Cobalt-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross-Coupling Enabled by Well-Defined Precatalysts with L,X-Type Ligands

Cobalt(II) halides in combination with phenoxyimine (FI) ligands generated efficient precatalysts in situ for the C(sp(2))-C(sp(3)) Suzuki-Miyaura cross-coupling between alkyl bromides and neopentylglycol (hetero)arylboronic esters. The protocol enabled efficient C-C bond formation with a host of nucleophiles and electrophiles (36 examples, 34-95%) with precatalyst loadings of 5 mol %. Studies with alkyl halide electrophiles that function as radical clocks support the intermediacy of alkyl radicals during the course of the catalytic reaction. The improved performance of the FI-cobalt catalyst was correlated with decreased lifetimes of cage-escaped radicals as compared to those of diamine-type ligands. Studies of the phenoxyimine-cobalt coordination chemistry validate the L,X interaction leading to the discovery of an optimal, well-defined, air-stable mono-FI-cobalt(II) precatalyst structure.

Automated summary

In this study, efficient precatalysts for the C(sp(2))-C(sp(3)) Suzuki-Miyaura cross-coupling reaction between alkyl bromides and neopentylglycol (hetero)arylboronic esters were generated in situ using Cobalt(II) halides in combination with phenoxyimine (FI) ligands. The protocol allowed for efficient C-C bond formation with various nucleophiles and electrophiles. The results also suggested that alkyl radicals play an important role in the catalytic reaction.