Cesium Carbonate Catalyzed Aza-Michael Addition of Pyrazole to α,β-Unsaturated Ketones

A Cs2CO3-catalyzed aza-Michael reaction of pyrazole to α,β-unsaturated ketones has been developed. With 5 mol% Cs2CO3 as catalyst, a series of β-N1-pyrazoly ketones were achieved in 86%~95% yields after 7~12 h in refluxing dioxane. Both aromatic and aliphatic α,β-unsaturated ketones as well as methacrylate and nitrostyrene are well tolerated. Broad scope of substrate and easily scale up make this protocol really practical. Furthermore, the product could be facilely transformed into corresponding γ-amino alcohol.