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Updated: Jun 11, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Iron(III)-catalyzed cyclization of alkynyl aldehyde acetals: experimental and computational studies
Tongyu Xu1, Qin Yang, Dongpo Li
1Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China.
Abstract:
FeCl(3)6 H(2)O- and FeBr(3)-catalyzed Prins cyclization/halogenation of alkynyl aldehyde acetals has been realized with acetyl chloride or bromide as halogen source in dichloromethane to afford 2-(1-halobenzylidene or alkylidene)-substituted five-membered carbo- and heterocycles, and thus provides an alternative route for vinylic C-Cl and C-Br bond formation. Five- to eight-membered cyclic enones were efficiently synthesized by FeCl(3)6.H(2)O-catalyzed intramolecular cyclization of alkynyl aldehyde acetals in acetone under mild conditions. An oxocarbonium species generated in situ is proposed to initiate the reaction, and the target products are formed via vinylogous carbenium cation and oxete intermediates according to DFT calculations. Intermolecular reactions of alkynes and aldehyde acetals were also investigated with 20-40 mol% FeCl(3)6.H(2)O catalyst, and produced alpha,beta-unsaturated enones and chlorinated indene derivatives. The present protocol has applications in the synthesis of carbo-, oxa- and azacycles.
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