Ph. D. THESIS 2009
Ph. D. THESIS 2009
Ph. D. THESIS 2009
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Figure 3. The 1 H-NMR spectrum (CDCl 3, 500 MHz, fragment) of compound 2<br />
Thus, the 2H multiplet at resonance δ= 2.20 ppm(J=3.0 Hz) is ascribed to the<br />
protons located at 9-C, whereas the most deshielded 2H multiplet at δ= 2.86<br />
ppm (J=3.0 Hz) corresponds to the bridgehead protons belonging to 1-C/5-C.<br />
The bridge protons 9-H2 are splitted by the 1-H and 5-H protons due to a vicinal<br />
coupling. The broadening of these peaks suggests an additional weak coupling<br />
in W path between the equatorial protons at 2,4,6,8-C and those at 9-C, whereas<br />
the protons 1-H and 5-H are coupled with the axial protons at 2,4,6,8-C. These<br />
two triplets suggest also the equivalence of the bridgehead protons and the C2<br />
symmetry of the molecule.<br />
The 4H doublet at δ= 2.41 ppm is attributed to the equatorial protons at<br />
2,4,6,8-C , which are connected with the corresponding axial protons through<br />
an AB geminal coupling (J=15.5 Hz). The lack of supplementary splitting of<br />
the doublet indicates that an equatorial-equatorial vicinal coupling with the<br />
bridgehead protons at 1-C/5-C is not possible because a dihedral angle close to<br />
90. The axial protons at 2,4,6,8-C are more deshielded and appear as a<br />
doublet of doublets at δ= 2.58 ppm due to the both splitting originating from<br />
the AB geminal coupling with the equatorial protons and the vicinal coupling<br />
with the protons 1-H/5-H.<br />
The most deshielded signal in the spectrum (Figure 4) has low intensity and is<br />
situated at δ= 208.59 ppm, very close to the chemical shift of the carbonyl in<br />
the cyclohexanone.<br />
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