Efficient Synthesis of Pyrazoles by pH Dependent Isomerization of Enaminodiones

A chromone-based Michael reaction using water as solvent and nucleophile was firstly developed to derivatize chromone via a multicomponent reaction (MCR) cascade sequence in absence of metal catalyst. A series of versatile enaminodiones was synthesized and further successfully transferred into two different pyrazoles with the same starting material under facile and mild condition by a pH control of the preferred isomer.