Naphthalene nucleus

Hyd.rogena.tlon. Hydrogen is added to the naphthalene nucleus by reagents that do not affect ben2ene. Two, four, six, eight, or ten hydrogen atoms may add. Of these, only the tetra- and decahydronaphthalenes are commercially significant. In addition to the commercially important... 

Several systems of nomenclature have been used for naphthalene, and many trivial and trade names are well estabUshed. The Chemicaly hstracts Index Guide is employed in this article. The numbering of the naphthalene nucleus is shown in (1) older practices are given in (2) and (3). 

I he diverse range of phannacological actions of this structural class documents the belief that the naphthalene nucleus consists of a scaffold upon which vanous functional groups can be arranged tnd that the action elicited is a consequence of receptor response to the kind and spatial arrange ment of these functions... 

The secular equation for 1,2-dihydroanthracene resulting from the consideration of (I) the symmetrical unexcited structure, (II) the two unsymmetrical unexcited structures, (III) the sixteen first-excited structures not involving conjugation of the double bond and the naphthalene nucleus, and (IV) the six first-excited structures involving this conjugation, is... 

Such activity enhancement can be ascribed to planarity of the naphthalene nucleus and its disposition for n-n stacking between the DNA base pairs. There is no literature precedence for involvement of naphthalene in such processes unless it is % electron deficient.211,212 However, our results suggest that both alkylated and acylated naphthalenes are intercalators with bacterial DNA. 

Reconstitution of the QSAR to incorporate an indicator variable 7 for the presence (7 = 1) or absence (7 = 0) of a naphthalene nucleus yields QSAR (4). 

Early studies of the affinity of acid dyes for wool revealed noteworthy correlations with dye structure. For example, in four pairs of monoazo dyes differing only by replacement of a benzene by a naphthalene nucleus, the affinity increase in each pair was consistently within the range -4-6 to -6.3 kj/mol. In three related pairs of dyes, an additional sulpho group reduced the affinity by about -4 kj/mol. In a series of alkylsulphuric acids (ethyl, octyl, dodecyl) and in two series of monoazo dyes containing alkyl chains of increasing length, the increment per methylene group was consistently about -1.66 kj/mol. A close correlation between affinity and Mr was also obtained for a series of substituted phenylazo-l-naphthol-4- sulphonic acid dyes [115]. 

A totally different picture is presented by 3-phenylazo-2-naphthol. This unusual isomer cannot be prepared by a normal coupling procedure but has been obtained by reaction of 3-amino-2-naphthol with thionyl chloride to give the N-sulphinylamine (4-24), condensation of which with N-phenylhydroxylamine yields the desired product [59]. Here, assumption of a ketohydrazone form would entail loss of aromatic character in both rings of the naphthalene nucleus and the energetic unfavourability of this situation ensures that the compound exists solely in the hydroxyazo form. 

Assignment of an anti configuration to a [2](2,5)furano[2](l,4)naph-thalenophane (42) synthesized by Wasserman and Keehn 65> followed from a comparison of its 1H—NMR spectrum with that of [2]paracyclo-[2](2,5)furanophane (41 a) 66>. The absorption band assigned to the /3-furanoid proton Ha in the spectrum of 42 (r=4.38) appears in the same region as the corresponding band for 41 a. In the case of syn-42, a chemical shift would be expected due to the transannular shielding effect of the naphthalene nucleus. 

The authors suggest a scheme for the reaction mechanism in which the initial step involves a 1,4-addition of oxygen to the substituted naphthalene nucleus (35-+131). This is followed by methanolysis and intramolecular Diels—Alder addition giving the cyclization product 130, which appears to be unstable compared to 127. 

Chromium(iii) has been shown to complex with arsenazo(i) at the hydroxy-groups on the naphthalene nucleus. ... 

Oxazoline-directed conjugate addition of nucleophiles to a naphthalene nucleus is one of the most useful methods to prepare dihydronaphthalenes. Since Meyers last comprehensive review, the focus has been directed to stereoselective synthesis of these important compounds. Meyers laboratory has continued their preeminence in this field and has expanded the scope and applications of this reaction. 

This process competes favorably with benzylic hydrogen abstraction in toluene, less in ethylbenzene, and least in cumene (31). Such reactions do not seem significant in the oxidation of benzene derivatives. However, naphthalene reacts about 20 times as rapidly with phenyl radical as does benzene (16), and radical addition to the naphthalene nucleus may at least partly account for the slow oxidation rate in the methylnapthalenes. Among the minor products from both methylnaphthalene oxidations were compounds of molecular weight 296 ... 

This appeared unlikely for several reasons firstly, o-hydroxydiarylazo compounds form copper complexes in which the metal atom forms a part of a six-membered chelate ring and, secondly, interaction between the hydrogen atom in the 8-position of the naphthalene nucleus and the lone pair on the fl-nitrogen atom of the azo group would not favour a structure such as (51). 

The construction of peri-annelated heterocyclic systems I-XXIII is carried out by the addition of a three carbon-atom fragment to the ben-zoheterocycle (3 — 2) or of a heterocycle to a naphthalene nucleus (4 — 2) (see Scheme 1). In practice, the second approach (4 — 2) is used more often. 1,8-Disubstituted naphthalene derivatives serve as the initial compounds, and they may be divided into three main types (5-7) as potential precursors of peri-heterocycles I-XXIII (Scheme 2). 

The interaction of peri-acyloxybromo ketones Til with aromatic aldehydes in the presence of sodium methylate gives rise to 2-arylmethy-lidene derivatives of naphtho[bc]pyran-3-one 274 (89TH1). In all reactions just described, the pyran ring-closure occurs by formation of a C—O bond between the /3-carbon atom of a substituent in position 1 of the naphthalene nucleus and the oxygen atom of an 8-hydroxy group. 

The most common compounds from the naphtho[crf]pyran series are naphthalic anhydride and its various derivatives 378 substituted in the naphthalene nucleus. These derivatives are formed on heating naphthalic acids 377, which are obtained on oxidation of the corresponding acenaph-thenes. The syntheses of naphthalic acids 377 and their anhydrides are described in a monograph (66MI1). The interaction between naphthalic acid and sulfur tetrafluoride leads to 2,2,9,9-tetrafluoronaphtho[cd]pyran 379 (73ZOR689). 

Benzo[/]annelated naphtho[bc]thiepine-4-one derivatives 482 are obtained by cyclization of 8-arylmercapto-1 -naphthoic or 1-naphthylmercap-tosalicylic acids 480 and 481 (38M440 75CCC1604 84JHC1737). In the latter case, in order to avoid ortho-acylation, the ortho-position (towards the sulfur atom) of the naphthalene nucleus is blocked by a substituent. 

Steric factors strongly influences the relative proportions of N-aand N- 3 coordination. Thus, the azo compound 13 strongly favors the N- 3 coordinated configuration as a result of the interaction of the 6-methyl group with the electron lone pair of the N- 3 atom, and the azo compound 14 coordinates predominantly through the N-a atom, because this atom interacts with the hydrogen atom in the 8-position of the naphthalene nucleus. 

Polycyclic Nuclei. In general, arylpropionic and arylbutyric acids in which the aryl group is a polycyclic aromatic nucleus cyclize readily. Cyclization into the a-position of the naphthalene nucleus, for example, takes place more easily than into the benzene ring. The ring closure of the substituted naphthylpropionic acids XXXIII and XXXV proceeded smoothly. 

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