1,2,3-Trisubstituted naphthalenes

The number of naphthalene derivatives is very large, since the number of positional isomers is large 2 for monosubstitution, 10 for disubstitution—same substituent, 14 for disubstitition—different substituents, 14 for trisubstitution—same substituent, 42 for trisubstitution—two different substituents, 84 for trisubstitution—three different substituents, and so on with multiplying complexity. 

It should be noted that the 1 1 adducts of benzyne with pyrrylmag-nesium iodide, and A -methyl- and iV-benzylpyrrole were isolated and characterized only as the hydrobromide (113), the methiodide (115), and the picrate of 102, respectively. The low yields of all these derivatives are due in part to further reactions of thenaphthalen-l,4-imines with benzyne (see Section III, F and G). Yields are better where the starting pjnrole has an electron-withdrawing N-substituent. Some analogous naphthalen-l,4-imines expected from 1,2,5-trisubstituted pyrroles apparently rearrange spontaneously to j3-naphthylamine derivatives under the conditions for their formation (see Section III, F). The related adducts 107 and 108 are formed from tetrahalobenzynes and N-methy Ipyrrole. 

Surprisingly, in view of the preparation of 1,2,3,4-A-penta-substituted naphthalen-l,4-imines (109-112), the 1,4-iV-trisubstituted compoimds... 

The methodology was extended to an asymmetric introduction of snbstitnents to a naphthalene ring. When chiral naphthyloxazolines 13 were used as substrates, di- or trisubstituted dihydronaphthalenes 15 were obtained in high diastereomeric ratio (dr) after the treatment of intermediate azaenolate 14 with an electrophile (equation 7) °. Analogous reactions with a chiral naphthaldehyde imine were also reported . 

Citronellal, an aldehyde with a trisubstituted double bond, was hydrogenated to citronellol over a ruthenium catalyst poisoned with lead acetate in 90-100% yields (eq. 5.22)46 or over chromium-promoted Raney Ni in 94% yield in methanol at 75°C and about 0.31 MPa H2.47 Court et al. studied the selective hydrogenation of citral (1, eq. 5.24) to citronellol over unsupported Nij. o catalysts, prepared by reduction of mixtures of metal iodides with naphthalene-sodium as reducing agent, in cyclohexane and in 2-propanol at 80°C and 1.0 MPa H2.48 Higher yields of citronellol were obtained in 2-propanol than in cyclohexane, primarily via citronellal as the predominant intermediate. The yields of citronellol for the overall hydrogenation in 2-propanol over Mo-promoted catalysts were Mo0 03 96%, Mo0 06 98%, and Mo012 96%. 

As is to be expected from non-dipolar 2D NLO-phores, the ir system of simple benzene or naphthalene derivatives is too small to show practically useful NLO responses (Wortmann et al., 1993 Wolff et al., 1997). Especially the perpendicular transition is of quite low intensity as indicated by the smaller double-pointed arrow in Scheme 25. Therefore, the tri- and tetrasubstituted blueprint structures [98]-[100] (Scheme 20) were systematically elongated in one, two or all three directions by the interpolation of phenyl-ethynyl bridges. The use of triple bonds eliminates possible conformational isomerism. The trisubstituted type [124]-[127] is shown. By a combination of EOAM and polarization-dependent EFISHG and HRS, all four independent tensor components were evaluated (Wolff et al., 1997). Results are given in Table 5. The dipole moment ju, lies parallel to the z axis, the y axis within the molecular plane and the x axis perpendicular to the molecular plane. The /3 values (at 1064 nm) are in units of 10 ° C m° V . ... 

Reductive cleavage of imidazolidines 641 was implicated in the one-pot synthesis of N,N,N -trisubstituted ethylenediamines 643 from V,V -disubstituted ethylene diamines and an aldehyde R CHO. Presumably the intermediate iminium ion 642 is reduced by NaBH4 (Scheme 154) <2003SC3193>. Naphthalene-catalyzed lithiation of l,3-dimethyl-2-phenylimidazoline 644 leads to benzylic C-N bond cleavage. The intermediate dianion can be trapped with electrophiles (HjO, alkyl halides, ketones, and aldehydes) to afford diamines 645 <2005T3177>. 

Of the hydrocarbon components of gasoline, only xylenes, trisubstituted benzenes, and naphthalenes have been reported to undergo photolysis and photooxidation in aqueous solution. 

Alkanes, benzenes, and monosubstituted benzenes have been found to be resistant to photolytic breakdown in aqueous systems. The rate of reaction of trisubstituted benzenes and naphthalenes is competitive with that of volatilization from surface waters (Air Force 1981). 

Products derived from the two silenes (163) and (164), formed by competing 1,3-trimethylsilyl migrations, were obtained on irradiation of l-(3,4-dihydro-2H-6-pyranyl)-1-phenyltetramethyl-disilane (165)Separate studies have shown that silenes are intermediates in the photorearrangement of analogous benzenoid disilanes. 1,4-Bis(pentamethyldisilanyl)naphthalene (166), however, behaves in a different fashion, and in the absence of a trapping agent is converted on irradiation into the trisubstituted naphthalene (167) In the presence of methanol, the adduct (168) is also obtained the proposed pathway is outlined in Sotaeme 8. 

Alkoxybenzenes and -naphthalenes when treated at elevated temperatures with acylated a-amino acids in the presence of polyphosphoric acid react to give 2,4,5-trisubstituted oxazoles.69 A typical reaction is illustrated in Eq. (3). 

In aqueous environments, photooxidation of trisubstituted benzenes and naphthalenes may be quite rapid, while alkanes, benzenes, and monosubstituted benzenes are relatively resistant to photooxidation (Air Force 1989a). 

Pyrylium intermediates have been widely used as a four carbon atoms unit in various [4-1-2] cycloaddition reactions. The in situ gold(III)-catalyzed formation of pyrylinm intermediates from a 2-alkynylbenzaldehyde followed by the [4-1-2] cycloaddition with alkynes and bond shift afforded trisubstituted naphthalenes (Scheme 21.42) [49]. 

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