Conformational analysis of 2,4,5-trimethyl-1,3,2-dioxaborinane individual stereoisomers |
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Authors: | O. Yu. Valiakhmetova S. A. Bochkor V. V. Kuznetsov |
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Affiliation: | (1) Ufa State Petroleum Technological University, ul. Kosmonavtov 1, Ufa, 450062, Russia;(2) Institute of Molecular and Crystal Physics, Ufa Scientific Centre, Russian Academy of Sciences, pr. Octyabrya 151, Ufa, 450075, Russia |
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Abstract: | The study of the conformational isomerization of cis- and trans-isomers of 2,4,5-trimethyl-1,3-dioxaborinane I by means of RHF//STO-3G, 3-21G and 6-31G(d) quantumchemical methods led to the conclusion that its route includes equilibrium between sofa conformers with a different steric orientation of substituents at the C-4 and C-5 ring atoms. These conformers are interconverted through the maxima, the conformations of equatorial and axial 2,5-twist-forms. A comparison between experimental 1H NMR and theoretical vicinal spin-spin coupling constants was used to determine the quantitative conformational composition of stereoisomers and a value of ΔG 0 for conformational equilibrium. |
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