13C NMR/DFT/GIAO Studies of Phenylene Bis(1,3-dioxolanium) Dications and 2,4,6-triphenylene Tris(1,3-dioxolanium) Trication
The o-, m-, and p-phenylene bis(1,3-dioxolanium) dications (4-6) and 2,4,6-triphenylene tris(1,3-dioxolanium) trication (7) have been prepared by the ionization of the corresponding 2-methoxyethyl benzoates in FSO3H or CF3SO3H at 40 and 60 °C, respectively. The charge delocalization in these carbocations was probed by 13C NMR chemical shifts and substantiated by GIAO/DFT calculations. Relatively less charge is delocalized into the aromatic ring of the carbotrication 7. The rotational barrier around the C+-Ar bond for carbodications 4 and 5 was also estimated to be 8-10 kcal/mol.
P. Reddy et al., "13C NMR/DFT/GIAO Studies of Phenylene Bis(1,3-dioxolanium) Dications and 2,4,6-triphenylene Tris(1,3-dioxolanium) Trication," Journal of Organic Chemistry, American Chemical Society (ACS), May 2003.
The definitive version is available at http://dx.doi.org/10.1021/jo020753z
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