1,4-Naphthoquinone diene syntheses with

Diels-Alder reactions. This diene reacts with 2-chloro-1,4-quinones to give adducts that undergo aromatiz tion when heated. Yields tend to be low in reactions with benzo-quinones, but are usuajlly satisfactory with naphthoquinones. The reagent was developed to provide a synthesis pf the trimethyl ether (2) of erythrolaccin. 

Oxidation of thiophene with peracid under carefully controlled conditions gives a mixture of thiophene sulfoxide and 2-hydroxythiophene sulfoxide. These compounds are trapped by addition to benzoquinone to give ultimately naphthoquinone (225) and its 5-hydroxy derivative (226) (76ACS(B)353). The further oxidation of the sulfoxide yields the sulfone, which may function as a diene or dienophile in the Diels-Alder reaction (Scheme 88). An azulene synthesis involves the addition of 6-(A,A-dimethylamino)fulvene (227) to a thiophene sulfone (77TL639, 77JA4199). 

Gates, M. (1950) The Synthesis of Ring Systems Related to Morphine. III. 5,6-Dimethoxy-4-cyanomethyl-1,2-naphthoquinone and its Condensation with Dienes. Journal of the American Chemical Society, 72, 228-234. 

The synthesis started from commercially available 3,5-dihydroxy-2-naphthoic acid (A), which was converted to lactonic naphthoquinone B. Diels-Alder reaction of B with diene C gave a 1 1 mixture of the... 

Wemerova M, Hudlicky T (2010) On the practical limits of determining isolated product yields and ratios of stereoisomers reflections, analysis, and redemption. Synlett 2701-2707 Gulland JM, Robinson R (1925) Mem Proc Manchester Lit Phil Soc 69 79 Gates M (1950) The synthesis of ring systems related to morphine. 3. 5,6-Dimethoxy-4-cyanomethyl-1,2-naphthoquinone and its condensation with dienes. J Am Chem Soc 72 228-234... 

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