Fluorene, acidity

As enolate precursors can be used CH-acidic carbonyl compounds such as malonic esters, cyanoacetic esters, acetoacetic esters and other /3-ketoesters, as well as aldehydes and ketones. Even CH-acidic hydrocarbons such as indene and fluorene can be converted into suitable carbon nucleophiles. 

Shortly before this work by Pschorr, similar ring closures had been described for other compounds in which two benzene rings are already linked. Thus Graebe and Ullmann (1894) found that 2-diazobenzophenone can be converted into fluorenone in the analogous manner (Scheme 10-74). Similarly, when Staedel (1894) added nitrous acid to 2,2 -diaminobenzophenone he obtained some 1-hydroxyfluorenone. The ring closure of 2-benzylbenzenediazonium ion to give fluorene (Scheme 10-75) was described by Fischer and Schmidt (1894). 

Intramolecular arylations can also be carried out photochemically. Huisgen and Zahler (1963 a) prepared fluoren-9-one by irradiation of benzophenone-diazonium salts in dilute sulfuric acid. The classical Pschorr synthesis of phenanthrene-9-carb-... 

In 75 % aqueous acetic acid, the bromination of fluorene at 25 °C obeys second-order kinetics in the presence of bromide ion and higher orders in its absence287, with Ea (17.85-44.85 °C) = 17.4, log A = 10.5 and AS = —12.4 however, these values were not corrected for the bromine-tribromide ion equilibrium, the constant for which is not known in this medium, and so they are not directly comparable with the proceeding values. In the absence of bromide ion the order with respect to bromine was 2.7-2.0, being lowest when [Br2]initial was least. Second- and third-order rate coefficients were determined for reaction in 90 and 75 wt. % aqueous acetic acid as 0.0026 and 1.61 (k3/k2 = 619), 0.115 and 12.2 (k3/k2 = 106) respectively, confirming the earlier observation that the second-order reaction becomes more important as the water content is increased. A value of 7.25 x 106 was determined for f3 6 (i.e. the 2 position of fluorene). 

Blackley548 measured the rates of deuteration of biphenylene, fluorene, tri-phenylene, and phenanthrene relative to o-xylene as 6.15 5.85 1.08 1.32, which is in very good agreement with the values of 8.80 7.00 - 1.14 which may be deduced from the detritiation data in Table 159, obtained using anhydrous trifluoroacetic acid. Aqueous trifluoroacetic acid (with the addition in some cases of benzene to assist solubility) was used by Rice550, who found that triptycene was 0.1 times as reactive per aromatic ring as o-xylene (cf. 0.13 derivable from Table 159) whereas the compound (XXXI) was 0.9 times as reactive as o-xylene. An exactly comparable measure is not available from Table 158, but dihydroanthracene (XXXII), which is similar, was 0.51 times as reactive as o-xylene and... 

This reaction is illustrative of a general procedure for the alkylation of active methylene functions in the presence of concentrated aqueous alkali catalyzed by tetraalkylammonium salts. This catalytic method has been used to alkylate arylacetonitriles with monohaloalkanes,2 dihaloalkanes,3 a-chloroethers,4 chloronitriles,.5 haloacetic acid esters,6 and halonitro aromatic compounds.7 It has also been used to alkylate ketones,8 lf/ indene,9 9i/-fluorene,ll) and the Reissert compound.11 The reaction is inhibited by alcohols and by iodide ion.2... 

Piperidinedicarboxylic acid, 4-[ [(9H-fluoren-9-ylmethyloxy)carbonyl] amino]-... 

To a 50-mL polypropylene vial (Note 1) are added 0.839 g (2.67 mmol) of 2-[ethyl[4-[(lE)-(4-nitrophenyl)azo]phenyl]amino]ethanol (Disperse Red 1, Note 2), 0.985 g of (2.39 mmol) N-[(9H-fluoren-9-ylmethoxy)carbonyl]-L-aspartic acid,l-(l, 1-dimethylethyl) ester (Fmoc-L-Asp-OtBu, Note 3), 3.26 g (4.73 mmol) of polystyrylsulfonyl chloride resin (Note 4), and 30 mL anhydrous methylene chloride (Note 5). The vial is capped and the mixture is shaken for five min (Note 6). N-Methylimidazole (0.764 mL, 9.58 mmol) is then added to the deep red mixture (Note 7) and the resulting mixture is shaken for 2 hr (Note 8). 

N-[(9H-fluoren-9-ylmethoxy)carbonyl]-L-aspartic acid, l-(l,l-dimethylethyl) ester L-Aspartic acid, N-[(9H-fluoren-9-ylmethoxy)carbonyl]-, l-(l,l-dimethylethyl ester (129460-09-9). 

Epoxidation of substituted spiro[cyclopentane-l,9 -fluorene]-2-enes 68 with a peroxidic reagent was studied [98], The spiro olefins react with m-chloroperbenzoic acid (mCPBA) in chloroform at 3 °C to give a mixture of the epoxides. In all cases (2-nitro (68b), 4-nitro (68c), 2-fluoro (68d) and 2-methoxyl (68e) groups), the iyn-epoxides, i.e., the syn addition of the peroxidic reagent with respect to the substituent, is favored. For example, for 6 nsyn anti = 63 31 for 68c syn anti = 65 35. Thus, a similar bias is observed in both the reduction of the carbonyl derivatives of 30 and the epoxidation of the derivatives of 68. 

Electron-rich aromatic compounds such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene can be benzoylated or acetylated by the corresponding Af-acylimidazole in trifluoroacetic acid to give the corresponding benzophenone or acetophenone derivative in good yield (Method A). As the actual acylating agent, a mixed anhydride of trifluoroacetic acid and benzoic acid has been proposed 1973... 

The acidity of 30 has been measured with reference to Streitwieser s acidity scale (87) a pKA value of 15.8 for 30 as compared to 22.8 for fluorene and 18.5 for 9-phenylfluorene demonstrates a significant increase in acidity (87). 

S)-N-(9-PHENYLFLUOREN-9-YL) ALANINE AND (S)-DIMETHYL N-(9-PHEN YLFLU0REN-9-YL)ASPARTATE L-Alanlne, N-(9-phenyl-9H-fluoren-9-yl)- and L-Aspartic acid, N-(9-phenyl-9H-fluoren-9-yl>, dimethyl ester)... 

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