Stereoselective (exo-specific) synthesis, dynamic 1H NMR and quantum chemical conformational and configurational analysis of norbornene-aziridine-E-imidoyl system |
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Authors: | Hossein A Dabbagh Alireza Najafi Chermahini |
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Institution: | 1. Department of Chemistry, Isfahan University of Technology, 8415483111, Isfahan, Iran
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Abstract: | 3) were investigated. Aziridine nitrogen inversion gives rise to two sets of configurations where the N-substituent is Syn (S) or Anti (A) to C7 of the norbornyl ring. At lower temperature, the proton signals of aziridine exo-E-3 decoalesces to show two syn conformers and one anti conformer (exo-E-3 1 S ? $ \leftrightharpoons $ ?exo-E-3 2 S ? $ \leftrightharpoons $ ?exo-E-3 3 A ) with ratio of 60:20:20, respectively. Experimentally, the Gibbs free energy of activations ??G ? (kcal/mol) ?±?0.08] were calculated 11.96, 12.45 for 3 isomerizations. The standard Gibbs free energy (??G o kcal/mol) 0.174, 0, 0.174, and 0.298 at 213?K and energy minimum 6.64, 4.77 and 1.78 were calculated for 3 1S? $ \leftrightharpoons $ ?3 2S, 3 2S? $ \leftrightharpoons $ ?3 3 A , 3 1 S? $ \leftrightharpoons $ ?3 3 A isomerizations, respectively. The enthalpy (??H ?, kcal/mol) and entropy (??S ?, cal?mol?1?K?1) of activation for the nitrogen inversion of aziridine of 3 were calculated 11.2 and ?0.80, respectively. |
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