Guided selectivity Carbon–hydrogen bond activation

the figure above demonstrates use of pyridine directing group activate selectively c-h bond form c-halogen bond. pyridine derivatives commonly used ortho-selective c-h functionalization. such reactions use metals palladium catalyze sp c-h activation. similar system uses pyridine acetoxylate c-h bond, forming c-oac bond, instead of c-x halogen bond.

the mechanism pyridine based pd-catalyzed c-h activation reactions involves catalytic cycle in ligand directs molecule interact pd form metallacycle intermediate. intermediate oxidized form pd species, followed reductive elimination form c-o bond , release product.

see meta-selective c-h functionalization more examples of directed c-h activation.