CN104313635A - Electrochemical catalytic synthesis method of alpha-carbonyl ketone compounds - Google Patents

Abstract

An electrochemical catalytic synthesis method for α-carbonyl ketone compounds belongs to the technical field of preparation of α-carbonyl ketone compounds. The method is in a single-chamber electrolytic cell, in a certain electrolyte solution, using α-hydroxy ketones as raw materials, halides as catalysts, and constant current electrolysis at a certain temperature and current density to obtain α-carbonyl ketone compounds . Compared with other existing electrochemical methods for synthesizing such compounds, the method of the invention adopts a single-chamber electrolytic cell, uses cheap electrode materials, and regenerates the oxidant by electrochemical methods. The invention does not need to add supporting electrolyte, only uses catalytic amount of halide as the catalyst, greatly reduces the cost, is simple in post-treatment, and is more convenient for industrialized production.

Description

Electrochemical catalytic synthesis method of α-carbonyl ketones

technical field

The invention relates to an electrochemical catalytic synthesis method of α-carbonyl ketone compounds, belonging to the technical field of preparation of α-carbonyl ketone compounds.

Background technique

α-Carbonyl ketones are important solvents, reaction intermediates or chemical reagents. In addition, many α-carbonyl ketones are also widely used as fragrances. For example, 3,4-hexanedione has a buttery aroma, and diacetyl has a creamy aroma. They are widely used in the production of cream, cheese, chocolate, candy, jelly and pudding. Therefore, the efficient use of α-carbonyl ketones Synthesis is in the spotlight.

The electrochemical oxidation of α-hydroxy ketones is one of the ways to synthesize these compounds. Torii (Inokuchi, T.; Matsumoto, S.; Torii, S.J.Org.Chem.1991,56,2416) etc. in sodium bromide and N-oxo-2,2,6,6-tetramethylpiperidinium In the presence of the double catalyst composed, benzil was prepared by constant current electrolysis in a single chamber electrolytic cell with sodium carbonate buffer solution and dichloromethane as solvent; Wang Jiangmei et al. (Wang Jiangmei, Zhang Yinxin, Ding Shiling, Liu Hui, Chen Fanli, Jiang Wenqiang , Liaoning Chemical Industry, 2011, 40, 451) In a single-chamber electrolytic cell, KI was used as a catalyst to electrolyze acetoin to prepare diacetyl, and hydrogen peroxide was slowly added dropwise to reduce KI during the reaction. Nishiguchi (Maekawa, H.; Sguino, Y.; Nishiguchi, I. Chem. Lett.1994, 1017) synthesized α-carbonyl ketone by oxidation of α-hydroxy ketone with sodium bromide as a catalyst in a double-chamber electrolytic cell . The main problems with the above methods are:

(1) Although Torii and Wang Jiangmei used a simple single-chamber electrolytic cell for electrolytic synthesis, the types of α-hydroxy ketones synthesized were limited, and it was necessary to use a complex dual-catalyst system or regenerate the catalyst by adding an oxidant, which increased the reaction cost and The complexity of post-processing.

(2) Nishiguchi found that the reaction cannot be carried out effectively in a single-chamber electrolytic cell, and a double-chamber electrolytic cell must be used, while using expensive metal platinum as an electrode material. Compared with the single-chamber electrolytic cell, the use of the double-chamber electrolytic cell increases the cost of the equipment, increases the energy consumption, and the operation is more complicated.

(3) The reaction solution cannot be recycled, resulting in a large discharge of high-concentration organic waste liquid.

At present, in a single-chamber electrolytic cell, a single catalyst is used, and the preparation method of α-carbonyl ketone, in which the catalyst can be regenerated in situ and the reaction solution can be recycled, has not been reported in the literature at home and abroad.

Contents of the invention

The object of the present invention is to provide an electrochemical catalytic synthesis method of α-carbonyl ketone compounds with simple operation, low cost and environmental protection.

The electrochemical catalytic synthesis method of α-carbonyl ketone compounds provided by the present invention comprises the following steps: in a single-chamber electrolytic cell, in a certain electrolyte system, the α-hydroxy ketone represented by formula (II) is used as a raw material , using halides as catalysts, and constant current electrolysis under certain current density conditions, to obtain α-carbonyl ketone compounds represented by formula (I).

Among them, R ¹ and R ² in formula (I) and formula (II) represent straight-chain alkyl groups with a chain length of 1-8 carbon atoms, straight-chain alkyl groups substituted by aromatic hydrocarbons, phenyl groups, substituted benzenes, aromatic heterocycles, etc., and R ^1. R ² are the same or different.

Above-mentioned catalyst is tetrabutylammonium iodide, tetraethylammonium iodide, sodium iodide, potassium iodide, tetrabutylammonium bromide, tetraethylammonium bromide, sodium bromide or potassium bromide, preferably sodium bromide or potassium bromide.

The amount of the catalyst used is 5-50 mol%, preferably 5-10 mol%, of the α-hydroxy ketone raw material.

The above electrolyte system is water or a two-phase mixed solution of water and dichloromethane, preferably a two-phase mixed solution of water and dichloromethane, and more preferably the volume ratio of water to dichloromethane is (1-2):1.

The pH value of the above electrolyte system is between 1-8, preferably 3-7.

The aforementioned current density is 10-60 mA/cm ² , preferably 10-20 mA/cm ² .

The above-mentioned anode for electrolysis is a glassy carbon electrode, a graphite electrode or a platinum electrode, preferably a graphite electrode. The cathode is preferably iron.

The above-mentioned reaction temperature is generally 0-room temperature, preferably room temperature.

Compared with other existing methods, the inventive method has the following beneficial effects:

(1) The single-chamber electrolytic cell replaces the double-chamber electrolytic cell, which avoids the increase of equipment cost caused by the use of the diaphragm. At the same time, the energy consumption is reduced and the operation is simple.

(2) Using the anode to regenerate the catalyst avoids the addition of double catalysts or additional oxidants for regeneration, thereby reducing the reaction cost and the complexity of post-treatment, and also reducing the use of co-oxidants to generate a large amount of reduction waste.

(3) The reaction solution can be recycled to reduce environmental pollution.

(4) The method of the present invention uses cheap electrode materials, has mild reaction conditions, is simple to operate, and is easy to industrialize.

(5) High yield.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples. In the following examples, every 100 mmol of 2-hydroxy-3-pentanone corresponds to 300 mL of electrolyte solution.

Embodiment 1: the electrocatalytic synthesis of 2,3-pentanedione

In a 400 mL single-chamber electrolytic cell, 100 mmol of 2-hydroxy-3-pentanone was dissolved in 200 mL of NaBr (10 mmol) aqueous solution, and 100 mL of dichloromethane was added. Stirring at room temperature, with graphite as anode and iron sheet as cathode, electrolyze at a constant current of 30mA/ ^cm2 . When the current efficiency reaches 59%, the electrolysis is stopped, the stratification is static, and the dichloromethane in the lower organic phase is removed under normal pressure to obtain 2,3-pentanedione with a yield of 78%.

Yellow-green liquid; bp 110-112°C; ¹ H NMR (400MHz, CDCl ₃ ): δ1.09(t, 3H, J=7.6Hz), 2.17(s, 3H), 2.44(q, 2H, J=7.6 Hz).

Example 2: Electrocatalytic synthesis of 2,3-pentanedione

As in Example 1, 2,3-pentanedione was synthesized by electrocatalysis using 3-hydroxy-2-pentanone as a raw material, with a yield of 76%.

Yellow-green liquid; bp 110-112°C; ¹ H NMR (400MHz, CDCl ₃ ): δ1.09(t, 3H, J=7.6Hz), 2.17(s, 3H), 2.44(q, 2H, J=7.6 Hz).

Example 3: Electrocatalytic synthesis of 3,4-hexanedione

As in Example 1, 3,4-hexanedione was electrocatalytically synthesized using propioin as a raw material, with a yield of 85%.

Yellow-green liquid; bp 131°C; ¹ H NMR (400MHz, CDCl ₃ ): δ1.10(t, 3H, J=7.6Hz), 2.47(q, 2H, J=7.6Hz).

Example 4: Electrocatalytic synthesis of dodecane-6,7-dione

As in Example 1, dodecane-6,7-dione was electrocatalytically synthesized with axoin as a raw material, and the yield was 89%.

Yellow-green liquid; bp 110-113°C; ¹ H NMR (400MHz): δ0.88(m, 6H), 1.22-1.32(m, 8H), 1.57(m, 4H), 2.72(t, J＝7.6Hz ,4H).

Embodiment 5: the electrocatalytic synthesis of benzil

Same as Example 1, using benzoin as raw material, electrocatalytically synthesized benzil, yield: 71%.

Yellow-green solid; mp 94-95°C; ¹ H NMR (400MHz, CDCl ₃ ): δ7.98(d, J=7.2Hz, 4H), 7.67-7.64(m, 2H), 7.53-7.50(m, 4H ).

Embodiment 6: the electrocatalytic synthesis of 4-methoxybenzil

Same as Example 1, using 4-methoxybenzoin as raw material, electrocatalytically synthesized 4-methoxybenzil, yield: 77%.

Yellow-green powder; mp 132-134°C; ¹ H NMR (400MHz, CDCl ₃ ): δ7.16(t, 1H, J=7.2Hz, Ar-H), 7.30(d, 2H, J=8.8Hz, Ar -H),3.77(s,6H).

Example 7: Electrocatalytic synthesis of 4-chlorobenzil

Same as Example 1, using 4-chlorobenzoin as raw material, electrocatalytically synthesized 4-chlorobenzil, yield: 80%. .

Yellow-green powder; mp 224-226°C; ¹ H NMR (400MHz, CDCl ₃ ): δ7.00(d, 4H, J=8.8Hz), 7.48(d, 4H, J=8.8Hz).

Embodiment 8: the electrocatalytic synthesis of diacetyl

Same as Example 1, using acetoin as the raw material, the volume ratio is 1:1, and the yield: 62%.

Yellow-green liquid; bp: 88-90°C; ¹ H NMR (400MHz, CDCl ₃ ): δ2.17(s, 3H).

Embodiment 9: the electrocatalytic synthesis of diacetyl

Same as Example 8, the catalyst is potassium bromide, and the GC yield of diacetyl is 53%.

Embodiment 10: the electrocatalytic synthesis of diacetyl

Same as Example 8, the catalyst is sodium iodide, and the GC yield of diacetyl is 45%.

Example 11: Electrocatalytic synthesis of diacetyl

Same as Example 8, the catalyst is potassium iodide, and the GC yield of diacetyl is 48%.

Example 12: Electrocatalytic synthesis of diacetyl

Same as Example 8, the catalyst is tetrabutylammonium bromide, and the GC yield of diacetyl is 56%.

Example 13: Electrocatalytic synthesis of diacetyl

Same as Example 8, the catalyst is tetraethylammonium bromide, and the GC yield of diacetyl is 57%.

Example 14: Electrocatalytic synthesis of diacetyl

As in Example 8, the current density was 10 mA/cm ² , and the GC yield of diacetyl was 45%.

Example 15: Electrocatalytic synthesis of diacetyl

As in Example 8, the current density was 20 mA/cm ² , and the GC yield of diacetyl was 61%.

Example 16: Electrocatalytic synthesis of diacetyl

As in Example 8, the current density was 40 mA/cm ² , and the GC yield of diacetyl was 58%.

Example 17: Electrocatalytic synthesis of diacetyl

As in Example 8, the current density was 50 mA/cm ² , and the GC yield of diacetyl was 55%.

Example 18: Electrocatalytic synthesis of diacetyl

Same as Example 8, the current density was 60 mA/cm ² , and the GC yield of diacetyl was 32%.

Embodiment 19: Electrocatalytic synthesis of diacetyl

Same as Example 8, NaBr (5mmol), the GC yield of diacetyl was 61%.

Example 20: Electrocatalytic synthesis of diacetyl

Same as Example 8, NaBr (20mmol), the GC yield of diacetyl was 55%.

Example 21: Electrocatalytic synthesis of diacetyl

Same as Example 8, NaBr (50mmol), the GC yield of diacetyl was 39%.

Example 22: Electrocatalytic synthesis of diacetyl

Same as Example 8, glassy carbon is used as the anode, and the GC yield of diacetyl is 55%.

Example 23: Electrocatalytic synthesis of diacetyl

Same as Example 8, platinum was used as the anode, and the GC yield of diacetyl was 58%.

Claims (10)

1. The electrochemical catalytic synthesis method of α-carbonyl ketone compounds is characterized in that, the step is, in a single chamber electrolytic cell, in a certain electrolyte system, the α-hydroxy ketone represented by formula (II) is used as raw material , using halides as catalysts, constant current electrolysis under certain current density conditions, to obtain α-carbonyl ketone compounds represented by formula (I); In formula (I) and formula (II), R ¹ and R ² represent straight-chain alkyl groups with a chain length of 1-8 carbon atoms, straight-chain alkyl groups substituted by aromatic hydrocarbons, phenyl groups, substituted benzenes, aromatic heterocycles, and R ¹ , R ² are the same or different; The catalyst is tetrabutylammonium iodide, tetraethylammonium iodide, sodium iodide, potassium iodide, tetrabutylammonium bromide, tetraethylammonium bromide, sodium bromide or potassium bromide; the electrolyte system is water or water Two-phase mixed solution with dichloromethane. the 2. according to the method for claim 1, it is characterized in that, catalyst is that the consumption of catalyst is 5-50mol% of α-hydroxy ketone raw material. the 3. The method according to claim 1, characterized in that the catalyst is used in an amount of 5-10 mol% of the alpha-hydroxy ketone starting material. the 4. according to the method for claim 1, it is characterized in that, the volume ratio of water and methylene chloride is (1-2):1. the 5. The method according to claim 1, characterized in that the pH of the electrolyte system is between 1-8. the 6. The method according to claim 5, characterized in that the pH of the electrolyte system is between 3-7. the 7. The method according to claim 1, characterized in that the current density is 10-60 mA/cm ² . 8. The method according to claim 7, characterized in that the current density is 10-20 mA/cm ² . 9. according to the method for claim 1, it is characterized in that, the anode that electrolysis is used is glassy carbon electrode, graphite electrode or platinum electrode. the 10. The method according to claim 1, characterized in that the reaction temperature is generally 0-room temperature. the