Naphthalene ring 3,4-dihydro

Benzene and naphthalene rings having an electron withdrawing carboxylic acid or ester substituent are more easily reduced by an electron transfer process than the parent hydrocarbons themselves, Phthalic acid 13 and terephthalic acid 14 are converted to the dihydro derivatives at a lead cathode in sulphuric acid [49, 50]. These... 

Alkylnaphthalene-2-carboxylates [82] have been prepared in a similar way to benzoate esters and they give compounds with values 60-80°C higher comparable increases (= 80-90 °C) are obtained by replacing a benzene by naphthalene in cyano-biphenyls [83-85]. A naphthalene ring also has several possible states of reduction ranging from the dihydro compound to the... 

The dihydro naphthalene 12 was aromatized by first in situ reduction of the carbonyl functionality with lithium aluminum hydride in THF at 60°C for 4 h. Treatment of the carbinol solution with HCl gas provided rapid dehydration of the carbinol to the naphthalene ring 13. The benzo[a]fluorene derivative, cyclization of the 2-aryl ring onto the carbinol group, was not observed.5 Naphthalene 13 was obtained in 68% yield. Demethylation of the methoxy groups with excess gaseous BCI3 in methylene chloride provided 1 as the HCl salt. 

Table 2 summarizes pK measurements for the simplest protonated aromatic hydrocarbons. The columns to the right and left of the benzenonium ion correspond to benzoannelation of ions subject to protonation at the 2- and 4-positions of the benzene ring, respectively. In the parent ion the two positions correspond to resonance forms (one of which has been rotated through 120° in the table). The naphthalenonium ion 17 is shown as being formed from the 1,4-water adduct (hydrate) of naphthalene. It may also be formed from the isomeric 2,1 hydrate (l,2-dihydro-2-naphthol) with pAR = -6.7 and pAn2o = 13.7. 

One carbon ring and chain extension of two different kinds of 1,3-diketones have been reported (Scheme 114).167 For the l,3-diarylpropane-l,3-dione system, the chain extension reaction has a high yield, whereas the 2-aroyl-3,4-dihydro-2//-naphthalen-1-one system results in a mixture of chain-extension and ring-expansion products with chain extension being the major process. 

The numbering in thiophene 1 starts at the sulfur atom and continues around the ring. The C-2 and C-5 carbon atoms are also designated as C-a the C-3 and C-4 carbons as C-/3. Substituted thiophenes arc named similarly to substituted benzenes. Some of the more common radicals (2-5) are shown in Figure 1. There are two dihydro derivatives, 2,3- 4 and 2,5-dihydrothiophene 5 and a single tetrahydrothiophene 6. The benzo derivatives benzo[/)]- 7 and benzo[r]thiophene 8 are considered analogues of naphthalene while dibenzothiophene (DBT) 9 is related to phenanthrene. 

Naphthalene (49) reacts with sodium in liquid ammonia to form a red complex which is quenched by methanol to form the 1,4-dihydro derivative (51), and may therefore be assumed to be the dianion (50).- If alcohol is present in the reaction mixture, then the 1,4,5,8-tetrahydro derivative (52) is formed (Scheme 6). 1-Naphthyl derivatives are reduced in the unsubstituted ring, whereas there is a maiked preference for reduction of the substituted ring in 2-methyl- and 2-methoxy-substituted isomers. This preference is not as well defined for bulkier substituents, however, and is reversed in the case of 2-f-butylnaphthalene further details are in a 1970 review. Because of the facile isomerization of the 1,4-dihydro isomers to conjugated derivatives, overreduction occurs readily and ether groups are fairly readily hydrogenolyzed. It is therefore important to select the reaction conditions with care.- ... 

Staggered configurations have also been observed for the tricarbonyl chromium complexes of phenanthrene 294, 295), 9,10-dihydro-phenanthrene 293, 295), anthracene 202), naphthalene 262), and 1-aminonaphthalene 58). The eclipsed configuration has been observed for the tricarbonyl complexes of anisole (57, 229), toluidine 60, 61), methylbenzoate (59), o-methoxyacetylbenzene, o-hydroxyacetylbenzene 101), 2-methoxy-[l-hydroxy-ethyl]benzene (99), and 2-methyl-[l-hydroxy-l-phenylpropyl]benzene (97). It is apparent that the orientation of the chromium tricarbonyl moiety is in many cases controlled by the substituents on the ring to which it is coordinated, and this has been attributed to mesomeric electron repulsion or withdrawal by the substituents 374). 

Reduction of aromatic rings by the action of Li metal in ammonia generally gives 1,4-addition and yields a dihydro compound. Thus from naphthalene, CioHs one can obtain CioHiq. (a) Draw the structure of this dihydro compound. 

When the double bond formed is conjugated to an aromatic ring, the yield can be much higher. Thus, a 97% yield of la,7b-dihydro-7b-(benzenesulfonyl)-l//-cyclopropa[a]naphthalene (4) was obtained by reaction of the corresponding bromo compound 3 and potassium /er/-butoxide in tetrahydrofuran. ... 

Dibromo-7-bromomethylene-7,7a-dihydro-l,l-dimethyl-lH-azirino[l,2-a]mdole, 3474 2,2 -Di-ierZ-butyl-3,3 -bioxaziridine, 3359 Dicyclopropyldiazomethane. 2824 1,4-Dihydrodicyclopropa[h, naphthalene, 3452 N-Dimethylethy 1-3,3 -dinitroazetidine, 2848 Dinitrogen pentaoxide, Strained ring heterocycles, 4748... 

It is accepted5-7 8 that at least for simple unsubstituted aromatics (these are the usual model compounds that are employed they are recognized as an oversimplification but a necessary first step in this kind of work), they are hydrotreated to the corresponding naphthenes, with stepwise saturation of the aromatic rings in the case of polyaromatics. Figure 8.2 shows the reactions that can occur with (a) benzene to cyclohexane, (b) naphthalene to tetralin to decalin, and (c) phenanthrene to the dihydro-, tetrahydro-, octahydro-, and perhydrophenanthrene forms. 

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