Hydroxynaphthoquinone

A hydroxynaphthoquinone (formula: C
₁₀H
₆O
₃) is any of several organic compounds that can be viewed as derivatives of a naphthoquinone through replacement of one hydrogen atom (H) by a hydroxyl group (-OH).

In general, the term may mean any naphthoquinone derivative where any number n of hydrogens have been replaced by n hydroxyls, so that the formula is C
₁₀H
₆O
_2+n. In this case the number n (which is between 1 and 6) is indicated by a multiplier prefix (mono-, di-, tri-, tetra-, penta-, or hexa-).

The unqualified term "hydroxynaphthoquinone" usually means a derivative of 1,4-naphthoquinone. Other hydroxy- compounds can be derived from other isomers of the latter, such as 1,2-naphthoquinone and 2,6-naphthoquinone. The IUPAC nomenclature uses dihydronaphthalenedione instead of "naphthoquinone", with the necessary prefixes to indicate the positions of the carbonyl oxygens (=O) — as in 5,8-dihydroxy-1a,8a-dihydronaphthalene-1,4-dione (= 5,8-dihydroxy-1,4-naphthoquinone).

The hydroxynaphtoquinones (in the particular or the general sense) include many biologically and industrially important compounds, and are a building-block of many medicinal drugs.^[1][2][3]

(Mono)hydroxynaphtoquinones

From 1,4-naphthoquinone

Due to its symmetry there are only three isomers:

• 2-Hydroxy-1,4-naphthoquinone (lawsone), coloring principle of henna.
• 5-Hydroxy-1,4-naphthoquinone (juglone), coloring principle of black walnut.^[4] Also active antimicrobial principle in Caesalpinia sappan heartwood.^[5]
• 6-Hydroxy-1,4-naphthoquinone, can be prepared from 1,7-dihydroxynaphthalene.^[6] One of the main products of photochemical oxidation of 1-naphthol.^[7]

From 1,2-naphthoquinone

From 1,2-naphthoquinone (ortho-naphthoquinone) there are 6 possible isomers:

• 3-Hydroxy-1,2-naphthoquinone
• 4-Hydroxy-1,2-naphthoquinone^[8][9]
• 5-Hydroxy-1,2-naphthoquinone
• 6-Hydroxy-1,2-naphthoquinone
• 7-Hydroxy-1,2-naphthoquinone
• 8-Hydroxy-1,2-naphthoquinone

From 2,3-naphthoquinone

From 2,3-naphthoquinone, also a symmetric molecule there are only three isomers:

• 1-Hydroxy-2,3-naphthoquinone
• 5-Hydroxy-1,2-naphthoquinone
• 6-Hydroxy-1,2-naphthoquinone

From 2,6-naphthoquinone

From the symmetrical 2,6-naphthoquinone (amphi-naphthoquinone) there are only three:

• 1-Hydroxy-2,6-naphthoquinone
• 3-Hydroxy-2,6-naphthoquinone
• 4-Hydroxy-2,6-naphthoquinone

(Poly)hydroxynaphthoquinones

• Dihydroxynaphthoquinone
• Trihydroxynaphthoquinone
• Tetrahydroxynaphthoquinone
• Pentahydroxynaphthoquinone
• Hexahydroxynaphthoquinone

See also

• Hydroxybenzoquinone
• Hydroxyanthraquinone

References

1. Khalafy, J.; Bruce, J. M. (2002). "Oxidative Dehydrogenation of 1-Tetralones: Synthesis of Juglone, Naphthazarin, and α-Hydroxyanthraquinones" (pdf). Journal of Sciences, Islamic Republic of Iran. 13 (2): 131–139.
2. Thomson, R. H. (1971). Naturally Occurring Quinones. London: Academic Press. Quoted by Khalafy and Bruce.
3. Thomson, R. H. (1987). Naturally Occurring Quinones III. London: Chapman and Hall. Quoted by Khalafy and Bruce.
4. Taylor, R. T.; Flood, L. A. (1983). "Polystyrene-Bound Phenylseleninic Acid: Catalytic Oxidations of Olefins, Ketones, and Aromatic Systems". The Journal of Organic Chemistry. 48 (26): 5160–5164. doi:10.1021/jo00174a003.
5. Lim, M.-Y.; Jeon, J.-H.; Jeong, E. Y.; Lee, C. H.; Lee, H.-S. (2007). "Antimicrobial Activity of 5-Hydroxy-1,4-Naphthoquinone Isolated from Caesalpinia sappan toward Intestinal Bacteria". Food Chemistry. 100 (3): 1254–1258. doi:10.1016/j.foodchem.2005.12.009.
6. Teuber, H.-J.; Götz, N. (1954). "Reaktionen mit Nitrosodisulfonat, V. Mitteilung: Über die Bildung von Naphtochinonen". Chemische Berichte. 87 (9): 1236–1251. doi:10.1002/cber.19540870908.
7. Brahmia, O.; Richard, C. (2005). "Photochemical Transformation of 1-Naphthol in Aerated Aqueous Solution". Photochemical & Photobiological Sciences. 4 (6): 454–458. doi:10.1039/B504309C. PMID 15920628.
8. Garge, P.; Padhye, S.; Tuchagues, J.-P. (1989). "Iron(II) Complexes of ortho-Functionalized para-Naphthoquinones 1. Synthesis, Characterization, Electronic Structure and Magnetic Properties". Inorganica Chimica Acta. 157 (2): 239–249. doi:10.1016/S0020-1693(00)80548-4.
9. Rane, S. Y.; Ahmed, K.; Salunke-Gawali, S. (2006). "Temperature Effect on Ancillary μ-Carbonato Ligand Modes in Hydroxy Naphthoquinonato Copper(II) Complex: An EPR Spectroscopic and Magnetic Coupling Evidences". Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry. 36 (5): 391–398. doi:10.1080/15533170600729037.