Palladium-Catalyzed Direct Ortho Aroylation of 2‑Phenoxypyridines with Aldehydes and Catalytic Mechanism Investigation

A direct
ortho aroylation of 2-phenoxypyridines with aldehydes leading to aryl
ketones by the use of palladium­(II) acetate, tert-butyl hydroperoxide, and chlorobenzene as the catalyst, oxidant,
and solvent, respectively, is presented. Intra- and intermolecular
kinetic isotope effects, radical trapping, and controlled experiments
were carried out to support the proposed catalytic mechanism for the
reaction. Syntheses of (2-hydroxyphenyl)­(phenyl)­methanones and 1-hydroxy-9H-fluoren-9-ones directed from ortho-aroylated 2-phenoxypyridines
were demonstrated.