American Chemical Society
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Tf2O‑Mediated Cyclization of 7‑Enamides: Bioinspired Construction of Fused Eight-Membered Carbocyclic Enimines and Enones

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journal contribution
posted on 2021-11-09, 20:13 authored by Si-Jia Yu, Jian-Liang Ye, Ya-Cheng Hong, Pei-Qiang Huang
In this paper, we document the construction of functionalized and fused eight-membered carbocycles by the triflic anhydride-mediated cyclization of 7-enamides. Taking advantage of the high electrophilicity of the nitrilium ion intermediates, generated in situ from secondary N-(2,6-dimethyl)­anilides, the nonactivated, trisubstituted alkene–nitrilium cyclization reactions proceeded smoothly to afford nonconjugated β,γ-enimines (for fused 6/6/8 ring systems), conjugated α,β-enimines (for 6/5/8), or fused 5/8 ring systems in good yields. When the cyclization reactions were followed by one-pot acidic hydrolysis, the reaction led directly to the corresponding α,β-enones. For some substrates, the reaction afford an efficient access to pendent cyclic β,γ-enimines/enones.