Anthracene disubstituted

Cyclopenta[fc]dioxanes (44) are accessible from the reaction of the dioxenylmolybdenum carbene complex (43) with enynes <96JOC159>, whilst an intramolecular and stereoselective cyclisation of (Ti5-dienyl)tricarbonyliron(l+) cations affords chiral frans-2,3-disubstituted 1,4-dioxanes <96JOC1914>. 2,3-Dimethylidene-2,3-dihydro-1,4-benzodioxin is a precursor of the 3,8-dioxa-lff-cyclopropa[i]anthracene, which readily dimerises to dihydrotetraoxaheptacene (45) and the analogous heptaphene <96AJC533>. 

It should be noted that there are special features of the 9-substituted anthracenes that may introduce complications. The materials dimerize also in solution, yielding exclusively the centrosymmetric dimers, which are analogous to 87. Further, the few 9,9 -disubstituted dianthracenes that have been prepared are very unstable. Thus the head-to-head approach of two monomers is apparently an energetically unfavorable process. This is not so for the head-to-tail approach, and it is therefore not surprising that structures in which there are overlapped monomers related by centers of symmetry yield topochemical dimers. 

Anthracene and its 9,10-disubstituted derivatives add singlet oxygen to form the 9,10-endoperoxide,825-827 but strong directing effect is displayed by substituents in the 1,4 positions 827... 

The primary product (153) is photochemically converted into a derivative of benz[fl]anthracene-7,12-dione (154). A variety of heteroatom-containing polycyclic aromatic compounds was synthesized by using a 1,1-disubstituted ethene in which one of the substituents is a phenyl group and the other a 2-furyl, 2-benzo[ ]furyl, 2-thienyl, 3-... 

For aromatic hydrocarbons which form carbenium ions upon protonation, the order of oxidation potentials conforms to the rule. The peak potential for the proton adduct in methylene chloride/7% CF3SO3H was found (Hammerich and Parker, 1974) to be displaced about 1 5 V towards more positive potentials than that of the parent hydrocarbon for a series of 9,10-disubstituted anthracenes. We can use this potential difference to estimate p/2 for protonated hydrogen at about 1 5 V versus the Pt/H2 electrode and, accordingly, a methyl cation coordinated to a hydrogen molecule (= CHj ) would be expected to have its half peak potential somewhere around this value. For protonated hydrocarbons, half peak potentials fall in the region of 1 9- 2 2 V versus the Pd/H2 electrode. 

Nitration with mixed acid of benzo[g]isoquinoline and various methyl derivatives gave 5- and 9-substitution, with overall yields as shown in 11.80. Just as anthracene is very reactive (positional order 9 >> 1 > 2), here too the reactivity was such that, even at 0°C, dinitration could not be prevented (81 CHE 1217). 9-Substitution is somewhat surprising, since the 9-position is conjugated with nitrogen, but presumably the expected 5,6-disubstitution is prevented by steric hindrance. 

A new palladium-catalyzed enantioselective C(3)-allylation of 3-substituted 1/7-indoles 520 using trialkylboranes leads to the corresponding 3,3-disubstituted indolenines 522 (Equation 125) and indolines <2006JA6314>. The anthracene derived ligand 521 gave the best enantioselectivities. 

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. 

In 1,2-disubstituted series such as cis- and frans-2-alkyl-l-alkoxybenzocyclobutenok, the traits isomer is more likely to lead to a high yield of cycloaddition product than the cis since the 1,5-hydrogen shift is precluded, llie forced inward rotation of an aryl substituent in 1-methoxy-l-phenylbenzocyclobutene is potentially advantageous and leads to anthracene derivatives." See also the anthraquinone synthesis fiom the corresponding benzocyclobutenones (Section 6.1.5). 

The epoxidation reaction of arene oxide-oxepins has been encountered in the formation of the arene dioxides of naphthalene and anthracene rings A similar approach to the synthesis of epoxides of benzene oxide-oxepin using a peroxyacid oxidant, however, was unsuccessful (Z,Z)-muconaldehyde was isolated presumably via an oxepin-epoxide intermediate. The disubstituted benzene... 

In the case of fluorescence, that is, chemienergized by energy transfer, an energy acceptor is chosen that exhibits efficient fluorescence, for example, polycyclic aromatic hydrocarbons and, particularly, 9,10-disubstituted anthracene derivatives. Consequently, in the presence of such fluorescers (FI), the feeble direct chemiluminescence emission intensity is significantly enhanced. Such a phenomenon is commonly referred to as enhanced chemOuminescence (EC). 

Silylation of cyclopropa[ ]naphthalene proceeded indirectly to the disubstituted product 1,1-bis(trimethylsilyl)-l//-cyclopropa[Z ]naphthalene in 60% yield,and a sequential double deprotonation/silylation procedure was used to synthesize l,l-bis(trimethylsilyl)-1//-cyclo-propa[A]anthracene in 92% yield.Silylation of dicyclopropa[A,g]naphthalene has so far been unsuccessful. ... 

Appending two anthraeene subunits to an open-chain tetramine receptor brings some new interesting effects related to Zn" complexation [26]. The disubstituted system 13 in an aqueous basic solution shows (i) a weak structured emission band with >-max = 414nm, which is due to the normal anthracene emission and is quenched in most part via the amine-to-An eT mechanism, and (ii) a weak... 

Figure 18 The ball-and-stick model of the Zn" complex of the disubstituted tetramine 11, as calculated through a semi-empirical molecular orbital method. Hydrogen atoms have been omitted for clarity. The Zn" centre (black ball) chose a tetrahedral stereochemistry. Five-coordination (including a solvent molecule) is possible, too. Both stereochemical arrangements put the A/ A -dimethylaniline and anthracene subunits at a distance favourable to the occurrence of a donor-to-fluorophore eT process.

Cycloadditions with ynamines proceed readily at room temperature in carbon tetrachloride solution to yield a-pyrones (106) <77S252>. Likewise, a-pyrones (107) are also formed with cyclo-octyne <83TL1481>, whereas with benzyne the a-benzopyrone (108), produced initially, enters into a second [4 + 2] cycloaddition with benzyne to give ultimately the 9,10-disubstituted anthracene (109) (Scheme 12) <77S252>. 

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