Synthesis, NMR and computational studies on tautomerism of dichloroacetate of hydroxyanthraquinone

Three dichloroacetate derivatives of hydroxyanthraquinone were synthesized. NMR studies showed that only monoesterified derivative compound 1 had a tautomerization. Since monoetherified derivative of hydroxyanthraquinone did not show tautomerization, a hypothesis that nucleophilicity played an important role in the tautomerization was proposed. The molecular structures of monoesterified derivative compound 1 and diesterified derivative compound 2 were calculated by using DFT method, and the result showed that the electronic density of carbonyl at 9-position of compound 1 was much larger than that of compound 2, which indicated that the hypothesis mentioned above was reasonable.