A new efficient synthesis of pyrazoles from hydrazonoyl halides and β-oxophosphonates

A new practical and efficient synthesis of 1,3,5-trisubstituted pyrazoles has been developed by reacting of hydrazonoyl halides with β-oxophosphonates under mild conditions in good yields with excellent regioselectivity. This process employs an addition–elimination sequence. Wide scope, functional group compatibility has been established.