Mechanistic Origins of Regioselectivity in Cobalt-Catalyzed C(sp²)-H Borylation of Benzoate Esters and Arylboronate Esters.

ABSTRACT: Synthetic and mechanistic investigations into the C(sp²)-H borylation of various electronically diverse arenes catalyzed by bis(phosphine)pyridine (^iPrPNP) cobalt complexes are reported. Borylation of various benzoate esters and arylboronate esters gave remarkably high selectivities for the position para to the functional group; in both cases, this regioselectivity was found to override the ortho to fluorine regioselectivity previously reported for (^iPrPNP)Co borylation catalysts which arises from thermodynamic control of C(sp²)-H oxidative addition. Mechanistic studies support two distinct pathways that result in para-to-ester and para-to-boronate ester regioselectivity by thermodynamic and kinetic control, respectively, of C(sp²)-H oxidative addition. Borylation of a particularly electron-deficient fluorinated arylboronate ester resulted in acceleration of C(sp²)-H oxidative addition and concomitant inversion of regioselectivity, demonstrating that subtle changes in the relative rates of individual steps of the catalytic cycle can enable unique and switchable site selectivities.

SUBMITTER: Pabst TP 

PROVIDER: S-EPMC7945986 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature