2-Substituted naphthalenes, reduction

Methoxytetralin, substituted naphthalene reduction to tetralin, 132-133 Methyl-2-(phenylcarbamoyl)butanoate, a,-unsaturated ester hydrocarbamoylation, 134 4-Methylbenzyl chloride [reductive... 

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. 

Substitution. Substitution products retain the same nuclear configuration as naphthalene. They are formed by the substitution of one or more hydrogen atoms with other functional groups. Substituted naphthalenes of commercial importance have been obtained by sulfonation, sulfonation and alkah fusion, alkylation, nitration and reduction, and chlorination. 

The above generalities apply particularly to palladium. Hydrogenation over platinum or rhodium are far less sensitive to the influence of steric crowding. Reduction of 1-t-butylnaphthalene over platinum, rhodium, and palladium resulted in values of /ci//c2 of 0.42, 0.71, and 0.024, respectively. Also, unlike mononuclear aromatics, palladium reduces substituted naphthalenes at substantially higher rates than does either platinum or rhodium. For example, the rate constants, k x 10 in mol sec" g catalyst", in acetic acid at 50 C and 1 atm, were (for 1,8-diisopropylnaphthalene) Pd (142), Pt(l8.4), and Rh(7.1)(25). 

Methoxytetralin [Partial Reduction of a Substituted Naphthalene to a Tetralin].262 1,5-Dimethoxynaphthalene (300 mg, 1.0 mmol) dissolved in... 

Tetrahydropyran (THP), aldehyde etherification, 67-68 Tetralin compounds, 5-methoxytetralin reduction of substituted naphthalene, 132-133... 

Table 9. Reduction potentials of silyl-substituted naphthalenes [68]...

In one of the more frequently utilized Birch reactions (the reduction of alkyl/alkoxy-substituted naphthalenes), two reduction products are obtained as shown in Scheme 7.10. The acidity of the alcohol employed for protonation determines the ratio of these two products. For example, the ratio of the product hydrogenated in the substituted fused ring to the product hydrogenated in the unsubstituted fused ring was compared for methanol... 

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. 

The ESR data for several silaacenaphthene and silaphenalene radical anions (Table VI) obtained by electrolytic reduction (101), are similar to the results for trimethylsilyl-substituted naphthalenes (Table V) (49). The polarographic reduction potentials were 0.2-0.4 volt more positive than that of naphthalene (101). Similarly, some silaphenalene derivatives of the type X[R = H(R ,R = H,H H,Me Me,Me) and R = Ph R1 = R2 = Me] were shown by polarographic analysis to reduce more easily than silylnaphthalene or naphthalene and the unassigned ESR spectra of the radical anions were reported (99). 

Radical cations have also been trapped with the hydride ion. Irradiation of aromatic hydrocarbons such as phenanthrene, anthracene and naphthalene in aqueous acetonitrile containing sodium borohydride and an electron acceptor produces the dihydroarenes (Yasuda et ai, 1981b). With monoalkyl naphthalenes reduction in both the unsubstituted and substituted rings occurs... 

The deactivating effects of alkyl and alkoxy substituents on the regiochemistry of reduction of substituted naphthalenes are exemplified below. ... 

The most widely used reductive degradation methods are zinc distillation and sodium amalgam reduction. Fused aromatic structures (methyl substituted naphthalene, anthracene, pyrene, and perylene) are the major digest products of this reduction of humic substances. 

It has not yet been found possible to find conditions under which naphthalene (CioHs) can be cleanly alkylated to provide simple products. Thus, alternative methods that involve reduction of more highly oxidized substituents to alkyl groups have been used when specific alkyl-substituted naphthalenes are sought. 

The perturbation of the yr-systems of radical anions of R3M substituted naphthalenes, formed by polarographic reduction, is discussed in terms of their ionization potentials, charge transfer excitations, reduction potential, and e.s.r. spin distribution. Base cleavage of arylsilanes is consistent with the formation of the carbanion XCeH4 as the rate determining step. The nature of the Ar—M... 

The reduction of substituted naphthalene with CgK demonstrates the high selectivity of the reduction, as only the 1,4-dihydronaphthalene is obtained [29]. This method can be used as an alternative route to the Birch reduction and its... 

The reduction of PAHs with CgK (reduction of substituted naphthalenes) is carried out as follows The compounds (1 mmol) in dry THF (50 mL) are added to freshly prepared CgK (12.5 mmol). The mixture is stirred at 0 °C for a few hours under argon, and quenched with water (10 mL). The reaction mixture is then filtered and washed with water and dichloromethane, and dried over MgS04. 

Complex hydrides have been used rather frequently for the conjugate reduction of activated dienes92-95. Just and coworkers92 found that the reduction of a,ft-unsaturated ketene 5,5-acetals with lithium triethylborohydride provided mixtures of 1,4- and 1,6-reduction products which were transformed into enals by treatment with mercuric salts (equation 27). Likewise, tetrahydro-3//-naphthalen-2-ones can be reduced with L-Selectride to the 1,6-reduction products93 -95 this reaction has been utilized in the stereoselective synthesis of several terpenes, e.g. of (/ )-(—)-ligularenolide (equation 28)95. Other methods for the conjugate reduction of acceptor-substituted dienes involve the use of methylcopper/diisobutylaluminum hydride96 and of the Hantzsch ester... 

Lund and coworkers [131] pioneered the use of aromatic anion radicals as mediators in a study of the catalytic reduction of bromobenzene by the electrogenerated anion radical of chrysene. Other early investigations involved the catalytic reduction of 1-bromo- and 1-chlorobutane by the anion radicals of trans-stilhene and anthracene [132], of 1-chlorohexane and 6-chloro-l-hexene by the naphthalene anion radical [133], and of 1-chlorooctane by the phenanthrene anion radical [134]. Simonet and coworkers [135] pointed out that a catalytically formed alkyl radical can react with an aromatic anion radical to form an alkylated aromatic hydrocarbon. Additional, comparatively recent work has centered on electron transfer between aromatic anion radicals and l,2-dichloro-l,2-diphenylethane [136], on reductive coupling of tert-butyl bromide with azobenzene, quinoxaline, and anthracene [137], and on the reactions of aromatic anion radicals with substituted benzyl chlorides [138], with... 

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