Esters of Diphenic Acid

III. Synthesis of Chlorine-Substituted Aliphatic and Aliphatic-Aromatic Esters of Diphenic Acid

L. P. Kulev, R. P. Gireva, P. T. Khalfina

In connection with the search for new insecticides, we undertook the synthesis of a series of chlorine-substituted esters of diphenic acid: monotrichloroethyl, hexachlorodiethyl, and aryltrichloroethyl esters.

The literature [1] describes the preparation of a series of complex esters of mono- and dibasic carboxylic acids by esterification of trihalo-substituted alcohols with acids or acid chlorides in the presence of anhydrous metal halides \((\mathrm{FeCl_3}, \mathrm{AlCl_3}, \mathrm{SbCl_3}\), etc.). Ferric chloride proved to be the most active catalyst among them.

We used this reaction of catalytic esterification with metal halides to obtain chlorine-substituted esters of diphenic acid.

The trichloroethyl alcohol required for the synthesis was obtained from chloral by an exchange of oxidation states between the aldehyde and ethyl alcohol in the presence of aluminum ethylate [2].

Diphenic acid chloride was obtained by treating the acid with thionyl chloride.

The synthesis of hexachlorodiethyl diphenate from diphenic acid chloride and trichloroethanol was carried out according to the scheme:

\[ \mathrm{ \text{diphenoyl\ chloride} + 2\,CCl_3CH_2OH \ \xrightarrow[\,-2HCl\,]{(AlCl_3)}\ \text{di}(2,2,2\text{-trichloroethyl})\ \text{diphenate} } \]

That is, schematically:

\[ \mathrm{ (C_6H_4COCl)_2 + 2\,CCl_3CH_2OH \ \xrightarrow[\,-2HCl\,]{AlCl_3}\ (C_6H_4COOCH_2CCl_3)_2 } \]

It was not possible to obtain this ester from diphenic acid or its anhydride.

Chlorine-substituted aliphatic-aromatic esters were synthesized according to the scheme:

\[ \mathrm{ \text{diphenic\ anhydride} \ \xrightarrow[\,(FeCl_3)\,]{CCl_3CH_2OH}\ HOOC{-}\text{diphenyl}{-}COOCH_2CCl_3 \ \xrightarrow[\,-H_2O\,]{AzOH,\ (POCl_3)}\ AzOOC{-}\text{diphenyl}{-}COOCH_2CCl_3 } \]

Monotrichloroethyl diphenate is formed from diphenic anhydride under the action of a catalyst—anhydrous ferric chloride or aluminum chloride. Heating the acid ester with phenols in the presence of phosphorus oxychloride gave mixed esters [3].

All the esters obtained are crystalline substances soluble in ordinary organic solvents.

Fig. 1. Absorption spectra of diphenic acid esters in ethyl alcohol.
I—monotrichloroethyl diphenate, II—hexachlorodiethyl diphenate, III—phenyl trichloroethyl diphenate, IV—2-nitrophenyl trichloroethyl diphenate, V—2,4-dinitrophenyl trichloroethyl diphenate.

The ultraviolet absorption spectra of these esters were recorded on an SF-4 spectrophotometer.

Experimental Part

Monotrichloroethyl ester of diphenic acid (I). A mixture of 8.96 g of diphenic acid anhydride, 5.98 g of trichloroethanol, 1.94 g of anhydrous ferric chloride, and 30 ml of chloroform in a round-bottomed flask equipped with a reflux condenser and stirrer is heated on a water bath at 25–50° for 6 hours. The mixture is filtered. The residue after evaporation of the solvent—a white crystalline substance—is recrystallized from ethyl alcohol. Yield 8 g (54%). M.p. 142.5–143°. Found, %: Cl 28.11. \( \mathrm{C}_{16}\mathrm{H}_{11}\mathrm{O}_{4}\mathrm{Cl}_{3} \). Calculated, %: Cl 28.51.

Hexachlorodiethyl ester of diphenic acid (II). Obtained analogously to (I) from 5.58 g of the complete acid chloride of diphenic acid, 5.98 g of trichloroethanol, 0.8 g of anhydrous aluminum chloride, and 25 ml of carbon tetrachloride. Heating is continued until the evolution of hydrogen chloride ceases, which requires about 8 hours. Yield 3.35 g (33.1%). A white crystalline substance with m.p. 67–68°.

Found, %: Cl 41.33. $\mathrm{C}_{18}\mathrm{H}_{12}\mathrm{O}_{4}\mathrm{Cl}_{3}$. Calculated, %: Cl 42.17.

Phenyl trichloroethyl ester of diphenic acid (III). 3 g of monotrichloroethyl diphenate, 0.754 g of phenol, and 0.25 ml of phosphorus oxychloride are heated with constant stirring to 150° for 3–4 hours, until the evolution of hydrogen chloride ceases. The hot reaction mass is poured into water and washed with sodium carbonate solution and with water. The resinous product is recrystallized from ethyl alcohol. 2.58 g (72%) of a white crystalline substance with m.p. 53–55° is obtained.

Found, %: Cl 23.67. $\mathrm{C}_{22}\mathrm{H}_{15}\mathrm{O}_{4}\mathrm{Cl}_{3}$. Calculated, %: Cl 23.69.

2-Nitrophenyl trichloroethyl ester of diphenic acid (IV). Obtained analogously to (III) from 3 g of monotrichloroethyl diphenate, 1.12 g of 2-nitrophenol, and 0.25 ml of phosphorus oxychloride. White crystals with m.p. 101–103°.

Found, %: N 2.83; Cl 21.42. $\mathrm{C}_{22}\mathrm{H}_{16}\mathrm{O}_{6}\mathrm{NCl}_{3}$.

Calculated, %: N 2.61; Cl 21.45.

2,4-Dinitrophenyl trichloroethyl ester of diphenic acid (V). Obtained analogously to (III) from 1.86 g of monotrichloroethyl diphenate, 0.92 g of 2,4-dinitrophenol, and 0.16 ml of phosphorus oxychloride. Slightly yellowish crystals with m.p. 106–107°. Found, %: N 5.09; Cl 19.57. $\mathrm{C}_{22}\mathrm{H}_{13}\mathrm{O}_{8}\mathrm{N}_{2}\mathrm{Cl}_{3}$.

Calculated, %: N 5.19; Cl 19.74.

Conclusions

1. Monotrichloroethyl, hexachlorodiethyl, phenyltrichloroethyl, 2-nitro- and 2,4-dinitrophenyltrichloroethyl esters of diphenic acid have been synthesized. UV spectra of the compounds obtained were recorded.

Literature

1. M. E. Hill, J. Am. Ch. Soc. 76, 2329, 1954.
2. Synthesis of Organic Preparations, 2, 485, Inlit, Moscow, 1949.
3. A. M. Berkentheim, Chemistry and Technology of Synthetic Medicinal Agents, 419, ONTI, Moscow, 1935.