Naphthalene, reduction reaction

Naphthalene undergoes electrophilic substitutions on the ring, resulting in its various derivatives. In addition to the usual electrophilic substitutions, naphthalene can also undergo oxidation and reduction reactions under specific conditions as outlined below. 

In addition to oxidation and reduction reactions, naphthalene readily undergoes substitution reactions such as nitration, halogenation, sulfonation, and acylation to produce a variety of other substances, which are used in the manufacture of dyes, insecticides, organic solvents, and synthetic resins. The principal use of naphthalene is for the production of phthalic anhydride, CgbLO,. 

Sodium-naphthalene reduction of organotrineopentoxyphosphonium salts led to the instantaneous loss of phosphonium ion phosphonates and phosphites were obtained748 (reaction 224). Alkali metal amalgams are efficient reagents for the reductive cleavage of both achiral and optically active phosphonium salts configuration is retained750 (Table 23). 

There is surprisingly little reliable information on the sulfonation of benzo[6]thiophene or its derivatives. Benzo[6]thiophene is more readily sulfonated than naphthalene.699 Reaction with concentrated sulfuric acid at 80° gives a mixture of mono-, di-, and trisulfonic acids, reaction with 70% sulfuric acid at 80° gives a monosulfonic acid,699 and reaction with 18% oleum gives a disulfonic acid 86 in each case the orientation of the products is unknown. Treatment of benzo[6]thiophene with concentrated sulfuric acid in acetic anhydride at 20° gives 3-acetylbenzo[6]thiophene (ca. 10%) and a sulfonation product (isolated as the potassium salt), which was believed to be the 3-sulfonic acid.660 Recently, the sulfonation product has been shown to contain the 2- (8%) and 3-isomer (92%), by conversion into the sulfonyl chlorides and reduction to a separable mixture of 2- and 3-mercaptobenzo[6]thiophene.84... 

While such a device has yet to be constructed, Debreczeny and co-workers have synthesized and studied a linear D-A, -A2 triad suitable for implementation in such a device.11641 In this system, compound 6, a 4-aminonaphthalene monoimide (AN I) electron donor is excited selectively with 400 nm laser pulses. Electron transfer from the excited state of ANI to Ai, naphthalene-1,8 4,5-diimide (NI), occurs across a 2,5-dimethylphenyl bridge with x = 420 ps and a quantum yield of 0.95. The dynamics of charge separation and recombination in these systems have been well characterized.11651 Spontaneous charge shift to A2, pyromellitimide (PI), is thermodynamically uphill and does not occur. The mechanism for switching makes use of the large absorption cross-section of the NI- anion radical at 480 nm, (e = 28,300). A second laser pulse at 480 nm can selectively excite this chromophore and provide the necessary energy to move the electron from NI- to PI. These systems do not rely on electrochemical oxidation-reduction reactions at an electrode. Thus, switching occurs on a subpicosecond time scale. 

The observations presented in Table II reveal that biphenyl is superior to both naphthalene and anthracene as an electron transfer agent for the reduction reaction. 

The results presented in Figure 1, Curve C, reveal that Illinois No. 6 coal undergoes an initial, very rapid reduction reaction. There is no initial, rapid reaction when the insoluble alkylation products are treated with potassium and naphthalene in tetrahydrofuran in a second alkylation reaction. The observations suggest that accessible acidic hydrogen atoms and other very readily reduced functional groups, e.g., quinoid... 

It is peripherally relevant that in reductions ol hexyl tluoride by NaNaph there is clear evidence against a practically reversible electron transfei to hexyl lluoride I55. Thus, the reactions arc cleanly lirst order in NaNaph and u large excess of naphthalene has no elTect on the rate. The possible influence of excess naphthalene on reactions of I-halo-I-mcihyl-2.2-diphenylcvclopropanes has not been reported [06.1 101. 

The identification of substrates for human P450 2S1 has been somewhat controversial. Reports of two oxidations—retinoic acid and naphthalene [1206, 1207]—have not been repeatable, at least withan . coli recombinant enzyme [350, 1208]. Bui etal. [1209] reported that P450 2S1 could not be reduced by NADPH-P450 reductase, but this was disproven in a series of reduction reactions [263, 1208, 1210]. 

In contrast, for reaction of organic halides with metallic magnesium, Whitesides ( 7) found a poor correlation with the rates of tri-n-butyltin hydride, and a reasonable correlation, especially with primary bromides, with reduction potentials, suggesting the formation of RXT. Sodium naphthalene reductions also correlate with reduction potentials for primary halides (4b). Moreover, reaction rates are faster in solvents favoring loose ion pairs over tight, further evidence for an early transition state involving election transfer and little bond dissociation. (4c)... 

In this case, the photoproduct was the p-methoxyacetophenone (13), a reduction product. The proposed mechanism (Scheme 2) was a simple homolysis of the carbon-oxygen bond. Ethanol serves as a hydrogen atom donor during this process, and in the presence of 1-M benzophenone or naphthalene the reaction was completely quenched, indicating a triplet reaction pathway. Benzophenone and naphthalene are known quenchers of acetophenones and have triplet energies of 68 and 62 kcal/mol, respectively. 

The first reaction was involved in a synthesis of morphine, the starting ketone being made by reduction of a substituted naphthalene O. Amer. Chem. Soc., 1950, 72, 3704). No doubt an epoxide could have been used as the electrophile. 

Reactions other than those of the nucleophilic reactivity of alkyl sulfates iavolve reactions with hydrocarbons, thermal degradation, sulfonation, halogenation of the alkyl groups, and reduction of the sulfate groups. Aromatic hydrocarbons, eg, benzene and naphthalene, react with alkyl sulfates when cataly2ed by aluminum chloride to give Fhedel-Crafts-type alkylation product mixtures (59). Isobutane is readily alkylated by a dipropyl sulfate mixture from the reaction of propylene ia propane with sulfuric acid (60). 

In the benzene and naphthalene series there are few examples of quinone reductions other than that of hydroquinone itself. There are, however, many intermediate reaction sequences in the anthraquinone series that depend on the generation, usually by employing aqueous "hydros" (sodium dithionite) of the so-called leuco compound. The reaction with leuco quinizarin [122308-59-2] is shown because this provides the key route to the important 1,4-diaminoanthtaquinones. 

The complex thioamide lolrestat (8) is an inhibitor of aldose reductase. This enzyme catalyzes the reduction of glucose to sorbitol. The enzyme is not very active, but in diabetic individuals where blood glucose levels can. spike to quite high levels in tissues where insulin is not required for glucose uptake (nerve, kidney, retina and lens) sorbitol is formed by the action of aldose reductase and contributes to diabetic complications very prominent among which are eye problems (diabetic retinopathy). Tolrestat is intended for oral administration to prevent this. One of its syntheses proceeds by conversion of 6-methoxy-5-(trifluoroniethyl)naphthalene-l-carboxyl-ic acid (6) to its acid chloride followed by carboxamide formation (7) with methyl N-methyl sarcosinate. Reaction of amide 7 with phosphorous pentasulfide produces the methyl ester thioamide which, on treatment with KOH, hydrolyzes to tolrestat (8) 2[. 

The following reductions have been carried out at 80° with the use of an excess of 2-propanol as the reaction medium (see Note 3) carbon tetrachloride to methane (47%), 1-bromonaph-thalene to naphthalene (90%), /3-bromostyrene to styrene (72%), jfi-bromoaniline to aniline (61%), p-bromophenol to phenol (66%), and monochloroacetone to acetone (30%). 

A convenient route to highly enantiomerically enriched a-alkoxy tributylslannanes 17 involves the enanlioselective reduction of acyl stannanes 16 with chiral reducing agents10. Thus reaction of acyl stannanes with lithium aluminum hydride, chirally modified by (S)-l,l -bi-naphthalene-2,2 -diol, followed by protection of the hydroxy group, lead to the desired a-alkoxy stannanes 17 in optical purities as high as 98 % ee. 

For some halides, it is advantageous to use finely powdered lithium and a catalytic amount of an aromatic hydrocarbon, usually naphthalene or 4,4 -di- -bu(ylbiphcnyl (DTBB).28 These reaction conditions involve either radical anions or dianions generated by reduction of the aromatic ring (see Section 5.6.1.2), which then convert the halide to a radical anion. Several useful functionalized lithium reagents have been prepared by this method. In the third example below, the reagent is trapped in situ by reaction with benzaldehyde. 

A number of products in which one of the naphthalene rings has been reduced have interesting pharmacological properties. Reaction of tetralone 30 with dimethylamine under TiCl catalysis produces the corresponding enamine (31). Reaction with formic acid at room temperature effects reduction of the... 

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