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Updated: Jul 3, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Development of highly regioselective amidyl radical cyclization based on lone pair-lone pair repulsion
Xinting Yuan1, Kun Liu, Chaozhong Li
1Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, People's Republic of China.
Abstract:
The substituent effect on the reactivity and regioselectivity of N-(4-pentenyl)amidyl radical cyclization was investigated. Exclusive 6- endo cyclization was observed for N-(4-pentenyl)amidyl radicals with internal vinylic heteroatom substitution (Cl, Br, I, OMe, SEt). The substituent on the carbonyl group also showed a significant influence on the reactivity of amidyl radicals, which increases in the order of Ph < Me < OEt. As a result, the photostimulated reactions of N-(4-halopent-4-enyl)amides and carbamates (X = Cl, Br, I) with DIB/I 2 or Pb(OAc) 4/I 2 led to the efficient and exclusive formation of the corresponding piperidines while those of N-(5-halopent-4-enyl)amides afforded the pyrrolidine products only. The halogen-substitution effect also allowed the 6- exo and 7- endo amidyl radical cyclization to proceed in a highly regioselective manner. The above experimental results, in combination with theoretical analyses, revealed that the lone pair-lone pair repulsion between the nitrogen radical and the vinylic heteroatom played an important role in controlling the regioselectivity of cyclization.
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