1,4-Naphthoquinone

The industrial synthesis involves aerobic oxidation of naphthalene over a vanadium oxide catalyst: :CH + 3/2 O → CHO + HO However, naphthoquinone rapidly oxidizes to phthalic anhydride under these conditions, and the latter is the major product. 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 that is used as a dye precursor. ==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 , a compound produced by black walnut trees. • 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 ==See also==