Copper Salt Anchored on a Covalent Organic Framework as Heterogeneous Catalyst for Chan-Lam Coupling Reaction

A bipyridine containing covalent organic framework (COF), namely TpBpy, modified with copper ions was prepared. The obtained Cu @ TpBpy was used as a heterogeneous catalyst for C-N cross-coupling reaction of arylboronic acid with imidazole. To optimize the reaction conditions, we have screened various parameters such as the catalyst, solvent, base and reaction time. The experimental result showed that using the polar solvent MeOH gives the best yield with the promotion of base TEA, while Cu (OAc)(2)@ TpBpy is the optimal catalyst. The reaction achieves maximum yield of 66% after 4 h reaction catalyzed by Cu (OAc)(2)@ TpBpy with TEA in MeOH at 70 degrees C. In the optimal reaction conditions, arylboronic acid with different substituents were examined in the coupling reaction with imidazole, among them, 4-chlorophenylboric acid showed the best yield of 62%.