1,4-Naphthoquinone

Preparation

The industrial synthesis involves aerobic oxidation of naphthalene over a vanadium oxide catalyst: :CH + 3/2 O → CHO + HO In the laboratory, naphthoquinone can be produced by the oxidation of a variety of naphthalene compounds. An inexpensive route involves oxidation of naphthalene with chromium trioxide.

Reactions

1,4-Naphthoquinone acts as strong dienophile in Diels-Alder reaction. Its adduct with 1,3-butadiene can be prepared by two methods: 1) long (45 days) exposure of naphthoquinone in neat liquid butadiene taken in huge excess at room temperature in a thick-wall glass tube or 2) fast catalyzed cycloaddition at low temperature in the presence of 1 equivalent of tin(IV) chloride:

Reduction of 1,4-naphthoquinone with dithionite gives 1,4-dihydroxynaphthalene. The reaction is reversible: oxidation of the diol give back the quinone.

Uses

1,4-Naphthoquinone is mainly used as a precursor to anthraquinone by reaction with butadiene followed by oxidation. Nitration gives 5-nitro-1,4-naphthalenedione, precursor to an aminoanthroquinone that is used as a dye precursor.

Naphthoquinone functions as a ligand through its electrophilic carbon-carbon double bonds.

Derivatives

Naphthoquinone forms the central chemical structure of many natural compounds, most notably the K vitamins. 2-Methyl-1,4-naphthoquinone, called menadione, is a more effective coagulant than vitamin K. Some naphthoquinone derivatives are cytotoxic, they have significant antibacterial, antifungal, antiviral, insecticidal, anti-inflammatory, and antipyretic properties. Plants with naphthoquinone content are widely used in China and the countries of South America, where they are used to treat malignant and parasitic diseases.

Natural 1,4-naphthoquinones

• Alkannin, commercial red-brown dye from Alkanna tinctoria
• Dichlone, a chlorinated derivative of 1,4-naphthoquinone, a fungicide.
• Droserone, found in plants of the genus Plumbago
• Hexahydroxy-1,4-naphthalenedione
• Juglone, growth-stunting exudate of black walnut trees
• Lapachol, yellow irritant from lapacho tree
• Lawsone, dye in henna
• Menatetrenone, a polyhydroxylated 1,4-naphthoquinone found in some sea urchins
• 2-Methoxy-1,4-naphthoquinone, a compound found in Impatiens species
• Nigrosporin B, lightly studied compound found in the fungus Nigrospora sp
• Plumbagin, yellow toxin found in plants of the genus Plumbago
• Spinochrome B, a marine pigment
• Spinochrome D, a marine pigment
• Vitamin K and related compounds
  • Phylloquinone
  • Vitamin K2
  • Menadione (2-Methyl-1,4-naphthoquinone)
• Naphthazarin, red solid that occurs naturally and is earily prepared

Synthetic 1,4-naphthoquinones

• Atovaquone, a drug
• Buparvaquone, an antiprotozoal drug used in veterinary medicine

References

References

1. ''Merck Index'', 11th Edition, '''6315'''.
2. (1965). "Structure de l'α-Naphtoquinone". Acta Crystallographica.
3. (February 1940). "The Vitamin K Activity of Naphthoquinones". Journal of the American Chemical Society.
4. Grolig, J.. "Naphthoquinones".
5. Braude, E. A.. (1953). "1,4-Naphthoquinone". Organic Syntheses.
6. M.A. Filatov. (2012). "Tetraaryltetraanthra[2,3]porphyrins: Synthesis, Structure, and Optical Properties". J. Org. Chem..
7. (2000). "Ullmann's Encyclopedia of Industrial Chemistry".
8. (2004). "Desymmetrization of a ''meso''-Diol Complex Derived from [Cr(CO){{sub". Chemical Communications.
9. (2007). "Naphthoquinones and their Pharmacological Properties". Ceská a Slovenská Farmacie.