Efficient and recyclable Cu2(BDC)2(BPY)-catalyzed oxidative amidation of terminal alkynes: role of bipyridine ligand

Abstract

We have described an efficient method for oxidative cross coupling reactions between activated N–H amines and terminal alkynes using heterogeneous Cu₂(BDC)₂(BPY) as recyclable catalyst (BDC = benzene-1,4-dicarboxylate; BPY = 4,4′-bipyridine). The optimal conditions involved the use of inexpensive NaHCO₃ base and oxygen as terminal oxidant in toluene solvent at 80 °C. Reactions proceeds efficiently, and high selectivity with only trace amount of diynes as well as good yields were achieved in a short reaction time. The Cu₂(BDC)₂(BPY) exhibited excellent catalytic activity and selectivity as compared to other Cu-MOFs on a broad reaction scope. Interestingly, the presence of bipyridine ligand was shown to enhance the catalyst stability. Thus, the Cu₂(BDC)₂(BPY) could be facilely separated from the reaction mixture by simple centrifugation and could be reused several times with only a slight decrease in catalytic activity.