Pd-Catalyzed Asymmetric Allylic Substitution Cascade of Substituted 4-Hydroxy-2H-pyrones with meso-Allyl Dicarbonates
Yan Zheng1, Siqi Dong1, Kai Xu2
1Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P. R. China.
Abstract:
An efficient Pd-catalyzed asymmetric allylic substitution cascade of 4-hydroxy-2H-pyrones with meso-allyl dicarbonates has been developed for the synthesis of kinetic chiral tetrahydro-1H-pyrano[4,3-b]benzofuran-1-one products in ≤87% yield and ≤99% ee. The protocol was achieved via a temperature-controlled kinetic control process, which has been illustrated by means of the experimental results and control experiments. The reaction could be conducted on a gram scale, and the resulting product allows for several transformations.
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Preparation of Alcohols via Substitution Reactions
Alcohols can be synthesized from alkyl halides via nucleophilic substitution reactions. The highly polar carbon-halogen bond in the substrate makes halide a good leaving group. The hydroxide ion or water can act as a nucleophile to take the place of halide and form an alcohol. The substitution reactions occur via two different reaction pathways, SN1 or SN2, depending on the nature of carbon attached to the halide.
Primary alcohols are synthesized from primary alkyl halides, and the...

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