RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES

XX. INTERACTION OF CERTAIN HALOGEN-SUBSTITUTED CARBAZOLES WITH ETHYLENE OXIDE

V. P. Lopatinskii, I. P. Zherebtsov, E. E. Sirotkina,
S. K. Vereshchagina

(Presented by the scientific seminar of the problem laboratories
of the Chemical-Technological Faculty)

A simple and convenient method for the synthesis of 9-(β-hydroxy)ethylcarbazole from carbazole and ethylene oxide in the presence of caustic alkalis in a medium of lower aliphatic ketones was described earlier [1]. We have not encountered information in the literature on 9-(β-hydroxy)ethyl derivatives of substituted carbazoles, although their synthesis could be of considerable interest, first of all for obtaining 9-vinyl derivatives, and also for other purposes.

In the present study we set ourselves the task of developing a method for the synthesis of 9-(β-hydroxy)ethyl derivatives of 3-chloro-, 3,6-dichloro-, 3-bromo-, and 3,6-dibromocarbazoles from halogenocarbazoles and ethylene oxide, using the previously studied method for obtaining 9-(β-hydroxy)ethylcarbazole. The starting halogen-substituted carbazoles were prepared by previously known procedures [2, 3], verified and refined.

A study of various factors affecting the yield of the final oxyethylation products showed that, in order to obtain good yields of 9-(β-hydroxy)ethyl derivatives of halogen-substituted carbazole, approximately the same conditions must be observed as in the oxyethylation of carbazole.

Oxyethylation proceeds most vigorously in the presence of caustic potash in a medium of lower aliphatic ketones (acetone or methyl ethyl ketone). Under these conditions, high degrees of conversion are achieved in 50–70 minutes at a temperature of 40–50°C, with an excess of ethylene oxide of about 0.1–0.3 mole and an equimolecular amount of caustic potash. Under these conditions the starting halogenocarbazole can scarcely be regenerated. Pure 3-halogeno- and 3,6-dihalogeno-9-(β-hydroxy)ethylcarbazoles are colorless crystalline substances, insoluble in water, readily soluble in alcohol and aromatic hydrocarbons, and less readily in aliphatic hydrocarbons. Identification of the products was carried out from the data of elemental analyses and the content of hydroxyl groups (by Verley).

Experimental Part

3-Chlorocarbazole

Into a flask equipped with a reflux condenser, stirrer, and dropping funnel were charged 50 g of carbazole and 350 ml of chloroform. After heating to 30°C, with vigorous stirring, there was added,

dropwise, 47.3 g of sulfuryl chloride. Heating was continued simultaneously at such a rate that, by the end of the addition, the temperature had reached 50°C. The mixture was then boiled for one hour. After cooling, a crystalline precipitate with m.p. 189°C separated; after recrystallization from ethanol it gave 26.2 g of substance with m.p. 192–193°C. From the mother liquor, an additional 6 g of 3-chlorocarbazole was isolated. The total yield was 52% of theory (according to the literature, 3-chlorocarbazole melts at 192–193°C [2], 195°C [4]).

3-Chloro-9-(β-hydroxy)ethylcarbazole

Into a flask of heat-resistant glass were charged 44 g of 3-chlorocarbazole, 90 ml of acetone, and 12.3 g of caustic potash. After cooling to 0°C, 12.6 ml of ethylene oxide was introduced. The flask was tightly stoppered and kept for 1 hour in a thermostat at 45–50°C. After cooling, the reaction mass was poured into water; the solidified mass was washed with water until free of alkali. The yield of product with m.p. 84°C was 51 g. After distillation in vacuo at 220–230°C (4–5 mm Hg), 44.1 g of substance with m.p. 92–93°C was collected. Recrystallization from a mixture of benzene and ligroin (1:1) gives 37.5 g (69.5% of theory) of 3-chloro-9-(β-hydroxy)ethylcarbazole with m.p. 92.5–93°C. Analyses: found, %: N 5.50; Cl 13.90; OH 6.70. \( \mathrm{C}_{14}\mathrm{H}_{12}\mathrm{ONCl} \). Calculated, %: N 5.7; Cl 14.4; OH 6.93.

3,6-Dichlorocarbazole

Into a flask equipped with a stirrer, reflux condenser, and dropping funnel were charged 75 g of carbazole and 625 ml of chloroform. After heating to 50° and with vigorous stirring, 76 ml of sulfuryl chloride was added over 5 minutes. The reaction mass was stirred for 40 minutes at 50°C and then boiled for 1 hour. After cooling, 81.3 g of a crystalline precipitate with m.p. 190–193°C separated. On recrystallization from ethanol and then from glacial acetic acid, 28 g of colorless needles of 3,6-dichlorocarbazole with m.p. 204–205.5°C was obtained. From the mother liquor an additional 18.7 g of substance was isolated. The total yield was 50% of theory (according to the literature, 3,6-dichlorocarbazole melts at 202–203°C [2, 6, 7, 8, 9], 203°C [10], 206°C [11]).

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

Into a flask of heat-resistant glass were charged 100 g of 3,6-dichlorocarbazole, 23.6 g of powdered caustic potash, and 200 ml of methyl ethyl ketone. After cooling to 0°, 21.2 ml of ethylene oxide was introduced. The flask was tightly stoppered and kept for 50 minutes in a thermostat at 50°C. After cooling, the contents of the flask were poured into water, and the precipitated solidified mass was washed with water until free of alkali. The yield of product with m.p. 139–140°C was 110 g. After recrystallization from ethanol, 91.2 g (80% of theory) of 3,6-dichloro-9-(β-hydroxy)ethylcarbazole was obtained in the form of fine colorless needles with m.p. 160–162°C. Analyses: found, %: N 4.94; OH 6.15. \( \mathrm{C}_{14}\mathrm{H}_{11}\mathrm{ONCl}_{2} \). Calculated, %: N 5.0; OH 6.07.

3-Bromocarbazole

A mixture of 16.7 g of carbazole, 17.8 g of bromosuccinimide, and 0.18 g of benzoyl peroxide in 270 ml of dry carbon tetrachloride was boiled for 1 hour on a water bath. After cooling, the reaction mass was filtered, and the precipitate on the filter was washed with hot water to remove succinimide. The yield of crude product was 18.5 g. After threefold re-

crystallization from ethanol yielded 7.38 g (30% of theory) of 3-bromocarbazole with m.p. 194–195°C (according to the literature, 3-bromocarbazole melts at 194–195°C [4,15], 195–196°C [12], 197–198°C [13]).

3-Bromo-9-(β-hydroxy)ethylcarbazole

Into a flask of heat-resistant glass were placed 12.5 g of 3-bromocarbazole, 25 ml of acetone, and 1.12 g of caustic potash. After cooling to 0°C, 9.5 ml of ethylene oxide was introduced. The tightly stoppered flask was kept for one hour in a thermostat at 55°C, and then the reaction mixture was poured into water, where it solidified.

The yield of crude product (m.p. 104°C), washed with water to remove alkali, was 15 g. On vacuum distillation at 240–245°C (5 mm Hg), a viscous liquid was distilled off, which solidified on standing. After recrystallization from benzene and then from a mixture of benzene with n-hexane (1:1), 9.17 g (61% of theory) of 3-bromo-9-(β-hydroxy)ethylcarbazole with m.p. 128.5–129°C was obtained. Analyses: found, %: Br 25.57; OH 6.27. C₁₄H₁₂NBr. Calculated, %: Br 27.6; OH 5.90.

3,6-Dibromocarbazole

A mixture of 33.4 g of carbazole, 68 g of bromosuccinimide, 0.36 g of benzoyl peroxide, and 400 ml of carbon tetrachloride was boiled for one hour on a water bath. The cooled reaction mixture was filtered, and the residue was washed with hot water to remove succinimide. After two recrystallizations from ethanol, 32.6 g (51.5% of theory) of 3,6-dibromocarbazole with m.p. 208.5–209°C was obtained (according to the literature, 3,6-dibromocarbazole melts at 208–209°C [5], 211–213°C [13]).

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

Into a flask of heat-resistant glass were charged 15 g of 3,6-dibromocarbazole, 2.55 g of caustic potash, and 30 ml of acetone. After cooling to 0°C, 2.7 ml of ethylene oxide was added. The tightly stoppered flask was kept for 50 minutes in a thermostat at 50°C. After cooling, the contents of the flask were poured into water, and the precipitate (17.6 g) was washed free of alkali. After recrystallization from a mixture of benzene and hexane (1:1), 11.1 g (65.5% of theory) of 3,6-dibromo-9-(β-hydroxy)ethylcarbazole with m.p. 168–169°C was obtained. Analyses: found, %: Br 42.64; OH 5.04. C₁₄H₁₁NBr₂. Calculated, %: Br 42.3; OH 4.6.

Conclusions

1. A method has been developed for preparing 3-chloro-9-(β-hydroxy)ethyl-, 3,6-dichloro-9-(β-hydroxy)ethyl-, 3-bromo-9-(β-hydroxy)ethyl-, and 3,6-dibromo-9-(β-hydroxy)ethylcarbazoles by the interaction of the corresponding halogenocarbazoles with ethylene oxide.

2. Procedures for the synthesis of 3-chloro-, 3,6-dichloro-, 3-bromo-, and 3,6-dibromocarbazoles have been checked and refined.

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