Synthesis process of alkali metal trialkyl borohydride

Abstract

The invention discloses a synthesis process of alkali metal trialkyl borohydride. A synthesis process of alkali metal trialkyl borohydride comprises: alkali metal borohydride and olefin are subjected to addition reaction in an organic solvent to prepare alkali metal trialkyl borohydride. Compared with the prior art, the synthesis process of alkali metal trialkyl borohydride provided by the invention does not need to prepare and purify sensitive intermediate trialkyl boron, has high yield of target product, has few reaction steps, strong operability, and easy to obtain raw materials, and is suitable for industrialized scale-up production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic reactions, and in particular relates to a synthesis process of alkali metal trialkyl borohydride. Background Art

[0002] Alkali metal trialkyl borohydrides are very strong nucleophilic reducing agents that can quickly and quantitatively cut off cyclic ethers, reduce hindered halides, epoxides, and active olefins to obtain the corresponding reduction products. Their reducing ability is much stronger than that of their corresponding alkali metal borohydrides. On the other hand, due to the different steric hindrance of the alkyl group, this type of compound also shows excellent properties in regio- and stereoselective reduction.

[0003] There are two main processes for synthesizing such products: 1. First, an alkyl Grignard reagent is reacted with boron trifluoride to generate trialkylborane, and the purified trialkylborane is reacted with a metal hydride in an ether solvent to obtain an alkali metal trialkylborohydride. 2. An olefin is reacted with a borane dimethyl sulfide solution to generate trialkylborane, and then reacted with a metal hydride to generate the target product. The existing synthesis process requires the preparation and purification of very sensitive trialkylborane, with a low synthesis yield, and the intermediate is very easy to deteriorate. The process has strict requirements, and the scale-up production has high requirements for equipment and operation. Summary of the invention

[0004] To this end, the present invention provides a synthesis process of alkali metal trialkyl borohydride.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A synthesis process of alkali metal trialkyl borohydride comprises: carrying out addition reaction between alkali metal borohydride and olefin in an organic solvent to prepare alkali metal trialkyl borohydride.

[0007] The invention uses alkali metal borohydride and olefin as raw materials, and generates an addition reaction in the presence of an organic solvent to obtain a target product in one step. The invention not only has a high reaction yield, but also has a small number of reaction steps, strong operability, and readily available raw materials, and is suitable for industrialized large-scale production.

[0008] In some preferred embodiments, the alkali metal borohydride includes lithium borohydride, potassium borohydride, and sodium borohydride.

[0009] In some preferred embodiments, the organic solvent is an ether solvent, or a mixed solvent of an ether solvent and toluene.

[0010] In some preferred embodiments, the ether solvent is tetrahydrofuran or diethyl ether.

[0011] In some preferred embodiments, the olefin comprises ethylene, 2-butene or 3-hexene.

[0012] In some preferred embodiments, the alkali metal trialkyl borohydride includes lithium triethylborohydride, lithium tri-sec-butylborohydride, lithium tri(hexane-3-yl)borohydride, sodium triethylborohydride, sodium tri-sec-butylborohydride, sodium tri(hexane-3-yl)borohydride, potassium triethylborohydride, potassium tri-sec-butylborohydride, and potassium tri(hexane-3-yl)borohydride.

[0013] In some preferred embodiments, the molar ratio of the alkali metal borohydride to the olefin is 1:(3.5-10).

[0014] In some preferred embodiments, the temperature of the addition reaction is 25-80°C and the time is 0.5-3h. After the reaction is completed, an appropriate amount of the reaction solution is taken and the hydrogen concentration after hydrolysis is detected by the gas generation method. When the hydrogen concentration is 1-1.5M, it indicates that there is substantially no alkali metal borohydride remaining in the reaction solution.

[0015] In some preferred embodiments, the synthesis process comprises the following steps:

[0016] dissolving an alkali metal borohydride in an organic solvent to obtain an alkali metal borohydride solution;

[0017] An alkali metal trialkyl borohydride is prepared by adding an olefin into the alkali metal borohydride solution to carry out an addition reaction.

[0018] The present invention has the following advantages:

[0019] Compared with the prior art, the synthesis process of alkali metal trialkyl borohydride provided by the invention does not need to prepare and purify sensitive intermediate trialkyl boron, has high yield of target product, has few reaction steps, strong operability, and readily available raw materials, and is suitable for industrialized scale-up production. DETAILED DESCRIPTION

[0020] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0022] Example 1

[0023] This embodiment provides a synthesis process of lithium triethylborohydride:

[0024] In a 2000mL three-necked flask, add 1000mL of tetrahydrofuran and 30g of lithium borohydride, stir thoroughly at 35°C until the lithium borohydride is completely dissolved to obtain a lithium borohydride solution, and keep the temperature constant;

[0025] Ethylene gas was introduced into the lithium borohydride solution at a rate of 10 g / min. After 15 minutes, gas began to overflow from the system. The aeration was stopped and stirred for 10 minutes. 50 ml of the reaction solution was taken and the hydrogen concentration was measured by the gas evolution method to be 1.35 M, indicating that the lithium borohydride had been basically completely converted into lithium triethylborohydride, with a yield of 95%. A certain amount of tetrahydrofuran was added to adjust the concentration of lithium triethylborohydride to 1.05 M.

[0026] Example 2

[0027] This embodiment provides a synthesis process of sodium tri-sec-butylborohydride:

[0028] In a 2000mL three-necked flask, add 1000mL of tetrahydrofuran and 50g of sodium borohydride, stir thoroughly at 45°C until the sodium borohydride is completely dissolved to obtain a sodium borohydride solution, and keep the temperature constant;

[0029] After 2-butene gas was introduced into the sodium borohydride solution at a rate of 10 g / min for 30 minutes, gas began to overflow from the system. The gas was stopped and stirred for 10 minutes. 50 ml of the reaction solution was taken and the hydrogen concentration was measured by the gas evolution method to be 1.31 M, indicating that the sodium borohydride had been basically completely converted into sodium tri-sec-butylborohydride, with a yield of 96%. A certain amount of tetrahydrofuran was added to adjust the concentration of lithium triethylborohydride to 1.0 M.

[0030] Example 3

[0031] This embodiment provides a synthesis process of potassium triethylborohydride:

[0032] In a 2000mL three-necked flask, add 1000mL of tetrahydrofuran and 70g of potassium borohydride, stir thoroughly at 40°C until the potassium borohydride is completely dissolved to obtain a potassium borohydride solution, and keep the temperature constant;

[0033] Ethylene gas was introduced into the potassium borohydride solution at a rate of 10 g / min. After 15 minutes, a small amount of gas began to overflow from the reaction system. The gas was stopped and stirred for 10 minutes. 50 ml of the reaction solution was taken and the hydrogen concentration was measured by the gas evolution method to be 1.28 M, indicating that potassium borohydride had been basically completely converted into potassium triethylborohydride, with a yield of 95%. A certain amount of tetrahydrofuran was added to adjust the concentration of potassium triethylborohydride to 1.0 M.

[0034] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A process for synthesizing an alkali metal trialkyl borohydride, characterized in that: include: Alkali metal borohydride and olefin undergo addition reaction in an organic solvent to prepare alkali metal trialkyl borohydride; The alkali metal borohydride includes lithium borohydride, potassium borohydride, and sodium borohydride; The olefin includes ethylene, 2-butene or 3-hexene; The alkali metal trialkyl borohydride includes lithium triethylborohydride, lithium tri-sec-butylborohydride, lithium tri(hexane-3-yl)borohydride, sodium triethylborohydride, sodium tri-sec-butylborohydride, sodium tri(hexane-3-yl)borohydride, potassium triethylborohydride, potassium tri-sec-butylborohydride, potassium tri(hexane-3-yl)borohydride; The temperature of the addition reaction is 25-80°C and the time is 0.5-3h; The molar ratio of the alkali metal borohydride to the olefin is 1:(3.5-10).

2. The synthesis process of alkali metal trialkyl borohydride according to claim 1, characterized in that: The organic solvent is an ether solvent, or a mixed solvent of an ether solvent and toluene.

3. The synthesis process of alkali metal trialkyl borohydride according to claim 2, characterized in that: The ether solvent is tetrahydrofuran or diethyl ether.

4. The process for synthesizing alkali metal trialkyl borohydride according to any one of claims 1 to 3, characterized in that: The steps include: dissolving an alkali metal borohydride in an organic solvent to obtain an alkali metal borohydride solution; An alkali metal trialkyl borohydride is prepared by adding an olefin into the alkali metal borohydride solution to carry out an addition reaction.