CN113277936A - Method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-stage alkyl substituted aromatic compounds under catalysis of iron - Google Patents

Method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-stage alkyl substituted aromatic compounds under catalysis of iron Download PDF

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CN113277936A
CN113277936A CN202110562796.XA CN202110562796A CN113277936A CN 113277936 A CN113277936 A CN 113277936A CN 202110562796 A CN202110562796 A CN 202110562796A CN 113277936 A CN113277936 A CN 113277936A
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iron
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ferrous
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曾荣
张国祥
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Xian Jiaotong University
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
    • C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
    • C07C201/06—Preparation of nitro compounds
    • C07C201/12—Preparation of nitro compounds by reactions not involving the formation of nitro groups
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/30—Preparation of carboxylic acid nitriles by reactions not involving the formation of cyano groups
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
    • C07C303/02—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of sulfonic acids or halides thereof
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    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
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    • C07D333/04—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom not condensed with other rings not substituted on the ring sulphur atom
    • C07D333/26—Heterocyclic compounds containing five-membered rings having one sulfur atom as the only ring hetero atom not condensed with other rings not substituted on the ring sulphur atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D333/38—Carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C07D333/40—Thiophene-2-carboxylic acid

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Abstract

The method for preparing the aromatic acid by the oxidation reaction of the 1, 2 and 3-level alkyl substituted aromatic compounds under the catalysis of iron comprises the following steps: under the action of an iron compound, providing proper temperature and/or light energy, and in the presence of an oxidant and/or an additive, carrying out C-C bond cleavage on a benzyl position of an aromatic compound in a solvent to realize selective oxidation so as to obtain a corresponding oxidized compound ketone or acid; the method selectively breaks and oxidizes the C-C bond directly at the benzyl position of the aromatic compound, and has the advantages of simple reaction, simple operation, mild oxidation condition, high atom economy, high reaction yield, easy separation and purification of the product, suitability for synthesizing benzoic acid derivative compounds and the like; the air can be directly used as an oxidant, so that the use of a large amount of heavy metal salt is avoided, the method is very attractive in industrial production, and meanwhile, the reaction by using cheap metal also has very large application potential in the fields of metal catalysis, chemical synthesis and the like.

Description

Method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-stage alkyl substituted aromatic compounds under catalysis of iron
Technical Field
The invention relates to the technical field of chemical synthesis, in particular to a method for preparing aromatic acid by oxidation reaction of alkyl substituted aromatic compounds of 1, 2 and 3 levels under iron catalysis, which is an oxidation reaction of breaking of benzylic C-H, C-C and C-X bonds of alkyl aromatic compounds of 1, 2 and 3 levels, namely, a series of benzoic acid derivatives with different substituent groups are generated by oxidation reaction of toluene or substituted toluene under the promotion of iron catalyst and additive and the irradiation of visible light through oxidant.
Background
The preparation of aromatic acid from alkyl substituted aromatic compounds by deep oxidation of alkyl is an important organic transformation in chemical synthesis. Wherein, the oxidation of 2 and 3-level alkyl substituent aromatic compounds relates to the breaking of C-C bonds.
The cleavage of C-C bonds typically requires noble metal catalysis, for example: ruthenium, rhodium, palladium, etc., or rigid rings such as three-membered, four-membered, multiple and cyclic compounds may be used as reactants. Or carboxylic acid compounds are used for decarboxylation, and beta bonds of alcohol compounds are broken to realize C-C-bond breakage. These methods all require the presence of specific functional groups, which directly exploit the hydrocarbon compounds for the cleavage of the C-C bond, due to C (sp)3) The bond energy of the-C bond is higher and more stableAnd the reactivity is poor, and the C-C bond is difficult to break. The traditional method generally needs to use some heavy metal oxidants, such as potassium permanganate, potassium dichromate and the like, and also needs some strong acids or harsh conditions such as high temperature and the like, and the oxidation process is difficult to control in the reaction process, and is easy to generate over oxidation, and the strong oxidants are not suitable for tert-butyl benzene aromatic compounds without benzyl C-H bonds, so that the selective deep oxidation for preparing aromatic carboxylic acid by selectively breaking the benzyl C-C bonds of the aromatic compounds still faces huge challenges and is very significant.
Organic acid is an important chemical raw material and is widely applied to industries such as food, solvent, pharmaceutical synthesis intermediates and the like. The traditional method for synthesizing organic acid is oxidation through alcohol or aldehyde, but usually needs to use some strong oxidants such as potassium permanganate, sodium hypochlorite and the like in a certain dosage, and generates a large amount of inorganic salt and other oxides after oxidation, so that selective oxidation cannot be well realized, and pollution is serious.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-grade alkyl substituted aromatic compounds under iron catalysis, which can selectively perform C-C bond breaking and oxidation directly at the benzyl position of the aromatic compounds and has the advantages of simple reaction, mild oxidation conditions, high atom economy and the like; the method provides a convenient and rapid oxidation mode for the oxidation of various organic compounds, can avoid using a large amount of heavy metal salt by directly using air as an oxidant, is very attractive in industrial production, and has very large application potential in the fields of metal catalysis, chemical synthesis and the like by using cheap metal for reaction.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the method for preparing the aromatic acid by the oxidation reaction of the 1, 2 and 3-level alkyl substituted aromatic compounds under the catalysis of iron comprises the following steps:
the selective oxidation is realized by providing proper temperature and/or light energy under the action of an iron compound, and in the presence of an oxidant and/or an additive, in a solvent, carrying out C-C bond breakage on a benzyl position of an aromatic compound to obtain a corresponding oxidized compound ketone or acid, wherein the reaction equation is as follows:
Figure BDA0003079605940000021
the structural formula of the aromatic compound is shown as
Figure BDA0003079605940000031
The corresponding oxygenated compounds are
Figure BDA0003079605940000032
Wherein Ar comprises substituted or unsubstituted phenyl, naphthyl, pyridine, thiophene, furan, pyrrole; the substitution is fluorine, chlorine, bromine, iodine, hydroxyl, carboxyl, sulfydryl, amino, primary amino, secondary amino, imino, nitro, cyano or alkyl;
R1、R2、R3each independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, hydroxy, carbonyl, carboxy, methoxy, cyano, halogen, borate, ether, alkene, alkyne.
The iron compound is an iron-containing compound, including ferric or ferrous compounds.
The ferric iron is ferric chloride, ferric tribromide, ferric trifluoromethanesulfonate, ferric tetrafluoroborate, ferric hexafluorophosphate, ferric sulfate, ferric nitrate, ferric acetate, ferric trifluoroacetate, ferric citrate, ferric oxalate, ferric acrylate, tris (2,2,6, 6-tetramethyl-3, 5-heptanedionato) iron, ferric hydroxide, ferric acetylacetonate, ferric fluoride and other iron-containing compounds and hydrates thereof.
The ferrous iron is ferrous chloride, ferrous bromide, ferrous iodide, ferrous trifluoromethanesulfonate, ferrous tetrafluoroborate, ferrous hexafluorophosphate, ferrous sulfate, ferrous nitrate, ferrous acetate, ferrous trifluoroacetate, ferrous citrate, ferrous oxalate, ferrous acrylate, ferrous bis (2,2,6, 6-tetramethyl-3, 5-heptanedionate), ferrous hydroxide, ferrous acetylacetonate, ferrous fluoride and other iron-containing compounds and hydrates thereof.
The solvent is one or more of water, a hydrocarbon solvent, an aromatic hydrocarbon solvent, a halogenated hydrocarbon solvent, a nitrohydrocarbon solvent, an ether solvent, a nitrile solvent, an ester solvent, an alcohol solvent, an amine solvent, an amide solvent, a sulfone solvent and a sulfoxide solvent;
the hydrocarbon solvent is one or more of benzene, toluene and saturated alkane compounds, the halogenated hydrocarbon solvent is one or more of trifluoromethylbenzene, chlorobenzene, dichloromethane, 1, 2-dichloroethane, chloroform and carbon tetrachloride, and the nitrohydrocarbon solvent is one or more of nitrobenzene and nitromethane; the ether solvent is one or more of tetrahydrofuran, 1, 4-dioxane, methyl tert-butyl ether and diethyl ether; the nitrile solvent is one or more of acetonitrile, benzonitrile and tert-butyl acetonitrile; the ester solvent is one or more of ethyl acetate, n-butyl acetate and isobutyl acetate; the alcohol solvent is one or more of methanol, ethanol, tert-butyl alcohol, n-butyl alcohol and cyclohexanol, and the amine solvent is one or more of triethylamine, diethylamine and diisopropylethylamine; the amide solvent is one or more of dimethylformamide and dimethylacetamide; the sulfoxide solvent is dimethyl sulfoxide, and can be used in any proportion in various cases.
Preferably, the solvent is acetonitrile, tert-butyl acetonitrile, ethyl acetate or dichloromethane.
The oxidant is a substance with oxidation capacity, and comprises oxygen, air or oxygen-containing mixed gas, peroxide, a high-valence iodine organic compound, persulfate and bromate,
wherein the peroxides include, but are not limited to, hydrogen peroxide, t-butyl peroxide, di-t-butyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dilauroyl peroxide, cumene peroxide, dicumyl peroxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, 3-chloroperoxybenzoic acid, 1, 1-di-t-butyl peroxycyclohexane; the persulfate is potassium persulfate, sodium persulfate and ammonium persulfate; the bromate is sodium bromate, potassium bromate or calcium bromate.
Preferably, the oxidizing agent is oxygen, t-butanol peroxide or hydrogen peroxide.
The additive is an alkali metal salt of a halide, an alkali metal salt of an organic acid compound, an alkali metal salt of a phenolic compound, an ammonium salt of a halide, an ammonium salt of an organic acid compound, an ammonium salt of a phenolic compound,
wherein the halide is fluoride, chloride, bromide or iodide; the alkali metal salt is lithium salt, sodium salt, potassium salt or cesium salt; the organic acid compound is substituted or unsubstituted aryl carboxylic acid, substituted or unsubstituted alkyl carboxylic acid, substituted or unsubstituted aryl sulfonic acid, substituted or unsubstituted alkyl sulfonic acid, substituted or unsubstituted aryl phosphoric acid and substituted or unsubstituted alkyl phosphoric acid; the phenols are substituted or unsubstituted phenol compounds; the ammonium salt is tetramethylammonium salt, tetraethylammonium salt or tetrabutylammonium salt.
Preferably, the additive is sodium chloride, potassium chloride, tetrabutylammonium chloride or pentafluorophenol potassium salt.
The molar ratio of the iron compound to the aromatic compound is less than 1: 1.
preferably, the molar ratio of the iron compound to the aromatic compound is x1：x2＝(0.01-0.1)：1。
The suitable temperature is: the reaction system was placed at-78-300 ℃.
Preferably, the system of the reaction is placed at 25 ℃ to 100 ℃.
The providing light energy comprises: the reacted system is exposed to visible light and/or monochromatic or mixed light of a wavelength of less than 500 nm.
Preferably, the system of the reaction is irradiated under light with a wavelength of 350-450 nm.
The method for preparing the aromatic acid by oxidation reaction of the 1, 2 and 3-level alkyl substituted aromatic compounds under the catalysis of iron comprises the following reaction steps:
(1) sequentially adding iron compound [ Fe ] into the dried reaction tube](x1mol%), oxidizing agents and/or additives (x)2mol percent), aromatic compound and organic solvent, stirring and dissolving the mixture in oxygen atmosphere after the charging, uniformly mixing the mixture, and continuously stirring the mixture after the reaction tube is placed under the light (hv) with specific power and wavelength for irradiation, or heating the reaction tube;
the aromatic compound and the organic solvent are added in excess;
(2) and (2) after the reaction in the step (1) is completed, removing the reaction tube from the light source, transferring the reaction mixed solution to a flask, carrying out reduced pressure distillation to obtain a crude product, and carrying out flash column chromatography to obtain the benzoic acid compound.
The invention has the following beneficial effects:
(1) the reaction only needs cheap and easily available iron catalyst.
(2) The reaction can be realized by using visible light as a light source and a blue LED lamp with the power of 1-200W.
(3) Oxygen which is widely available, cheap and easily available is used as the oxidant.
(4) The benzoic acid derivative, the picolinic acid derivative and the thiophenecarboxylic acid derivative with different substituents can be quickly and simply synthesized.
(5) The product is easy to separate and purify.
The innovation point of the invention is that a method for preparing benzoic acid derivatives by using toluene derivatives through a one-step method is developed, and the yield of the obtained corresponding benzoic acid compounds is 30-87%.
The oxidation method of the benzyl position of the aromatic compound provided by the invention can efficiently and quickly obtain a corresponding oxidized compound under the catalysis of an iron compound and the action of an oxidant under the condition of providing heat energy and/or light energy and/or microwaves; the reaction method has mild oxidation conditions, can directly utilize air as an oxidant, is safe and green, is simple to operate, does not need inert gas protection, does not need a large amount of high-valence metal salt, has wide substrate applicability, and has great significance in the aspect of industrial production.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described in the following embodiments to fully understand the objects, aspects and effects of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The following examples are helpful in understanding the present invention, but are not intended to limit the scope of the present invention.
Example 1
Iron catalyst (x) was added to the dried reaction tube in sequence1mol%) additives (x)2mol%), toluene (2mmol) and anhydrous acetonitrile (4 ml), stirring and dissolving after the addition is finished, mixing uniformly, placing the reaction tube under the light (hv) with the wavelength of 390nm for irradiation and stirring continuously, removing the reaction tube from a light source after the reaction is finished, transferring the reaction mixed solution to a flask, carrying out reduced pressure distillation to obtain a crude product, and carrying out flash column chromatography to obtain 190.7 mg of benzoic acid, wherein the yield is 78%, and the product is a white solid.1H NMR(400MHz,CDCl3)δ12.25(brs,1H,-COOH),8.15(d,J＝7.4Hz,2H,Ar-H),7.63(t,J＝7.4Hz,1H,Ar-H),7.49(t,J＝7.5Hz,2H,Ar-H).13C NMR(101MHz,CDCl3)δ172.7,133.8,130.2,129.3,128.5.
Example 2
The procedure is as described in example 1, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), 4-cyanotoluene (46.9 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); the reaction tube was heated to 50 ℃ to obtain 50.4 mg of 4-cyanobenzoic acid in 86% yield.1H NMR(400MHz,DMSO-d6)δ13.58(s,1H,-COOH),8.07(d,J＝8.3Hz,2H,Ar-H),7.97(d,J＝8.3Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.1,134.8,132.7,130.0,118.2,115.1.IRν(neat,cm-1)3418,2987,1700,1653,1430,1323,1288,1131,768,749.
Example 3
The procedure is as described in example 1, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol％)，4-Fluorotoluene (44.1 mg, 44 μ l, 0.4 mmol), anhydrous acetonitrile (4 ml); irradiation with light (hv) at 350nm gave 34.4 mg of 4-fluorobenzoic acid in 61% yield.1H NMR(400MHz,DMSO-d6)δ13.07(brs,1H,-COOH),8.00(dd,J1＝8.7,J2＝5.7Hz,2H,Ar-H),7.31(t,J＝8.9Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.4,165.0(C-F,d,1JC-F＝252.5Hz),132.1(C-F,d,3JC-F＝9.5Hz),127.4(C-F,d,4JC-F＝2.8Hz),115.7(C-F,d,2JC-F＝30.3Hz).19F NMR(376MHz,DMSO-d6)δ-106.9.
Example 4
The procedure described in example 1, iron catalyst (x)1mol%) additives (x)2mol%), 4-trifluoromethyltoluene (64.1 mg, 56. mu.l, 0.4 mmol), anhydrous acetonitrile (4 ml), light (hv) at 400 nm; 50.4 mg of 4-trifluoromethylbenzoic acid was obtained in 66% yield.1H NMR(400MHz,DMSO-d6)δ13.49(s,1H,-COOH),8.13(d,J＝8.1Hz,2H,Ar-H),7.86(d,J＝8.2Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.2,134.6,132.5(C-F,q,2JC-F＝32.3Hz),130.1,125.6(C-F,q,3JC-F＝3.0Hz),123.8(C-F,q,1JC-F＝271.7Hz).19F NMR(376MHz,DMSO-d6)δ-61.6.IRν(neat,cm-1)3446,1684,1653,1576,1419,1321,1276,1132,758.
Example 5
The procedure described in example 1, iron catalyst (x)1mol%) additives (x)2mol%), 4-methylbenzenesulfonic acid (68.9 mg, 0.4 mmol), anhydrous acetonitrile (4 ml), irradiation with light (hv) at a wavelength of 450 nm; 69.7 mg of 4-sulfobenzoic acid was obtained in 86% yield.1H NMR(400MHz,DMSO-d6)δ13.19(s,1H,-COOH),7.94(d,J＝8.5Hz,2H,Ar-H),7.56(d,J＝8.5Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ167.0,138.3,131.7,130.1,129.3.
Example 6
According to implementationThe method of example 1, except that the amounts of reagents used were: iron catalyst (x)1mol%) additives (x)2mol%), p-nitrotoluene (54.9 mg, 0.4 mmol), anhydrous acetonitrile (4 ml), and the reaction tube was heated to 100 ℃; 37.9 mg of p-nitrobenzoic acid was obtained in 57% yield.1H NMR(400MHz,DMSO-d6)δ13.21(s,1H),7.94(d,J＝8.3Hz,2H,Ar-H),7.56(d,J＝8.3Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ167.0 138.3,131.7,130.2,129.3.
Example 7
The procedure is as described in example 1, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), 4-methyl diphenyl ether (73.7 mg, 67 μ l, 0.4 mmol), anhydrous acetonitrile (4 ml), the reaction tube was heated to 70 ℃; 51.2 mg of 4-phenoxybenzoic acid was obtained in 60% yield.1H NMR(400MHz,DMSO-d6)δ12.82(brs,1H,-COOH),7.92–7.96(m,2H,Ar-H),7.45(t,J＝7.9Hz,2H,Ar-H),7.23(t,J＝7.4Hz,1H,Ar-H),7.12(d,J＝8.2Hz,2H,Ar-H),7.01–7.04(m,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.8,161.0,155.1,131.7,130.3,125.2,124.7,120.0,117.2.
Example 8
The procedure described in example 1, iron catalyst (x)1mol%) additives (x)2mol%), 2-methyl-6- (trifluoromethyl) pyridine (64.5 mg, 53 μ l, 0.4 mmol), anhydrous acetonitrile (4 ml), the reaction tube was heated to 80 ℃; 58.2 mg of 6- (trifluoromethyl) pyridine-2-carboxylic acid were obtained in 76% yield.1H NMR(400MHz,DMSO-d6)δ13.72(s,1H,-COOH),8.32–8.25(m,2H,Ar-H),8.12(d,J＝7.0Hz,J＝1.8Hz,1H,Ar-H),13C NMR(101MHz,DMSO-d6)δ165.1,149.1,146.5(C-F,q,2JC-F＝35.4Hz),140.2,128.0,123.8,121.3(C-F,q,1JC-F＝275.7Hz).19F NMR(376MHz,DMSO-d6)δ-66.4.
Example 9
The procedure is as described in example 1, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), pentafluorotoluene (73.2 mg, 51 μ l, 0.4 mmol), anhydrous acetonitrile (4 ml); 56.3 mg of pentafluorobenzoic acid was obtained in 66% yield.1H NMR(400MHz,DMSO-d6)δ14.11(bs,1H,-COOH).13C NMR(101MHz,DMSO-d6)δ159.9145.6–145.8(m),143.8–142.4(m),139.1–138.0(m),135.9–136.3(m),109.7–108.8(m).19F NMR(376MHz,DMSO-d6)δ-140.6(d,J＝19.6Hz,2F,Ar-F),-151.0(t,J＝19.6Hz,1F,Ar-F),-160.8–-162.1(m,2F,Ar-F).
Example 10
The procedure is as described in example 2, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), deuterated toluene (200.4 mg, 2.0 mmol), anhydrous acetonitrile (4 ml) gave deuterated benzoic acid 233.1 mg, 92% yield.1H NMR(400MHz,DMSO-d6)δ12.97(bs,1H,-COOH).13C NMR(101MHz,DMSO-d6)δ167.8,132.8–132.3(t,J＝23.0Hz),131.0 129.5–129.0(t,J＝25.3Hz),128.5–128.0(t,J＝25.3Hz).
Example 11
The procedure described in example 3, iron catalyst (x)1mol%) additives (x)2mol%), 2-methylthiophene (196.3 mg, 2.0 mmol), anhydrous acetonitrile (4 ml) to give 77.5 mg of 2-thiophenecarboxylic acid in 30% yield.1H NMR(400MHz,DMSO-d6)δ12.97(bs,1H,-COOH),7.87–7.82(m,1H,Ar-H),7.72(d,J＝4.3Hz,1H,Ar-H),7.16(t,J＝4.4Hz,1H,Ar-H).13C NMR(101MHz,DMSO-d6)δ163.0,134.8,133.3,128.3.
Example 12
The procedure described in example 4, iron catalyst (x)1mol%) additives (x)2mol%), 2-fluoro-4-chlorotoluene (57.9 mg, 49 μ l, 0.4 mmol), anhydrous acetonitrile (4 ml); 61.5 mg of 2-fluoro-4-chlorobenzoic acid was obtained in 88% yield.1H NMR(400MHz,DMSO-d6)δ13.43(bs,1H,-COOH),7.87(t,J＝8.3Hz,1H,Ar-H),7.53(d,J＝10.5Hz,1H,Ar-H),7.38(dd,J＝8.2,J＝1.5Hz,1H,Ar-H).13C NMR(101MHz,DMSO-d6)δ164.2(d,3JC-F＝3.0Hz),161.2(d,1JC-F＝260.9Hz),138.3(d,3JC-F＝10.6Hz),133.3,124.9(d,4JC-F＝3.6Hz),118.3(d,3JC-F＝10.1Hz),117.6(d,2JC-F＝26.2Hz).19F NMR(376MHz,DMSO-d6)δ-107.6.
Example 13
The procedure described in example 5, iron catalyst (x)1mol%) additives (x)2mol%), p-bromotoluene (68.5 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); p-bromobenzoic acid 55.7 mg was obtained in 69% yield.1H NMR(400MHz,DMSO-d6)δ13.21(bs,1H,-COOH),7.86(d,J＝8.3Hz,2H,Ar-H),7.70(d,J＝8.3Hz,2H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.6,131.7,131.31,130.0,127.0.
Example 14
The procedure described in example 5, iron catalyst (x)1mol%) additives (x)2mol%), cumene (48.1 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 27.9 mg of benzoic acid was obtained in 69% yield.1H NMR(400MHz,CDCl3)δ11.90(brs,1H,-COOH),8.32–8.05(m,2H,Ar-H),7.63(t,J＝7.4Hz,1H,Ar-H),7.49(t,J＝7.7Hz,2H,Ar-H).
Example 15
The procedure described in example 6, iron catalyst (x)1mol%) additives (x)2mol%), cyclohexylbenzene (64.1 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 32.1 mg of benzoic acid are obtained in 66% yield.1H NMR(400MHz,CDCl3)δ8.18–8.08(m,2H,Ar-H),7.66–7.58(m,1H,Ar-H),7.53–7.43(m,2H,Ar-H).
Example 16
The procedure is as described in example 7, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), acetophenone (48.1 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 27.6 mg of benzoic acid was obtained in 57% yield.1H NMR(400MHz,CDCl3)δ12.97(brs,1H,-COOH),7.95(d,J＝7.6Hz,2H,Ar-H),7.62(t,J＝7.3Hz,1H,Ar-H),7.50(t,J＝7.6Hz,2H,Ar-H).
Example 17
The procedure is as described in example 8, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), p-xylene (42.5 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 61.0 mg of terephthalic acid was obtained in 92% yield.1H NMR(400MHz,DMSO-d6)δ8.03(s,4H,Ar-H).13C NMR(101MHz,DMSO-d6)δ166.7,134.5,129.5.
Example 18
The procedure is as described in example 9, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), o-xylene (42.5 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 36.6 mg of phthalic anhydride were obtained in 62% yield.1H NMR(400MHz,CDCl3)δ8.03(dd,J1＝4.7Hz,J2＝3.0Hz,2H,Ar-H),7.92(dd,J1＝4.7Hz,J2＝3.0Hz,2H,Ar-H).13C NMR(101MHz,CDCl3)δ162.8,136.0,131.2,125.7.
Example 19
The procedure is as described in example 10, except that the amounts of reagents used are: iron catalyst (x)1mol%) additives (x)2mol%), m-xylene (42.5 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); isophthalic acid 40.2 mg was obtained in 60% yield.1H NMR(400MHz,DMSO-d6)δ13.30(s,2H,-COOH),8.48(d,J＝1.2Hz,1H,Ar-H),8.16(d,J＝7.7Hz,2H,Ar-H),7.63(t,J＝7.7Hz,1H,Ar-H).13C NMR(101MHz,DMSO-d6)δ167.2,134.0,131.7,130.5,129.7.
Example 20
The procedure described in example 1, iron catalyst (x)1mol%) additives (x)2mol%), mesitylene (48.1 mg, 0.4 mmol), anhydrous acetonitrile (4 ml); 31.0 mg of trimesic acid was obtained in 37% yield.1H NMR(400MHz,DMSO-d6)δ8.63(s,3H,Ar-H).13C NMR(101MHz,DMSO-d6)δ172.3,166.0,133.8,132.1.
In conclusion, the method can use oxygen as an oxidant to selectively oxidize various organic compounds with different structures, has mild conditions, simple operation, greenness and high efficiency, and has wide application space.
The method adopts the reaction condition of providing heat energy and/or light energy and/or microwaves, can realize the selective breaking oxidation reaction of the benzylic C-C bond of the aromatic compound even under the condition of directly irradiating the blue LED lamp by one or more modes of simple heating, illumination or microwaves, does not need harsh reaction conditions such as high temperature, strong oxidant and the like or the addition of noble metal catalysts, has mild reaction conditions, is green and environment-friendly, is suitable for industrial production, and provides a new strategy for the diversity of chemical synthesis.

Claims (9)

1. The method for preparing the aromatic acid by the oxidation reaction of the 1, 2 and 3-level alkyl substituted aromatic compounds under the catalysis of iron is characterized by comprising the following steps:
the selective oxidation is realized by providing proper temperature and/or light energy under the action of an iron compound, and in the presence of an oxidant and/or an additive, in a solvent, carrying out C-C bond breakage on a benzyl position of an aromatic compound to obtain a corresponding oxidized compound ketone or acid, wherein the reaction equation is as follows:
Figure FDA0003079605930000011
the structural formula of the aromatic compound is shown as
Figure FDA0003079605930000012
The corresponding oxygenated compounds are
Figure FDA0003079605930000013
Wherein Ar comprises substituted or unsubstituted phenyl, naphthyl, pyridine, thiophene, furan, pyrrole; the substitution is fluorine, chlorine, bromine, iodine, hydroxyl, carboxyl, sulfydryl, amino, primary amino, secondary amino, imino, nitro, cyano or alkyl;
R1、R2、R3each independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, hydroxy, carbonyl, carboxy, methoxy, cyano, halogen, borate, ether, alkene, alkyne.
2. The method for preparing aromatic acid by oxidation reaction of alkyl substituted aromatic compounds of grade 1, 2 and 3 under the catalysis of iron according to claim 1, wherein the iron compound is iron-containing compound, and comprises ferric iron or ferrous iron compound;
the ferric iron is ferric chloride, ferric tribromide, ferric trifluoromethanesulfonate, ferric tetrafluoroborate, ferric hexafluorophosphate, ferric sulfate, ferric nitrate, ferric acetate, ferric trifluoroacetate, ferric citrate, ferric oxalate, ferric acrylate, tris (2,2,6, 6-tetramethyl-3, 5-heptanedionato) iron, ferric hydroxide, ferric acetylacetonate, ferric fluoride and other iron-containing compounds and hydrates thereof;
the ferrous iron is ferrous chloride, ferrous bromide, ferrous iodide, ferrous trifluoromethanesulfonate, ferrous tetrafluoroborate, ferrous hexafluorophosphate, ferrous sulfate, ferrous nitrate, ferrous acetate, ferrous trifluoroacetate, ferrous citrate, ferrous oxalate, ferrous acrylate, ferrous bis (2,2,6, 6-tetramethyl-3, 5-heptanedionate), ferrous hydroxide, ferrous acetylacetonate, ferrous fluoride and other iron-containing compounds and hydrates thereof.
3. The method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-grade alkyl substituted aromatic compounds under the catalysis of iron according to claim 1, wherein the solvent is one or more of water, hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, nitrohydrocarbon solvents, ether solvents, nitrile solvents, ester solvents, alcohol solvents, amine solvents, amide solvents, sulfone solvents and sulfoxide solvents;
the hydrocarbon solvent is one or more of benzene, toluene and saturated alkane compounds, the halogenated hydrocarbon solvent is one or more of trifluoromethylbenzene, chlorobenzene, dichloromethane, 1, 2-dichloroethane, chloroform and carbon tetrachloride, and the nitrohydrocarbon solvent is one or more of nitrobenzene and nitromethane; the ether solvent is one or more of tetrahydrofuran, 1, 4-dioxane, methyl tert-butyl ether and diethyl ether; the nitrile solvent is one or more of acetonitrile, benzonitrile and tert-butyl acetonitrile; the ester solvent is one or more of ethyl acetate, n-butyl acetate and isobutyl acetate; the alcohol solvent is one or more of methanol, ethanol, tert-butyl alcohol, n-butyl alcohol and cyclohexanol, and the amine solvent is one or more of triethylamine, diethylamine and diisopropylethylamine; the amide solvent is one or more of dimethylformamide and dimethylacetamide; the sulfoxide solvent is dimethyl sulfoxide, and can be used in any proportion in various cases.
4. The method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-grade alkyl substituted aromatic compounds catalyzed by iron according to claim 1 or 3, wherein the solvent is acetonitrile, tert-butyl acetonitrile, ethyl acetate and dichloromethane.
5. The method for preparing aromatic acid by oxidation reaction of alkyl substituted aromatic compounds of grade 1, 2 and 3 under catalysis of iron according to claim 1, wherein the oxidant is a substance with oxidation capability, and comprises oxygen, air or oxygen-containing mixed gas, peroxide, high-valence iodine organic compound, persulfate and bromate;
wherein the peroxides include, but are not limited to, hydrogen peroxide, t-butyl peroxide, di-t-butyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dilauroyl peroxide, cumene peroxide, dicumyl peroxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, 3-chloroperoxybenzoic acid, 1, 1-di-t-butyl peroxycyclohexane; the persulfate is potassium persulfate, sodium persulfate and ammonium persulfate; the bromate is sodium bromate, potassium bromate or calcium bromate.
6. The method for preparing aromatic acid by oxidation of 1, 2 and 3-grade alkyl substituted aromatic compound catalyzed by iron according to claim 1 or 5, wherein the oxidant is preferably oxygen, tert-butyl peroxide or hydrogen peroxide.
7. The method for preparing aromatic acid by oxidation of alkyl substituted aromatic compound of grade 1, 2 or 3 under catalysis of iron according to claim 1, wherein the additive is alkali metal salt of halide, alkali metal salt of organic acid compound, alkali metal salt of phenolic compound, ammonium salt of halide, ammonium salt of organic acid compound, ammonium salt of phenolic compound;
wherein the halide is fluoride, chloride, bromide or iodide; the alkali metal salt is lithium salt, sodium salt, potassium salt or cesium salt; the organic acid compound is substituted or unsubstituted aryl carboxylic acid, substituted or unsubstituted alkyl carboxylic acid, substituted or unsubstituted aryl sulfonic acid, substituted or unsubstituted alkyl sulfonic acid, substituted or unsubstituted aryl phosphoric acid and substituted or unsubstituted alkyl phosphoric acid; the phenols are substituted or unsubstituted phenol compounds; the ammonium salt is tetramethylammonium salt, tetraethylammonium salt or tetrabutylammonium salt.
8. The method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-grade alkyl substituted aromatic compounds catalyzed by iron according to claim 1, wherein the molar ratio of the iron compound to the aromatic compounds is less than 1: 1;
the suitable temperature is: placing the reaction system at-78-300 ℃;
the providing light energy comprises: the reacted system is exposed to visible light and/or monochromatic or mixed light of a wavelength of less than 500 nm.
9. The method for preparing aromatic acid by oxidation reaction of 1, 2 and 3-grade alkyl substituted aromatic compounds under the catalysis of iron according to claim 1, which is characterized by comprising the following reaction steps:
(1) sequentially adding iron compound [ Fe ] into the dried reaction tube](x1mol%), oxidizing agents and/or additives (x)2mol percent), aromatic compound and organic solvent, stirring and dissolving the mixture in oxygen atmosphere after the charging, uniformly mixing the mixture, and placing the reaction tube under the light (hv) with specific wavelength for irradiation and continuously stirring, or heating the reaction tube;
the aromatic compound and the organic solvent are added in excess;
(2) and (2) after the reaction in the step (1) is completed, removing the reaction tube from the light source, transferring the reaction mixed solution to a flask, carrying out reduced pressure distillation to obtain a crude product, and carrying out flash column chromatography to obtain the benzoic acid compound.
The additive is sodium chloride, potassium chloride, tetrabutyl ammonium chloride or pentafluorophenol sylvite;
the molar ratio of the iron compound to the aromatic compound is x1：x2＝(0.01-0.1)：1；
Heating the reaction tube to 25-100 ℃;
the sample is irradiated under light with the wavelength of 350-450 nm.
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