Pd-Catalyzed Highly Enantioselective Synthesis of Planar Chiral Ferrocenylpyridine Derivatives

A highly
efficient synthesis of planar chiral ferrocenylpyridine
derivatives via Pd-catalyzed intramolecular C–H arylation was
developed, and quantitative yields and excellent enantioselectivity
were obtained for a wide range of substrates. Notably, the catalyst
loading could be lowered to 0.2 mol %, which represents the highest
catalytic efficiency found for asymmetric C–H bond activation
(TON up to 495). These compounds could be easily transformed to pyridine N-oxides, displaying promising catalytic reactivity in the asymmetric opening of meso-epoxide. Moreover, computational investigations were
conducted to clarify the origin of the excellent enantioselectivity.
The compatibility of large-scale synthesis and low catalyst loading
should enhance the practicality of the synthetic application of the
current method.