Preparation method of (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide

Abstract

The invention discloses a preparation method of (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide. The invention provides a preparation method of (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide. The preparation method provided by the invention has the advantages of high yield, high purity, safety, environmental protection, high efficiency and cost, and provides a new solution for industrial production of the (2, 4, 6-trimethylbenzoyl) diphenyl phosphine oxide.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical synthesis, and specifically relates to a method for preparing (2,4,6-trimethylbenzoyl)diphenylphosphine oxide. Background Art

[0002] Acylphosphine oxide compounds (such as (2,4,6-trimethylbenzoyl) diphenylphosphine oxide) have important applications in the fields of photoinitiators and polymer functional materials, but their efficient synthesis has always faced technical challenges. The current mainstream method relies on diphenylphosphine chloride as a raw material and is prepared through two routes: one is the esterification of diphenylphosphine chloride with methanol to form an intermediate, which is then condensed with 2,4,6-trimethylbenzoyl chloride; the other is the hydrolysis of diphenylphosphine chloride to diphenylphosphine oxide, which is then condensed with 2,4,6-trimethylbenzaldehyde and oxidized. However, the core pain point of these two processes is that there are serious safety hazards and environmental problems in the synthesis process of diphenylphosphine chloride, and the yield of diphenylphosphine chloride is low (multiple steps of separation and purification are required). In addition, the oxidation step in the second method further increases the operational risk and restricts the feasibility of large-scale production.

[0003] Although an alternative solution has been proposed in a patent (WO2020113585A1), there is still room for improvement in terms of product purity, process stability or cost control. For example, although the existing alternative methods claim to be environmentally friendly and safe, the reaction conditions (such as catalyst selection and solvent system) are not optimized enough, which may lead to side reactions or difficulties in product separation, affecting industrial efficiency.

[0004] Based on the above technical bottlenecks, the present invention proposes an innovative method for preparing acylphosphine oxide compounds. By abandoning the diphenylphosphine chloride raw material and the high-risk oxidation step, the high-activity intermediate and the specific acyl chloride are directly condensed under an optimized catalytic system, which significantly simplifies the process flow. In addition, by designing a new catalyst combination and a precise temperature control strategy, this method achieves a simultaneous improvement in reaction selectivity and product purity, while reducing energy consumption and raw material loss. Compared with the prior art, the present invention has the advantages of safety, environmental protection, high efficiency and cost, and provides a new solution for the industrial production of acylphosphine oxide compounds. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing preparation method of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide has low synthesis efficiency. To this end, the present invention provides a preparation method of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide. The preparation method provided by the present invention has the advantages of high yield, high purity, safety, environmental protection, high efficiency and cost, and provides a new solution for the industrial production of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a method for preparing a compound as shown in II, which comprises the following steps: .

[0008] (1) The compound of formula I, triethylamine and toluene are mixed and stirred; then the silicon reagent is added dropwise at 40-50° C. After the addition is complete, the reaction is continued with stirring for 0.5-4 hours.

[0009] (2) Then, a toluene solution of 2,4,6-trimethylbenzoyl chloride is added dropwise; the mixture is stirred and reacted at 40-110° C. for 0.5-24 hours.

[0010] (3) Recovering toluene and silicon reagent under reduced pressure to obtain a crude product, and then slurrying the crude product with ethanol, filtering, and vacuum drying to obtain a compound as shown in Formula II.

[0011] Wherein, the silicon reagent is one or more of trimethylchlorosilane, dimethyldichlorosilane and methyltrichlorosilane.

[0012] In the present invention, optionally, the silicon reagent is dimethyldichlorosilane and / or methyltrichlorosilane.

[0013] In the present invention, optionally, the silicon reagent is methyltrichlorosilane.

[0014] In the present invention, in step (1), the molar ratio of the compound represented by formula I to the silicon reagent is 1:(0.8-1.2); for example, 1:1.2.

[0015] In the present invention, the molar ratio of the compound as shown in formula I to 2,4,6-trimethylbenzoyl chloride is 1:(1-1.2); for example, 1:1.1.

[0016] In the present invention, in step (3), the toluene and silicon reagent recovered under reduced pressure can be applied to the next batch of reactions.

[0017] In the present invention, the compound as shown in formula I is prepared by the following preparation method, which comprises the following steps: .

[0018] (1) Mix 1,4-dimethylbenzene and Lewis acid at 50°C-74°C.

[0019] (2) Add phosphorus trichloride dropwise at 50°C-74°C. After the addition is completed, stir at 74°C-78°C for 0.5-1 hour.

[0020] (3) Then, the reaction system is heated to 137°C-140°C and the reaction is continued with stirring for 0.5-24 hours.

[0021] (4) Then, an organic solvent is added to the reaction system, and water is added dropwise, and the reaction is stirred at 25-40° C. for 0.5-8 hours.

[0022] (5) Then the aqueous phase is separated, extracted with dichloromethane, the organic phases are combined, and the solvent in the organic phase is removed by reduced pressure distillation to obtain a crude product, which is then slurried with ethanol, filtered, and dried to obtain the compound shown in Formula I.

[0023] In the present invention, the Lewis acid is anhydrous aluminum chloride and / or trifluoromethanesulfonic acid.

[0024] In the present invention, the Lewis acid is anhydrous aluminum chloride and trifluoromethanesulfonic acid.

[0025] In the present invention, the Lewis acid is anhydrous aluminum chloride and trifluoromethanesulfonic acid, and the molar ratio of anhydrous aluminum chloride to trifluoromethanesulfonic acid is 9:(0.1-2); preferably 9:1 or 8:2.

[0026] In the present invention, in step (4), the organic solvent is an ether solvent, a hydrocarbon solvent or a halogenated hydrocarbon solvent.

[0027] In the present invention, in step (4), the organic solvent is dichloromethane or petroleum ether; more preferably dichloromethane.

[0028] The present invention also provides a method for preparing the compound as shown in Formula I, wherein the compound as shown in Formula I is prepared by the method for preparing the compound as shown in Formula I: .

[0029] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0030] The reagents and raw materials used in the present invention are commercially available.

[0031] The positive progressive effect of the present invention is that the preparation method of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide provided by the present invention has high yield, high purity, safety, environmental protection, high efficiency and cost advantages, and provides a new solution for the industrial production of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a phosphine spectrum for tracking the formation of the compound represented by formula I in the reaction of Example 1.

[0033] Figure 2 This is a phosphine spectrum for tracking the consumption of the compound represented by formula I in the reaction of Example 3.

[0034] Figure 3This is a phosphine spectrum for tracking the formation of the compound represented by formula II in the reaction of Example 3. DETAILED DESCRIPTION

[0035] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0036] Embodiment 1: .

[0037] (1) Under nitrogen protection, dry 1,4-dimethylbenzene (213.2 g, 2.0 mol) and Lewis acid (anhydrous aluminum chloride (361.5 g, 2.7 mol), CF 3 SO 3 H (45.2 g, 0.3 mol) was added into the reaction flask and stirred at 50°C-74°C to mix well.

[0038] (2) Phosphorus trichloride (137.9 g, 1.0 mol) was added dropwise at 50°C-74°C. After the addition was completed, stirring was continued at 74°C-78°C for 0.5-1 hour.

[0039] (3) Then, the reaction system is heated to between 137°C and 140°C and stirred to allow the reaction to fully occur.

[0040] (4) The reaction system was cooled to room temperature, and then 500 mL of dichloromethane was added, and 500 mL of water was added dropwise; the mixture was stirred at 25-40° C. for 0.5-8 hours, and the phosphine spectrum of the compound represented by formula I was tracked by NMR until the reaction was completed. Figure 1 As shown, its phosphine spectrum ( 31 P is 20.38ppm), and its purity is 97.0%.

[0041] (5) Then the organic phase was separated; the pH of the aqueous phase was adjusted to 8-11, and extracted with dichloromethane, and the organic phases were combined; then the organic phase was dried over anhydrous magnesium sulfate, filtered, and the organic solvent was removed under reduced pressure to obtain a crude product, and then the crude product was slurried with ethanol, filtered, and dried to obtain the compound shown in Formula I (238.62 g, yield 92.01%); 31 P NMR: 20.38 ppm.

[0042] In this article, the phosphine spectrum mentioned, unless otherwise specified, is tested by taking 10 μL of reaction liquid or solution from the system, diluting it with 0.5 mL of deuterated chloroform, and then directly performing NMR phosphine spectrum testing on it.

[0043] Example 2: Lewis acid screening.

[0044] The method of Example 1 is adopted, except that: the amount of raw materials is reduced by 20 times. In addition, the Lewis acid is different, and the total molar amount of Lewis acid is 3 times that of phosphorus trichloride. The use of Lewis acid is shown in Table 1 below, and the experimental results are shown in Table 1 below, wherein the yield in Table 1 refers to the isolated yield.

[0045] Table 1:

[0046] The above experimental results show that among the Lewis acids screened, only aluminum chloride and trifluoromethanesulfonic acid can catalyze the above reaction; however, unexpectedly, when 9AlCl 3 +1CF 3 SO 3 The catalytic effect was best when the molar ratio of H was 9:1, and the yield was 92.01%.

[0047] Embodiment 3: .

[0048] Under nitrogen protection, the compound shown in Formula I (51.7 g, 0.2 mol), 25 mL of triethylamine and 100 mL of toluene were added to the reaction bottle and stirred at room temperature for 15 minutes. Then, a toluene (60 mL) solution of methyltrichlorosilane (35.9 g, 0.24 mol) was added dropwise. After the addition was completed, stirring was continued, and the progress of the reaction of the compound shown in Formula I was tracked by nuclear magnetic resonance phosphine spectrum; when the phosphine spectrum results showed that most of the compound shown in Formula I had reacted, for example, its phosphine spectrum was as follows Figure 2 As shown; then add a toluene (80mL) solution of 2,4,6-trimethylbenzoyl chloride (40.2 g, 0.22 mol) dropwise, after the addition is complete; raise the temperature to 50°C to maintain the reaction, and track the compound shown in formula II by nuclear magnetic resonance, and wait until the phosphine spectrum shows that the reaction is complete, for example, its phosphine spectrum is as follows Figure 3 shown.

[0049] Then, toluene and silicon reagent are recovered under reduced pressure, wherein the recovered toluene and silicon reagent can be applied to the next reaction; after the solvent and silicon reagent are recovered, a crude product can be obtained, and the crude product is slurried with ethanol, filtered, and vacuum dried to obtain a compound as shown in Formula II (74.6 g, yield 92.14%); 31 P NMR: 21.23 ppm.

[0050] The experimental results show that when methyltrichlorosilane is added, although the intermediates are complex, such as Figure 2 As shown, its final experimental results are the most effective and easy to separate and purify.

[0051] Embodiment 4: .

[0052] Under nitrogen protection, the compound shown in formula I (20.0 g, 0.077 mol), 10 mL triethylamine and 40 mL toluene were added to the reaction bottle and stirred at room temperature for 15 minutes. Then, a mixed solution of dimethyldichlorosilane (12.0 g, 0.093 mol) and 60 mL toluene was added dropwise, and the addition was completed in 30 minutes, and the reaction was continued by stirring for 1-4 hours. Then, a mixed solution of 2,4,6-trimethylbenzoyl chloride (15.6 g, 0.085 mol) and 30 mL toluene was added dropwise, and after the addition was completed; the temperature was raised to 50°C and the reaction was maintained for 4-8 hours. Then, toluene and silicon reagent were recovered under reduced pressure, and the recovered toluene and silicon reagent could be applied to the next reaction; after the solvent and silicon reagent were recovered, a crude product was obtained, and the crude product was pulped with ethanol, filtered, and vacuum dried to obtain a compound shown in formula II (28.6 g, with a yield of 91.3%).

[0053] Embodiment 5: .

[0054] Under nitrogen protection, the compound shown in formula I (25.0 g, 0.097 mol), 13 mL triethylamine and 50 mL toluene were added to the reaction bottle and stirred at room temperature for 15 minutes. Then, a mixed solution of trimethylsilyl chloride (12.62 g, 0.12 mol) and 60 mL toluene was added dropwise, and the addition was completed in 30 minutes, and the reaction was continued by stirring for 1-4 hours. Then, a mixed solution of 2,4,6-trimethylbenzoyl chloride (19.4 g, 0.11 mol) and 40 mL toluene was added dropwise, and after the addition was completed; the temperature was raised to 50°C and the reaction was maintained for 4-8 hours. Then, toluene and silicon reagent were recovered under reduced pressure, and the recovered toluene and silicon reagent could be applied to the next reaction; after the solvent and silicon reagent were recovered, a crude product was obtained, and the crude product was pulped with ethanol, filtered, and vacuum dried to obtain a compound shown in formula II (33.2 g, with a yield of 84.8%).

[0055] Comparative Example 1: Under nitrogen protection, 1,4-dimethylbenzene (213.2 g, 2.01 mol), Lewis acid (anhydrous aluminum chloride, 253.9 g, 1.9 mol) and phosphorus trichloride (137.3 g, 1.0 mol) were added into the reaction bottle at one time; then the temperature was raised to 137-140°C for reaction. After reacting for 12 hours, the reaction system was cooled to room temperature, and then 3*500mL of dichloromethane was used to extract the organic matter to obtain an organic phase, and the solid insoluble matter was removed (post-treatment of the solid insoluble matter: the solid insoluble matter was dissolved in water to become aluminum chloride wastewater); then the organic phase was concentrated under reduced pressure to about 500 mL, and then water was added dropwise to the organic phase, stirred at 25-40°C for 8 hours, and then the organic phase was separated; the aqueous phase was extracted with dichloromethane, and the organic phases were combined; then the organic phase was dried over anhydrous magnesium sulfate, filtered, and the organic solvent was removed under reduced pressure to obtain a crude product, and then the crude product was slurried with ethanol, filtered, and dried to obtain a compound as shown in Formula I (195.3 g; yield 75.3%).

[0056] Comparative Example 2: .

[0057] Under nitrogen protection, the compound shown in Formula 1 (10.0 g, 0.038 mol), 10 mL of triethylamine and 20 mL of toluene were added to the reaction bottle and stirred at room temperature for 15 minutes. Subsequently, a mixed solution of 2,4,6-trimethylbenzoyl chloride (7.8 g, 0.042 mol) and 16 mL of toluene was added dropwise for 1 hour. The temperature was raised to 50°C and the reaction was maintained for 3 hours, and then naturally cooled to room temperature. Toluene and silicon reagents were then recovered under reduced pressure, wherein the recovered toluene and silicon reagents could be applied to the next reaction; after the solvent and silicon reagent were recovered, a crude product was obtained, and the crude product was slurried with ethanol, filtered, and vacuum dried to obtain a compound shown in Formula II (10.56 g, with a yield of 67.4%), wherein the phosphine spectrum purity of the compound shown in Formula II was less than 90%.

Claims

1. A method for preparing the compound as shown in II, characterized in that: It includes the following steps: , (1) mixing the compound shown in formula I, triethylamine and toluene and stirring; then dropping a silicon reagent at 40-50°C, and continuing to stir and react for 0.5-4 hours after the dropping is complete; (2) then dropping a toluene solution of 2,4,6-trimethylbenzoyl chloride; stirring and reacting at 40-110°C for 0.5-24 hours; (3) recovering toluene and silicon reagent under reduced pressure to obtain a crude product, and then beating the crude product with ethanol, filtering, and vacuum drying to obtain a compound shown in formula II; wherein the silicon reagent is dimethyldichlorosilane and / or methyltrichlorosilane.

2. The method for preparing the compound as shown in II according to claim 1, characterized in that: The silicon reagent is methyltrichlorosilane.

3. The method for preparing the compound as shown in II according to claim 1, characterized in that, In step (1), the molar ratio of the compound represented by formula I to the silicon reagent is 1:(0.8-1.2).

4. The method for preparing the compound as shown in II according to claim 1, characterized in that: The molar ratio of the compound shown in formula I to 2,4,6-trimethylbenzoyl chloride is 1:(1-1.2).

5. The method for preparing the compound as shown in II according to claim 1, characterized in that: The preparation method of the compound shown in formula I comprises the following steps: , (1) 1,4-dimethylbenzene and Lewis acid are mixed uniformly at 50°C-74°C; (2) phosphorus trichloride is added dropwise at 50°C-74°C; after the addition is completed, the mixture is stirred at 74°C-78°C for 0.5-1 hour; (3) the reaction system is heated to 137°C-140°C, and the reaction is continued with stirring for 0.5-24 hours; (4) an organic solvent is added, the insoluble solid is separated and an organic phase is obtained; (5) water is added dropwise to the organic phase, and the mixture is stirred at 25-40°C for 0.5-8 hours; (6) the aqueous phase is separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, and the solvent in the organic phase is removed by vacuum distillation to obtain a crude product, which is then slurried with ethanol, filtered, and dried to obtain the compound shown in Formula I.

6. The method for preparing the compound as shown in II as claimed in claim 5, characterized in that: The Lewis acid is anhydrous aluminum chloride and trifluoromethanesulfonic acid.

7. The method for preparing the compound as shown in II according to claim 6, characterized in that: The molar ratio of anhydrous aluminum chloride to trifluoromethanesulfonic acid is 9:(0.1-2).

8. The method for preparing the compound as shown in II as claimed in claim 5, characterized in that: In step (4) of the method for preparing the compound of formula I, the organic solvent is an ether solvent, a hydrocarbon solvent or a halogenated hydrocarbon solvent.

9. The method for preparing the compound as shown in II as claimed in claim 5, characterized in that: In step (4) of the method for preparing the compound of formula I, the organic solvent is dichloromethane or petroleum ether.

10. A method for preparing a compound as shown in formula I, characterized in that: It includes the following steps: , (1) 1,4-dimethylbenzene and Lewis acid are mixed uniformly at 50°C-74°C; (2) phosphorus trichloride is added dropwise at 50°C-74°C; after the addition is completed, the mixture is stirred at 74°C-78°C for 0.5-1 hour; (3) the reaction system is heated to 137°C-140°C, and the reaction is continued with stirring for 0.5-24 hours; (4) an organic solvent is added to the reaction system, water is added dropwise, and the reaction is stirred at 25-40°C for 0.5-8 hours; (5) the aqueous phase is separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, and the solvent in the organic phases is removed by reduced pressure distillation to obtain a crude product, which is then pulped with ethanol, filtered, and dried to obtain a compound as shown in formula I; the Lewis acid is anhydrous aluminum chloride and trifluoromethanesulfonic acid, and the molar ratio of anhydrous aluminum chloride to trifluoromethanesulfonic acid is 9:(0.1-2).

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