Study on the iodine-catalyzed reaction of 3-aminopyrazine-2-carbohydrazide and 2-(arylethynyl)benzaldehydes

At 60 °C in DMSO, the iodine-catalyzed reaction of 3-aminopyrazine-2-carbohydrazide and 2-(arylethynyl)benzaldehydes led hydrazones. Increasing the reaction temperature to 100 °C, the amino and amido still indicated inactive, only the imine took part in the addition of acetylene bond to give 2-arylisoquinolines in high yields with the cleavage of N-N bond unexpectedly under metal-free conditions.