Asymmetric Alkene Boration and <i>Z</i> -Retentive Allylic Substitution Reactions under Cu/Pd Relay Catalysis

Cu/Pd-cocatalyzed cascade asymmetric alkene boration and Z -retentive allylic substitution reactions are described. Taking advantage of palladium catalysts that well tune the rates of both the π–σ–π isomerization process of the π-allyl-palladium species and nucleophilic substitution, either Z -retentive or Z -to- E allylic substitution reactions can be achieved, with alkyl copper nucleophiles generated in situ via Cu-catalyzed alkene boration. Chiral Z - and E -olefins containing an organoboronate functional group are afforded under Cu/Pd relay catalysis from the same starting materials. Both reactions proceed with high yields (up to 95%), excellent Z / E ratios (up to >19:1), and good enantioselectivity (up to 94% ee).