A '''dihydroxynaphthoquinone''' is any of several [[organic compound]]s with formula {{chem|C|10|H|6|O|4}}, which can be viewed as derivatives of [[naphthoquinone]] through replacement of two [[hydrogen]] atoms (H) by [[hydroxyl]] groups (OH).

The unqualified term "dihydroxynaphthoquinone" usually means a derivative of [[1,4-naphthoquinone]].  Due to the symmetry of the latter, there are only nine isomers:

*[[2,3-Diydroxy-1,4-naphthoquinone]].<!-- symmetric -->
*[[2,5-Diydroxy-1,4-naphthoquinone]].<!-- = 3,8 -->
*[[2,6-Diydroxy-1,4-naphthoquinone]].<!-- = 3,7 -->
*[[2,7-Diydroxy-1,4-naphthoquinone]].<!-- = 3,6 -->
*[[2,8-Diydroxy-1,4-naphthoquinone]].<!-- = 3,5 -->
*[[5,6-Diydroxy-1,4-naphthoquinone]].<!-- = 7,8 -->
*[[5,7-Diydroxy-1,4-naphthoquinone]].<!-- = 6,8 -->
*[[5,8-Diydroxy-1,4-naphthoquinone]] (naphthazarin).<ref name=khalafy>
  J. Khalafy and J.M. Bruce (2002), ''Oxidative dehydrogenation of 1-tetralones: Synthesis of juglone, naphthazarin, and [alpha]-hydroxyanthraquinones''. Journal of Sciences, Islamic Republic of Iran, volume 13 issue 2, pages 131-139.
</ref><!-- symmetric -->
*[[6,7-Diydroxy-1,4-naphthoquinone]].<!-- symmetric -->

Other isomers can be derived from the two other known [[naphthoquinone]]s. From [[1,2-naphthoquinone]] (''ortho''-naphthoquinone) there are 12 possible isomers:
*[[3,4-Dihydroxy-1,2-naphthoquinone]]
*[[3,5-Dihydroxy-1,2-naphthoquinone]]
*[[3,6-Dihydroxy-1,2-naphthoquinone]]
*[[3,7-Dihydroxy-1,2-naphthoquinone]]
*[[3,8-Dihydroxy-1,2-naphthoquinone]]
*[[4,5-Dihydroxy-1,2-naphthoquinone]]
*[[4,6-Dihydroxy-1,2-naphthoquinone]]
*[[4,7-Dihydroxy-1,2-naphthoquinone]]
*[[4,8-Dihydroxy-1,2-naphthoquinone]]
*[[5,6-Dihydroxy-1,2-naphthoquinone]]
*[[5,7-Dihydroxy-1,2-naphthoquinone]]
*[[5,8-Dihydroxy-1,2-naphthoquinone]]
*[[6,7-Dihydroxy-1,2-naphthoquinone]]
*[[6,8-Dihydroxy-1,2-naphthoquinone]]
*[[7,8-Dihydroxy-1,2-naphthoquinone]]

From the symmetrical [[2,6-naphthoquinone]] (''amphi''-naphthoquinone) there are only nine isomers:

*[[1,3-Dihydroxy-2,6-naphthoquinone]]<!-- = 5,7 -->
*[[1,4-Dihydroxy-2,6-naphthoquinone]]<!-- = 5,8 -->
*[[1,5-Dihydroxy-2,6-naphthoquinone]]<!-- symmetric -->
*[[1,7-Dihydroxy-2,6-naphthoquinone]]<!-- = 3,5 -->
*[[1,8-Dihydroxy-2,6-naphthoquinone]]<!-- = 4,5 -->
*[[3,4-Dihydroxy-2,6-naphthoquinone]]<!-- = 7,8 -->
*[[3,7-Dihydroxy-2,6-naphthoquinone]]<!-- symmetric -->
*[[3,8-Dihydroxy-2,6-naphthoquinone]]<!-- = 4,7 -->
*[[4,8-Dihydroxy-2,6-naphthoquinone]]<!-- symmetric -->

==See also==
*[[Hydroxynaphthoquinone]]
*[[Trihydroxynaphthoquinone]]
*[[Dihydroxyanthraquinone]]

==References==
{{reflist}}

{{chem-stub}}

[[Category:Naphthoquinones]]

<!--Move to proper pages:
 "Silver(I) oxide in 1,4-dioxane converted 9,10-dihydroxy-1-oxo (14), 9,10-dihydroxy-1,5-dioxo (15), and
1,8-dioxo-1,2,3,4,5,6,7,8-octahydro anthracene (16) into, respectively, 1-hydroxy-5,6,7,8-tetrahydro (23), 1,5-dihydroxy (6), and 1,8-dihydroxy-9,10-anthraquinone (4), in high yield.

  naphthazarin, 5,8-dihydroxy-1,4-naphthoquinone, also occurs naturally<ref name=thomson71>
    Thomson R.H. Naturally Occurring Quinones. Academic Press, London (1971).  Quoted by Khalafy and Bruce.
</ref> <ref name=thomson87>
    Thomson R.H. Naturally Occurring Quinones III. Chapman and Hall, London (1987).  Quoted by Khalafy and Bruce.
</ref>, and can be prepared by condensation of 1,4-dimethoxybenzene with 2,3-dichloromaleic anhydride followed by reductive dechlorination and reoxidation [13].<ref name=lewis>
  Lewis J.R. and Paul J.J.(1977). Z. Naturforsch., B, 32: 1473. Quoted by Khalafy and Bruce.
<ref><ref name=huot>
  Huot R. and Brassard P. (1974). Can. J. Chem., 52: 838. Quoted by Khalafy and Bruce.
</ref>

  The dihydroxy-9,10-anthraquinone moiety occurs widely in natural products,<ref name=thomson71/> and is an important feature of the anthracycline antitumour antibiotics.<ref name=arac>
  Arcamone F. (1981). Doxorubicin Anticancer Antibiotics. Academic Press, New York. Quoted by Khalafy and Bruce.
</ref><ref name=kelly>
  Kelly T.R. (1984). Tetrahedron, 40: 22. Quoted by Khalafy and Bruce.
</ref>

  1,8-Dihydroxy-9,10-anthraquinone is the precursor for the important topical antipsoriatic drug anthralin, 1,8-dihydroxy-9-anthrone,<ref name=ashton>
  Ashton R.E., Andre P., Lowe N.J. and Whitefield M. J. (1983). Am. Acad. Dermatol., 9: 173. Quoted by Khalafy and Bruce.
</ref><ref name=kemeny>
  Kemeny L., Ruzicka T. and Braun-Falco O. (1990). Skin Pharmacol., 3: 1. Quoted by Khalafy and Bruce.
</ref>

  Intramolecular hydrogen bonding is common to hydroxyquinones with -OH adjacent to the =O, and is important in controlling their redox properties, which are vital for their roles in biochemistry.<ref name=khalafy/>
  
  Dipole-dipole repulsions between the adjacent carbonyl groups probably account for the nonplanarity of 1,4,5,8-naphthodiquinone.<ref name=khalafy/>
  
  5,8-dihydroxy-1,4-naphthoquinone can be obtained by oxidizing 5,8-Dihydroxy-1-tetralone with manganese dioxide in dioxane.  It crystallizes as deep red needles m.p.228-232[deg] C.<ref name=khalafy/> 

  1-hydroxy-9,10-anthraquinone can be obtained (with other products) by treating 9,10-Dihydroxy-3,4,5,6,7,8-hexahydro-1(2H)-anthracenone with manganese dioxide in dioxane. 

  1,4-dihydroxy-9,10-anthraquinone can be obtained (with other products) by treating 9,10-Dihydroxy-3,4,5,6,7,8-hexahydro-1(2H)-anthracenone with manganese dioxide in dioxane. 

  1,5-dihydroxy-9,10-anthraquinone can be obtained (with other products) by treating 9,10-Dihydroxy-3,4,5,6,7,8-hexahydro-1(2H)-anthracenone with manganese dioxide in dioxane. 
  1,5-dihydroxy-9,10-anthraquinone can be obtained from 1,2,3,4,5,6,7,8-Octahydro-9,10-dihydroxy-1,5-anthracenedione with silver oxide in dioxane. Crystallized from solution in glacial acetic acid as yellow needles m.p. 279-281°C.

  1,8-dihydroxy-9,10-anthraquinone can be obtained (with other products) by treating 9,10-Dihydroxy-3,4,5,6,7,8-hexahydro-1(2H)-anthracenone with manganese dioxide in dioxane. 
  1,8-dihydroxy-9,10-anthraquinone can be obtained from 1,2,3,4,5,6,7,8-Octahydro-9,10-dihydroxyanthracene-1,8-dione with silver oxide in dioxane affords which. It crystallizes from dioxane as orange yellow needles, m.p.=189-191°C.
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