A practical synthesis of substituted 2,6-diaminopyridines via microwave-assisted copper-catalyzed amination of halopyridines

A microwave assisted copper-catalyzed amination protocol is reported utilizing a series of 2,6-dihalo- and 2-amino-6-halo pyridine precursors. Using this procedure, selective substitution of one or two halogens by aryl or alkylamines was achieved within 2–6 h with temperatures between 80 and 225 °C affording 2,6-diaminopyridines in good to excellent isolated yields. The reaction allows easy variation between educts and different N -substitutions. The target compounds are valuable precursors for the synthesis of bis-phosphorylated 2,6-diaminopyridines which are used as PNP pincer ligands in transition metal complexes.