A highly enantioselective organocatalytic [2,3]-rearrangement of oxindole derivatives is presented. The reaction was catalyzed by squaramide, and this provides access to 3-hydroxy 3-substituted oxindoles in high enantiomeric purities.
Two different approaches for asymmetric catalytic Wittig [2,3]-rearrangement were developed. Allyloxymalonate derivatives were converted into homoallyl alcohols via organocatalytic or Ca-catalyzed pathways in moderate to high enantioselectivities.
The enantioselective [2,3]-Wittig
rearrangement of cinnamyloxycyclopentanone
derivatives was performed in the presence of a Cinchona-based primary amine. The described method provides synthetically
valuable α-hydroxy ketones with quaternary stereogenic centers
in excellent enantiomeric purities. Relying on the X-ray crystal structure
of the product and the DFT calculations, we propose that the rearrangement
is promoted by an intramolecular hydrogen bond between the substrate
and the catalyst.
Asymmetric rearrangement reactions are one of the perfect tools for the construction of new carbon-carbon bonds in an enantioselective manner. The enantioselective [2,3]-Wittig rearrangement of cinnamyloxycyclohexanone derivatives, catalyzed by a commercially available primary amine, provided α-hydroxy ketones with high diastereo-and enantioselectivity. A new and straightforward procedure for the synthesis of cinnamyloxycyclohexanone derivatives was developed.
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