Highly reusable support-free copper(II) complex of para-hydroxy-substituted salen: Novel, efficient and versatile catalyst for C-N bond forming reactions

An air-stable, highly active and versatile method for C-N bond forming reactions is reported. Under mild conditions using a highly reusable support-free Cu(II)-salen complex, structurally diverse N-aryl-substituted compounds were obtained via direct C-N bond forming reaction of HN-heterocycles with aryl iodides or three-component C-N bond forming reaction of 2-bromobenzaldehyde, aniline derivatives and sodium azide in good to excellent yields. C-N bond forming reaction for benzimidazole derivatives was also performed in the presence of the catalyst under ambient conditions. A series of hybrid benzimidazoles bearing morpholine, tetrazole and quinoxaline backbones were produced using this method. All reactions were performed in short times under air. The Cu(II) catalyst could be reused up to eight times in the direct cross-coupling reaction of 9H-carbazole with iodobenzene without any decrease in its catalytic activity.