SU1747440A1 - Method of producing 2,2@-dipyridyl - Google Patents

Abstract

The invention relates to heterocyclic compounds, in particular, a process for the preparation of 2,2-dipyridyl used as complexone and an intermediate in the preparation of herbicides, which may be used in the chemical industry. The goal is to simplify the process and increase the yield of the target product. The process is carried out by catalytic hetarylation of 2-bromohydridine at 140-165 ° C in mesitylene or its mixture with xylene in the presence of bronze powder containing at least 90% of particles up to 100 µm in size, with a mass ratio of 2-bromopyridine and catalyst 1: (0.5-1). Output 68-82 against 53-54% in the known method. 2 tab.

Description

This invention relates to a process for the preparation of 2,2-dipyridyl. used as an analytical reagent for the photometric determination of tantalum, niobium, vanadium and other elements.

Several methods are known for the preparation of 2,2-dipyridyl derivatives.

Closest to the present invention is a method for the preparation of 2,2-dipyridyl, which consists in catalytic hetarylation of pyridine. The reaction proceeds by treating 2-bromopyridine in anhydrous p-cymole with activated freshly precipitated copper powder at an elevated temperature (170 ° C) for 2 hours. The yield is 53-54% of the substance with m.p. 69-70 ° C.

The disadvantage of the prototype method is the need to use in the synthesis of freshly precipitated activated copper. The process of obtaining freshly precipitated copper is laborious and quite expensive, along with

this produces zinc and copper-containing wastewater. The activation of copper is particularly difficult, since for this it is necessary to use extremely scarce raw materials - metallic iodine. The use of non-activated copper in the synthesis leads to a significant decrease in the yield of the target product (up to 30%). In addition, the resulting copper powder has a non-reproducible particle size distribution, predominantly particles over 150-200 µm in size (see Table 1). Another disadvantage is the use of highly inaccessible and expensive raw materials in the reaction as a solvent of the high boiling aromatic hydrocarbon of h-cymol.

The purpose of the invention is to increase the yield of the target product and simplify the process of its production.

The goal has been achieved by improving the catalytic hydrogenation of pyridine. Synthesis of 2.2 -VJ

4 4

&

pyridyl is carried out from 2-bromopyridine by heating in a mixture with an inert anhydrous solvent (for example, methylene or its mixture with xylene) in the presence of a fine catalyst, for example bronze powder (aluminum containing BPO, BPI or VPK bronze, cm Table 2) in an amount of from 0.5 to 1.0 by weight of 2-bromopyridine within 1.5-3.0. The use of finely dispersed powder with a stable fractional dispersed composition, with a predominant content of a part in the range of 10-50 microns (up to 90 wt.%), Provides a more complete flow of a heterogeneous reaction, allows using lower boiling liquids as a solvent. mesitylene and its mixtures with xylene, which ultimately allows reducing the tar during the reaction and increasing the yield of the target product to 68-82%. The process is carried out at 140-160 ° C.

Example 1. Synthesis of 2,2-dipyridyl.

In a half-liter three-neck flask equipped with a stirrer with a stopper, a cooler and a dropping funnel, 50 g of BPI bronze powder, 75 g of finely ground sodium chloride and 150 ml of azeotropic mesitylene, previously dried by azeotropic distillation, are placed. 79 g (0.5 mol) of 2-bromopyridine was added to the mixture heated to boiling with mechanical stirring over 30 minutes, after which the reaction mass was boiled for another 1.5 hours. After the reaction and cooling the reaction mass 100 ° C the flask is made with 150 ml of hydrochloric acid diluted 1: 1 with water; wherein the speck is converted into a fine powder. Mesitylene is distilled off with steam and distilled after drying is reused in the reaction, the residue is made alkaline with 40% sodium hydroxide and distilled with steam until it is not distilled 2,2-dipyridyl (sample with ferrous sulphate II). About 3 liters of aqueous distillate are extracted with chloroform or dichloroethane 5-6 times in portions of 30-40 ml per liter of distillate. The extract is dried and evaporated to dryness. 30.6 + 0.6 g (78 ± 2%; average in five parallel experiments) of the product are obtained with mp. 68-69.5 ° C. If necessary, the product is recrystallized from petroleum ether,

Examples 2-14. Carried out analogously to example 1. The conditions of the experiments — the reaction temperature, the catalyst, its quantity, and the yield of the target product — are listed in Table. 2

Examples 15-19. Determination of the boundary conditions of the experiment. Carried out analogously to example 1. The conditions of the experiments and its results are shown in Table. 2

Examples 20-24. Comparative experiments. Carried out analogously to example 1. As the catalyst use freshly precipitated activated

copper.

Example 25. Use as a hetarylation catalyst a bronze powder containing 75-90% of particles larger than 100 microns,

In a three-necked flask equipped with a stirrer, a condenser and a dropping funnel, 25 g of catalyst (bronze powder), 40 g of finely divided sodium chloride and 80 ml of dried

mesitylene. 39.5 g (0.25 mol) of 2-bromopyridine are added to the mixture heated to boiling with vigorous stirring over a period of 20-30 minutes, after which the reaction mixture is boiled for an additional 1.5-2.0 hours. cooled to 100 ° C, 75 ml of diluted hydrochloric acid (1: 1) are introduced. Mesitylene is distilled off from the resulting suspension with water vapor, the residue is made alkaline with 40% sodium hydroxide and distilled with water vapor until 2,2-dipyridyl is not in distillate (sample with iron sulfate II). The distillate is extracted with chloroform 5-6 times 30-40 ml / l, the extract is dried and evaporated to dryness.

Obtain 7.3 g (35.3%) of the product with so pl. 68-68.5 ° C.

The reaction temperature is determined by the boiling point of the solvent (mesitylene 164.5 ° C, xylene 140 ° C).

The following are examples of conducting the reaction in xylene and in a higher boiling solvent — gwa cola (bp 205 ° C).

Example 26. Synthesis of 2,2-dipyridyl in the medium of n-xylene. In a three-neck flask,

equipped with a stirrer, a reflux condenser and a dropping funnel, 50 g of bronze BPI powder, 75 g of finely divided sodium chloride and 150 ml of pre-dried p-xylene are placed. 79 g (0.5 mol) of 2-bromopyridine are added to the mixture heated to boiling with vigorous stirring over 30 minutes and then heated for another 2 hours. After cooling the reaction mass to 100 ° C.

adding 150 ml of dilute (1: 1) hydrochloric acid, remove xylene by azeotropic distillation, the residue is alkalinized with 40% sodium hydroxide and dipyridyl is distilled off with water vapor to a negative sample with ferric sulfate (II). The aqueous distillate was extracted in the same manner as in Example 25. 17.3 g (44.7%) of 2,2-dipyridyl were obtained, with a pl. 68 ° C.

Example 27. Synthesis of 2,2-dipmridil in gua-cola. The reaction is carried out similarly to Example 26. 150 ml of anhydrous gua-cola was used as a solvent. The reaction is carried out at boiling gva cola (205 ° C). The subsequent treatment of the reaction mass is very difficult due to the intensive tarification and only minor amounts of 2,2-dipyridyl (yield about 3%) of the heavily contaminated product (mp. 62-65 ° C) are obtained.

Example 28. Synthesis of 2,2-dipyridyl in gua-cola medium. The reaction is carried out analogously to example 27 at 175-180 ° C. A strong resinification is also observed during the reaction. By distillation with steam it is possible to obtain 10-15% of 2,2-dipyridyl heavily contaminated with resinous substances.

The use of copper powder (copper content 99.9%) of the PMS and PMR types gives results comparable to the prototype, despite the fact that their dispersion composition is similar to the bronze powder.

Example 29. Synthesis of 2,2-dipyridyl using copper powder PMS. In a half-liter three-neck flask equipped with a stirrer with a stopper, a cooler and a dropping funnel, 50 g of PMS copper powder, 75 g of finely divided sodium chloride and 150 ml of pre-dried azeotropic distillation of mesylenes are placed. 79 g (0.5 mol) of 2-bromopyridine are added to the mixture heated to boiling with mechanical stirring during 30 minutes, after which the reaction mixture is boiled

another 1.5 hours. After the completion of the reaction and the cooling of the reaction mass to 100 ° C, 50 ml of hydrochloric acid diluted 1: 1 with water are applied to the flask. Mesitylene is distilled off with steam and the distillate after drying is reused in the reaction, the residue is made alkaline with 40% sodium hydroxide and distilled with steam until absent in distillate 2,2-dipyridyl. The aqueous distillate is extracted with dichloroethane. The extract is dried and evaporated to dryness. Obtain 22.7 g (56.6%) of the product with so pl. 68-69.5 ° C.

Example 30. Synthesis using copper powder PMR. Carried out analogously to example 29. The yield of the target product was 58.0%.

Thus, this method allows to increase the yield of the target product by 15-20%. At the same time, lowering the reaction temperature reduces gum formation and results in a cleaner product. The economic effect of the invention is to reduce the consumption rate of 2-bromopyridine.

Claims (1)

Invention Formula The method of producing 2,2-dipyridyl by catalytic hetarylation of 2-bromo-pyridine with heating in an organic solvent, characterized in that, in order to simplify the process and increase the yield of the target product, bronze powder containing at least 90 wt.% Is used as a catalyst. % of particles up to 100 microns with a mass ratio of bromopyridine catalyst equal to 1: 0.5-1 and the process is carried out in mesitylene and its mixture with xylene at 140-165 ° C. Notes. PDS is determined by microscopic method. The average data for the three parties m. Trace amounts. Table 1 Examples of the synthesis of 2,2-dipyridyl table 2