Development of Chemo‐ and Enantioselective Palladium‐Catalyzed Decarboxylative Asymmetric Allylic Alkylation of α‐Nitroesters

We describe the development of a Pd‐catalyzed decarboxylative asymmetric allylic alkylation of α‐nitro allyl esters to afford acyclic tetrasubstituted nitroalkanes. Optimization of the reaction parameters revealed unique ligand and solvent combinations crucial for achieving chemo‐ and enantioselective C‐alkylation of electronically challenging benzylic nitronates and sterically encumbered 2‐allyl esters. Substrates were efficiently accessed in a combinatorial fashion by a cross‐Claisen/ α‐arylation sequence. The method provides functional group orthogonality that complements nucleophilic imine allylation strategies for α‐tertiary amine synthesis.     

Regio‐ and Enantioselective Preparation of Chiral Allylic Sulfones Featuring Elusive Quaternary Stereocenters

We describe here the first general asymmetric synthesis of sterically encumbered α,α‐disubstituted allylic sulfones via Pd‐catalyzed allylic substitution. The design and application of a new and highly efficient phosphoramidite ligand ( L10 ) proved to be crucial, and a wide variety of challenging allylic sulfones featuring quaternary stereocenters could be obtained in good yields and with good to excellent levels of regio‐ and enantioselectivities under attractive process conditions. The developed methodology employs easily accessible chemical feedstock including racemic allylic precursors and sodium sulfinates. The utility of the method is further demonstrated by the synthesis of the sesquiterpene (?)‐Agelasidine A.