RU2417212C1 - Method of producing dihydrate of 1,1,1,5,5,5-hexafluoroacetylacetone - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to a method of producing dihydrate of 1,1,1,5,5,5-hexafluoroacetylacetone, which is an initial compound in producing low-boiling metal chelates used to separate isotopes, in manufacturing electric boards, polyfluorinated heterocyclic compounds: pyrazoles, isoxazoles, pyrimidines etc. The method involves acylation of diethyl malonate with trifluoroacetic anhydride in the presence of catalytic amounts of magnesium metal in an autoclave at 1255C for 15 hours, distillation of the reaction mass, dehydration and extraction of the end product. ^ EFFECT: method has less wastes and enables to obtain a highly-pure end product. ^ 1 tbl, 1 ex

Description

The present invention relates to the field of organic chemistry and relates to a method for producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, which is the starting compound for the preparation of metal chelates, polyfluorinated heterocyclic compounds: pyrazoles, isoxazoles, pyrimidines, etc.

1,1,1,5,5,5-Hexafluoroacetylacetone is obtained in various ways, among which the most commonly used is the condensation of ethyl trifluoroacetate with trifluoroacetone in ether solvents in the presence of alkali metals, their hydrides or alcoholates [H. Gilman, R.G. Jones, E. Bindschadler et. al., J. Am. Chem. Soc., V.78, N 12, 2790-2792 (1956). A. L. Henry, M. S. Newman, L. L. Quill, R. A. Staniforth, J. Am. Chem. Soc., V. 69, No. 7, 1819-1820 (1947); US 6,384,286; B2; 05/07/2002; US 6392101; B2; (2002); US 6393101; B2; 05/21/2002; US20010034462; A1; 10/10/2001; US2002000010373; A1; January 24, 2002]:

B = Na, K, AlkO ^- , H ^-

Also known is a method of producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate by diketone dihydration by the action of two equivalents of water in the presence of catalytic amounts of alkali [E.V.Dikarev, H.Zhang, B. Li; Angew. Chem., Int. Ed; V. 45, N 33, 5448-5451 (2006)].

A known method for producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate by ammonolysis of perfluoropentan-2-ene followed by acid hydrolysis of the ammonolysis product (O.E. Petrova, M.A. Kurykin. Izv. RAS, ser. Chem. ., N 1, pp. 149-150 (2001)):

According to this method, 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is obtained in two stages. In the first stage, 23.5 g (0.1 mol) of 3H-perfluoropent-2-ene, dissolved in 200 ml of acetone, is treated with 39 g (0.57 mol) of 25% aqueous ammonia at 2-5 ° C for 1 hour. After treatment, the reaction mass is distilled to obtain 19.3 g (87%) of 2-amino-3-hydro-4-iminoperfluoropentene. In the second stage, the ammonolysis product is boiled for 3 hours with 60 ml of concentrated hydrochloric acid. The product is extracted with sulfuric ether, the extract is dried over magnesium sulfate, the solvent is distilled off. 19.2 g (79%) of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate are obtained. The total yield of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate based on 3H-perfluoropent-2-ene is 69%.

The disadvantage of this method is the difficult accessibility, the high cost of the starting perfluoroalkene, the use of flammable acetone and sulfuric ether as solvents and extractants, a large amount of organic and inorganic waste, a low yield of the target product 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate.

The closest analogue of the proposed method is the method described in [US 6392101; IN 2; (2002)], in which the 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is prepared as follows. A 0.5-liter three-necked round-bottom flask equipped with a thermometer, dropping funnel and reflux condenser was charged with 34.6 g (0.64 m) of sodium methylate and 240 ml of t-butyl methyl ether. To the suspension obtained, while stirring on a magnetic stirrer for 30 minutes at a temperature not exceeding 30 ° C, a solution of 71.7 g (0.64 m) of 1.1.1 trifluoroacetone and 90.9 g (0.64 m) of ethyl trifluoroacetate in 120 ml of t-butyl methyl ether is added dropwise. After adding the solution, the reaction mixture was stirred for 4 hours at 40 ° C. Then, the solvent was distilled off under reduced pressure. To the obtained sodium salt of 1,1,1,5,5,5-hexafluoroacetylacetone is added 120 ml of water and 160 g of 24% sulfuric acid are added dropwise at a temperature not exceeding 20 ° C. After that, the reaction mass was kept under stirring for 6 h at 60 ° C, cooled to room temperature and extracted with t-butyl methyl ether (2 times 100 ml). After distilling off the solvent under reduced pressure, 118.8 g (75.6%) of technical dihydrate 1,1,1,5,5,5-hexafluoroacetylacetone are obtained, to which 270 ml of toluene is added, stirred for 1 hour at room temperature, the product is filtered off, and it is dried in air . Obtain 105 g (67%) of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. To clean the dihydrate 1,1,1,5,5,5-hexafluoroacetylacetone in the prototype also used hexane, its mixture with t-butyl methyl ether, methanol, tetrahydrofuran and other solvents.

The disadvantages of the method are its multi-stage, the need to use large quantities of fire and explosive solvents and reagents (esters, toluene, hexane, tetrahydrofuran, methanol, alkali metals, their hydrides or alcoholates), a large amount of organic and inorganic waste, the yield of the target product is dihydrate 1 1,1,5,5,5-hexafluoroacetylacetone - does not exceed that in the present method, a large amount of organic and inorganic waste.

The objective of the present invention is to develop a fundamentally new efficient low-waste method for producing dihydrate 1,1,1,5,5,5-hexafluoroacetylacetone of high purity.

The goal is achieved by a method for producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, including acylation of diethyl malonate with trifluoroacetic acid anhydride in an autoclave at 125 ± 5 ° C in the presence of a catalyst-metal magnesium (5 mol%). The proposed method is characterized in that the reaction mass obtained by acylation is distilled, collecting a fraction boiling to 100 ° C, which is treated with water while cooling with ice. The precipitated crystalline product, 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, is filtered off and dried in air.

Achieving this goal contributes to the observance of a number of conditions.

Since moisture impurities cause hydrolysis of trifluoroacetic anhydride, the latter, as well as diethyl malonate, must be used freshly distilled, the autoclave must be well dried. The reaction temperature - 125 ± 5 ° C - is optimal. The process at a temperature outside the specified limits, reduces the yield of the target product. When distilling the reaction mass, products boiling above 100 ° C should not be collected, since the presence of high boiling impurities in the pursuit leads to contamination of the target product. When precipitating 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate from the stream, catalytic amounts of alkali (NaOH or KOH) should be added to the added water. The addition of water should be done dropwise and when the reaction mixture is cooled, since the hydration of 1,1,1,5,5,5-hexafluoroacetylacetone occurs with heating. The content in pursuit of 1,1,1,5,5,5-hexafluoroacetylacetone was determined using ¹⁹ F NMR, GLC.

In the proposed method, as the starting compound for obtaining the target product, relatively cheap and readily available diethyl malonate is used and ether and other solvents and alkali metals are not used at all, which is undoubtedly an advantage of the proposed method.

The following examples illustrate the essence of the invention.

Example 1. Obtaining dihydrate 1,1,1,5,5,5-hexafluoroacetylacetone.

950 g (5.92 mol) of diethyl malonate, 2677 g (12.74 mol) of trifluoroacetic acid anhydride (freshly distilled over phosphorus pentoxide), 7.2 g (0.3 g · mol) of magnesium metal in the form of chips. The autoclave is sealed, heated by rotating it to 125 ± 5 ° С and maintained at this temperature for 15 hours. Then the autoclave is cooled, depressurized (12-15 atm), opened, the contents of the autoclave (3582 g) are dark red liquid with a sharp, suffocating odor - pour into a glass flask with a capacity of 4 liters. The reaction mass is distilled at atmospheric pressure, collecting the fraction with so bales. 55-80 ° C. Get 3160 g of shoulder straps containing according to NMR ¹⁹ F and GLC 27% 1,1,1,5,5,5-hexafluoroacetylacetone, 70% ethyl ester of trifluoroacetic acid. To a shoulder cooled by ice water, 150 g of water in which 1 g of sodium hydroxide is dissolved are added dropwise with stirring. A white granular precipitate begins to precipitate immediately. After the addition of water was complete, the reaction mass was stirred at room temperature for 1 hour, kept in a refrigerator overnight (~ 5 ° C), the product was filtered off, squeezed out well on a filter, and dried in air at room temperature to a free-flowing state. 832 g (67.6%) of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate are obtained. Product purity 98% (NMR data ¹⁹ F and ¹ H). T. pl. 88-90 ° C (with decomposition). 1 H-NMR spectrum (300 MHz, DMSO-d ₆ , ppm): 3.2 (br.s., CH ₂ ), 5.8 (br.s., OH). ¹⁹ F NMR spectrum (300 MHz, DMSO-d ₆ , standard C ₆ F ₆ , ppm): 84.0.

The effect of changes in temperature and time regimes of the process of obtaining 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate on the yield of the latter is shown in the table.

Table The effect of changes in temperature and time conditions of the process for producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate on the yield and purity of the latter Experiment number Autoclaving temperature, ° С Autoclaving time, h Exit, % Purity%
(NMR ¹⁹ F) one 110-115 24 19.5 93 2 140 fifteen 59.6 93 3 * 125 fifteen 66 90 * During the distillation of the autoclaving products, a fraction was collected with so on. 55-100 ° C

Waste disposal: the cube from the distillation of the reaction mixture (~ 415 g) is combined with the filtrate obtained after separation of 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate (~ 2360 g). To the resulting mixture was added 500 ml of water, boiled for 1 hour and distilled, collecting the fraction boiling at 85-100 ° C. Receive ~ 2500 g of trifluoroacetic acid hydrate, which is first dehydrated by distilling over 250 g of 98% sulfuric acid. Dehydrated trifluoroacetic acid (~ 1600 g, bp. 70-75 ° C) is converted into anhydride by its interaction with phosphorus pentoxide. The yield of trifluoroacetic anhydride is 850-900 g. The resulting cube, polyphosphoric acid, can also be used to dehydrate trifluoroacetic acid hydrate.

Claims (1)

A method for producing 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, including acylation of diethyl malonate with trifluoroacetic acid anhydride in the presence of catalytic amounts of magnesium metal in an autoclave at (125 ± 5 ° С) for 15 h, distillation of the reaction mixture, dihydration and the selection of the target product.