- Evolution of structure and reactivity in a series of iconic carbenes
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We present experimental activation parameters for the reactions of six carbenes (CCl2, CClF, CF2, ClCOMe, FCOMe, and (MeO) 2C) with six alkenes (tetramethylethylene, cyclohexene, 1-hexene, methyl acrylate, acrylonitrile, and α-chloroacrylonitrile). Activation energies range from -1 kcal/mol for the addition of CCl2 to tetramethylethylene to 11 kcal/mol for the addition of FCOMe to acrylonitrile. A generally satisfactory analysis of major trends in the evolution of carbenic structure and reactivity is afforded by qualitative applications of frontier molecular orbital theory, although the observed entropies of activation appear to fall in a counterintuitive pattern. An analysis of computed cyclopropanation transition state parameters reveals significant nucleophilic selectivity of (MeO)2C toward α-chloroacrylonitrile.
- Zhang, Min,Moss, Robert A.,Thompson, Jack,Krogh-Jespersen, Karsten
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- Phase-transfer catalysed (PTC) reactions of 1,1-dichloro-2-cyanocyclopropane with nucleophiles. Identification of intermediates
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An addition-elimination mechanism for PTC reactions of phenols with 1,1-dichloro-2-cyanocyclopropane (1) is supported by trapping of intermediate cyclopropenes 3 and 5. PTC reactions of 1 with a series of phenols 2a-d, thiophenol (2e), alcohols 2f,g and dithioles 11a,b led to formation of disubstituted cyanocyclopropanes 6a-d, 6e, 6f,g or spiroproducts 12a,b, respectively. Under acidic conditions or thermally, dialkoxycyclopropanes 6f,g or spirane 12a were transformed into alkyl 3-cyanopropionates 10f,g and ketene dithioacetal 13a.
- Jonczyk, Andrzej,Kocmierowski, Tomasz,Zdrojewski, Tadeusz
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p. 295 - 299
(2007/10/03)
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