Features of the Diels-Alder reaction between 9,10-diphenylanthracene and 4-phenyl-1,2,4-triazoline-3,5-dione |
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Authors: | V D Kiselev D A Kornilov E A Kashaeva L N Potapova D B Krivolapov I A Litvinov A I Konovalov |
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Institution: | 1. Butlerov Institute of Chemistry, Kazan Federal University, Kazan, 420008, Russia 2. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, Kazan, 420088, Russia
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Abstract: | The Diels-Alder reaction between substituted anthracenes 1a?1j and 4-phenyl-1,2,4-triazoline-3,5 (2) is studied. In all cases except one, the reaction proceeds on the most active 9,10-atoms of substituted anthracenes. The orthogonality of the two phenyl groups at the 9,10-position of diene 1a is found to shield 9,10-reactive centers. No dienophiles with C=C bonds are shown to participate in the Diels-Alder reaction with 1a; however, the reaction 1a + 2 proceeds with the very active dienophile 2,4-phenyl-1,2,4-triazoline-3,5-dione. It is shown that attachment occurs on the less active but sterically accessible 1,4-reactive center of diene 1a. The structure of adduct 3a is proved by 1H and 13C NMR spectroscopy and X-ray diffraction analysis. The following parameters are obtained for reaction 1a + 2 ? 3a in toluene at 25°C: K eq = 2120 M?1, ΔH f ≠ = 58.6 kJ/mol, ΔS f ≠ = ?97 J/(mol K), ΔV f ≠ = ?17.2 cm3/mol, ΔH b ≠ = 108.8 kJ/mol, ΔS b ≠ = 7.3 J/(mol K), ΔV b ≠ = ?0.8 cm3/mol, ΔH r-n = ?50.2 kJ/mol, ΔS r-n = ?104.3 J/(mol K), ΔV r-n = ?15.6 cm3/mol. It is concluded that the values of equilibrium constants of the reactions 1a?1j + 2 ? 3a?3j vary within 4 × 101?1011 M?1. |
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