Bis(imino)pyridine Cobalt-Catalyzed Alkene Isomerization-Hydroboration: A Strategy for Remote Hydrofunctionalization with Terminal Selectivity

Bis(imino)pyridine cobalt methyl complexes are active for the catalytic hydroboration of terminal, geminal, disubstituted internal, tri- and tetrasubstituted alkenes using pinacolborane (HBPin). The most active cobalt catalyst was obtained by introducing a pyrrolidinyl substituent into the 4-position of the bis(imino)pyridine chelate, enabling the facile hydroboration of sterically hindered substrates such as 1-methylcyclohexene, alpha-pinene, and 2,3-dimethy1-2-butene. Notably, these hydroboration reactions proceed with high activity and anti-Markovnikov selectivity in neat substrates at 23 degrees C. With internal olefins, the cobalt catalyst places the boron substituent exclusively at the terminal positions of an alkyl chain, providing a convenient method for hydrofunctionalization of remote C-H bonds.