Fluoroarenes with imidazoles

Particularly noteworthy is that fluoroarenes composed of o- or p-electron-withdrawing groups are also coupled with imidazole to afford the corresponding A(-arylated products in excellent yields (Table 12). Similar behavior has been observed for greater reactivity of C-F over C-Cl bonds for fluoroarenes in the Suzuki reactiOTi [45],... 

Kantam et al. (2007) studied the synthesis of A -arylheterocycles via the nanocrystalline CuO-catalyzed N-arylation of heterocycles with activated chloro- and fluoroarenes (Scheme 4.25). Various V-aryl/V-heteroaryl imidazoles, benzimidazoles, indoles, pyrroles, and pyrazoles were synthesized in moderate to excellent yields (76%-94% yield in 23 h). Much higher reactivity was observed when fluoroarenes were used (81%-94% yield in 3 h). The Cu catalyst could be recovered by centrifugation and reused for five runs without obvious loss of activity. Transmission electron microscopy (TEM) studies of both fresh and used catalysts revealed that the shape and size of the particles remained unchanged, supporting the assumption that the morphology of the Cu catalyst remained the same after recycling. However, one of the major shortcomings of the above methods developed by Hyeon and Kantam... 

Table 5 iV-Arylation of imidazole with chloro- and fluoroarenes ... 

---