Pyrano[2,3-c]pyrazoles are a large class of heterocyclic compounds possessing many important biological activi...
Hongfei Zhang,Zhengqing Ye,Gang Zhao~* and Shizheng Zhu~* Key Laboratory of Synthetic Chemistry of Natural Substances and Key Laboratory of Organofluorine Chemistry,Shanghai Institute of Organic Chemistry,Chinese Academy of Science,345 Lingling Road,Shanghai 200032,China
Asymmetric epoxidation of α,β-unsaturated ketones has been extensively studied and several important procedures have been developed in the last decade. This review addresses the most significant advances in asymmetric epoxidation of α,β-unsaturated ketones using proline-derived α,α-diarylprolinols as catalysts. Special attention has been paid to the enantioselective epoxidation of chalcones, α,β-unsaturated trifluoromethyl, trichloromethyl ketones and β,γ-unsaturated α-keto esters based on the reseach of our group.
Enantioselective synthesis of functionalized fluorinated dihydropyrano[2,3-c]pyrazoles has been achieved via a diaminocyclohexane-thiourea catalyzed cascade Michael addition and Thorpe-Ziegler type cyciization in high yields(up to 98%) with moderate to good enantioselectivity(up to 90% ee).
