Vicinal coupling constants table

Many vicinal coupling constants (Table 8) are known, with different combinations of intervening atoms. In most cases the V( Sn,X) data are dependent on the respective dihedral angles and follow a Karplus-type relationship. The sign of V( Sn, H) and V( Sn, 2Q) negative and the magnitudes of V( Sn, H) and are usually greater than... 

TABLE 2.5. Vicinal Coupling Constants as a Function of Multiple Electronegative Substituents... 

Corsaro and co-workers studied the reaction of pyridazine, pyrimidine, and pyrazine with benzonitrile oxide and utilized H NMR spectral analysis to determine the exact structure of all the cyclized products obtained from these reactions <1996T6421>, the results of which are outlined in Table 1. The structure of the bis-adduct product 21 of reaction of pyridazine with benzonitrile oxide was determined from the chemical shifts of the 4- and 5-isoxazolinic protons at 3.76 and 4.78 ppm and coupled with the azomethine H at 6.85 ppm and with the 5-oxadiazolinic H at 5.07 ppm, respectively. They determined that the bis-adduct possessed /(-stereochemistry as a result of the large vicinal coupling constant (9.1 Hz). Similarly, the relative stereochemistry of the bis-adducts of the pyrimidine products 22-25 and pyrazine products 26, 27 was determined from the vicinal coupling constants. 

The 1H NMR spectrum of the four central protons of 48h was analyzed as an AA BB spin system. The coupling constants between II7/II7 and the deuterium nuclei on C6/C6 (ca 2 Hz) were taken into account as first-order perturbations. In all cases coupling constants over four (—0.58 to —0.87 Hz) and five (+0.32 to +0.69 Hz) bonds were also considered in performing the spectral analysis. Chemical shifts and vicinal coupling constants for 48a-f are reported in Table 14. 

A linear relationship between the ratio of the vicinal coupling constants and the resonance energy has been found, indicating that the electron delocalization of the indole 7r-system is more pronounced than that of isoindole and indolizine respectively (77TL535) (see Table 5 and Section 3.08.2.1 for theoretical considerations). 

Table 5 Ratio of Vicinal Coupling Constants and REPE Values of Nitrogen Heterocycles <77TL535) Compound /ab/- bc REPE Compound Ab//bc REPE...

Unlike [3.3.3]cyclazine (230), the cyclopentacyclazines (285) are unequivocally diatropic compounds (see Table 11). The five-membered ring double bonds have been shown to be delocalized on the basis of the vicinal coupling constants of the corresponding protons. These observations suggest that the cyclazines (285) may be considered as [13]annulene anions weakly coupled to a localized azomethinium cross-link represented as in (286). The mutual interaction between the two closed shell systems may be small since the bonding MOs of the peripheral [13]annulene can interact only weakly with the antibonding MO of the azomethine group by reason of symmetry. 

Snider and Duvall published the first geminal coupling constant in the case of the 1,2-oxazetidine carboxylate derivative 28a (Table 1 Figure 9) and confirmed the formation of the four-membered ring by means of heteronuclear multiple bond correlations (HMBC) (Table 1) <2003TL3067>. Vicinal coupling constant values 37h-h are now available in the... 

Reports that have improved the data base (see Tables VI-XI), or utilized a new NMR sequence for accurate measurements of vicinal coupling constants for mono-and oligosaccharides, have been published during the past decade.60 62,136 137 139 143-... 

Analysis of the vicinal coupling constants in a selection of 2,5,6-trisubstituted dihydrothiopyran-4-ones <2000SL1804, 2005JOC10886, 2005RJ0283> leads to the inference that the 2-substituent preferentially occupies a pseudo-equatorial site (Table 4). 

TABLE 9.4 Typical Heteronuclear Vicinal Coupling Constants"... 

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