Naphthols, 3,4-disubstituted

Substituted amino naphthols were synthesized with reactions of 1-naphthols and the appropriate aldehydes. Some new 2,4-disubstituted-3,4-dihydro-2/f-naphth [i,2-e][i,i]oxazines that are expected to show biological activities were obtained by the ring-closure reactions with these aminonaphthols and various aldehydes. In addition, substituted-1,3-amino-hydroxy compounds, 2, can be used in chiral ligands synthesis. 

Stabilized ketene 6S. For l, 2 -disubstituted epoxide, species 6S undergoes 6-endo-dig electrocyclization (path b) [24] to form the six-membered ketone 66, ultimately giving naphthol products. l, 2, 2 -Trisubstituted epoxide species 6S undergoes 5-endo-dig cyclization (path a) to give the ketone species 67, finally producing l-alkylidene-2-indanones. The dialkyl substituent of the epoxide enhances the 5-endo-dig cyclization of species 65 via formation of a stable tertiary carbocation 67. We observed similar behavior for the cyclization of (o-styryl)ethynylbenzenes [15, 16]. Formation of 2,4-cyclohexadien-l-one is explicable according to 6-endo-dig cyclization of a ruthenium-stabilized ketene, vhich ultimately afforded the observed products [25]. 

The starting materials required for preparing the 2,3-disubstituted tetrahydronaphthalenes were 5,6,7,8-tetrahydro-2-naphthol (obtainable from tetrahydronaphthalene) and methyl 3-hydroxy-2-naphthoate, which was reduced to the known tetrahydro ester (Vc) and the latter saponified to the known tetrahydroacid. 

The starting material for the 1,2-disubstituted tetrahydro-naphthalenes was 5,6,7,8-tetrahydro-2-naphthol. This compound was converted in low yield to the known Via by the Reimer-Tiemann reaction. VI6 and Vic both were prepared from 1-bromo-2-methoxy-5,6,7,8-tetrahydronaphthalene. Although VI6 was prepared according to the method of O Farrell et al. [3], we obtained a much higher yield,... 

Coupling of alkynes with 1,.2-aryl dialdehydesThe complexes of Nb-CI3 DME (1) with alkynes react with phthalic dicarboxaldehyde to give, after workup with aqueous KOH, 2,3-disubstituted naphthols. In the case of unsymmetrical... 

Similar substitutions are obtained with the carbanions of esters [129, 131], /V,7V-disubstituted amides [137-138] and nitriles [139-140]. The anion of cyclohexylideneacetonitrile reacts with p-bromoanisole exclusively at the y position (Scheme 26) [141]. The ambient anions of phenols and anilines react as carbon nucleophiles, as observed in the reactions of halobenzenes with 2-naphthylamine [142], 2-naphthol [143] and various phenols (Scheme 27) [144-145],... 

The effect of polyoxyethylene(9-5) diisobutylphenol, Triton X-100, on the rate of oxidative coupling between disubstituted p-phenylenedi-amines and phenols or naphthols (see, for example, equation 46) has been investigated by Tong and Glesmann (1957b). The observed rate constants were resolved into those for the reactions occurring in the micellar phase and in the bulk aqueous phase. The rate of oxidative coupling... 

In 1994, a review on the further development and improvement of the n scale was given by Laurence, Abboud et al. [227], They redetermined n values for a total of 229 solvents, this time using only two (instead of seven) solvatochromic nitroaromatics as indicator compounds, i.e. 4-nitroanisole and A,A-dimethylamino-4-nitroaniline, for good reasons see later and reference [227] for a more detailed discussion. A thermodynamic analysis of the n scale [and the t(30) scale] has been reported by Matyushov et al. [228]. Using six novel diaza merocyanine dyes of the type R-N=N-R (R = N-methylpyridinium-4-yl or A-methylbenzothiazolium-2-yl, and R = 2,6-disubstituted 4-phenolates or 2-naphtholate) instead of nitroaromatics as positively solvatochromic probe compounds, an analogous n azo scale was developed by Buncel et al., which correlates reasonable well with the n scale, but has some advantages for a detailed discussion, see references [333], Another n scale, based solely on naphthalene, anthracene, and y9-carotene, was constructed by Abe [338], n values are mixed solvent parameters, measuring the solvent dipolarity and polarizability. The differences in the various n scales are caused by the different mixture of dipolarity and polarizability measured by the respective indicator. The n scale of Abe is practically independent of the solvent dipolarity, whereas Kamlet-Taft s n and Buncel s n azo reflect different contributions of both solvent dipolarity and polarizability. 

The formation of this product of a consecutive disubstitution is apparently not easy to understand. It is known that an arylazo residue diecreases the reactivity of a phenol or a naphthol for substitution by a second diazonium ion by 3 to 5 orders of ten. In phenols and naphthol the favorable effect of promoting the dissociation of a proton from the substrate does not work it was found only for C-acids (see discussion in the preceding Sect. 4.1). 

A regular incorporation of the phenolic units into calix[4]arenes has been observed, if 2-or 6-hydroxymethyl derivatives of 3,4-disubstituted phenols (including cyclic compounds like S-naphthol) are condensed under these conditions (Scheme 5). The resulting calix[4]arenes 8 assume an inherently chiral, C4-symmetrical cone conformation which can be fixed by O-alkylation (see below). In an analogous manner a 2-hydroxymethyl phenol substituted at the 4-position with a porphyrin moiety has been converted to the corresponding calix[4]arene 9 in 60% yield by treatment with NaOH in refluxing diphenyl ether. ... 

The most general method for the synthesis of benzothiazoles and benzothiazolines is the cycli-zation of or(/io-disubstituted benzenes, o-aminothiophenols, or naphthols with electrophilic reagents. This approach is well-documented in CHEC-I <84CHEC-l(6)32i>. 

NbCI3-(DME) and NbCI4(THF)2 catalysts in the synthesis of Vic diamines, 2-aminoalcohols or 2,3-disubstituted-1-naphthols by coupling of imines, imines with ketones or dialdehydes acetylenes... 

Benzo[l)]furan-6-carbonitrile and 6-cyanobenzo[l>]furan-2-boronic acid pinacol ester were prepared in the presence of Cu. (13SC1974) 2-Substituted benzo[ ]furans were synthesized by employing easily accessible A/-tosylhy-drazones and o-hydroxy or o-amino phenylacetylenes as substrates. (13OBC1490) One-pot access to either 2-naphthols or benzo[l>]furans via the aerobic Wacker-type oxidation/intramolecular aldol cyclization was accomplished. (13T1532 ) 5,5-Disubstituted-2,2 -bisbenzofuran derivatives were produced by treatment of 4-substituted-2-(2-trimethylsilylethynyl) phenyl tert-butyldimethylsilyl ether analogues with CuCl as a catalyst (13TL2655). 

A survey has appeared of the reactivity of 2,6-disubstituted phenols and 2-methyl-l-naphthol with A -methoxymethylmonoaza-12-crown-4 ether in the Mannich reaction. The acidity and the electrostatic charge of the aromatic compounds are indicators of their reactivity. Compound (20) was formed from the above naphthol in this reaction. In the presence of aluminium chloride, chlorothiophenes react with activated aromatic compounds to form arylthiophenes. The aluminium chloride-catalysed selfcondensation of chlorothiophenes produces mainly bi- and ter-thiophenes. 

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