Research in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This paper reports the synthesis of a series of esters of 9-(beta-hydroxyethyl)carbazole and its 3-chloro and 3,6-dichloro derivatives, motivated by their potential use in preparing 9-vinylcarbazole and possible physiological activity. The authors compare esterification approaches, including reaction with acids in benzene in the presence of p-toluenesulfonic acid with azeotropic removal of water, and reactions with benzoyl chloride or acetic anhydride in pyridine for less suitable cases. The study provides reaction conditions, yields, melting points, nitrogen analyses, and molecular-weight data for the prepared compounds, and finds that azeotropic esterification can shorten reaction times and reduce acylating-agent consumption for several esters.
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PROCEEDINGS
OF THE TOMSK ORDER OF THE RED BANNER OF LABOR
POLYTECHNIC INSTITUTE
Volume 163 1970
RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES
37. Synthesis of Esters of 9-(β-Hydroxyethyl)carbazole and Its Chloro-Substituted Derivatives
V. P. LOPATINSKII, I. P. ZHEREBTSOV, L. I. SHELKOVNIKOVA
(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)
Flauers et al. synthesized a series of esters of 9-(β-hydroxyethyl)carbazole and showed that the esters can be used for obtaining 9-vinylcarbazole [1]. The synthesis of esters is also of interest in connection with their possible physiological action. With the latter in mind, in the present work we prepared a number of new esters of 9-(β-hydroxyethyl)carbazole, as well as its 3-chloro- and 3,6-dichloro-substituted derivatives.
In [1] the esters were obtained by the action of acids, their anhydrides, or acid chlorides upon heating with 9-(β-hydroxyethyl)carbazole. It proved that, by treating 9-(β-hydroxyethyl)carbazoles with acids in the presence of p-toluenesulfonic acid, with simultaneous removal of water as an azeotrope with benzene, the time required to obtain sufficiently high yields of esters can be considerably reduced, while decreasing the consumption of the acylating agent (method I). However, when benzoic acid was used, we did not succeed in achieving the same effect, owing to its reduced reactivity; therefore the synthesis of benzoates was carried out by us through the action of benzoyl chloride in pyridine (method II).
It was also found that, by treating 9-(β-hydroxyethyl)carbazoles with acetic anhydride in pyridine, the corresponding acetates can be obtained in a shorter time than described previously [1]. The synthesized substances were identified by the results of analysis for nitrogen and by the amount of acyl groups obtained upon saponification with alkali in methanol for two hours according to the known procedure [2].
Experimental Part
Starting Reagents
9-(β-Hydroxyethyl)carbazoles were prepared by the procedures described by us earlier [3, 4]. Acetic acid, benzoyl chloride, and acetic anhydride were of “chemically pure” grade. Monochloroacetic acid, trichloroacetic acid, phenoxyacetic acid, benzene, and p-toluenesulfonic acid were of “pure” grade. Pyridine was purified by the known method [5].
Table 1
| Complex esters | Esterifying agent and its amount, g | Solvent and its amount, ml | Amount of alcohol, g | Amount of catalyst, g | Duration, h | Yield, % | m.p., °C | Nitrogen found, % | Nitrogen calculated, % | Molecular weight found | Molecular weight calculated |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 9-(β-Hydroxyethyl)carbazole acetate | Acetic acid 5.4 | Benzene 150 | 20 | 2 | 2 | 78.3 | 75 | 5.80 | 5.55 | 255 | 253 |
| 9-(β-Hydroxyethyl)carbazole acetate | Acetic anhydride 10 | Pyridine 50 | 10 | — | 1 | 85.4 | 74 | 5.80 | 5.55 | 250 | 253 |
| 9-(β-Hydroxyethyl)carbazole benzoate | Benzoyl chloride 16 | Pyridine 38 | 50 | — | 0.5 | 70.1 | 142 | — | — | 310 | 315.5 |
| 9-(β-Hydroxyethyl)carbazole chloroacetate | Chloroacetic acid 13.4 | Benzene 150 | 20 | 2.5 | 2 | 79.4 | 80 | 5.03 | 4.88 | 280 | 287.7 |
| 9-(β-Hydroxyethyl)carbazole 3-chloroacetate | Chloroacetic acid 4.26 | Benzene 37.5 | 5 | 0.37 | 2 | 76 | 144 | 3.96 | 3.93 | 354 | 356 |
| 9-(β-Hydroxyethyl)carbazole phenoxyacetate | Phenoxyacetic acid 3.6 | Benzene 50 | 5 | 0.5 | 2 | 80.2 | 77 | 4.11 | 4.06 | 343 | 345 |
| 3-Chloro-9-(β-hydroxyethyl)carbazole acetate | Acetic acid 3.6 | Benzene 75 | 10 | 1.0 | 2 | 76 | 99 | 5.0 | 4.86 | 286 | 287.7 |
| 3-Chloro-9-(β-hydroxyethyl)carbazole acetate | Acetic anhydride 10 | Pyridine 50 | 10 | — | 2 | 86 | 98 | 5.1 | 4.86 | 284 | 287.5 |
| 3-Chloro-9-(β-hydroxyethyl)carbazole chloroacetate | Chloroacetic acid 6.35 | Benzene 112 | 15 | 1.5 | 2 | 79.2 | 85 | 4.16 | 4.35 | 315 | 322 |
| 3-Chloro-9-(β-hydroxyethyl)carbazole 3-chloroacetate | Chloroacetic acid 15 | Benzene 112 | 15 | 1.1 | 2 | 91.6 | 124 | 3.65 | 3.57 | 384.5 | 391 |
| 3-Chloro-9-(β-hydroxyethyl)carbazole benzoate | Benzoyl chloride 16 | Pyridine 70 | 25 | — | 1.5 | 80.5 | 149 | — | — | 364 | 349.5 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole acetate | Acetic anhydride 10 | Pyridine 24 | 45 | — | 1.5 | 87.5 | 123 | 4.51 | 4.35 | 320 | 321 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole acetate | Acetic acid 4.1 | Benzene 150 | 20 | 1.3 | 2 | 77.8 | 127 | 4.36 | 4.35 | 332 | 321 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole chloroacetate | Chloroacetic acid 7.42 | Benzene 150 | 20 | 1.3 | 2 | 82.3 | 119 | 4.10 | 3.92 | 349 | 356.5 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole trichloroacetate | Trichloroacetic acid 17.6 | Benzene 150 | 20 | 1.3 | 2 | 81.6 | 123 | 3.27 | 3.29 | 423 | 425.5 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole phenoxyacetate | Phenoxyacetic acid 7 | Benzene 150 | 20 | 1.2 | 2 | 74.5 | 130 | 3.62 | 3.38 | 422 | 414 |
| 3,6-Dichloro-9-(β-hydroxyethyl)carbazole benzoate | Benzoyl chloride 10 | Pyridine 12 | 20 | — | 1 | 84 | 173 | — | — | 390 | 384 |
Synthesis of Esters by Method I
To the alcohol dissolved in benzene are added p-toluenesulfonic acid and the acid whose ester is to be synthesized. The mixture is boiled on a water bath with a reflux condenser connected to a Dean–Stark trap. After two hours of boiling, the separation of water ceases, which indicates the completion of the reaction. The benzene is distilled off, and the residue is recrystallized from a suitable solvent.
Synthesis of Esters by Method II
To the alcohol dissolved in benzene is added benzoyl chloride (or acetic anhydride); the mixture is kept at 50°C for 0.5–1.5 hours, poured into water, and the precipitate that forms is recrystallized from a suitable solvent.
The synthesis conditions and the results obtained are summarized in Table 1.
Conclusions
- A series of esters of 9-(β-hydroxyethyl)carbazoles has been synthesized.
- It has been shown that, by esterification with acids with simultaneous removal of water, some esters of 9-(β-hydroxyethyl)carbazole can be obtained in a shorter time and with a lower consumption of acylating agent than by the method known in the literature.
References
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- I. Guben-Weyl. Methods of Organic Chemistry. Methods of Analysis. Goskhimizdat, 1963.
- V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Izv. TPI, 112, 42, 1963.
- V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov, S. K. Vereshchagina. Izv. TPI, 136, 1964.
- Yu. K. Yur’ev. Practical Work in Organic Chemistry. Goskhimizdat, 1961.