Cross-Coupling Reaction of Alkenyl Sulfoximines and Alkenyl Aminosulfoxonium Salts by Dual Nickel Catalysis and Lewis Acid Promotion.

In this article we describe the cross-coupling reaction (CCR) of exocyclic, axially chiral and acyclic alkenyl (N-methyl)sulfoximines with alkyl- and arylzincs. The CCR generally requires dual Ni-catalysis and MgBr2 promo¬tion, which is effective in ether but not in THF. NMR spectroscopy revealed a complexation of alkenyl sulfoximines by MgB2 in ether. This suggests an acceleration of the oxidative addition through nucleofugal activation. The CCR proceeds with Ni(dppp)Cl2 as precatalyst and alkyl- and arylzincs with a high degree of stereoretention at both the C and S atom. While CCR of axially chiral alkenyl sulfoximines with Ni(PPh3)2Cl2 as precatalyst and ZnPh2 requires no salt promotion and is stereoretentive, that with Zn(CH2SiMe3)2 demands salt promo¬tion and is not stereoretentive. Ni-catalyzed and MgBr2 promoted CCR of (E)-configured acyclic alkenyl sulfoximines and aminosulfoxonium salts with ZnPh2 and Zn(CH2SiMe3)2 is stereoretentive with Ni(dppp)Cl2 and Ni(PPh3)2Cl2. Alkenyl (N-triflyl)sulfoximines engage in a stereoretentive CCR with Grignard reagents and Ni(PPh3)2Cl2. CCR of axially chiral α-methylated alkenyl sulfoximines afforded disubstituted axially chiral alkenes with high selectivity.