Cu(II)‐Catalyzed Asymmetric All‐Carbon‐Based Diels–Alder Reaction of Conjugated Vinyl Azides: Synthesis of Chiral Fused and Spiro Cyclohexenes
Ning Li, Wen-Jing Li, Xin-Yi Chen, Hai-Xia Wang, Mingsheng Xie, Haiming GuoA highly diastereo‐ and enantioselective all‐carbon‐based Diels–Alder reaction of conjugated vinyl azides with β,γ‐unsaturated α‐keto esters and amides was achieved. With C1‐symmetric imidazolidine‐pyrroloimidazolone pyridine as the tridentate ligand and Cu(OTf)2 as the Lewis acid, diverse chiral fused and spiro cyclohexenes with an azido group containing three continuous stereogenic centers were obtained in good yields (up to 92% yield), excellent diastereoselectivities (up to >20:1 dr) and excellent enantioselectivities (up to 99% ee). The developed method was applied to the derivatization of complex molecules including buspirone‐derived ketoamide. The functional group vinyl azide was capable of participating in a subsequent click reaction.