CN103420927A - Synthetic method of quinoxaline-2-carboxylic acid - Google Patents

Abstract

The invention belongs to the technical field of preparation of veterinary drugs, and in particular relates to a method for synthesizing a carbadox residue marker quinoxaline-2-carboxylic acid used for detection of veterinary drug residues. The preparation steps include: 1) using o-phenylenediamine as raw material, condensing with aceguvaldehyde to obtain the intermediate product 2-methylquinoxaline; 2) subjecting the obtained intermediate 2-methylquinoxaline to selenium dioxide Oxidation reaction to generate quinoxaline-2-carbaldehyde; 3) further oxidation of the obtained quinoxaline-2-carbaldehyde with acidic potassium permanganate to obtain the target product quinoxaline-2-carboxylic acid. The synthesis method of the invention has the advantages of reasonable reaction route design, simple operation, high yield and the like.

Description

A kind of synthetic method of quinoxaline-2-carboxylic acid

technical field

The invention belongs to the technical field of veterinary drug preparation, and in particular relates to a chemical synthesis method of quinoxaline-2-carboxylic acid (QCA).

Background technique

et al，1993：Yoshimura etal，1981；Scheutwinkel-Reich et al，1984)。鉴于此，欧盟于1999年禁止卡巴氧及喹乙醇用于动物抗菌促生长，即使在美国也对卡巴氧和喹乙醇的使用做出了严格规定。我国农业部明确规定禁用兽药目录中即包括喹噁啉类药物卡巴氧。喹噁啉-2-羧酸为卡巴氧的代谢物之一，目前被规定为卡巴氧残留标识物(见JECFA第36届会议(1991))。Carbadox belongs to the class of quinoxaline-1,4-dioxide drugs and is a broad-spectrum antibacterial drug synthesized by Pfizer in the 1970s. In the European Union, North America and many other countries, it has been widely used as an antibacterial growth promoter in livestock, poultry and aquaculture. Toxicological studies on carbadox in recent years have shown that carbadox and its deoxygenated and deoxygenated metabolites have strong toxic effects, mainly manifested as carcinogenicity, mutagenicity, reproductive toxicity, and liver toxicity (

et al, 1993: Yoshimura et al, 1981; Scheutwinkel-Reich et al, 1984). In view of this, the European Union banned carbadox and olaquindox from being used for antibacterial growth promotion in animals in 1999, and even in the United States, strict regulations have been made on the use of carbadox and olaquindox. The Ministry of Agriculture of my country clearly stipulates that the list of prohibited veterinary drugs includes the quinoxaline drug carbadox. Quinoxaline-2-carboxylic acid is one of the metabolites of carbadox, and is currently specified as a carbadoxy residue marker (see the 36th session of JECFA (1991)).

In order to ensure food safety and ensure the normal trade of animal foods in China, the Ministry of Agriculture and the National Entry-Exit Inspection and Quarantine Bureau have successively formulated regulations on 3-methylquinoxaline-2-carboxylic acid and quinoxaline-2- Carboxylic acid residue detection standard (GB/T20746-2006, Determination of carbadox, olaquindox and metabolite residues in liver and muscle of cattle and pigs by liquid chromatography-tandem mass spectrometry; Ministry of Agriculture 2006 No. 781-3, Animal Determination of 3-methylquinoxaline-2-carboxylic acid and quinoxaline-2-carboxylic acid residues in source foods by high-performance liquid chromatography; Announcement No. 236 of the Ministry of Agriculture [2003] Labeling residues of carbadox in animal source foods method of detection). The formulation of these standards provides technical support for the detection of quinoxaline-2-carboxylic acid in animal foods, but there has been no standard substance of quinoxaline-2-carboxylic acid (QCA) in the National Center for Reference Materials and the Veterinary Drug Inspection Institute. Most of the high-purity compounds provided by Sigma are used as reference substances for residue detection, so it is imperative to synthesize quinoxaline-2-carboxylic acid (QCA) and further make qualified standard substances.

The bibliographical information about quinoxaline-2-carboxylic acid synthesis is as follows at present:

1) U.S. Pfizer Wong, John W. etc. adopt Pseudomonas putida (ATCC33015) to biotransform 2-methylquinoxaline to synthesize quinoxaline-2-carboxylic acid (Wong, John W.et al.Biocatalytic oxidation of2-methylquinoxaline to 2-quinoxalinecarboxylic acid, Organic Process Research & Development, 6(4), 477-481; 2002).

The method adopts a biological fermentation method to synthesize QCA, avoids the use of toxic and harmful chemical reagents, and has a high yield. However, the strain Pseudomonas putida (ATCC33015) used is difficult to source and expensive, and the cultivation conditions are harsh, so it is difficult to achieve scale-up production under ordinary conditions.

2) Harms, Arthur E. etc. used 2-methylquinoxaline as a raw material, oxidized with potassium permanganate after condensation with benzaldehyde to obtain the target product QCA (Harms, Arthur E.An Efficient Synthesis of 2-Quinoxalinecarboxylic Acid. Organic Process Research & Development, 8(4), 666-669; 2004). This method obtains carboxylic acid by adopting potassium permanganate to oxidize the carbon-carbon double bond of intermediate, may well be a feasible way, but needs to use benzaldehyde condensation to obtain intermediate 2-styrene quinoxaline, obviously increases The reaction steps were eliminated, resulting in a lower final overall yield.

3) Kepez, Mustafa etc. reported that 2,3-dimethylquinoxaline was used as a raw material, and the target product QCA was obtained by one-step reaction of selenium dioxide oxidation (Kepez, Mustafa.Oxidation of 2,3-dimethylquinoxaline and2,4-dimethylquinazoline with selenium dioxide. Monatshefte fuer Chemie, 120(2), 127-30; 1989). In this method, xylene is used as a solvent, and selenium dioxide is used to oxidize two methyl groups on the quinoxaline ring into carboxyl groups at high temperature, and simultaneously decarboxylate to generate the target product QCA. The method is relatively simple, but the reaction conditions are high and the yield is too low. .

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a chemical synthesis method for the standard substance quinoxaline-2-carboxylic acid used for detecting carbadoxy residues. The method has easy-to-obtain raw materials and is easy to operate.

Realize overall technical route of the present invention is:

The present invention condenses o-phenylenediamine and aceguvaldehyde to obtain the intermediate product 2-methylquinoxaline, and then oxidizes the generated intermediate 2-methylquinoxaline with selenium dioxide to generate quinoxaline Line-2-formaldehyde; Afterwards, the obtained quinoxaline-2-formaldehyde is further oxidized with acidic potassium permanganate to obtain the target product quinoxaline-2-carboxylic acid.

Specifically, the synthetic method of the present invention comprises the following steps:

1) Add o-phenylenediamine in the three-necked flask, dissolve it with methanol, and heat to reflux; then take 40% aceguvaldehyde according to the amount of the same substance, dilute it with methanol solution, and slowly drop it into the three-necked flask, Reflux for 16-20 hours, filter; the filtrate is dried and evaporated to dryness under reduced pressure to obtain the intermediate 2-methylquinoxaline as a light yellow oily substance; as a preferred solution, aceglyoxal should be slightly excessive;

2) Dissolve 2-methylquinoxaline and selenium dioxide in ethyl acetate or other suitable solvents with a ratio of 1:1.2, reflux for 4-6 hours, filter, evaporate the filtrate to dryness under reduced pressure, and then add Proper amount of ethyl acetate to dissolve, stand still, and crystallize to obtain the khaki-yellow intermediate quinoxaline-2-carbaldehyde;

3) Dissolve quinoxaline-2-carbaldehyde and potassium permanganate in pyridine with a ratio of 1:1 to 5:1, then add dilute sulfuric acid, react at room temperature for 16 to 20 hours, and filter; add a small amount of distilled water to the filtrate , evaporate most of the pyridine; then use sodium hydroxide to adjust the pH=8~9, extract with ethyl acetate three times, discard the organic phase; bathe the water phase in ice, adjust the pH=2~3 with hydrochloric acid, a large amount of precipitation will appear, filter to obtain Solid quinoxaline-2-carboxylic acid.

The above synthetic route has the following advantages:

1. Raw materials are easy to get: the raw materials and reagents o-phenylenediamine, hydrochloric acid, potassium permanganate, sodium hydroxide, methanol, ethyl acetate, anhydrous magnesium sulfate, etc. used in the present invention are all commonly used raw materials and reagents, which are easy to obtain .

2. The reaction equipment and operating conditions are easy to realize and the yield is stable, which is suitable for further scale-up production.

Description of drawings

Fig. 1: is the biosynthetic route of quinoxaline-2-formic acid (QCA) reported by Pfizer of the prior art. In the figure: the upper English is the name of the strain Pseudomonas putida, the strain number in brackets is ATCC33015, and the reference signs are: R: PhCH ₂ OH, S: Glycerol 1.R: NH ₄ Cl, R: (NH ₄ ) ₂ SO ₄ .

Fig. 2: be prior art Harms, the synthetic route of the quinoxaline-2-formic acid (QCA) of Arthur E. report.

Fig. 3: is the synthetic route of quinoxaline-2-carboxylic acid (QCA) reported by prior art Kepez, Mustafa etc.

Fig. 4: is the synthetic route of quinoxaline-2-carboxylic acid (QCA) of the present invention.

Fig. 5: is the ultraviolet scanning spectrum (using methanol as solvent) of the obtained quinoxaline-2-carboxylic acid prepared in the present invention.

Fig. 6: Infrared spectrum (KBr tablet) of quinoxaline-2-carboxylic acid prepared by the present invention.

Fig. 7: ¹ HNMR spectrum (CDCl ₃ ) of quinoxaline-2-carboxylic acid prepared in the present invention.

Figure 8: Mass spectrum (ESI, negative ion mode) of quinoxaline-2-carboxylic acid prepared in the present invention.

Detailed ways

Example 1

Add 10.8g of o-phenylenediamine to the three-necked flask, dissolve it with 200mL of methanol, and heat to reflux; then take 18g of 40% methylglyoxal, dilute it with 50mL of methanol, and slowly drop it into the three-necked flask; reflux reaction 16 After ~20h, filter; dry over anhydrous magnesium sulfate, filter, evaporate methanol to obtain 12 g of light yellow oily substance 2-methylquinoxaline (yield 83%).

Add 10g of 2-methylquinoxaline into a three-neck flask, use ethyl acetate as solvent, heat to reflux, then add selenium dioxide in total 11g; reflux reaction for 4-6h, filter, evaporate a large amount of ethyl acetate from the filtrate, place Recrystallization was carried out at 4°C to obtain 8.3 g of an earthy yellow intermediate quinoxaline-2-carbaldehyde (yield 76%).

Add 2.2 g of the obtained product quinoxaline-2-carbaldehyde into a single-necked flask, and dissolve it with 20 mL of pyridine; then add 0.42 g of potassium permanganate and 6 mL of sulfuric acid of 3 mol L ^-1 , react at room temperature for 16 to 20 h, and filter; Add a small amount of distilled water to the filtrate to evaporate most of the pyridine; then adjust the pH to 8-9 ^with 2 mol L ^-1 sodium hydroxide, extract three times with ethyl acetate, discard the organic phase; hydrochloric acid to adjust the pH to 2-3, a large amount of precipitation occurred, and filtered to obtain 1.6 g of solid quinoxaline-2-carboxylic acid (67% yield).

Example 2

Add 21.6g of o-phenylenediamine to the three-necked flask, dissolve it with 250mL of methanol, and heat to reflux; then take 36g of 40% methylglyoxal, dilute it with 100mL of methanol, and slowly drop it into the three-necked flask; reflux reaction 16 After ~20h, filter; dry over anhydrous magnesium sulfate, filter, distill methanol off to obtain 25.2 g of light yellow oily substance 2-methylquinoxaline (yield 88%).

Add 20 g of 2-methylquinoxaline to a three-necked flask, use 1,4-dioxane as a solvent, heat to 90°C, add selenium dioxide in portions to a total of 10 g; stir for 4 to 6 hours, filter, and evaporate the filtrate to A large amount of solvent was removed, and an appropriate amount of ethyl acetate was used as a solvent and placed at 4°C for crystallization to obtain 15.8 g of an earthy yellow intermediate quinoxaline-2-carbaldehyde (yield 72%).

Add 5 g of the product quinoxaline-2-carbaldehyde into a single-necked flask, and dissolve it with 20 mL of pyridine; then add 0.42 g of potassium permanganate and 6 mL of sulfuric acid of 3 mol L ^-1 , react at room temperature for 16 to 20 h, and filter; add the filtrate A small amount of distilled water, evaporate most of the pyridine; then use 2mol L ^-1 sodium hydroxide to adjust the pH to 8-9, extract with ethyl acetate three times, discard the organic phase; water phase in ice bath, use 4mol L ^-1 hydrochloric acid After adjusting the pH to 2-3, a large amount of precipitates appeared, and filtered to obtain 3.8 g of solid quinoxaline-2-carboxylic acid (69% yield).

Example 3

The product prepared by the present invention is as follows through ultraviolet, infrared, nuclear magnetic resonance, mass spectrometry detection results:

The UV scanning spectrum (MeOH) of quinoxaline-2-carboxylic acid is shown in Figure 1.

The infrared scanning spectrum (potassium bromide tablet) of quinoxaline-2-carboxylic acid is shown in Figure 2. In the figure: the corresponding relationship between each main absorption peak and each group is: 3452cm ^-1 , υ _OH carboxyl hydroxyl stretching vibration; 3071cm ^-1 , υ _CH benzene ring CH stretching vibration; 1707cm ^-1 , υ _C=O carbonyl stretching vibration ; 1498cm ^-1 , 1467cm ^-1 benzene ring C=C stretching vibration.

The ¹ HNMR spectrum of quinoxaline-2-carboxylic acid (Mercury400 nuclear magnetic resonance instrument, deuterated chloroform as solvent) is shown in Figure 3. In the figure: 7.260ppm is the chemical shift of ¹ H of the solvent deuterated chloroform; 3.180ppm is the hydrogen shift of _-CH3 ; 7.826-8.155ppm is the hydrogen shift of the quinoxaline group; Chemical shifts of -COOH associative hydrogen bonds.

The mass spectrum of quinoxaline-2-carboxylic acid (LC/MS-IT-TOF mass spectrometer) is shown in Figure 4 (source temperature 200°C, electron energy 1.7KV, scanning mass range 125-225Da, negative ion mode). In the figure: m/z173.0388 is the molecular ion peak of quinoxaline-2-carboxylic acid; m/z129.0483 is the fragment ion peak of the molecular ion detaching _CO2 molecules.

Claims (1)

1. the synthetic method of an Oxoquinoxaline-2-carboxylic acid, it is characterized in that following steps: adopt O-Phenylene Diamine and pyruvic aldehyde to carry out obtaining intermediate product 2-Jia based quinoxaline after condensation reaction, intermediate 2-Jia based quinoxaline and the tin anhydride of generation are carried out to oxidizing reaction, De quinoxaline-2-formaldehyde, finally quinoxaline-2-formaldehyde is carried out to oxidation with potassium permanganate under acidic conditions, obtain the target product Oxoquinoxaline-2-carboxylic acid;

Synthesis step is as follows:

(1) get O-Phenylene Diamine, make it to dissolve with methyl alcohol or ethanol, then 40% the pyruvic aldehyde of measuring than 1: 1 by amount of substance, slowly splash in reaction solution, after back flow reaction 16～20h, stopped reaction, the reaction solution evaporated under reduced pressure obtains the intermediate 2-Jia based quinoxaline of faint yellow oily mater;

(2) upper step reaction product is dissolved in to solvent acetonitrile, ethyl acetate, methylene dichloride or dioxane, taking tin anhydride by 1.2 times of amount of substances adds in reaction solution, after back flow reaction 4～6h, stopped reaction, after boiling off most of solvent by reaction solution, in 4 ℃ standing, separate out khaki color crystallization Ji quinoxaline-2-formaldehyde;

(3) being dissolved in pyridine of to be 3: 1 by the amount of substance ratio measure quinoxaline-2-formaldehyde and oxidant potassium permanganate, with dilute sulphuric acid or dilute hydrochloric acid, adjust solution to acid, after at room temperature reacting 16～20h, filter, filtrate is adjusted pH to 8～9 with sodium hydroxide solution after boiling off most of pyridine, is extracted with ethyl acetate three times, discard organic phase, water intaking is adjusted to pH2～3 with dilute hydrochloric acid, separates out precipitation, filters and obtain the product Oxoquinoxaline-2-carboxylic acid.

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