2.5- Dimethyl-l,4-naphthoquinone

The anion derived from 2,3-dimethyl-l,4-naphthoquinone behaves as a quinone methide and undergoes a [l,4]-cycloaddition with the benzoquinone (193). The product is the xanthene derivative (194) (70JCS(C)722). There is no indication of the formation of the isomeric xanthene. A [l,3]-cycloaddition occurs simultaneously which leads to the fluorene derivative (195). 

Rhodium complexes with the derivatives of p-quinone (1,4-naphthoquinone and 2,3-dimethyl-l,4-benzoquinone) were also reported [236]. 

Figure 1. Comparison of the relative activities of different rhenium catalysts in the formation of 2,3-dimethyl-1,4-naphthoquinone (acidic conditions) L = 2,2 -bipyridine, L = 4-fert-butylpyridine, L" = pentamethyl(diethyl)triamine ([(CH3)2NC2H4]2NCH3).

The reagent has found some use for the oxidation of aromatic hydrocarbons and phenols to para quinones. Arnold and Lawson " heated a mixture of 10 g. of naphthalene, 25 ml. of 30% hydrogen peroxide, and 50 ml. of acetic acid just above 80° for 45 min., distilled off about half of the solvent, added water to precipitate the product, and by crystallization isolated satisfactory 1,4-naphthoquinone in 20% yield. Durene (5 g.) was heated with HjOa-AcOH for 15 hrs. on the steam bath and duroquinone (2.1 g.) was separated by steam distillation. Crude 2-methyl-1,4-naphthoquinone and 2,3-dimethyl-l, 4-naphlhoquinone were obtained in yields of 30 and 78%. Unchanged hydrocarbon wax present at the end of each oxidation. 

Dichloro-l,4-naphthoquinone and 3-methyl-1-phenylpyrazolone gave 400, and the tetracyclic quinone 401 was obtained from l,2-dimethyl-4-hydroxy-6-pyridone (47CB47). Cyclization of 6-acetylamino-7-chloroquin-oline-5,8-dione in the presence of acetic anhydride yielded the oxazolo derivative 402, and from the 7-mercapto analog the thiazole quinone 403 was... 

Reaction of 2,6-dimethyl-l,4-benzoquinone with the quinomethyl carbanion derived from 2,3-dimethyl-1,4-naphthoquinone is reported to give the tricyclo-[6,3,l,0 ]dodecane derivative (749). Pyrolysis of the sodium salt of the tosyl-hydrazone of 7-cycloheptatrienylmethyl methyl ketone in diglyme at 150 C afforded (750 7%) similar pyrolysis of the tosylhydrazone salt from l-(7-cycloheptatrienyl)-ethyl methyl ketone gave (751 9 %). Both compounds are examples of the previously... 

Qo 2,3-dimethoxy-5-methyl-l,4-benzoquinone DCIP dichlorophenol-indophenol BQ 1,4-benzoquinone PMS phenazine methosulphate DMBQ 2,6-dimethyl-l,4-benzoquinone NQ 1,4-naphthoquinone VK3 2-methyl-1,4-naphthoquinone (vitamin K3). 

The simplest and most well-known approach is to deposit silicate or other oxides by an electrophoretic driving force. For example, we used this approach to deposit a naphthoquinone redox group appended to a trimethoxy silane (Scheme 4.3), 1-propanaminium, N-[2[(3-chloro-l,4-dihydro-l,4-dioxo-2-naphthalenyl)amino] ethyl]-N, N-dimethyl-3-(trimethoxysilyl)-, bromide (NPQ), on a glassy carbon electrode (GC) [46]. 

A synthesis of the carbazolequinone alkaloid murrayaquinone-B, previously isolated from the root bark of Murraya euchrestifolia, is described and the compound was obtained in 13% yield (88JCS(P1)241). Photolysis of 2-amino-1,4-naphthoquinone afforded the pentacyclic quinone 61 (R = H) and some of its N-substituted derivatives (88TL591). From 2,3-dibromo-5,6-dimethyl-l,4-benzoquinone, ethyl acetoacetate, and pyridine, a derivative of the indoiequinone system related to 65 was prepared (87IJC180). 

Dimethyl-2-propenyl)-3-hydroxy-1,4-naphthoquinone, D-30290 l-(4-Hydroxyphenyl)ethanol 4 -Benzoyl, in H-20219... 

The pioneer work on this subject using simple 1-azadienes is due to Ghosez et al. (82TL3261 85JHC69) they succeeded in reacting 1-azadienes as 47r-electron components in Diels-Alder cycloadditions. Thus, l-dimethylamino-3-methyl-l-azabuta-l,3-diene (a,/3-unsaturated hydrazone) 54 did undergo [4 + 2] cycloaddition to typical electron-poor dienophiles, e.g., methyl acrylate, dimethyl fumarate, acrylonitrile, maleic anhydride, and naphthoquinone, producing pyridine derivatives 55-57 (Scheme 14). 

The dienol ether 3-cyclopropylidene-l-ethoxyprop-l-ene was reacted with methylmaleic anhydride, various alkyl-substituted 1,4-benzoquinones, 2-methyl-1,4-naphthoquinone (vitamin K3), and dimethyl acetylenedicarboxylate to give the corresponding Diels-Alder adducts, e.g. 4-6, in moderate to high yield.In complete analogy, 2-(trialkylsiloxy)allylidenecyclopropanes react with a variety of dienophiles to give 5-(trialkylsiloxy)spiro[2.5]oct-4-ene derivatives which can be hydrolyzed to spiro[2.5]octan-5-ones in high yield. For example, formation of 7 and 8. ... 

Triethyl l,3,5-triazine-2,4,6-tricarboxylate and 2,4,6-tris(methylsulfanyl)-1,3,5-triazine react in an inverse electron demand Diels-Alder reaction with several electron-rich dienophiles.6 The tricarboxylate 9 (R1 = C02Et) undergoes a well-defined [4 + 2] cycloaddition reaction with ynamines and enamines. In the case of ynamines, the [4 -1- 2] cycloaddition is followed by a retro Diels - Alder reaction at 40 100 °C with direct formation of the substituted pyrimidines 11. In the case of enamines, the cycloaddition provides stable, isolable [4 + 2] adducts 12. The subsequent retro Diels-Alder reaction and the final aromatization step is catalyzed by a mixture of hydrochloric acid and dioxane, anhydrous p-toluencsulfonic acid or acetic acid. This two-step process can be reduced to a single operation by conducting the reaction in a solution of dichloromethane and acetic acid at 40-100 °C.6 Electron-deficient dienophiles like dimethyl acetylenedicarboxylate or 1,4-naphthoquinone do not react with this triazine. 

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