Naphthoquinone, epoxidizing

Y. Harigaya, H. Yamaguchi, M. Onda, Syntheses and Absolute Configurations of a Chiral Naphthoquinone Epoxide and Chiral Naphtho[l,2-c]isocoumarins , Chem. Pharm. Bull. 1981, 29, 1321-1327, and references cited therein. 

Write a mechanism for the reaction of 2-methyl-1,4-naphthoquinone epoxide (10) with sulfuric acid to form phthiocol. 

Interest in naphthoquinone epoxides (300) has been reported by three research groups in the past year. Kato et a/.183 have shown that the epoxide (300a) undergoes ring-opening when irradiated (benzene solution, Pyrex filter). This unstable... 

Quinones of various degrees of complexity have antibiotic, antimicrobial, and anticancer activities, eg, a2iddinornitosene [80954-63-8] (36), (-)-2-methyl-l,4-naphthoquinone 2,3-epoxide [61840-91 -3] (37), and doxombicin [23214-92-8] (adriamycin) (38) (see Antibiotics Chemotherapeutics, anticancer), ah of these natural and synthetic materials have stimulated extensive research in synthetic chemistry. 

The epoxide of vitamin K is involved in the regeneration of the anticoagulant vitamin (a naphthoquinone) from the active hydroquinone form (81JA5939). 

Typically, the synthesis of block B involves the Diels-Alder reaction of 1,4-naphthoquinone with cyclopentadiene, followed by reduction and OH methylation to give 92 (Scheme 33). The next step involves a Ru-catalysed [2+2] cycloaddition of 92 with dimethyl acetylenedicarboxylate (DMAD), followed by epoxidation (MeLi, BuOOH) to give 94 as block B. 

S. Arai, M. Oku, M. Miura, T. Shioiri, Catalytic Asymmetric Epoxidation of Naphthoquinone Derivatives under Phase-Transfer Catalyzed Conditions , Synlett, 1998,1201-1202. 

Methyl-l,3-dioxolane, production from acetaldehyde, 1 104 (—) -2-M ethyl-1,4-naphthoquinone 2,3-epoxide, 21 242... 

Like for benzene, the cytotoxicity of naphthalene is not due to the epoxide but to the quinone metabolites, namely 1,2-naphthoquinone and 1,4-naphthoquinone [85], As shown in Table 10.1, naphthalene 1,2-oxide (10.2) is a better substrate than benzene oxide for epoxide hydrolase. Its rapid isomerization to naphthalen-l-ol, facile enzymatic hydration to the dihydrodiol and lack of reactivity toward nucleophiles such as glutathione may explain its absence of direct toxicity [85],... 

Naphthoquinone-2,3-epoxide, see Naphthalene 2-(a-Naphthoxy) -yV-ethylpropionamide, see Napropamide 2-(2-Naphthoxy)propanoic acid, see Napropamide 2-(a-Naphthoxy)propionamide, see Nanronamide 1-Naphthylamine, see Nantalam... 

I. 1.4.1] catalyzes the reaction of 2-methyl-3-phytyl-l,4-naphthoquinone with oxidized dithiothreitol and water to produce 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-l,4-naphthoquinone and 1,4-dithiothreitol. In the reverse reaction, vitamin K 2,3-epoxide is reduced to vitamin K and possibly to vitamin K hydroquinone by 1,4-dithioer-ythritol (which is oxidized to the disulfide). Some other dithiols and butane-4-thiol can also act as substrates. This enzyme is strongly inhibited by warfarin. 

SCHEME 48. Catalytic asymmetric epoxidation of naphthoquinone derivatives under phase transfer catalyzed conditions... 

Peroxo Fe(ni), Mn(III) and Ti(IV) porphyrins were reacted with a variety of electron-poor organic substrates in order to compare their activity with that of different metalloper-oxide complexes. Epoxidation of 2-cyclohexen-l-one and 2-methyl-1,4-naphthoquinone was observed, in 25 and 75% yield respectively, with the extremely nucleophilic Fe(III) complex . These results opened new perspectives in the oxidation mechanisms of some enzymatic reactions. 

CMral tpoxyiutphthoquinones. Pluim and Wynberg1 have prepared a number of Optically active epoxides of 2-alkyl- and 2,3-dialkyl-l,4-naphthoquinones by Oxidation with 30% H202, aqueous NaOH, and benzylquininium chloride. Enantiomeric excesses of 43% can be realized, and these can be improved by Oiyitallization. The authors also report that the most satisfactory method for preparation of 2-alkyl-1,4-naphthoquinones is that of Jacobsen (5, 17 8, 18). 

Asymmetric epoxidation catalyzed by chiral phase-transfer catalysts is another reaction which has been extensively studied following an initial report by Wynberg [2,44]. Shioiri et al. further improved the enantioselective epoxidation of naphthoquinones under cinchona alkaloid-derived chiral phase-transfer catalysis [45],... 

Dehmlow and coworkers [17] compared the efficiency of monodeazadnchona alkaloid derivatives 14a-c in the enantioselective epoxidation of naphthoquinone 50 with that of cinchona alkaloid-derived chiral phase-transfer catalysts 15a-c (Table 7.7) (for comparison of the alkylation reaction, see Table 7.1). Interestingly, the non-natural cinchona alkaloid analogues 14a-c afforded better results than natural cinchona alkaloids 15a-c. The deazacinchonine derivatives 14a,b produced epoxidation product 51 in higher enantioselectivity than the related cinchona alkaloids 15a,b. Of note, catalyst 14c, which possessed a bulky 9-anthracenylmethyl substituent on the quaternary nitrogen, afforded the highest enantioselectivity (84% ee). 

Sharpless and Flood682 observed reactions characteristic of monooxygenases, such as stereospecific epoxidation of olefins and arene hydroxylation, with oxotransition metal (M=0) oxidants. For example, Cr02X2 (X=C1, OAc) oxidized tritium labeled naphthalene to naphthoquinone accompanied by tritium migration. Rearrangement is suggestive of arene oxide transients. 

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