Enantioselective Organocatalytic Diels–Alder Trapping of Photochemically Generated Hydroxy‐o‐Quinodimethanes
نویسندگان
چکیده
The photoenolization/Diels-Alder strategy offers straightforward access to synthetically valuable benzannulated carbocyclic products. This historical light-triggered process has never before succumbed to efforts to develop an enantioselective catalytic approach. Herein, we demonstrate how asymmetric organocatalysis provides simple yet effective catalytic tools to intercept photochemically generated hydroxy-o-quinodimethanes with high stereoselectivity. We used a chiral organic catalyst, derived from natural cinchona alkaloids, to activate maleimides toward highly stereoselective Diels-Alder reactions. An unconventional mechanism of stereocontrol is operative, wherein the organocatalyst is actively involved in both the photochemical pathway, by leveraging the formation of the reactive photoenol, and the stereoselectivity-defining event.
منابع مشابه
Forging Fluorine‐Containing Quaternary Stereocenters by a Light‐Driven Organocatalytic Aldol Desymmetrization Process
Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon-fluorine unit. The ...
متن کاملThe first organocatalytic enantioselective inverse-electron-demand hetero-Diels-Alder reaction.
متن کامل
Enantioselective organocatalytic intramolecular Diels-Alder reactions. The asymmetric synthesis of solanapyrone D.
The first direct enantioselective organocatalytic intramolecular Diels-Alder reaction has been accomplished. The use of iminium catalysis has provided a new catalytic strategy for the enantioselective [4 + 2] cycloisomerization of a wide variety of tethered diene-enal systems. The use of imidazolidinones 1 and 2 as the asymmetric catalysts has been found to mediate the enantioselective construc...
متن کاملHighly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions
After prosperous domino reactions towards benzopyrans, the products were used as the starting material in Lewis acid catalyzed and organocatalytic Diels-Alder reactions to build up a tricyclic system. Herein, an asymmetric induction up to 96% enantiomeric excess was obtained by the use of imidazolidinone catalysts. This approach can be utilized to construct the tricyclic system in numerous natu...
متن کاملEnantioselective construction of lactone[2,3-b]piperidine skeletons via organocatalytic tandem reactions.
A highly enantioselective construction of delta- and gamma-lactone[2,3-b]piperidine skeletons was accomplished by tandem aza-Diels-Alder reaction-hemiacetal formation-oxidation from N-Tos-1-aza-1,3-butadienes and aliphatic dialdehydes.
متن کامل