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13-Methyl-2,6-dithia[7]metacyclophane:  A Useful Molecule To Connect VT NMR Results and Structure with Calculations

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journal contribution
posted on 21.01.2005 by Reginald H. Mitchell, Rachel Blunden, Gavin Hollett, Subhajit Bandyopadhyay, Richard Vaughan Williams, Brendan Twamley
Ground state energies (DFT) and 1H and 13C NMR chemical shifts are calculated for the conformers of 13-methyl-2,6-dithia[7]metacyclophane (1), and the results are compared with X-ray structural data and variable-temperature NMR data, including the determination of the activation barrier. Calculations predict the correct low energy conformer with good agreement with chemical shifts, bond distances, and angles. VT NMR data for the 10-tert-butyl-substituted derivative 2 indicate that it undergoes the same conformational equilibria as 1. This paper should enhance the confidence that organic chemists have in calculations to satisfactorily predict conformer energies.