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Iron(III)‐Catalyzed Cyclization of Alkynyl Aldehyde Acetals: Experimental and Computational Studies
Author(s) -
Xu Tongyu,
Yang Qin,
Li Dongpo,
Dong Jinhua,
Yu Zhengkun,
Li Yuxue
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000686
Subject(s) - chemistry , aldehyde , catalysis , medicinal chemistry , indene , halogenation , dichloromethane , intramolecular force , bromide , organic chemistry , solvent
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 CCl and CBr 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 α,β‐unsaturated enones and chlorinated indene derivatives. The present protocol has applications in the synthesis of carbo‐, oxa‐ and azacycles.