Asymmetric Diels–Alder and Inverse-Electron-Demand Hetero-Diels–Alder Reactions of β,γ-Unsaturated α-Ketoesters with Cyclopentadiene Catalyzed by N,N′-Dioxide Copper(II) Complex

✍ Scribed by Yin Zhu; Xiaohong Chen; Mingsheng Xie; Shunxi Dong; Zhen Qiao; Dr. Lili Lin; Dr. Xiaohua Liu; Prof. Dr. Xiaoming Feng

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 328 KB
• Volume: 16
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.201001365

✦ Synopsis

Abstract

Highly enantioselective Diels–Alder (DA) and inverse‐electron‐demand hetero‐Diels–Alder (HDA) reactions of β,γ‐unsaturated α‐ketoesters with cyclopentadiene catalyzed by chiral N,N′‐dioxide–Cu(OTf)~2~ (Tf=triflate) complexes have been developed. Quantitative conversion of β,γ‐unsaturated α‐ketoesters and excellent diastereoselectivities (up to 99:1) and enantioselectivities (up to >99 % ee) were observed for a broad range of substrates. Both aromatic and aliphatic β,γ‐unsaturated α‐ketoesters were found to be suitable substrates for the reactions. Moreover, the chemoselectivity of the DA and HDA adducts were improved by regulating the reaction temperature. Good to high chemoselectivity (up to 94 %) of the DA adducts were obtained at room temperature, and moderate chemoselectivity (up to 65 %) of the HDA adducts were achieved at low temperature. The reaction also featured mild reaction conditions, a simple procedure, and remarkably low catalyst loading (0.1–1.5 mol %). A strong positive nonlinear effect was observed.