[2,3]-Wittig Rearrangement as a Formal Asymmetric Alkylation of α-Branched Ketones.

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.