2- methylanthracene

The low solubility of fullerene (Ceo) in common organic solvents such as THE, MeCN and DCM interferes with its functionalization, which is a key step for its synthetic applications. Solid state photochemistry is a powerful strategy for overcoming this difficulty. Thus a 1 1 mixture of Cgo and 9-methylanthra-cene (Equation 4.10, R = Me) exposed to a high-pressure mercury lamp gives the adduct 72 (R = Me) with 68% conversion [51]. No 9-methylanthracene dimers were detected. Anthracene does not react with Ceo under these conditions this has been correlated to its ionization potential which is lower than that of the 9-methyl derivative. This suggests that the Diels-Alder reaction proceeds via photo-induced electron transfer from 9-methylanthracene to the triplet excited state of Ceo-... 

The decarboxylation of the caesium salt of 9-methylanthracene-10-acetic acid occurs at an even lower potential (0.7 V) and affords the dimer as well as the methyl ether (Eq. 40) [342], The low oxidation potentials for the decarboxylation of 54 (0.13 to 0.77 V) [306a] and 55 (—0.17 V) [306b] indicate too, that the initial electron transfer occurs from the amino or aryl group rather than from the carboxylate. 

The hydrogenation of arenes also has attracted interest, but until recently only a few catalytic systems have been found effective.56-60 The catalytic activity of [Rh(MeOH)2(diphos)]X and of [RuH2(H2)(PPh3)3] in the hydrogenation of 9-trifiuoroacetylanthracene and 9-methylanthracene has been explored.61,62... 

Chemical Name 9-methylanthracene CAS Registry No 779-02-2 Molecular Formula C15H12 Molecular Weight 192.256 Melting Point (°C) ... 

Reported aqueous solubilities of 9-methylanthracene at various temperature and the empirical temperature dependence equations... 

FIGURE 4.1.1.27.1 Logarithm of mole fraction solubility (In x) versus reciprocal temperature for 9-methylanthracene. 

The photo-induced single and double Diels-Alder reactions between [60]fullerene and 9-methylanthracene (212) which gave 213 and 214 were performed in the solid state by Mikami and colleagues (equation 60)141. The Diels-Alder reaction was considered to proceed following a photo-induced electron transfer from 9-methylanthracene to fullerene. The higher ionization potential of anthracene should explain its inreactivity toward the cycloaddition reaction with [60]fullerene. 

An even more pronounced retro-Diels-Alder reaction occurs by using 1,3-di-phenylisobenzofuran (DPIF), 9-methylanthracene or 9,10-dimethylanthracene as dienes [8, 10-12]. The monoadduct of DPIF cannot be isolated from the reaction mixture, while the monoadduct of the 9-methyl- or 9,10-dimethyl- derivatives of anthracene can be isolated at temperatures lower than room temperature [10]. Both anthracene derivatives decompose at room temperature, the adduct with one methyl group within hours, the adduct with two methyl groups within minutes. For DPIF and the anthracene compounds the retro-Diels-Alder reaction seems to be facilitated by steric repulsion due to the bulky groups. However, as shown by Wudl and coworkers [13], the cycloadduct of with isobenzofuran (Scheme 4.2), which was generated in situ from l,4-dihydro-l,4-epoxy-3-phenylisoquinoline, is stable in the solid state as well as in solution and shows no tendency to undergo cycloreversion. 

Figure 8.17 (i) Projection of the crystal structure of 1, 8-dichloro-9-methylanthracene in the ac-plane (ii) molecular arrangement in the same plane after the translation (201) [010] which brings neighbouring molecules to favourable geometry for the formation of trans-dimer. (After Thomas, 1974.)... 

In some molecules, the interaction can develop into a stronger force and the interplanar distance further reduced to form stable photodimers through covalent bonds. For example, anthracene forms a photodimer and no excimer emission is observed, whereas some of its derivatives with bulky substituents which hinder close approach give excimer fluorescence. In 9-methylanthracene both photodimer formation and excimer emission is observed. 9, 10-diphenylanthracene neither forms a photodimer nor emits excimer fluorescence due to steric hindrance. These observations are tabulated in the Table 6.3, which shows that the nature of the excited state is also important. 

---