A Classical but Short One-Pot Synthesis of Pyrazoles

Significance

Pyrazoles are a bread-and-butter class of heterocycles of the pharmaceutical industry (see book below). The reported method uses a conventional synthesis of 1,3-dicarbonyl derivatives, easily accessible ketones and acid chlorides, followed by hyrazinolysis, to deliver a range of pyrazoles in moderate to good yields. A broad scope, especially with respect to aryl substituents R¹ and R², was established.