PL159916B1 - Method for preparation of yhe new naphthyl compounds of the aminecarbazole derivatives - Google Patents

Abstract

A method of producing new naphthol compounds of aminocarbazole derivatives, characterised in that the derivatives of 3-(2-naphthylamino)-carbazole with formula 1, where R stands for hydrogen, alkyl or benzyl and 1-(2-naphthylamino)-carbazole with formula 2, are produced by melting 3-amino-9R-carbazole or respectively 1-aminocarbazole with a 5-15-fold molar excess of 2-naphthol at a temperature of 400-450 K.<IMAGE>

Description

The subject of the invention is a method for the preparation of new naphthyl aminocarbazole derivatives showing properties enabling their practical use in industry as antioxidants and thermal stabilizers of olefin polymers.

The mentioned compounds and their synthesis have not been described in the source literature so far. They show some structural analogies to the group of amine antioxidants known for years, used in the art as antiozonants and thermal stabilizers for rubbers and olefin polymers.

The preparation of arylamine carbazole derivatives in a manner analogous to the known synthesis of alkylamine derivatives presents a number of difficulties. Reactions are resistant, and under severe conditions, the products undergo extensive degradation, as a result of which the yields of the reaction are low and the isolation of pure products is extremely onerous.

The essence of the invention is a process for the preparation of new compounds of aminocarbazole derivatives, which consists in the fact that the 3- (2-naphthylamino) -carbazole derivatives of the formula 1, in which R is hydrogen, alkyl or benzyl, and 1- (2-naphthylamino) -carbazole of the formula 2, is prepared by fusing 3-amino-9R-carbazole or 1-aminocarbazole, respectively, at a temperature of 400-450K with a 5-15 fold molar excess of 2-naphthol.

During the search for new methods for the preparation of N-aryl aminocarbazole derivatives, it was surprisingly found that 3- (2-naphthylamino) -carbazole can be obtained in a simple, one-step synthesis from readily available starting materials by heating 3-aminocarbazole in excess molten 2-naphthol. 1-aminocarbazole and 3-amino-9-alkylcarbazole react similarly.

Synthesis trials on the decimole scale have shown that the condensation reaction can be carried out at a temperature of 400 to 450 K, the time required for complete conversion of the amine is 12 to 24 hours near the lower end of the temperature range given. An excess of 2-naphthol serves as a high-temperature solvent in this reaction. Lowering the molar ratio of 2-naphthol to aminocarbazole below 10: 1 causes a drop in product yield, e.g. to 50% at a ratio of 6: 1, and makes it difficult to process the reaction mixture due to partial solidification of the alloy.

According to Polish patent specification No. 133969, the synthesis of 3-aminocarbazole by nitration and reduction does not pose any major problems, however, as a result of carbazole nitration, a mixture containing about 70% 3-nitro and 30% 1-nitrocarbazole is formed, while

9-alkylcarbazoles give almost exclusively the substitution products in the 3-position. If the stabilizing properties of 3 - (: ^ - ^ t ^; ^ ft; ^ ll ^ ia ^ ino) ^^^^^ ll <illDcarbazoles turned out to be clearly better than 3- (2 -naphthylamino) -carbazole, it would be desirable to subject the carbazole to N-alkylation prior to the nitration reaction in order to avoid formation of the 1-nitro derivative. Therefore, a simple method for the preparation of 9-alkylcarbazoles was developed based on the known phenomenon of interfacial catalysis, consisting in the action of an alkyl halide on carbazole in a heterogeneous mixture of dimethylsulfoxide and concentrated aqueous alkali in the presence of triethylbenzylammonium chloride.

On the basis of theoretical premises, which was confirmed by preliminary application tests, it turned out that arylamine carbazole derivatives, especially naphthylaminocarbazoles,

159,916 have much higher efficiency in stabilizing polymers than the N-aralkyl derivatives of 9-amino-, 1-amino and 3-aminocarbazoles, known from PRL patents No. 107448 and No. 129 717, as thermal stabilizers of polyethylene. Naphthylaminocarbazoles are structurally similar to diphenylamine and paraphenylenediamine derivatives, such as N, N'-diefenyl-p-phenylenediamine or N-2-naphthyl-N'-phenyl-p-phenylenediamine, whose stabilizing effect consists in breaking the chain of propagation of destructive reactions of free radical macromolecules by deactivation of hydrocarbon radicals in the reaction of hydrogen transfer from the stabilizer molecule to the polymer macroradio, as well as by capturing and deactivating peroxide and other radicals. There are reasonable assumptions that arylamines also act according to the mechanism of hydroperoxide decomposers, hence their high activity, much higher than phenolic stabilizers, in stabilizing polymers exposed to high temperature. For these reasons, the development and optimization of methods for the synthesis of N-substituted arylamines is of great importance for the development of the processing of polymers, especially olefin polymers, the most common use in the art.

The similar structure of the isomeric naphthylaminocarbazoles, ie - the arylamino group in the ortho or para position relative to the pyrrole nitrogen - suggests that their stabilizing effect should be similar. Thus, a natural mixture of isomeric nitrocarbazoles can be a convenient starting material for the synthesis of the two-component stabilizer. In practice, it turned out to be expedient to synthesize both components separately, because both the aminocarbazoles and their N-naphthyl derivatives differ significantly in solubility in typical organic solvents. The mixture of l-amino and 3-aminocarbazole obtained as a result of reduction of the nitration product was separated by extraction with methanol into an insoluble fraction, consisting mainly of 3-aminocarbazole and a methanol-soluble fraction.

1-aminocarbazole. Both fractions were condensed separately with 2-naphthol. In contrast to naphthol, 3- (2-naphthylamino) -carbazole is practically insoluble in methanol, which allows the reaction product to be easily separated from the excess reagent. Water precipitates 2-naphthol from the concentrated methanolic solution, which, after filtering and drying, can be reused for the condensation reaction. In the synthesis of 1- (2-naphthylamino) -carbazole, excess 2-naphthol is washed off with an alkali solution and regenerated by precipitation with acid. Purification of the product is more cumbersome, as a result its yield is slightly lower, so that the two-component stabilizer contains 20% 1- (2-naphthylamino) -carbazole and 80% 3-substituted isomer.

The following examples explain the preparation of naphthylaminocarbazoles in more detail.

Example 1 In 145 g (1 mol) of molten 2-naphthol, 21 g (0.1 mol) of 3-amino-9-ethylcarbazole were dissolved. The alloy was kept at 410 ± 5K for 24 hours by passing a slow stream of nitrogen over the surface. 0.1 dm3 of Ν, Ν-dimethylformamide was added to lower the viscosity of the mixture, and then the reaction product was precipitated by pouring the solution into 0.8 dm3 of water, in which 80 g of sodium hydroxide were previously dissolved. The precipitate formed was filtered off, washed with water and dissolved in a 1: 1 mixture of tetrahydrofuran and toluene. The solution was washed with alkali to remove residual 2-naphthol and then the unreacted amine was extracted with 3N hydrochloric acid. After neutralization of the extract, 1.5 g (7%) of 3-amino-9-ethylcarbazole was recovered. The solution was concentrated to a small volume by distilling off mainly the more volatile tetrahydrofuran. On cooling, 22.5 g (67%) of 3- (2-naphthylamino) -9-ethylcarbazole (formula 1, R - ethyl) crystallized in the form of light yellow prisms with t> = 451-453 K with a polymorphic transformation at 438 K.

Example II. The crude product of carbazole nitration, containing approximately 70% of 3-nitrocarbazole and 30% of 1-nitrocarbazole, was reduced with sodium dithionite in a water-alcohol alkali solution. The reaction product was precipitated with water, filtered and washed with methanol to remove

1-aminocarbazole. Crude 3-aminocarbazole (365 g = 2 mol) was melted with 2-naphthol (2880 g = 20 mol) keeping the mixture at 425-430K under argon atmosphere for 16 hours. Alloy was poured into a 4 dm ^{3 of} chilled methanol, precipitate was filtered washed with methanol to remove

2-naphthol and batch crystallized from xylene to give 505 g (82%) of 3- (2-naphthylamino) carbazole (Formula 1, R = hydrogen) as light yellow crystals with mp - 518-519 K.

159 916

After the crude reaction product was separated off, the methanol filtrate was concentrated to a small volume and poured into cold water, then the unreacted 2-naphthol was filtered off. The xylene crystalline liquors were concentrated to a low volume and strongly cooled. The filtered precipitate was washed with methanol leaving 3- (2-naphthylamino) -carbazole (approx. 10-15 g) on the filter, and the filtrate was diluted with 5% aqueous alkali, precipitating 1- (2-naphthylamino) -carbazole (formula 2), which was then crystallized from a mixture of benzene and hexane by boiling with charcoal. The obtained product was 35 g of the product in the form of pearl gray plates with a mp = 484-485 K.

Sickness 1

Sick 2

Department of Publishing of the UP RP. Circulation of 90 copies. Price: PLN 10,000

Claims (1)

Patent claim A process for the preparation of new naphthyl aminocarbazole derivatives, characterized in that the 3- (2-naphthylamino) -carbazole derivatives of the formula 1, in which R is hydrogen, alkyl or benzyl, and 1- (2-naphthylamino) -carbazole of the formula 2, produces is fused at 400-450 K of 3-amino-9R-carbazole or 1-aminocarbazole, respectively, with a 5-15 fold molar excess of 2-naphthol.