Cu/Pd-catalyzed alkyne
allylboration with racemic allylic carbonates
proceeds with total inversion of configuration. Preliminary studies
show that this synergistic catalysis can be used to perform a dynamic
asymmetric allylic alkenylation that provides enantioenriched carboboration
products.
Allylic gem‐dichlorides are shown to be efficient substrates for catalytic asymmetric allylboration of alkynes. The method employs a chiral NHC−Cu catalyst capable of generating in a single step chiral skipped dienes bearing a Z‐alkenyl chloride, a trisubstituted E‐alkenyl boronate and a bis‐allylic stereocenter with excellent levels of chemo‐, regio‐ enantio‐ and diastereoselectivity. This high degree of functionalization makes these products versatile building blocks as illustrated with the synthesis of several optically active compounds. DFT calculations support the key presence of a metal cation bridge ligand–substrate interaction and account for the stereoselectivity outcome.
A copper-catalyzed protoboration of borylated dendralenes is reported. The method employs an NHC-Cu catalyst and provides access to 1,4-addition products with excellent levels of chemo-, regio- and stereoselectivity. The resulting...
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