Beilstein J. Org. Chem. 2019, 15, 1996–2002.
detected by NMR spectroscopy. Instead, this was likely the copic service and Dr M Stander and Mr M Taylor for the mass
result of the molecular ion losing the ruthenium and subse- spectroscopic service.
quently protonated in the mass spectrometer; this triazolium
ORCID® iDs
signal was also not seen in our model study. A final peak at
1030.4333 Da was assigned as [M – Cl + formic acid]+ (formic
acid was present in the injection media), which also shed no
light on whether this was the open or closed form of the ruthe-
References
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Conclusion
Whilst our inability to isolate and purify the calix[4]arene
ruthenacycle 13 for full characterization was frustrating, the ev-
idence did suggest that the reaction had worked, albeit in a very
low yield. The major mass spectrum peak might be interpreted
as successful formation of the ruthenacycle, but we believe that
this is not the case and that the ruthenium complex shown in
Figure 4 is the more likely interpretation. What was also impor-
tant to note was that the reaction did not result in the oxidative
bridge formation reported by Lhoták when they attempted a
meta-functionalization of a calix[4]arene with palladium. The
NMR and mass spectra were proof of this. We have also de-
veloped a more robust mononitration method applicable to
calix[4]arenes and an optimized method to azide/triazole-func-
tionalized calix[4]arenes which may be useful in other applica-
tions.
Supporting Information
Supporting Information File 1
Experimental details and spectral data for all compounds
(including failed reactions).
̈ller-Bunz, H.;
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Acknowledgements
This work was supported by the National Research Foundation
(Grant CPRR160428163281) and Stellenbosch University. We
thank Dr J. Brand and Ms. E Malherbe for the NMR spectros-
2001