A STUDY IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES

54. Synthesis of 9-Ethanolcarbazoles by the Reaction of Carbazoles with Ethylene Chlorohydrin

V. P. Lopatinskii, I. P. Zherebtsov, L. S. Alaberdina,
N. A. Khomyakova

(Presented by the scientific-methodological seminar of the organic departments of the Chemical-Technological Faculty of the Tomsk Polytechnic Institute)

9-Ethanolcarbazoles are of interest as intermediates for the synthesis of monomers based on carbazole [1, 2].

Two general methods for their preparation are: the action of ethylene oxide on potassium carbazole [1], or on carbazole and its substituted derivatives in the presence of alkalis in proton-acceptor solvents [3, 4, 5], and the action of ethylene chlorohydrin on carbazole in the presence of aqueous alkali solutions in methyl ethyl ketone [6] or acetone [7].

The latter method has been developed only for the preparation of 9-(β-hydroxy)ethylcarbazole.

In some cases, especially for preparative purposes, it is more convenient to use ethylene chlorohydrin as a reagent for introducing the hydroxyethyl group.

This method, however, as applied to the synthesis of 9-(β-hydroxy)ethylcarbazole, has significant disadvantages—a long duration and a low yield [6, 7].

The aim of our work was to study the possibilities of synthesizing 9-ethanolcarbazoles through ethylene chlorohydrin in order to improve the method for preparing 9-(β-hydroxy)ethylcarbazole by this route and to extend the synthesis to halogen-substituted 9-ethanolcarbazoles.

Preliminary experiments showed that, upon interaction of ethylene chlorohydrin and solid alkalis in such solvents as acetone or methyl ethyl ketone, ethylene oxide is liberated. When carbazole or its substituted derivatives are introduced into such a system and the reaction is carried out in a closed vessel, one could expect to obtain 9-ethanolcarbazoles in higher yields and with a shorter reaction time than described previously [6], since the reaction of ethylene oxide with carbazole [4] or its substituted derivatives [5] proceeds rapidly and gives good yields of 9-ethanolcarbazoles. This possibility was confirmed, and below are given the results of experiments on the preparation of 9-ethanolcarbazoles by the proposed method, the principal difference of which from the previously known method [6, 7] consists in carrying out the synthesis in the presence of solid caustic potash in a closed vessel.

Experimental Part

3-Chloro- and 3,6-dichlorocarbazoles were prepared by methods described previously [8, 9].

9-(β-Hydroxy)ethylcarbazole. A 2-liter flask is charged with 100 g of carbazole (m.p. 240°C), 100 g of freshly prepared powdered potassium hydroxide, 300 ml of methyl ethyl ketone, and 48 ml of ethylene chlorohydrin. The tightly closed flask is shaken for half an hour at room temperature, then kept for half an hour on a water bath heated to 45–50°, and shaken again. Half-hour cycles of shaking and heating are alternated so that the total duration of the reaction is 5–6 hours, after which the mixture is poured into water and washed free of alkali and solvent. The organic layer is separated and dried, giving 124 g (98%) of crude 9-(β-hydroxy)ethylcarbazole, which is purified as described in [4]. Pure 9-(β-hydroxy)ethylcarbazole melts at 81–82°C (literature 81–82, 83–83.5° [2]). Found, %: N 6.36; OH (Verley method) 8.1. C₁₄H₁₃ON. Calculated, %: N 6.63; OH 8.05.

3-Chloro-9-(β-hydroxy)ethylcarbazole. Under the conditions found for 9-(β-hydroxy)ethylcarbazole, from 200 g of 3-chlorocarbazole, 167 g of potassium hydroxide, 76.4 ml of ethylene chlorohydrin, and 600 ml of methyl ethyl ketone, 3-chloro-9-(β-hydroxy)ethylcarbazole is obtained in 98% yield. Purification of the crude product by vacuum distillation followed by recrystallization from a mixture of benzene and petroleum ether gives a substance with m.p. 93° (literature 93°C [5]).

Found, %: N 5.50; OH (Verley method) 6.75. C₁₄H₁₂ONCl.
Calculated, %: N 5.0; OH 6.02.

3,6-Dichloro-9-(β-hydroxy)ethylcarbazole

Under analogous conditions, from 174 g of 3,6-dichlorocarbazole, 124 g of potassium hydroxide, and 57 ml of ethylene chlorohydrin in 522 ml of methyl ethyl ketone, 3,6-dichloro-9-(β-hydroxy)ethylcarbazole is obtained in 97.5% yield. The crude product is purified by recrystallization from alcohol, giving a substance melting at 161–162° (literature 161–162°C [5]).

Found, %: N 4.97; OH (Verley method) 6.10. C₁₄H₁₁ONCl.
Calculated, %: N 5.0; OH 6.07.

Conclusions

1. A method has been improved for obtaining 9-(β-hydroxy)ethylcarbazole by the action of ethylene chlorohydrin on carbazole.

2. The method has been extended to 9-ethanolcarbazoles substituted in the nucleus.

LITERATURE

1. H. Otsuki, J. Okano, T. Takeda. J. Soc. Chem. Ind. Japan., 49, 169, 1946; C. A. 42, 6354, 1948.

2. Monomers, collection 2, IL, 1953.

3. V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Author’s certificate 159533, B. I. 1, 16, 1964.

4. V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Izvestiya TPI, 112, 42, 1963.

5. V. P. Lopatinskii, I. P. Zherebtsov, E. E. Sirotkina, S. K. Vereshchagina. Izvestiya TPI, 136, 11, 1965.

6. H. Miller, R. Flowers, L. Flowers. J. Am. Chem. Soc., 70, 3019, 1948.

7. British Thomson-Houston Co., British Patent 620733 (1949), C. A. 43, 6669 (1949).

8. V. P. Lopatinskii, I. P. Zherebtsov. Methods for the Preparation of Chemical Reagents and Preparations, IREA, 11, 1964.

9. V. P. Lopatinskii, I. P. Zherebtsov, S. K. Vereshchagina. Methods for the Preparation of Chemical Reagents and Preparations, IREA, 11, 1964.