Metal salt-catalyzed diazocoupling of 3-substituted-1H-pyrazol-2-in-5-ones in aqueous medium

Organic synthesis in water belongs to green chemistry. AlCl3-catalyzed diazocoupling of 3-substituted-1H-pyrazol-2-in-5-ones (1) in water with different aryldiazonium salts yielded (5-hydroxy-3-substituted-1H-pyrazol-4-yl)-azobenzene derivatives (2) as colored products with high yields.