Nickel-Catalyzed Anionic Cross-Coupling Reaction of Lithium Sulfonimidoyl Alkylidene Carbenoids With Organolithiums

Abstract

The mechanistic platform for a novel nickel(0)-catalyzed anionic cross-coupling reaction (ACCR) of lithium sulfonimidoyl alkylidene carbenoids (metalloalkenyl sulfoximines) with organometallic reagents is reported herein, affording substituted alkenylmetals and lithium sulfinamides. The Ni-0-catalyzed ACCR of three different types of metalloalkenyl sulfoximines, including acyclic, axially chiral and exocyclic derivatives, with sp(2) organolithiums and sp(2) and sp(3) Grignard reagents has been studied. The ACCR of metalloalkenyl sulfoximines with PhLi in the presence of the Ni-0-catalyst and precatalyst Ni(PPh3)(2)Cl-2 afforded alkenyllithiums, under inversion of configuration at the C atom and complete retention at the S atom. In a combination of experimental and DFT studies, we propose a catalytic cycle of the Ni-0-catalyzed ACCR of lithioalkenyl sulfoximines. Computational studies reveal two distinctive pathways of the ACCR, depending on whether a phosphine or 1,5-cyclooctadiene (COD) is the ligand of the Ni atom. They rectify the underlying importance of forming the key Ni-0-vinylidene intermediate through an indispensable electron-rich Ni-0-center coordinated by phosphine ligands. Fundamentally, we present a mechanistic study in controlling the diastereoselectivity of the alkenyllithium formation via the key lithium sulfinamide coordinated Ni-0-vinylidene complex, which consequently avoids an unselective formation of an alkylidene carbene Ni-complex and ultimately racemic alkenyllithium.