Naphthoquinones reactions

Coumarone, MA copolymerization, 660 Cracked waxes, MA ene adducts, 175 p-Cresol, acylation with MA, 95 Crotonaldehyde C4 oxidation by-product, 34 diethyl acetal, MA reactivity ratios, 299 dimerization, 110 furan adducts, 128 naphthoquinone reaction, 110 oxidation to MA, 18... 

Malamidou-Xenikaki E, Spyroudis S, Tsanakopoulou M. Studies on the reactivity of aryliodonium ylides of 2-hydroxy-l,4-naphthoquinone reactions with amines. J. Org. Chem. 2003 68 5627-5631. 

Rate Coefficients and Mechanisms for the Atmospheric Oxidation of the Ketones 731 V-F-5.2. O3+ 1,4-Naphthoquinone Reaction Kinetics... 

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

Oxidation. Naphthalene may be oxidized direcdy to 1-naphthalenol (1-naphthol [90-15-3]) and 1,4-naphthoquinone, but yields are not good. Further oxidation beyond 1,4-naphthoquinone [130-15-4] results in the formation of ortho- h. h5 ic acid [88-99-3], which can be dehydrated to form phthaUc anhydride [85-44-9]. The vapor-phase reaction of naphthalene over a catalyst based on vanadium pentoxide is the commercial route used throughout the world. In the United States, the one phthaUc anhydride plant currently operating on naphthalene feedstock utilizes a fixed catalyst bed. The fiuid-bed process plants have all been shut down, and the preferred route used in the world is the fixed-bed process. 

Diels-Alder Reaction. In 1928, Diels and Alder discovered that 1,3-unsaturated organic compounds reacted with quinoid systems to give partially hydrogenated, cycHc compounds. In the course of their work, they found that 1 mol of 1,4-naphthoquinone [130-15-4] reacted readily with 1 mol of 1,3-butadiene [106-99-0] to give a partially hydrogenated anthraquinone (11) l,4,4a,9a-tetrahydro-9,10-anthracenedione [56136-14-2] which, on oxidation with chromic oxide, produced anthraquinone (43) ... 

Nucleophilic Substitution Reactions. Many of the transformations reali2ed through Michael additions to quiaones can also be achieved usiag nucleophilic substitution chemistry. In some iastances the stereoselectivity can be markedly improved ia this fashion (100), eg, ia the reaction of ben2enethiol with esters (R = CH C O) and ethers (R = 3) 1,4-naphthoquiaones. 2-Bromo-5-acetyloxy-l,4-naphthoquiQone [77189-69-6J, R = Br, yields 75% of 2-thiophenyl-5-acetyloxy-l,4-naphthoquinone [71700-93-1], R = SC H. 3-Bromo-5-methoxy-1,4-naphthoquinone [69833-10-9], R = Br, yields 82% of 3-thiophenyl-5-methoxy-l,4-naphthoquinone [112740-62-2] R = SC H. ... 

A process has been disclosed in which the mixture of naphthoquinones is reacted with a diene such as butadiene. Owing to the fact that the undesked product is an unsubstituted naphthoquinone, this dieneophile readily reacts to form a Diels-Alder adduct. By appropriate control of reaction parameters, Htde reaction is observed with the substituted naphthoquinone. Differential solubiUty of the adduct and vitamin allows for a facile separation (57,58). 

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). 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

The only satisfactory method of preparing /3-naphthoquinone is by the oxidation of 1,2-aminonaphthol in acid solution, and the chief problem involved is that of the preparation of this intermediate in suitable yield and purity. This problem and the literature pertaining to it are discussed elsewhere. Most reports of the preparation of the aminonaphthol include some description of its oxidation, but the only particularly helpful comment on the reaction is that ferric chloride is a better oxidizing agent than chromic acid because at a low temperature it docs not attack the quinone, even when present in excess. ... 

When just a trace of dark impurity is present, as in some of the commercial preparations, a completely pure product is easily obtained by vacuum distillation, but the ordinary crude reaction product is likely to decompose when treated in this manner. The ether method introduced in the present procedure has the advantage of being simple and efficient. It is equally applicable to the purification of the homologues of a-naphthoquinone. 

The reaction mechanism has not been elucidated. It is possible that formaldehyde reacts by oxidation as in the Marquis reaction (see formaldehyde — sulfuric acid reagent), whereby colored salts are formed with naphthoquinone sulfonic acid. 

Tlie betaine 24, obtained from the reaction of 2,3-dichloro-l,4-naphthoquinone with a pyridine/water mixture, reacts with CI2 to form A-(l-... 

The y-nitrogen atom of a sulfonic acid azide is electrophilic and reacts in an electrophilic aromatic substitution with an activated benzene or naphthalene derivative, e.g., a phenoxide ion, forming a l-tosyl-3-aryltriazene (2.47). The 1,4-quinone diazide is obtained by hydrolysis (Scheme 2-30, Tedder and Webster, 1960). The general applicability of this reaction seems to be doubtful. With 1-naphthol the 1,2-naphthoquinone diazide was obtained, not the 1,4-isomer. 

Naphthoquinone diazides 32, 284ff., see also Quinone diazides 2,3-Naphthotriazole, formation 132 f. Negations, psycholinguistics of 215 Nesmeyanov reactions 273 ff. Nicotinamide-adenine nucleotide (NAD+) 328 f. 

A benzannulation reaction yielding the naphthoquinone 61 could also be performed with the ruthenium carborane-stabilised carbene 60 and 1-hexyne [56] (Scheme 36). The ruthenium carbene unit can be regarded as an 18-electron fragment containing a formal Ru(II) centre coordinated to a dianionic six-electron-donor cobaltacarborane ligand. 

The fact that pentacarbonyl carbene complexes react with enynes in a chemo-selective and regiospecific way at the alkyne functionality was successfully applied in the total synthesis of vitamins of the Kj and K2 series [58]. Oxidation of the intermediate tricarbonyl(dihydrovitamin K) chromium complexes with silver oxide afforded the desired naphthoquinone-based vitamin K compounds 65. Compared to customary strategies, the benzannulation reaction proved to be superior as it avoids conditions favouring (E)/(Z)-isomerisation within the allylic side chain. The basic representative vitamin K3 (menadione) 66 was synthesised in a straightforward manner from pentacarbonyl carbene complex 1 and propyne (Scheme 38). 

Nanaomycin A 103 and deoxyfrenolicin 108 are members of a group of naphthoquinone antibiotics based on the isochroman skeleton. The therapeutic potential of these natural products has attracted considerable attention, and different approaches towards their synthesis have been reported [65,66]. The key step in the total synthesis of racemic nanaomycin A 103 is the chemo-and regioselective benzannulation reaction of carbene complex 101 and allylacety-lene 100 to give allyl-substituted naphthoquinone 102 after oxidative workup in 52% yield [65] (Scheme 47). The allyl functionality is crucial for a subsequent intramolecular alkoxycarbonylation to build up the isochroman structure. However, modest yields and the long sequence required to introduce the... 

For that reason an intramolecular benzannulation was developed, which incorporates all components for the intramolecular alkoxycarbonylation into the naphthoquinone 105 [65]. Based on that strategy a short and convergent pathway for the synthesis of racemic deoxyfrenolicin 108 was accomplished. Xu et al. replaced the allylacetylene 100 in the reaction sequence for nanaomycin A by alkynoate 106. The benzannulation product 107 was an appropriate precursor for a subsequent tandem oxa-Pictet-Spengler cyclisation/DDQ-induced coupling reaction [66]. Following this strategy the total synthesis of enan-tiomerically pure deoxyfrenolicin could be accomplished (Scheme 48). 

Danishefsky et al. succeeded in preparing the benz[a] anthracene core structure 111 of angucycline antibiotics by performing a benzannulation reaction with the cycloalkynone 109 [69]. Deprotonation of the naphthoquinone 110 with DBU yields the desired anthraquinone 111 (Scheme 49). 

Studies of diastereoselectivity in Diels-Alder reactions of (S)S-4a,5,8,8a-tetrahydro-5,8-methane-2-(p-tolysulfinyl)-1,4-naphthoquinones with cyclopentadiene [147]... 

A broad study on the MW-assisted Diels Alder reactions of 2H-pyran-2-ones 50 and 51 with 1,4-naphthoquinone 52 and N-phenylmaleimide 53 (Equations 4.3) supported on silica-gel, K-10 montmorillonite, fitrol and alumina was carried out by Samant and colleagues [41]. 

The aqueous [4+2] cycloaddition reaction of 1,4-naphthoquinones 115 with methoxy cyclohexadiene performed in the presence of bovine serum albumin (BSA) is one of the first examples of protein-promoted Diels Alder reactions [79]. Some results are reported in Table 4.18. The globular protein does not affect the regioisomer ratio of adducts. The highest enantiomeric excess was obtained in the cycloaddition of juglone 115 (R = H) with 1-methoxy-1,3-cyclohexadiene 116. 

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