Study in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study examines an alternative synthesis of amides of 9-methylcarbazolecarboxylic acids, prompted by the inconvenience of carbamyl chloride and the absence of reported methods for 9-alkylcarbazole carboxamide derivatives. The authors test the reaction of 9-methylcarbazole with urea and find that it requires proton donors, proceeding most effectively in glacial acetic acid with aluminum chloride at reflux, while a hydrogen chloride and benzene variant gives lower yields. By varying reagent ratios, the method affords predominantly 9-methylcarbazole-3-carboxylic acid amide or 9-methylcarbazole-3,6-dicarboxylic acid diamide, reported in yields of 82 to 85% and 87 to 88%, respectively, with analytical data supporting the assigned compositions.
Full Text
Research in the Chemistry of Carbazole Derivatives
65. Synthesis of Amides of 9-Methylcarbazolecarboxylic Acids
V. V. Goldshtein, V. P. Lopatinskii, E. E. Sirotkina
(Presented by the Scientific-Methodological Seminar of the Faculty of Chemical Technology)
According to the literature data [1, 2], amides of carbazolecarboxylic acids are obtained by the interaction of carbazole with carbamyl chloride in the presence of anhydrous aluminum chloride at 70–80° in dichlorobenzene. However, the difficult accessibility and instability of carbamyl chloride make it an inconvenient reagent, which led us to seek other routes for the synthesis of amides. In addition, the literature contains no data on the preparation of amides of carboxylic acids of 9-alkylcarbazoles. It is known that, upon rapid heating, urea decomposes with formation of isocyanic acid, which, upon interaction with amines, leads to the formation of substituted ureas [3]. In the present work, the possibility of using this reaction for the synthesis of amides of carboxylic acids of 9-alkylcarbazoles was studied.
The study showed that the reaction between 9-alkylcarbazole and urea in a neutral medium in the presence of aluminum chloride does not occur, and for its realization the presence of proton donors, such as protonic acids, is necessary. The synthesis of amides proceeds most effectively in 100% acetic acid at the boiling temperature. Depending on the amounts of the reagents taken, either 3-monoamides or 3,6-diamides of carboxylic acids of 9-alkylcarbazoles are formed predominantly.
This reaction can also be carried out in benzene at room temperature, provided that gaseous hydrogen chloride is passed through the reaction mixture, but the yields of the products are thereby reduced.
Experimental Part
Amide of 9-methylcarbazole-3-carboxylic acid.
Into a flask equipped with a reflux condenser are charged 0.01 M of 9-methylcarbazole, 0.4 M of acetic acid (100%), and 0.01 M of anhydrous aluminum chloride. After the reaction mass has been heated to boiling, 0.01 M of urea is introduced into it in small portions over the course of 1 hour. The mixture is boiled for another 2–2.5 hours, until the white precipitate of the reaction product ceases to separate. The precipitate is filtered off, boiled with a 10% solution of sodium hydroxide to remove aluminum chloride, washed with water, and dried. The yield of the monoamide reaches 82–85% of the theoretical. The substance melts at 236–238°, is moderately soluble in dimethylformamide, and poorly soluble
in ethanol, insoluble in aromatic hydrocarbons, chlorobenzene, and acetic acid.
Analyses. Found, %: N 12.4. C₁₄H₁₂N₂O.
Calculated, %: N 12.5.
Saponification of the amide for 30 hours with a mixture of acetic and hydrochloric acids (1:1) under reflux led to 9-methylcarbazole-3,6-dicarboxylic acid in 20% yield.
9-Methylcarbazole-3,6-dicarboxylic acid diamide.
Obtained by the above-described procedure from 0.01 M 9-methylcarbazole and 0.028 M urea in the presence of 0.02 M aluminum chloride and 0.4 M acetic acid (100%) in 87–88% yield. The substance has no sharp melting point, is slightly soluble in dimethylformamide, and is insoluble in the other solvents listed above. It decomposes above 330°.
Analyses. Found, %: N 15.2. C₁₅H₁₃N₃O₂.
Calculated, %: N 15.7.
Conclusions
The synthesis of mono- and diamides of 9-methylcarbazole-3- and 3,6-carboxylic acids has been carried out by the reaction of 9-methylcarbazole with urea.
Literature
- I. G. Fr. pat. 797072, 1936; C. A. 30, 6389, 1936.
- H. Norff, H. Ohlinger. Am. pat. 2137287, 1938; C. A. 33, 1759, 1939.
- P. Karrer. Course of Organic Chemistry, GKhI, 1960.