Carbon-13 NMR of Quinone Methides

Article abstract of DOI:10.1002/mrc.1270220206

The 13C NMR spectra of four ortho- and seven para-quinone methides were assigned using chemical shift and long-range carbon-proton coupling information.The carbonyl shifts are compared with those in ortho- and para-benzoquinones.The chemical shifts of the carbonyls of the p-quinone methides are observed at δ 186.2-186.4 for the three ortho-di-tert-butyl-substituted compounds and at δ 180.7-181.5 for the four ortho-oxy-substituted compounds.In the three o-quinone methides with meta,para-dioxy substituents, the carbonyl signals are at δ 184.2-185.4.The carbonyl signal of the one o-quinone methide with no oxygen substitution is shifted downfield to δ 200.9, apparently as a result of hydrogen bonding to the nearby hydroxyl.