期刊
JOURNAL OF FLUORINE CHEMISTRY
卷 132, 期 3, 页码 175-180出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jfluchem.2010.12.013
关键词
Indolizines; Pyridines; Carbenes; Ylides; Dipolar cycloaddition
资金
- Federal Targeted Programme Scientific and Scientific-Pedagogical Personnel of the Innovative Russia in 2009-2013 [16.740.11.0442]
- Russian Foundation for Basic Research [11-03-00186]
According to OFF B3LYP/6-31G(+) calculations the reaction of difluorocarbene with pyridines proceeds reversibly with the formation of thermodynamically unstable intermediates, difluoro-substituted pyridinium ylides, which dissociate to carbene and pyridine with low activation barrier. The equilibrium constant of the reaction increases with increasing electron-withdrawing ability of substituents in the pyridine ring. Difluoroylides were generated from 4-cyano, 4-benzoyl- and 4-ethoxycarbonyl-substituted pyridines under difluorocarbene generation conditions (CF2Br2/Pb/Bu4NBr/CH2Cl2/ultrasound) and trapped with dimethyl maleate or fumaronitrile. 3-Fluoroindolizines were isolated as final products of the reaction which involves dehydrofluorination of the primary cycloadducts followed by dehydrogenation by active MnO2. (C) 2010 Elsevier B.V. All rights reserved.
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