Direct Synthesis of 4-Organylselanylpyrazoles by Copper-Catalyzed One-Pot Cyclocondensation and C-H Bond Selenylation Reactions

We describe herein an efficient protocol to synthesize selanyl-substituted pyrazoles by cyclocondensation and copper-catalyzed direct C-H bond selenation reactions. The products were obtained in moderate to excellent yields by the onepot 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.