Dimethoxynaphthalenes

Acylation of 1,4-dimethoxynaphthalene with acetic anhydride (1.2 equiv) and aluminum chloride (2.2 equiv) in ethylene dichloride (60°C, 3 h) gives two products, 6-acetyl-l,4-dimethoxynaphthalene (30%) and l-hydroxy-2-acetyl-4-methoxynaphtha-lene (50%). Suggest a rationalization for the formation of these two products and, in particular, for the differing site of substitution in the two products. 

Sulfonamides are very difficult to hydrolyze. However, a photoactivated reductive method for desulfonylation has been developed.240 Sodium borohydride is used in conjunction with 1,2- or 1,4-dimethoxybenzene or 1,5-dimethoxynaphthalene. The photoexcited aromatic serves as an electron donor toward the sulfonyl group, which then fragments to give the deprotected amine. The NaBH4 reduces the radical cation and the sulfonyl radical. 

The reactions of the tetrahalogenobenzynes with alkoxynaphtha-lenes, in accord with the results previously mentioned, result in addition at the 1,4-positions. Thus tetrafluorobenzyne reacts with 1,2,3,4-tetra-fluoro-5-methoxynaphthalene to form (82) in good yield 90>. Reactions with 2,3-dimethoxynaphthalene lead to the formation of the adducts [83, X = F or Cl) 123>. These compounds are relatively unstable and are transformed slowly in the open atmosphere. Thus [83, X = C1) affords the di-ester (84). 

Johnson has developed two linear approaches to synthesize the C-nor-D-homosteroid skeleton (Scheme 2.2). In his first approach [21], tetralone 19, obtained from reduction of 2,5-dimethoxynaphthalene, was used as the source of the C,D-rings. The B- and A-rings were constructed by sequential Robinson annulations (19 —> 20 —> 21). The Cl 1,12 olefin was then introduced to provide 22. Ozonolysis of 22 followed by an aldol reaction of the resulting dialdehyde gave 23. Subsequent deformylation and deoxygenation afforded the cyclopamine skeleton 24. 

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

In 1,8-bis(dimethylamino)naphthalene steric and lone pair interactions are minimised in a structure (Einspahr et al., 1973) having the amino groups twisted and displaced above and below the plane of the naphthalene ring, as in [53] in which the almost planar naphthalene ring is shown as a dashed line. In l,8-bis(dimethylamino)-2,7-dimethoxynaphthalene, steric interactions involving the methoxy substituents bring about a further distortion as in [54] (Woolf, 1980). 

The kinetics of proton transfer from protonated 1,8-bis(dimethyl-amino)-2,7-dimethoxynaphthalene to substituted phenolate ions (69) were studied in 70% (v/v) Me2SO—H20 using the temperature-jump technique with spectrophotometric detection to follow reactions with half-lives in the range 1-100 ms (Hibbert and Robbins, 1978). A limited... 

Fig. 17 Forward (k,) and reverse (kr) rate coefficients for the deprotonation of protonated l,8-bis(dimethylamino)-2,7-dimethoxynaphthalene (O and ) and proto-nated l,8-bis(diethylamino)-2,7-dimethoxynaphthalene ( and ) by bases...

Fig. 18 Rate coefficients (kf) for the deprotonation of protonated 1,8-bis-(dimethylamino)-2,7-dimethoxynaphthalene by phenolate ions in aqueous solution...

The photophysical results1391 for the giant porphyrin - dimethoxynaphthalene - naphthoquinone - vio -logen tetrad, P-DMN-NQ.-MV2, 24 (Figure 22), complement those obtained for 23. Photoinduced charge separation, to form the giant CS state, +P-DMN-NQ -MV+, readily occurs in the syn, syn isomer, but not in the anti,syn isomer. This result... 

The strength of the hydrogen bonds in the protonated amines can be increased by the use of larger and additional groups to provide further steric strain. For example, the difference in strain between l,8-bis(dimethylamino)-naphthalene [33] and 1,8-bis(diethylamino)naphthalene leads to a piC,-value for the ethyl derivative enhanced by 0.5 units (Hibbert, 1974), and a similar difference is also observed in the fluorene series for [41] and [42]. Further strain can be introduced into the naphthalene series by the use of 2- and 7-methoxyl groups as substituents. This is illustrated by the pA -values of 1,8-bis(dimethylamino)naphthalene [piC, = 12.1 (Hibbert, 1974)] and l,8-bis(di-methylamino)-2,7-dimethoxynaphthalene [p, = 16.1 (Hibbert and Simpson, 1987a)] and by the piC,-values of [35] pK = 7.49 (Hibbert and Hunte,... 

An aqueous pATg-value of 16.1 has been measured for l,8-bis(dimethyl-amino)-2,7-dimethoxynaphthalene from studies in 35% (v/v) Me SO-HjO (Hibbert and Simpson, 1987a). The values of Ap/f, in Table 14 imply that [50], [51] and [52] are more acidic and [53] is less acidic than l,8-bis(dimethyl-amino)-2,7-dimethoxynaphthalene. Correspondingly, the amines derived from [50], [51] and [52] are less basic and that derived from [53] is more basic than l,8-bis(dimethylamino)-2,7-dimethoxynaphthalene. It follows that the amine 1,6-dimethyl-1,6-diazacyclodecane [53] is an extremely strong base in aqueous solution,... 

In the same way, the displacement of the unpaired electron over the whole molecules was observed for cation-radicals from Scheme 1.4d and 1.4e, in which 1,4-dimethoxynaphthalene units are syn- or anti-annealed to [2.2]paracyclophane (Wartini et al. 1998a, 1998b). In another study, the electron transfer between 1,4-dimethoxybenzene and 7,7-dicyanobenzoquinone methide moieties... 

Methoxynaphthalenes may be lithiated in their ortho or peri positions according to conditions (see Table 1 in Section LA). 1,4-Dimethoxynaphthalene, for example, perilithi-ates cleanly with f-BuLi (Scheme 67) ... 

In order to increase the n-n interaction with the aromatic guests, two molecular clips with naphthalene walls (compounds 8 and 9) were synthesized. These molecules had quite unexpected properties. Surprisingly, the clip with 1,4-dimethoxynaphthalene cavity walls (8) did not bind guest molecules [15]. The reason for this behavior became clear when the X-ray structure was solved [16] (Fig. 6). All four methoxy groups of 8 were found to point into the cavity, completely blocking the access of a potential guest to the carbonyl groups. A similar structure may also be present in solution. 

The receptor with 2,7-dimethoxynaphthalene rings (9a), exists in solution as a mixture of three conformers [17] (Fig. 7). Due to the fact that each of the cavity walls can have two orientations, an anti-anti (aa), a syn-syn (ss), and a less symmetric syn-anti (sa) conformation are possible. These three conformations... 

Interestingly, the second reduction of the two bipyridinium units splits in the case of catenane 144+ (Fig. 13.15) obtained by interlocking cyclophane 124+ with a symmetric macrocycle containing two electron donor dimethoxynaphthalene (DMN)... 

Steric effects can also be caused by other types of strain, 1,8-Bis(diethylamino)-2.7-dimethoxynaphthalene (1) is an extremely strong base for a tertiary amine (p/f of the... 

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