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,
α-pinene, and 2,3-dimethyl-2-butene. Notably, these hydroboration
reactions proceed with high activity and anti-Markovnikov selectivity
in neat substrates at 23 °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.