Process for producing alkyllithium solutions

Abstract

The present invention relates to a method for preparing alkyllithium compounds for use as anionic polymerization initiators and in various organic reactions. More particularly, the present invention relates to a method for preparing alkyllithium compounds having anionic polymerization initiators in the range of 1 to 100 cm 2 The present invention relates to a method for producing an alkyllithium solution by reacting lithium metal having a specific surface area of ​​1 / g with an alkyl halide in an organic solvent medium under highly turbulent flow conditions, wherein the molar ratio of lithium metal to alkyl halide is 2.5:1 to 5.5:1. The technical result achieved by the present invention is that under highly turbulent flow conditions, lithium metal with a low specific surface area is used to achieve high yields of alkyllithium comparable to those achieved using finely dispersed lithium metal particles with a high specific surface area, at a lithium metal to alkyl halide molar ratio of 2.5:1 to 5.5:1.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing solutions of alkyllithium compounds for use as initiators for anionic polymerization and in various organic reactions.

[0002] Background technology Alkyllithium compounds are widely used as initiators for the polymerization of dienes and copolymerization of dienes with vinyl aromatic compounds.

[0003] Currently, in industry, alkyllithium is typically produced by melting lithium metal, dispersing the resulting lithium melt in oil or paraffin under high-speed stirring in an inert atmosphere, and then washing the dispersed lithium metal particles from the oil with a solvent, which is also used as the solvent in the subsequent steps of alkyllithium synthesis. An alkyl halide is then added to the resulting dispersion of lithium metal in the solvent to produce the alkyllithium. Such a method is disclosed, for example, in Russian Patent No. 2691649 (Glukhovskoy VS, Blinov EV, Papkov VN, Zemsky DN, Stepanov IM, published June 17, 2019), in which lithium metal is pre-dispersed in petrolatum oil and then washed with nefras (a petroleum solvent) from the oil.

[0004] The main drawback of this method is the need for prior preparation of the lithium metal dispersion. This is a time-consuming and expensive procedure that requires high energy consumption to carry out the melting of lithium metal, stirring of the resulting highly viscous melt using powerful stirring equipment, high consumption of organic solvents to wash the resulting dispersion from the oil, and the cost of separating the resulting oil emulsion and solvent. In addition, the resulting alkyllithium may contain impurities due to incomplete washing of the dispersed lithium particles from the oil residue and due to side reactions of lithium with aromatic and unsaturated impurities that may be contained in the oil.

[0005] It is also known from the prior art that in order to increase the efficiency of alkyllithium synthesis, it is preferable to use lithium metal in the form of particles with a particle size of less than 300 microns (U.S. Pat. No. 5,332,533, issued Jul. 26, 1994, FMC Corporation). This is explained by the fact that the reaction between alkyl halides and lithium occurs mainly on the surface of the metal, and therefore the smaller the metal particles, the greater the specific surface area and the faster the reaction proceeds.

[0006] Thus, Russian Patent No. 2095362 (Shcherban GT, published November 10, 1997) discloses a method for producing n-butyllithium in a hydrocarbon solvent and in the presence of an inert gas, comprising, in a first step, reacting n-butyl chloride with a lithium metal dispersion having a particle size of 5 to 300 microns in a reactor at a temperature of 0 to 60°C, followed by a second step of maintaining the reaction mass at a temperature of 65 to 90°C, characterized in that in the first step, the synthesis of n-butyllithium is carried out in a molar ratio of n-butyl chloride to lithium equal to the stoichiometrically required molar ratio of 0.65 to 0.85, the resulting reaction product is separated, and unreacted lithium is returned to the synthesis in the same ratio of components, and the resulting n-butyllithium solution isolated during the separation is sent to the second step of the synthesis, which is completed after adding a second portion of the n-butyllithium solution and the remaining amount of n-butylchloride. Furthermore, in the first step, the synthesis is carried out while continuously circulating the reaction mass through a condenser, and n-butyl chloride is added for 0.25 to 2.5 hours. -1 The lithium is introduced at a mass rate of 0.15 to 0.25g, preferably at the point of lowest temperature.

[0007] The main drawbacks of the process disclosed therein are the complexity of its practical implementation, as well as the possibility of the formation of a stable suspension of lithium chloride by-product in the n-butyllithium solution under the described conditions of prolonged vigorous mechanical stirring, with the result that the resulting n-butyllithium contains large amounts of lithium chloride that are not separated during filtration.

[0008] U.S. Patent No. 7,005,083 (published February 28, 2006, to SQM Lithium Specialties Limited Partnership) discloses a method for producing alkyllithium compounds by reacting an alkyl halide containing 3 to 16 carbon atoms with metal particles less than 300 microns in size in a liquid hydrocarbon solvent selected from the group consisting of liquid saturated aliphatic hydrocarbons containing 5 to 12 carbon atoms, liquid saturated alicyclic hydrocarbons containing 6 to 12 carbon atoms, or mixtures thereof (lithium-sodium alloys with a sodium content of 15 to 34 wt. % are used as the metal). This method allows for the production of high-purity alkyllithium compounds in at least 90% yield. Disadvantages of this method for producing alkyllithium compounds include the high risk of fire and explosion when handling the lithium-sodium alloy, and the formation of a slurry of lithium chloride and sodium chloride, which is difficult to separate from the target product.

[0009] There is a known method for producing alkyllithiums by reacting lithium metal in the form of a dispersion with a particle size of up to 300 microns, produced by atomizing molten lithium at temperatures of 200-230°C in an argon atmosphere, with an alkyl halide in a hydrocarbon solvent (U.S. Pat. No. 7,326,372, CHEMETALL GMBH, published February 5, 2008). A drawback of this method is the need to use complex equipment to atomize lithium at temperatures of 200-230°C.

[0010] Although the use of finely dispersed lithium particles ensures the completeness of the alkyllithium formation reaction, it presents technical problems, in particular, particles that are too small easily form cakes on the filter equipment, leading to frequent stoppages.

[0011] Another important factor is that handling finely dispersed lithium poses a high risk of fire.

[0012] U.S. Pat. No. 5,523,447 (FMC Corp., issued June 4, 1996) discloses a method for producing alkyllithium compounds by reacting lithium metal in the form of small pieces weighing more than 0.5 grams with an alkyl chloride in a molar ratio of lithium to alkyl chloride ranging from 3:1 to 20:1 in a hydrocarbon solvent in an inert atmosphere, with moderate or no stirring.

[0013] A drawback of the process is the high lithium to alkyl chloride ratio of 3:1 or more. Unreacted lithium can be entrained in the solution containing the target product and can also exit the reactor and clog tubing and fittings.

[0014] Furthermore, if stirring is slow or incomplete, the lithium metal quickly becomes contaminated with lithium chloride sludge, and subsequent washing with fresh solvent, as proposed in the above patents, does not completely remove the sludge. Also, as the reaction proceeds, lithium chloride forms on the surface of the lithium metal, thereby preventing access of butyl chloride to the uncontaminated lithium metal and initiating a preferential side reaction of the formed butyllithium with butyl chloride to produce lithium chloride and octane.

[0015] Therefore, there remains a need to provide a method for producing alkyllithium solutions that overcomes all of the above-mentioned drawbacks.

[0016] Summary of the Invention The object of the present invention is to provide an effective method for producing alkyllithium solutions using lithium metal with a relatively low specific surface area while ensuring a high yield of alkyllithium, which overcomes all of the above-mentioned drawbacks associated with the use of finely dispersed lithium metal particles (lithium with a high specific surface area).

[0017] The purpose is to measure the distance between 1 and 100 cm. 2The method for producing an alkyllithium solution is to react lithium metal having a specific surface area of ​​10000000 / g with an alkyl halide in an organic solvent medium under highly turbulent conditions, and the molar ratio of lithium metal to alkyl halide is 2.5:1 to 5.5:1.

[0018] The term "highly turbulent flow" in the context of the present invention should be understood to mean a flow regime of a reacting flow having a Reynolds number greater than 10,000, characterized by highly irregular, random velocity variations with time at each point in the reacting flow.

[0019] The technical results achieved by the present invention are in the range of 1 to 100 cm 2 The objective of this invention is to achieve alkyllithium yields of over 90% by using lithium metal having a specific surface area of ​​100000000 / g and alkyl halides in an organic solvent medium under highly turbulent flow conditions at a molar ratio of lithium metal to alkyl halide of 2.5:1 to 5.5:1, which is comparable to the alkyllithium yields achieved using finely dispersed lithium metal particles with high specific surface areas.

[0020] A further technical result achieved by the present invention is the reduction of the number of steps in the process for producing an alkyllithium solution, since it is not necessary to pre-disperse the lithium metal to obtain finely dispersed particles of lithium metal and then wash it from the dispersion medium (oil or paraffin), which also makes it possible to minimize the loss of lithium metal that may occur in each of these steps.

[0021] A further technical result achieved by the present invention is the increased fire and explosion safety of the process for producing alkyllithium solutions, since it is not necessary to use finely dispersed particles of lithium metal, which are highly pyrophoric.

[0022] In addition, the inventors have demonstrated that when the molar ratio of lithium metal to alkyl halide is between 2.5:1 and 5.5:1, the reaction can be carried out at a rate of 1 to 100 cm under highly turbulent conditions. 2It has been discovered that the use of lithium metal having a specific surface area of ​​1000 nm / g unexpectedly enables the synthesis of alkyllithium to achieve alkyllithium yields of greater than 90% without a significant increase in reaction time compared to the use of finely dispersed lithium metal particles.

[0023] MODE FOR CARRYING OUT THE INVENTION Below follows a detailed description of various aspects and embodiments of the invention.

[0024] The present invention is a method for measuring the concentration of a substance in a range of 1 to 100 cm 2 / g, preferably 5 to 70 cm 2 / g, most preferably 10 to 30 cm 2 In the method for producing an alkyllithium solution by reacting lithium metal having a specific surface area of ​​1000 nm / g with an alkyl halide in an organic solvent medium under highly turbulent conditions, the molar ratio of lithium metal to alkyl halide can be 2.5:1 to 5.5:1, preferably 2.5:1 to 5:1, more preferably 3:1 to 4.5:1.

[0025] The lithium metal may be used in any form, for example, in the form of a small piece or cylinder having a weight of 0.05 to 1 g, preferably 0.08 to 0.8 g, and most preferably 0.1 to 0.5 g.

[0026] The specific surface area of ​​the lithium metal used can be determined by any method known from the prior art, both calculation and experimental methods, for example, by low-temperature nitrogen adsorption according to the Brunauer-Emmett-Teller method (BET). The calculation method is based on the geometrical concept of the shape and size of the lithium metal. For example, the specific surface area of ​​lithium metal in the form of a cylinder can be determined using the following formula: surface area of ​​the cylinder 2πrh + 2πr 2 , where h is the height of the cylinder and r is the diameter of the cylinder, divided by the mass of the cylinder.

[0027] The sodium content of the lithium metal can vary from 50 to 2000 ppm, preferably from 100 to 1500 ppm, more preferably from 150 to 1000 ppm, more preferably from 250 to 500 ppm.

[0028] The alkyl halide may be chloride, bromide or iodide, and most preferably chloride.Alkyl chloride includes, but is not limited to, methyl chloride, ethyl chloride, n-propyl chloride, n-butyl chloride, sec-butyl chloride, tert-butyl chloride and n-hexyl chloride.Preferably, n-butyl chloride, sec-butyl chloride or tert-butyl chloride.

[0029] Suitable organic solvents include, but are not limited to, C5-C7 alkanes such as n-hexane and n-heptane; cycloalkanes such as cyclohexane; or mixtures thereof in various ratios, such as nefras and petroleum ether. Preferably, hexane, cyclohexane, or nefras is used, and most preferably, hexane and nefras, such as nefras P1 63 / 75, a hexane-heptane fraction, is used.

[0030] The rate at which the required amount of alkyl halide is added to lithium metal in an organic solvent can be any rate, and is selected so that the temperature of the alkyllithium synthesis does not exceed 75°C, preferably in the range of 50-73°C, more preferably 60-70°C. If the temperature exceeds 75°C, a dominant side reaction, the formation of lithium chloride, may occur.

[0031] The alkyllithium synthesis time can be any time sufficient to bring the alkyl halide content in the reaction mass to 0. In a preferred embodiment, the alkyllithium synthesis time can be up to 24 hours, preferably up to 18 hours, and most preferably up to 10 hours.

[0032] After the addition is complete, the reaction mass is maintained at a temperature of 55-85°C, preferably 65-75°C for 2-8 hours, preferably 4-8 hours.

[0033] The type of stirring device and the stirring speed are not critical when carrying out the method of the present invention, and may be in the range of 0.01 to 0.3 m / s. 2 / s 3 , preferably 0.02 to 0.2 m 2 / s 3 , more preferably 0.03 to 0.1 m 2 / s 3 Any stirring device and stirring speed can be used as long as the turbulent energy dissipation rate (ε) in the range of 0.3 m is guaranteed. By maintaining the turbulent energy dissipation rate (ε) in a given range, it is possible to provide the necessary conditions for high turbulence of the reaction mass flow in the reactor, which can prevent the lithium chloride sludge from adhering to the lithium metal surface and, as a result, ensure effective interaction between the lithium metal and the alkyl halide. 2 / s 3 At energy dissipation rates (ε) above , the yield of alkyllithium may decrease due to the fact that the mixture of solvent and alkyl halide distributes mainly near the reactor wall and interacts weakly with the lithium metal. In addition, separate circulation circuits of reaction masses may be formed, which also interact weakly with each other.

[0034] The stirring time corresponds to the total charging time and the holding time of the reaction mass after the alkyl halide charging is completed.

[0035] The process for producing the alkyllithium solution must be carried out in a reactor made of a material inert to the substances used in the process for producing the alkyllithium solution. In particular, the process for producing the alkyllithium solution can be carried out in a titanium reactor, a stainless steel reactor, or an enameled reactor.

[0036] The alkyllithium solution obtained as a result of the synthesis is purified from lithium chloride sludge by filtration, the content of which should not exceed 0.4%, and preferably should be completely free of sludge. Filtration can be carried out using any filtering device known in the prior art, such as a filter with a porous filter wall or a nutsche filter, at any temperature, preferably 20 to 40°C, more preferably 20 to 30°C, and is preferably carried out using a nutsche filter.

[0037] The filtered alkyllithium solution can be further diluted with organic solvent to obtain the concentration required for subsequent use as an initiator in diene polymerization and diene copolymerization, for example with vinyl aromatic compounds, and to comply with the European Agreement concerning the International Carriage of Dangerous Goods by Road (ARD). Specifically, n-butyllithium in the form of a solution with a concentration of 15-90% n-butyllithium belongs to the class of substances capable of spontaneous combustion (class 4.2) and can therefore only be transported in accordance with the ARD.

[0038] Alkyllithiums produced according to the methods of the present invention may include, but are not limited to, propyllithium, butyllithium, amyllithium, hexyllithium, preferably butyllithium.

[0039] Implementation of the invention Example 1 (Comparative) 151.5 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium has a specific surface area of ​​293 cm 2 The lithium was used in the form of a 0.15g / g dispersion. The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was dosed at 300 rpm over 7 hours so that the reaction temperature did not exceed 70°C. The molar ratio of lithium to n-butyl chloride was 2.02:1. Once the n-butyl chloride dose was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 99.2%.

[0040] Example 2 (Comparative) 151.5 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had dimensions of 6 × 12 mm and a specific surface area of ​​15.6 cm, calculated by the calculation method. 2 The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 300 rpm (0.05 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 1000 K (corresponding to an ε of 1000 K). The molar ratio of lithium to n-butyl chloride was 2.02:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 66.7%.

[0041] Example 3 (according to the present invention) The preparation of n-butyllithium was carried out as in Example 2, except that the molar ratio of lithium to n-butyl chloride was 3:1. The yield of n-butyllithium was 95.2%.

[0042] Example 4 (according to the present invention) The stirring speed was set to 500 rpm (0.15 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 3, except that the ε was 1.0 (corresponding to ε in Example 1). The yield of n-butyllithium was 97.2%.

[0043] Example 5 (according to the invention) The preparation of n-butyllithium was carried out as in Example 2, except that the molar ratio of lithium to n-butyl chloride was 4:1. The yield of n-butyllithium was 99.3%.

[0044] Example 6 (according to the invention) The stirring speed is 500 rpm (0.15 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 5, except that the ε was 1.0 (corresponding to ε in

[0045] Example 7 (according to the invention) The stirring speed is 600 rpm (0.28 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 5, except that the ε was 1.0 (corresponding to ε in

[0046] Example 8 (according to the invention) The preparation of n-butyllithium was carried out as in Example 2, except that the molar ratio of lithium to n-butyl chloride was 4.5:1. The yield of n-butyllithium was 99.2%.

[0047] Example 9 (according to the invention) 225 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had dimensions of 10 × 5 mm and a specific surface area of ​​15 cm, according to the calculation method. 2 The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 300 rpm (0.05 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 65°C (corresponding to an ε of 1000). The molar ratio of lithium to n-butyl chloride was 3:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 94.6%.

[0048] Example 10 (according to the invention) The preparation of n-butyllithium was carried out as in Example 9, except that the molar ratio of lithium to n-butyl chloride was 4.5:1. The yield of n-butyllithium was 99.2%.

[0049] Example 11 (Comparative) 300 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had a specific surface area of ​​6.3 cm2 calculated by the calculation method. 2The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 150 rpm (0.006 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 65°C (corresponding to an ε of 1000). The molar ratio of lithium to n-butyl chloride was 4:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 67.8%.

[0050] Example 12 (according to the invention) The stirring speed is 300 rpm (0.05 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 11, except that the ε was 1.0 (corresponding to ε in Example 11). The yield of n-butyllithium was 90.3%.

[0051] Example 13 (according to the invention) The stirring speed is 500 rpm (0.15 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 11, except that the ε was 1.0 (corresponding to ε in Example 11). The yield of n-butyllithium was 92.4%.

[0052] Example 14 (according to the invention) 225 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had dimensions of 6 × 6 mm and a specific surface area of ​​25.7 cm, calculated by the calculation method. 2 The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 150 rpm (0.006 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 65°C (corresponding to an ε of 1000). The molar ratio of lithium to n-butyl chloride was 3:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 92.5%.

[0053] Example 15 (according to the invention) The stirring speed is 300 rpm (0.05 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 14, except that the ε was 1.0 (corresponding to ε in the formula (2)). The yield of n-butyllithium was 97.3%.

[0054] Example 16 (according to the invention) The stirring speed is 600 rpm (0.28 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 14, except that the ε was 1.0 (corresponding to ε in Example 14). The yield of n-butyllithium was 99.3%.

[0055] Example 17 (Comparative) 225 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had a specific surface area of ​​0.42 cm2 calculated by the calculation method. 2 The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 300 rpm (0.05 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 65°C (corresponding to an ε of 1000). The molar ratio of lithium to n-butyl chloride was 3:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 61.3%.

[0056] Example 18 (Comparative) The stirring speed is 800 rpm (0.6 m 2 / s 3 n-Butyllithium was prepared in the same manner as in Example 17, except that the ε was 1.0 (corresponding to ε in Example 1). The yield of n-butyllithium was 63%.

[0057] Example 19 (according to the invention) 300 g of lithium and 2 kg of nefras (P1 63 / 75) were added to a 5 L reactor. The lithium had a specific surface area of ​​96.3 cm2 calculated by the calculation method. 2The reactor contents were heated to 60°C, and then 1 kg of n-butyl chloride was added at 300 rpm (0.05 m) so that the reaction temperature did not exceed 70°C. 2 / s 3 The charge was made over a period of 7 hours with stirring at a temperature of 65°C (corresponding to an ε of 1000). The molar ratio of lithium to n-butyl chloride was 4:1. Once the charge of n-butyl chloride was complete, the reaction mass was maintained at a temperature of 65°C for 8 hours. The yield of n-butyllithium was 99.2%.

Claims

1. 1 to 100 cm ２ 1. A method for producing alkyllithium by reacting lithium metal having a specific surface area of ​​1.05g / g with an alkyl halide in an organic solvent medium under highly turbulent conditions, wherein the molar ratio of lithium metal to alkyl halide is 2.5:1 to 5.5:

1.

2. The lithium metal used is 5 to 70 cm ２ / g, preferably 10 to 30 cm ２ 2. The method according to claim 1, characterized in that the specific surface area of ​​the silica gel is 0.15 wt.

3. 3. A process according to claim 1 or 2, characterized in that the alkyl halide used is an alkyl chloride, alkyl bromide or alkyl iodide, preferably an alkyl chloride.

4. 4. The process according to claim 3, characterized in that the alkyl chloride used is methyl chloride, ethyl chloride, n-propyl chloride, n-butyl chloride, sec-butyl chloride, tert-butyl chloride or n-hexyl chloride, preferably n-butyl chloride, sec-butyl chloride or tert-butyl chloride.

5. The reaction of the lithium metal with the alkyl halide is carried out in a range of 0.01 to 0.3 m ２ / s ３ , preferably 0.02 to 0.2 m ２ / s ３ , more preferably 0.03 to 0.1 m ２ / s ３ 5. The method according to claim 1, wherein the method is carried out at a turbulent energy dissipation rate (ε) of 0.05 to 0.

15.

6. A process according to any one of claims 1 to 5, characterized in that the molar ratio of lithium metal to alkyl halide is between 2.5:1 and 5.5:1, preferably between 3:1 and 4.5:

1.

7. 7. The method according to any one of claims 1 to 6, characterized in that the organic solvent used is a C5-C7 alkane, such as n-hexane, n-heptane; a cycloalkane, such as cyclohexane; or mixtures thereof in various ratios, such as nefras (petroleum solvents) and petroleum ether.

8. 8. The process according to claim 7, characterized in that the organic solvent used is hexane, cyclohexane or nefras, preferably hexane and nefras.

9. 9. The method according to any one of claims 1 to 8, characterized in that the introduction of alkyl halide into the lithium metal in the organic solvent is carried out in such a way that the temperature of the alkyllithium synthesis does not exceed 75°C, preferably in the range of 50 to 73°C, more preferably 60 to 70°C.

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