Magnesium-Catalyzed Hydroboration of Pyridines

Reaction of catalytic quantities of a β-diketiminato n-butylmagnesium complex with pinacol–borane in the presence of pyridine derivatives provides facile access to borylated dihydropyridines. The reaction is applicable to a wide range of monocyclic and fused-ring pyridine derivatives and catalytic turnover is proposed to occur through a well-defined sequence of Mg–H/pyridine dearomatization and Mg–N/B–H sigma bond metathesis steps.