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Organocatalytic alkylation of carbohydrate‐containing aldehydes with dihydroquinoline N,O‐acetals: Absolute configuration of 1,2‐dihydroquinolines
Ist Teil von
Chirality (New York, N.Y.), 2019-02, Vol.31 (2), p.127-137
Ort / Verlag
United States: Wiley Subscription Services, Inc
Erscheinungsjahr
2019
Quelle
Wiley-Blackwell Journals
Beschreibungen/Notizen
The direct catalytic α‐amidoalkylation of dihydroquinolines with aldehydes bearing oxygen functionalities at different positions in a Mannich‐type reaction has been studied. β‐Alkoxy‐aldehyde 1d gave high enantioselectivity, albeit with an inherently poor diastereoselectivity, while the use of α‐alkoxy aldehydes 1c was detrimental also to enantioselectivity. Mannich‐type reactions have been studied for the first time using new chiral carbohydrate‐derived aldehydes 1a,b showing a reactivity markedly influenced by the presence of water. The chiral glycidic backbone showed a slight but significant influence on the overall stereochemical outcome only when present in α‐position of the aldehyde. The absolute stereochemistry of the products was studied by electronic circular dichroism (ECD) spectra and compared with theoretical calculations. ECD analysis easily provides the absolute configuration of 1,2‐dihydroquinoline derivatives such as quinoline‐1(2H)‐carboxylates.