Regioselective Synthesis of 1,3,4,5-Tetrasubstituted Pyrazoles from α-Alkenyl-α,β-Enones Derived from Morita-Baylis-Hillman Adducts

Convenient synthetic method for 4-arylethylpyrazoles and 4-styrylpyrazoles was developed using α-alkenyl-α,β-enones readily accessed from the Morita-Baylis-Hillman reaction. For the synthesis of 4-arylethyl-pyrazole, the reactions with arylhydrazines needed to be carried out in o-dichlorobenzene under N2 balloon atmosphere. On the other hand, 4-styrylpyrazoles required the reactions in ethanol under O2 balloon atmosphere