Simple NMR method for assigning relative stereochemistry of bridged bicyclo[3.n.1]-2-enes and tricyclo[7.n.1.0]-2-enes |
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Authors: | Olga V. Patrusheva German A. Verbitskii Vladimir I. Vysotskii |
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Affiliation: | Department of Chemistry, Far Eastern National University, Octyabrskaya St. 27, Vladivostok 690600, Russian Federation |
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Abstract: | The stereochemistry of syn and anti-forms of bridged bicyclo[3.n.1]-2-ene, tricyclo[7.n.1.0]-2-ene (n=1-3) and bicyclo[4.3.1]dec-7-ene derivatives can be assigned from the 13C chemical shift difference of the double bond. Both syn-9-R-bicyclo[3.3.1]non-2-enes and syn-13-R-tricyclo[7.3.1.02,7]tridec-2(7)-enes have a large shielding difference between sp2 carbons, while the corresponding anti-forms have a smaller one. In contrast, 8-R-bicyclo[3.2.1]oct-2-enes and 12-R-tricyclo[7.2.1.02,7]dodec-2(7)-enes have an inverse correlation. The reason of this specificity is the influence of the γ-gauche effect on the chemical shift of C(2) atom. The GIAO theory has been applied to investigate the 13C chemical shifts. The conformational equilibrium in the formamide group of 13-formylamino-tricyclo[7.3.1.02,7]tridec-2(7)-enes has been studied. |
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Keywords: | 13C NMR GIAO-SCF Gauche effect Bicyclo[3.2.1]octane Bicyclo[3.3.1]nonane Tricyclo[7.2.1.02,7]dodecane Tricyclo[7.3.1.02,7]tridecane Bicyclo[3.1.1]heptane Bicyclo[4.3.1]decane |
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