posted on 2021-11-09, 20:13authored bySi-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.