Carbon-13 NMR Spectra of Some Methyl-Substituted Adamantanones

Article abstract of DOI:10.1021/jo00164a025

The synthesis of 1-methyl- (2), 1,5-dimethyl- (3), and 5,7-dimethyladamantanone (4) and their ¹³C NMR spectra have been investigated.For the preparation of 3 and 4, some discrepancies existing in the literature are revealed.The carbon-13 NMR resonances of 2, 3, and 4, have been completely assigned from conventional high-resolution spectra with the use of a ¹H-¹³C polarization transfer technique and lanthanide shift reagent experiments.Comparison of the chemical shift values with those of the parent adamantanone (1) and the tetramethyl derivative 5 indicates that the effects of methyl groups on the chemical shifts of adamantanone are similar in direction and magnitude to the effects observed in adamantane.The carbonyl group induces upfield shifts of the signals for carbons across the polycyclic system and for the methyl groups, especially at the adjacent bridgeheads.