Naphthazarin Explained

Naphthazarin, often called 5,8-dihydroxy-1,4-naphthoquinone or 5,8-dihydroxy-1,4-naphthalenedione (IUPAC), is a naturally occurring^{[1] [2]} organic compound with formula, formally derived from 1,4-naphthoquinone through replacement of two hydrogen atoms by hydroxyl (OH) groups. It is thus one of many dihydroxynaphthoquinone structural isomers.

Naphthazarin is soluble in 1,4-dioxane from which it crystallizes as deep red needles that melt at 228−232 °C.

Synthesis

Naphtharazin can be prepared by condensation of 1,4-dimethoxybenzene with 2,3-dichloromaleic anhydride followed by reductive dechlorination and reoxidation.^{[3] [4]}

Naphtharazin can also be obtained by oxidation of 5,8-dihydroxy-1-tetralone with manganese dioxide (MnO₂).^[5]

Notes and References

1. Thomson R.H. Naturally Occurring Quinones. Academic Press, London (1971). Quoted by Khalafy and Bruce.
2. Thomson R.H. Naturally Occurring Quinones III. Chapman and Hall, London (1987). Quoted by Khalafy and Bruce.
3. Lewis J.R. and Paul J.J.(1977). Z. Naturforsch., B, 32: 1473. Quoted by Khalafy and Bruce.
4. Huot R. and Brassard P. (1974). Can. J. Chem., 52: 838. Quoted by Khalafy and Bruce.
5. J. Khalafy and J.M. Bruce (2002), Oxidative dehydrogenation of 1-tetralones: Synthesis of juglone, naphthazarin, and α-hydroxyanthraquinones. Journal of Sciences, Islamic Republic of Iran, volume 13 issue 2, pages 131-139.