Highly Regioselective One‐Pot, Three‐Component Synthesis of 1‐Aryl‐3,4‐Substituted/Annulated‐5‐(Cycloamino)/(Alkylamino)pyrazoles from β‐Oxodithioesters

Abstract An efficient, highly regioselective protocol for the synthesis of the title compounds is reported. The reaction involves a one‐pot, three‐component cyclocondensation of β‐oxodithioester, amine, and hydrazine in ethanol at reflux in the presence of a catalytic amount of acetic acid. Densely functionalized pyrazoles were constructed through the cyclization of a thioamide intermediate generated in situ from the β‐oxodithioester. This method allows a rapid and general synthesis of previously inaccessible pyrazoles and synthetically demanding pyrazoles containing fused rings.