Synthesis of Heteroarylated Pyridines via a Double C-H Bond Functionalization using Palladium-catalyzed 1,4-Migration Combined with Direct Arylation

The C-H bond functionalization of pyridyl C3-position of 4-arylpyridines using Pd 1,4-migration has been investigated. Under suitable reaction conditions, oxidative addition of 4-(2-bromoaryl)pyridines to palladium followed by a Pd 1,4-migration activates these pyridyl C3-positions. Next, the Pd-catalyzed coupling via C-H bond activation of the heteroarenes affords the C3-heteroarylated 4-arylpyridines. The new C-C bond created in this coupling reaction results from the functionalization of two C-H bonds. For this coupling reaction, a bromo-substituent on the aryl unit of 4-arylpyridines was employed as a traceless directing group. This heteroarylation method tolerates a range of substituents on the benzene ring as well as several heteroarenes. Moreover, from 3-arylpyridines, C2- or C4-functionalization of the pyridine ring also proved possible. In addition, this procedure uses an air-stable catalyst and an inexpensive base. Bromo-substituent as a traceless directing group was successfully employed to access heteroarylated pyridine derivatives via Pd 1,4-migration combined with direct heteroarylation. The new C-C bond created during this coupling reaction results from the functionalization of two C-H bonds.image