A base-promoted tandem cycloaddition/air oxidation reaction of electron-deficient conjugated enynes and hydrazines: synthesis of highly substituted pyrazoles.

Rapid access: A base-mediated cycloaddition/oxidation reaction of hydrazines and electron-deficient 1,3-conjugated enynes gives pyrazole derivatives, some of which are not easily accessible by other methods (see scheme). The reaction conditions are mild, thus enabling a variety of functional groups to be tolerated.