1.5- Dimethylanthracene

Deoxygenation of benzyl nitrosoformate, generated by retro-Diels-Alder reaction of its [4 + 2] cycloadduct 27 with 9,10-dimethylanthracene, with triphenylphosphane in anhydrous benzene yields the unstable benzyl 1//-azepine-1-carboxylate (28).143... 

We may now proceed to an analysis of the significance of the d values. If the transition state were close to the product, then the P values of the disubstituted ethylenes should be small, because in the product, the substituent is bonded to an sp hybridized carbon atom. Thus, it is incapable of resonance interaction. As the observed values of p for the trans-disubstituted dienophiles are very large, we conclude that the transition state is closer to reactants than to products. The cis-disubstituted dienophiles show a much smaller value of P than do the trans compounds. It therefore seems likely that the transition state for the CIS compounds will be closer to product than is the transition state for the trans compounds. The values of p for the reaction of the tnws-disubstituted dienophiles with 9,10-dimethylanthracene, while large, are much smaller than... 

Direct preparation of the gas is potentially hazardous, and explosive decomposition of the impure gas in the condensed state (below -20°C) has occurred. A safe procedure involving isolation of the 1 1 adduct with 9,10-dimethylanthracene is preferred. The impure gas contains nitrogen oxide and it is known that nitrosyl cyanide will react with the latter to form an explosive compound [1], The need to handle this compound of high explosion risk in small quantities, avoiding condensed states, is stressed [2],... 

Figure 10. A. Effects of varying methanol levels on the fluorescence quenching of 9,10-dimethylanthracene and 8,9,10,11-tetrahydro-BA by native DNA ([pOt ] - 5.0+x 10 M).

Chemical Name 9,10-dimethylanthracene CAS Registry No 781-43-1 Molecular Formula C16H14 Molecular Weight 206.282 Melting Point (°C) ... 

Reported aqueous solubilities of 9,10-dimethylanthracene at various temperature and the empirical temperature dependence equations... 

FIGURE 4.1.1.28.1 Logarithm of mole fraction solubility (In x) versus reciprocal temperature for 9, 10-dimethylanthracene. 

The partial reduction of 9,10-dimethylanthracene gave rise to two isomers in a 6 1 ratio. The major product was the ds-isomer, and the minor product the trans-isomer. The system is not suitable for the reduction of simple aromatics such as benzene or naphthalene. The yields there were quite low with 2% and 15%, respectively. 

Acyl nitroso compounds react with 1, 3-dienes as N-O heterodienophiles to produce cycloadducts, which have found use in the total synthesis of a number of nitrogen-containing natural products [21]. The cycloadducts of acyl nitroso compounds and 9,10-dimethylanthracene (4, Scheme 7.3) undergo thermal decomposition through retro-Diels-Alder reactions to produce acyl nitroso compounds under non-oxidative conditions and at relatively mild temperatures (40-100°C) [11-14]. Decomposition of these compounds provides a particularly clean method for the formation of acyl nitroso compounds. Photolysis or thermolysis of 3, 5-diphenyl-l, 2, 4-oxadiazole-4-oxide (5) generates the aromatic acyl nitroso compound (6) and ben-zonitrile (Scheme 7.3) [22, 23]. Other reactions that generate acyl nitroso compounds include the treatment of 5 with a nitrile oxide [24], the addition of N-methyl morpholine N-oxide to nitrile oxides and the decomposition of N, O-diacylated or alkylated N-hydroxyarylsulfonamides [25-29]. 

Extensive structure-activity relationships for the oxidative formation of C-acyl nitroso compounds or the release of NO or HNO from C-acyl nitroso compounds do not exist. However, the -R group of the cycloadducts of acyl nitroso compounds and 9, 10-dimethylanthracene (4, Scheme 7.3) appears to strongly influence the rate that these compounds undergo retro-Diels-Alder reactions to produce acyl nitroso compounds. 

In general, C-acyl nitroso compounds-9,10-dimethylanthracene cycloadducts derived from hydroxamic acids (-R = alkyl, aryl, ti/2 = 4.1 h for -R = -Ph at 60°C) decompose more slowly than those derived from N-hydroxycarbamates or N-hydroxyureas [11, 13, 14]. Further addition of alkyl groups to the N atom of N-hydroxyurea-derived cycloadducts produces a further increase in the rate of the retro-Diels-Alder reaction of these cycloadducts [36]. These general trends suggest the possibility of the development of acyl nitroso compound-9, 10-dimethylanthracene cycloadducts as a general class of HNO or NO donors with varied release profiles. 

Fig. 6 Typical PET probes (a) and representative fluorescence light-up responses toward selected metal ions in tabulated (b) and graphical form (c trace 1 = 14, trace 2 = 14-(Zn2+)2, trace DMA = 9,10-dimethylanthracene in MeCN). Color code coordinating atoms in blue, atoms which take part in the complexation and show (main, in 14) PET activity in orange, fluorophore in green. Lincoln and co-workers have demonstrated that the attachment of two dimethylamino groups through propylene spacers to the 9,10-positions of anthracene has a more than 100-fold weaker PET activity than the attachment through methylene spacers [62]. The blue N atoms in 14 are thus predominantly responsible for coordination. For symbols, see Fig. 3. Quantum yield of 14 in MeCN estimated from intensity readings published in [61] and quantum yield data of the parent compound without active PET, DMA, published in [63]. (Reprinted in part with permission from [61]. Copyright 1988 American Chemical Society)...

Nitrosyl cyanide, generated from nitrosyl chloride and silver cyanide in chloroform at — 20 °C, affords unstable products with various dienes, e.g. butadiene and 2,3-di-methyl-1,3-butadiene. With methyl sorbate, compound 182 is produced (equation 103), thebaine (183) gives 184 (equation 104)97 and 9,10-dimethylanthracene yields the stable cycloadduct 185, which decomposes into its components on heating and consequently can serve as a source of nitrosyl cyanide. Thus heating 185 with 1,4-diphenylbuta-1,3-diene gives the dihydrooxazine 186 and dimethylanthracene (equation 105)98. 

O-Nitrosocarbonyl compounds (nitrosoformates) 187 (R = t-Bu or Bn) are obtained from the hydroxylamines ROCONHOH. They can be trapped by reaction with butadiene to give the cycloadducts 188 (equation 107). With 9,10-dimethylanthracene the benzyl... 

Figure 3.3. Fluorescence emission spectra of compounds 1, 2, and 9,10-dimethylanthracene (DMA) in acetonitrile (all 10"4 M solutions). (Reproduced from Ref. 3i. Copyright 1988 American Chemical Society.)...

Comparison with the 9,10-dihydro-9,10-dimethylanthracene also listed clearly shows the aliphatic character of the proton-carrying C-atom. Whereas one of the methyl group signals practically remains at 6-3-6 6 p.p.m., the second methyl group is displaced to higher fields and thus approaches the position of an aliphatic methyl group. 

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. 

To improve the yield of six-times cyclopropanated adducts such as Tfj-C55(COOEt)i2 (17) a very efficient one-pot method has been developed (Scheme 10.7) [1, 25, 26, 58, 59]. The lynchpin of this strategy was the discovery that 9,10-dimethylanthracene... 

The 3-acyl-2(3F/)-oxazolones function as good dienophiles in cycloaddition reactions with cyclic 2,4-dienes such as cyclopentadienes and anthracenes. Thus, the thermal reaction of 3-acetyl-2(37/)-oxazolone with cyclopentadiene and the hexachloro and hexamethyl derivatives gives endo-cycloadducts exclusively. In particular, the chiral cycloadducts 221 and 223 derived from the diastereoselective Diels-Alder reactions of 3-(2-exo-alkoxy-l-apocamphanecarbonyl)-2(3/7)-oxazo-lones with hexamethylcyclopentadiene and 9,10-dimethylanthracene, respectively, are highly useful as chiral 2-oxazolidinone auxiliaries. The conformationally rigid roofed structures play a crucial role in affording excellent chiral induction (Fig. 5.54). 

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