SYNTHESIS OF IODINE DERIVATIVES OF PHENANTHRENEQUINONE AND DIPHENIC ACID

A. N. NOVIKOV, V. T. SLYUSARCHUK, E. F. MATANTSEVA

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

Phenanthrenequinone and its derivatives have been recommended as valuable fungicides replacing highly toxic and scarce organomercury preparations [1]. It is known that the introduction of iodine into the benzene ring of aromatic compounds often increases the activity of toxic chemicals. Therefore, it was of interest to obtain iodine derivatives of phenanthrenequinone by the method we had previously developed—direct iodination in the presence of a sulfuric–nitric acid mixture.

Phenanthrenequinone is obtained from products of coal-tar processing; consequently, it has a reliable and accessible raw-material base. A comprehensive study of the properties of substances obtained from coal tar is important in order to determine the possibility of their broader application in organic synthesis.

The literature describes a method for preparing 2,7-diiodophenanthrenequinone in four stages via nitro, amino, and diazonium compounds [2]. This method is very labor-intensive, as a result of which iodine derivatives of phenanthrenequinone are not readily available.

We obtained 2-iodo- and 2,7-diiodophenanthrenequinones from phenanthrenequinone in a single stage by the reaction of electrophilic substitution of hydrogen by iodine in the presence of a sulfuric–nitric acid mixture [3].

2-Iodophenanthrenequinone has not been described in the literature. Its structure was proved by conversion into the known 2,7-diiodophenanthrenequinone. It was characterized by several derivatives at the carbonyl group.

Previously, by this method we iodinated fluorene-carboxylic and benzoic acids [4, 5]. We therefore assumed that diphenic acid might be iodinated in the presence of a sulfuric–nitric acid mixture. However, in numerous attempts to introduce iodine into diphenic acid by the direct method, we were unsuccessful. Apparently this is due to the reduced electron density in the ring owing to the presence of the carboxyl group and the carboxylated phenyl. 4,4′-Diiododiphenic acid was obtained by oxidation of 2,7-diiodophenanthrenequinone. Apparently no one had previously used this method because 2,7-diiodophenanthrenequinone was not sufficiently well known. Diiododiphenic acid has become an accessible compound. Obtaining it by the proposed method is simpler and cheaper than obtaining it from diphenic acid by a multistage method via dinitro, diamino, and diazonium compounds [6].

Experimental Part

The iodination reaction was carried out in a flask equipped with a stirrer, reflux condenser, and dropping funnel. To a mixture of 0.01 mole

of the starting product, 0.01 g-atom or 0.01 mole of iodine, 150 ml of glacial acetic acid, and 5 ml of carbon tetrachloride were added, at the specified temperature, gradually with stirring, to a mixture of nitric acid, d 1.4, and sulfuric acid, d 1.84. After completion of the synthesis the mass was diluted with water, the precipitate was filtered off and washed with water, the unreacted iodine was removed by treating the reaction product with sodium sulfite solution, and then it was crystallized twice from glacial acetic acid.

At molar ratios of substrate to iodine of 1 : 0.5, iodophenanthrenequinone was isolated, and at a ratio of 1 : 1, diiodophenanthrenequinone. The melting point of iodophenanthrenequinone is 225°C; that of 2,7-diiodophenanthrenequinone is 310°C (literature value 310°C).

Found, %: I 38.0, C₁₄H₇IO₂. Calculated, %: I 38.0.

Found, %: I 55.2, C₁₄H₆I₂O₂. Calculated, %: I 56.0.

For the characterization of 2-iodophenanthrenequinone, not described in the literature, the monooxime (mp 131–132°C), the monothiosemicarbazone (mp 152°C), and the mono-2,4-dinitrophenylhydrazone (mp 282°C) were obtained by known methods.

The dependence of the yield of the obtained iodine derivatives of phenanthrenequinone on the reaction temperature, the synthesis time, and the amounts of sulfuric and nitric acids is presented in Fig. 1 (curves 1–8).

It follows from Fig. 1 that, for the optimal conditions for obtaining 2-iodophenanthrenequinone, the following are required: 0.01 mole of phenanthrene, 0.01 g-atom of iodine, 150 ml of glacial acetic acid, 5 ml of carbon tetrachloride, 0.018 mole of nitric acid, and 0.045 mole of sulfuric acid. The reaction temperature is 100°C. The synthesis time is 4 hours.

Under the optimal conditions for the synthesis of 2,7-diiodophenanthrenequinone, the following changes are introduced into the preceding procedure. Iodine, 0.01 mole; sulfuric acid, 0.40 mole; nitric acid, 0.110 mole. Reaction temperature 120°C; synthesis time 3.5 hours.

Preparation of 4,4′-diiododiphenic acid. 1.5 g of 2,7-diiodophenanthrenequinone was dissolved in 100 ml of tetrahydrofuran, a solution of 5 g of potassium dichromate in 40 ml of water was added, and the mixture was stirred at the boiling temperature for three hours. Then the mixture was diluted with water, filtered, and from the filtrate a white product with a melting point of 262°C (literature value 262°C) was precipitated with hydrochloric acid. The yield of diiododiphenic acid was 60%.

Fig. 1. Dependence of product yield on reaction conditions. 2-Iodophenanthrenequinone. Reaction temperature 95–100°C, sulfuric acid 0.044 mole, nitric acid 0.016 mole, reaction time 4 hours. 1—from reaction time; 3—from the amount of nitric acid; 4—from the amount of sulfuric acid; 7—from reaction temperature. 2,7-Diiodophenanthrenequinone. Reaction time 3.5 hours, reaction temperature 120°C, sulfuric acid 0.36 mole, nitric acid 0.105 mole. 2—from reaction temperature; 5—from the amount of nitric acid; 6—from the amount of sulfuric acid; 8—from reaction time.

Conclusion

Optimal conditions have been developed for the synthesis of 2-iodophenanthrenequinone and 2,7-diiodophenanthrenequinone. A simple, accessible method for obtaining 4,4′-diiododiphenic acid has been proposed.

References

1. A. A. Shamshurin, M. Z. Krimer, Physicochemical Properties of Organic Iodine Compounds. Moscow, “Nauka,” 135, 1966.
2. K. D. Desei, R. H. Kunde, J. Indian Chem. Soc., 29, 238, 1952.
3. A. N. Novikov, V. T. Slyusarchuk. Author’s certificate No. 197545; Byull. izobr., No. 13, 1967.
4. V. T. Slyusarchuk, A. N. Novikov. ZhOKh, 3, 7, 1323, 1967.
5. B. V. Tronov, A. N. Novikov. ZhOKh, 23, 6, 1022, 1953.
6. Beilstein, 9 main volume, 924, 1927.