Direct Synthesis of 4‐Organylselanylpyrazoles by Copper‐ Catalyzed One‐Pot Cyclocondensation and CH Bond Selenylation Reactions

We describe herein an efficient protocol to synthesize selanyl-substituted pyrazoles by cyclocondensation and copper-catalyzed direct CH bond selenation reactions. The products were obtained in moderate to excellent yields by the one-pot multicomponent reactions of hydrazines, 1,3-diketones and diorganyl diselenides, using catalytic amounts of copper bromide and bipyridine. These reactions tolerated a range of substituents in the starting materials and proved to be an efficient methodology for combinatorial synthesis of new selenium-containing pyrazoles with potential applications in biological studies.