Copper-Mediated Diamination of Arylboronic Acids for the Synthesis of 2-Aryl Benzimidazoles Using Trimethylsilyl Azide as the Amino Sources with Aldehydes

A direct and versatile copper-mediated three-component reaction of arylboronic acids, trimethylsilyl azide and aldehydes for the synthesis of benzimidazoles is reported. The reaction is well tolerated by a wide range of substituted aromatic aldehydes and aromatic boronic acids to produce the corresponding benzimidazoles in moderate to high yields. Mechanism investigations demonstrated that copper-promoted Chan-Evans-Lam coupling, C-H amination, and oxidative cycloaddition are involved in the tandem processes.