric conjugate addition reactions and the results compared with those of known cinchona alkaloid catalysts. This study shows that modification of the quinuclidine ring can have a substantial influence on catalyst activity and enantioselectivity. To acquire more insight into the characteristics of the new catalysts, the p KaH values were determined by means of fluorescence spectroscopy. Furthermore, relative reaction rates of conjugate thiol additions reactions catalyzed by these quinidine analogues were measured through polarimetry.
- Subjects
QUINIDINE; QUINUCLIDINES; ORGANOCATALYSIS; FLUORESCENCE spectroscopy; THIOL synthesis; POLARIMETRY
- Publication
Chemistry - A European Journal, 2016, Vol 22, Issue 40, p14247
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201601917