15012-53-0Relevant academic research and scientific papers
Chemistry of naphthazarin derivatives 9. Direct observation of prototropic tautomerism of (poly)hydroxynaphthazarins by IR spectroscopy
Glazunov,Yakubovskaya,Pokhilo,Bochinskaya,Anufriev
, p. 198 - 207 (2003)
A series of substituted (poly)hydroxylated naphthazarins (5,8-dihydroxy-1,4-naphthoquhiones) were synthesized. In general, (poly)hydroxynaphthazarins exist in organic aprotic solvents as mixtures of tautomeric 1,4-naphthoquinonoid forms (IR data). The ratio of tautomers was determined for the first time. The effects of the nature of substituents and the solvent polarity on the tautomeric equilibrium were qualitatively estimated.
NMR Studies of Intramolecular Proton Exchange in Alkylated Naphthazarins
Eloeve, Guelnur A.,Schauble, J. Herman
, p. 194 - 200 (2007/10/02)
Three groups of alkyl-substituted naphthazarins were studied by 1H and 13C NMR in chloroform-d at ambient temperature.Preliminary 1H NMR studies were carried out on selected members of each group at low temperatures (down to-120 deg C) in dichloromethane-d2 solutions.Monoalkylnaphthazarins were found to exist predominatly as the 2-alkyl tautomers (I) and the dimethylalkyl species as the 2,3-dimethyl-6-alkyl tautomers (I).However, both symmetrically and unsymmetrically substituted 2,6- and 2,7-dialkylnaphthazarins exhibited averaged chemical shifts and coupling constants indicating rapid proton exhange between the two minimum energy 1,4-dione tautomers (I and II). 13C NMR shifts were utilized to calculate tautomer populations of the unsymmetrical 2,6- and 2,7-(methyl, alkyl)naphthazarins.KEY WORDS 1H NMR 13C NMR Intramolecular proton exhange Alkylated naphthazarins
