Synthesis of Esters of 9-Bromofluorene-4-carboxylic Acid
Abstract Generated abstract
This paper reports the preparation of new esters of 9-bromofluorene-4-carboxylic acid as part of work on chemical utilization of coal-tar phenanthrene oxidation products. The authors synthesize phenyl, nitrophenyl, aminophenyl, and ethyl derivatives using 9-bromofluorene-4-carboxylic acid obtained from 9-fluorenone-4-carboxylic acid, with esterification carried out in several cases through in situ formation of the acid chloride rather than prior isolation. Six previously undescribed crystalline esters are characterized by melting points and elemental analyses, with reported yields of 63 to 75 percent. The work shows that acylation of alcohols and phenols with this acid can be performed without isolating and purifying the corresponding acid chloride, simplifying the synthetic procedure.
Full Text
SYNTHESIS OF ESTERS OF 9-BROMOFLUORENE-4-CARBOXYLIC ACID
G. M. STEPNOVA, V. A. TRIGUBENKO, G. P. BELOKONEVA
(Presented by the scientific seminar of the Faculty of Chemical Technology)
At the Department of Technology of Organic Synthesis, a series of phenyl and substituted ethyl esters of 9-fluorenone-4-carboxylic acid had previously been obtained, and preliminary biological tests were carried out in order to determine the insecticidal activity of these compounds [1].
Continuing work on finding rational ways to utilize coal-tar phenanthrene [2], we obtained esters of 9-bromofluorene-4-carboxylic acid, which have been synthesized for the first time and may find application in the synthesis of agents acting predominantly in the region of efferent nerve endings.
The 9-bromofluorene-4-carboxylic acid required for the syntheses is obtained from 9-fluorenone-4-carboxylic acid by reduction with zinc dust in an ammoniacal medium to 9-hydroxyfluorene-4-carboxylic acid, followed by bromination [3]. Phenyl esters of 9-bromofluorene-4-carboxylic acid are obtained by the interaction of the corresponding phenol with the acid chloride of 9-bromofluorene-4-carboxylic acid. The ester syntheses were carried out without preliminary isolation and treatment of the acid chloride of 9-bromofluorene-4-carboxylic acid, which made it possible to avoid losses of the acid chloride associated with isolation and purification and to reduce significantly the time required to obtain the esters.
The o-aminophenyl ester of 9-bromofluorene-4-carboxylic acid is obtained from the o-nitrophenyl ester of 9-fluorenone-4-carboxylic acid by reduction with cast-iron turnings in an aqueous medium to the o-aminophenyl ester of 9-hydroxyfluorene-4-carboxylic acid, followed by bromination.
The esters of 9-bromofluorene-4-carboxylic acid are crystalline substances of white color with a yellowish tint, soluble in common organic solvents. The properties of the esters of 9-bromofluorene-4-carboxylic acid are given in Table 1.
Experimental Part
Phenyl esters of 9-bromofluorene-4-carboxylic acid
To a mixture of 0.02 gram-moles of 9-bromofluorene-4-carboxylic acid and 0.02 gram-mole of the corresponding phenol in xylene solution, heated to
Table 1
Physical properties of the esters obtained
| R | Melting point, °C | Carbon, %, calculated | Carbon, %, found | Hydrogen, %, calculated | Hydrogen, %, found | Nitrogen, %, calculated | Nitrogen, %, found |
|---|---|---|---|---|---|---|---|
| Ethyl | 105 | 60.6 | 59.7 | 4.08 | 4.04 | — | — |
| Phenyl | 98 | 65.75 | 65.2 | 3.56 | 3.47 | — | — |
| o-Nitrophenyl | 164 | 58.5 | 58.9 | 2.92 | 3.1 | 3.41 | 3.34 |
| p-Nitrophenyl | 153 | 58.5 | 57.93 | 2.92 | 3.17 | 3.41 | 3.4 |
| m-Nitrophenyl | 213 | 58.5 | 57.85 | 2.92 | 3.05 | 3.41 | 3.32 |
| o-Aminophenyl | 217 | 63.15 | 62.7 | 3.68 | 3.59 | 3.68 | 3.87 |
\[ \text{ROOC—fluorene framework bearing CHBr} \]
At \(90^\circ\mathrm{C}\), \(0.024\) gram-mole of phosphorus oxychloride is added gradually, dropwise. The reaction is then carried out at \(140\)—\(145^\circ\mathrm{C}\) for 4 hours. The reaction product, which precipitates from xylene on cooling, is dried, washed with a 10% sodium carbonate solution, and recrystallized from benzene. Yield: 75% of theory.
o-Aminophenyl ester of 9-bromofluorene-4-carboxylic acid
The synthesis of the o-nitrophenyl ester of 9-fluorenone-4-carboxylic acid is carried out by the procedure described above.
Reduction of the o-nitrophenyl ester of 9-fluorenone-4-carboxylic acid with cast-iron filings in an aqueous medium, with heating for 3 hours on a boiling water bath, gives the o-aminophenyl ester of 9-hydroxyfluorene-4-carboxylic acid.
To \(0.05\) gram-mole of the o-aminophenyl ester of 9-hydroxyfluorene-4-carboxylic acid in glacial acetic acid, \(0.15\) gram-mole of hydrobromic acid is added dropwise. The mixture is kept for 1 hour on a boiling water bath. The reaction product, which precipitates from the reaction mixture on cooling, is dried, washed with sodium carbonate solution, and recrystallized from alcohol. Yield: 64% of theory.
Ethyl ester of 9-bromofluorene-4-carboxylic acid
\(0.02\) gram-mole of 9-bromofluorene-4-carboxylic acid, \(0.02\) gram-mole of phosphorus pentachloride, and 20 ml of xylene are heated to \(70^\circ\mathrm{C}\) and kept at this temperature for 2—2.5 hours. Then \(0.06\) gram-mole of absolute ethyl alcohol is added to the reaction mixture, and it is heated on a boiling water bath for 1 hour. The reaction product, which precipitates from xylene on cooling, is dried, treated with sodium carbonate solution, and recrystallized from alcohol. Yield: 63% of theory.
Conclusions
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On the basis of the oxidation products of technical phenanthrene, 6 new esters of 9-bromofluorene-4-carboxylic acid, not described in the literature, were obtained.
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It has been established that the acylation reaction of alcohols and phenols can be carried out without preliminary isolation and treatment of 9-bromofluorene-4-carboxylic acid chloride.
References
- Kulev L. P., Gireva R. N., Kovalenok A. V. ZhOKh, vol. 1, No. 8, 1965.
- Kulev L. P. All-Union Interuniversity Conf. on the Chemistry and Technology of Monomers. Abstracts of reports and communications. MITKhT, 93, 1960.
- Staudinger, Kliegel. Berichte, 1909, vol. 134, 370.