Magnesium-Induced Shifts in the Proton Magnetic Resonance Spectra of Phenols

It was observed that in numerous phenols the phenolic hydroxyl and ortho proton resonances in the proton nuclear magnetic resonance (1H NMR) spectrum moved downfield on addition of anhydrous magnesium chloride to the dimethyl sulfoxide-d6 or dimethylformaide-d7 solution. The selective shifts of phenolic ortho proton resonances in the presence of magnesium chloride were shown to be a useful tool for 1H NMR signal assignments and structure elucidation of naturally occurring phenols.