Carboxylic acid esterification method

Abstract

The invention discloses a carboxylic acid esterification method, which takes an alcohol compound and a carboxylic acid compound as raw materials, takes an alkaline substance as an additive, takes an organic solvent as a reaction solvent, and reacts under the conditions of sulfur hexafluoride, a photocatalyst and illumination to obtain an ester compound. According to the method disclosed by the invention, SF6 is activated under a photocatalytic condition, and an esterification reaction of carboxylic acid is realized by utilizing an SF6 decomposition product, so that an ester compound is obtained; wherein the decomposition product of SF6 is used as a condensation reagent, the greenhouse gas SF6 is effectively activated by the method, carboxylic acid esterification is realized by fully utilizing the decomposition product of SF6, and the SF6 is turned into wealth from waste; the raw materials required by the method are simple and easy to obtain, the reaction conditions are simple and convenient, and the method is green and energy-saving and has higher application value.

Description

Technical Field

[0001] The invention relates to the technical field of organic intermediate synthesis, and in particular to a carboxylic acid esterification method. Background Art

[0002] As a common group, ester group is widely present in many drug molecules. It can not only increase the lipophilicity of drugs, but also is a necessary structure-effect group in many drug molecules. Ester compounds are also an important class of chemical products in the chemical industry and indispensable in our lives. Ester compounds are also an important class of solvents. They play a very obvious role in dissolving cellulose and also play a very important role in the field of food additives and spices. Therefore, promoting the condensation esterification reaction of alcohol and carboxylic acid has important use value. At present, the methods of esterification are:

[0003] Method 1: Fischer-Speier esterification reaction is the most classic esterification reaction. Under the action of acidic catalysts (sulfuric acid, sulfonic acid, phosphoric acid, hydrochloric acid, etc.), carboxylic acid and alcohol undergo a reversible reaction to generate ester compounds. Because it is a reversible reaction, it is often necessary to add an excess of one of the raw materials, or use a Dean-Stark device to remove water.

[0004]

[0005] This method uses an acidic catalyst, which has the characteristics of high catalytic activity, low price and easy preparation. However, the disadvantage is that the yield in the esterification of secondary and tertiary alcohols is low and the raw materials are wasted (or additional equipment is required to remove water).

[0006] Method 2: Esterification reaction catalyzed by N,N-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine

[0007]

[0008] This method has the advantages of mild reaction conditions, high yield, good selectivity, etc., but it produces a by-product, dicyclohexylurea, and the post-processing is cumbersome.

[0009] Method 3: Use elemental iodine alone to catalyze the esterification reaction of carboxylic acid and alcohol.

[0010]

[0011] The advantages of this reaction system are simple operation, non-toxicity, strong applicability, relatively mild conditions and high yield; however, the post-processing is complicated and the reactant alcohol is in excess, resulting in great waste.

[0012] Therefore, there is still a need to develop a carboxylic acid esterification method that has simple and readily available raw materials, simple operation, high reaction yield, good functional group tolerance, is environmentally friendly, and is easy to promote in industrial production.

[0013] And for the following reasons: SF6 gas is a colorless, odorless, non-toxic, non-combustible, non-corrosive gas at room temperature and pressure. It is an inert gas with high stability. It does not decompose at high temperatures of 500-600°C, and does not react with acids, alkalis, water, etc. It is also an insulating gas with excellent insulating properties. The gas can adsorb free discrete electrons in the electric field, effectively reducing ionization collisions in the gas, which actually has an insulating effect and can be used to eliminate high-voltage arcs. Therefore, SF6 is widely used in the power sector, but SF6 has a strong greenhouse effect, and its climate warming power is 23,900 times that of CO2. Secondly, because SF6 is an artificially synthesized gas with quite stable chemical properties, SF6 is extremely difficult to decompose, and its natural lifespan in the atmosphere can be as long as more than 3,000 years. With continuous accumulation in the atmosphere, the greenhouse effect it brings is also continuously increasing. SF6 is currently subject to strict emission restrictions, and the treatment of large amounts of SF6 stored in the power sector faces difficulties.

[0014] SF6 itself has a high potential for utilization. One SF6 molecule contains one sulfur atom and six fluorine atoms. The decomposition products of SF6 contain high-valent sulfur-fluorine intermediates, which can be used as condensation reagents in the field of organic synthesis. Summary of the invention

[0015] The technical problem to be solved by the present invention is how to synthesize ester compounds simply and safely.

[0016] The present invention solves the above technical problems through the following technical means:

[0017] A carboxylic acid esterification method uses alcohol compounds and carboxylic acid compounds as raw materials, alkaline substances as additives, and organic solvents as reaction solvents, and reacts under sulfur hexafluoride, a photocatalyst and light conditions to obtain ester compounds.

[0018] The present invention is a carboxylic acid esterification method with a wide range of applications. The method is suitable for synthesizing various ester compounds and their derivatives, and has good tolerance to aromatic carboxylic acids, alkyl carboxylic acids, substituted alkyl carboxylic acids, and heteroaryl carboxylic acids. Therefore, there is actually no particularly strict restriction on the number and type of substituents in alcohol compounds, carboxylic acid compounds, and their derivatives.

[0019] Preferably, the structural formula of the carboxylic acid compound is Wherein, R is one of aryl or substituted aryl, alkyl or substituted alkyl.

[0020] Preferably, the aryl group is one of biphenyl, phenyl, pyrazolyl, benzyl, benzalkenyl, and benzofuranyl.

[0021] Preferably, the substituents in the substituted aryl and substituted alkyl are C1-C 20 Alkyl, C2-C 20 Alkenyl, C1-C 20 Hydrocarbyloxy, C6-C 20 Aryl, 5-10 membered heteroaryl containing 1-3 O, N, S heteroatoms or more, C2-C 30 The invention further comprises one of an ester group, a cycloalkyl group having 2 to 20 carbon atoms and containing 1 to 5 one or more heteroatoms of O, N, and S, a trifluoromethyl group, a halogen group, a dimethylamino group, a cyano group, an amino group, and a carboxyl group.

[0022] Preferably, the substituted aryl group is one of a substituted phenyl group, a substituted pyrazolyl group, a substituted benzyl group, a substituted biphenyl group, and a substituted benzalkenyl group.

[0023] Preferably, the substituted alkyl group is a substituted methyl group.

[0024] Preferably, the carboxylic acid compound is one of 4-phenylbenzoic acid, benzoic acid, 4-vinylbenzoic acid, 2-iodobenzoic acid, 4-(N,N-dimethylamino)benzoic acid, 4-methoxybenzoic acid, 4-bromobenzoic acid, 4-trifluoromethylbenzoic acid, 4-cyanobenzoic acid, monomethyl isophthalate, 1-benzofuran-5-carboxylic acid, 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid, p-methoxyphenylacetic acid, 4-biphenylacetic acid, 4-methoxycinnamic acid, and phthalic acid.

[0025] Preferably, the structural formula of the alcohol compound is Wherein, R1 and R2 are respectively one of H, alkyl or substituted alkyl, and aryl or substituted aryl.

[0026] Preferably, the alcohol compound is one of ethanol, 1-naphthylethanol, isopropanol, diethylaminoethanol, isopentanol, benzyl alcohol and methanol.

[0027] Preferably, the photocatalyst is an organic photocatalyst or a transition metal photocatalyst, or a mixture of both.

[0028] Preferably, the organic photocatalyst is 4CZIPN, Mes-Acr + ClO4 — 、Mes-Acr-Me + ClO4 - A mixture of one or more of.

[0029] Preferably, the transition metal photocatalyst is one or a mixture of Ir[dF(CF3)ppy]2(dtbbpy)PF6, Ir(dtbbpy)ppy2PF6.

[0030] Preferably, the photocatalyst is Ir[dF(CF3)ppy]2(dtbbpy)PF6.

[0031] Preferably, the alkaline substance is an organic base.

[0032] Preferably, the organic base is a tertiary amine, preferably N,N-diisopropylethylamine. When the base is N,N-diisopropylethylamine, the yield of the ester compound is the highest.

[0033] Preferably, the wavelength of the light source is 365-480 nm.

[0034] Preferably, the power of the light source is 15-25W.

[0035] Preferably, the molar ratio of the alcohol compound to the carboxylic acid compound is 1:1 to 20:1.

[0036] Preferably, the molar ratio of the alcohol compound to the carboxylic acid compound is 10:1.

[0037] Preferably, the molar ratio of the alkaline substance to the carboxylic acid compound is 1:1 to 10:1.

[0038] Preferably, the molar ratio of the alkaline substance to the carboxylic acid compound is 5:1.

[0039] Preferably, the molar ratio of the photocatalyst to the carboxylic acid compound is 0.010:1 to 0.002:1.

[0040] Preferably, the molar ratio of the photocatalyst to the carboxylic acid compound is 0.005:1.

[0041] Preferably, during the reaction, the sulfur hexafluoride gas pressure is 1 atm. When the pressure is 1 atm, the yield of the ester compound is the highest.

[0042] Preferably, the reaction temperature is 0 to 50° C., and the reaction time is 5 to 48 hours.

[0043] Preferably, the reaction temperature is room temperature and the reaction time is 20 hours.

[0044] The reaction temperature and reaction time of the present invention can be determined by technicians according to different alcohol compounds and carboxylic acid compounds and actual needs.

[0045] Preferably, the reaction solvent is a mixture of one or more of tetrahydrofuran, acetonitrile, dichloromethane and N,N-dimethylformamide.

[0046] The present invention is carried out in a system with a single organic solvent; if necessary, other organic solvents may also be present in the system, but from the perspective of reaction yield and simplicity of operation, it is preferred not to add other organic solvents, that is, to use a single organic solvent as the reaction solvent.

[0047] Preferably, the usage ratio of the carboxylic acid compound to the reaction solvent is 0.5-0.1 mmol:1 mL.

[0048] Preferably, the usage ratio of the carboxylic acid compound to the reaction solvent is 0.17 mmol:1 mL; when the usage ratio is 0.17 mmol:1 mL, the yield of the ester compound is the highest.

[0049] The present invention also provides an ester compound, which is prepared by adopting the carboxylic acid esterification method.

[0050] In the present invention, the alcohol compound and the carboxylic acid compound undergo esterification reaction, and the reaction formula is as follows:

[0051]

[0052] The advantages of the present invention are:

[0053] The present invention uses easily available alcohol and carboxylic acid compounds as reaction substrates, commercially available Ir[dF(CF3)ppy]2(dtbbpy)PF6 as photocatalysts, and cheap and easily available alkaline substances such as N,N-diisopropylethylamine as additives, and synthesizes ester compounds simply and efficiently under SF6 gas and room temperature illumination. Compared with other methods for synthesizing ester compounds, the present invention has mild reaction conditions, and the reaction raw materials used (including alcohol compounds and carboxylic acid compounds, N,N-diisopropylethylamine, etc.) are all cheap and easily available, and have the characteristics of cost saving, environmental friendliness, and industrial promotion. The method effectively activates and utilizes SF6, a greenhouse gas, and fully utilizes the decomposition products of SF6 to realize the esterification reaction of carboxylic acids, turning SF6 into treasure.

[0054] The present invention is applicable to a variety of carboxyl-containing compounds. After simple substrate exploration, we directly applied the reaction to the synthesis of drugs.

[0055] The invention can be widely applied to drug synthesis and total synthesis of natural products in industry and academia, and has high application value.

[0056] The present invention provides a carboxylic acid esterification reaction with easy-to-obtain raw materials, simple and safe operation, and green energy saving. SF6 is activated under photocatalytic conditions, and its decomposition product is used in the carboxylic acid esterification reaction, and is used in the synthesis reaction of practical and high-demand ester compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is the H NMR spectrum of ethyl benzoate described in Example 1 of the present invention;

[0058] Figure 2 is the NMR carbon spectrum of ethyl benzoate described in Example 1 of the present invention;

[0059] Figure 3 is the H NMR spectrum of ethyl 4-vinylbenzoate described in Example 2 of the present invention;

[0060] Figure 4 is the NMR carbon spectrum of ethyl 4-vinylbenzoate described in Example 2 of the present invention;

[0061] Figure 5 This is the H NMR spectrum of ethyl 2-iodobenzoate described in Example 3 of the present invention;

[0062] Figure 6 This is the NMR carbon spectrum of ethyl 2-iodobenzoate described in Example 3 of the present invention;

[0063] Figure 7 This is the H NMR spectrum of ethyl 4-(dimethylamino)benzoate described in Example 4 of the present invention;

[0064] Figure 8 The carbon-NMR spectrum of ethyl 4-(dimethylamino)benzoate described in Example 4 of the present invention;

[0065] Fig. 9 This is the H NMR spectrum of ethyl 4-methoxybenzoate described in Example 5 of the present invention;

[0066] Fig.10 This is the NMR carbon spectrum of ethyl 4-methoxybenzoate described in Example 5 of the present invention;

[0067] Fig.11 is the H NMR spectrum of ethyl 4-bromobenzoate described in Example 6 of the present invention;

[0068] Fig.12 is the NMR carbon spectrum of ethyl 4-bromobenzoate described in Example 6 of the present invention;

[0069] Fig.13 is the H NMR spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of the present invention;

[0070] Fig.14 is the NMR carbon spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of the present invention;

[0071] Fig.15 This is the NMR fluorine spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of the present invention;

[0072] Fig.16 This is the H NMR spectrum of ethyl 4-cyanobenzoate described in Example 8 of the present invention;

[0073] Fig.17 is the NMR carbon spectrum of ethyl 4-cyanobenzoate described in Example 8 of the present invention;

[0074] Fig.18 This is the H NMR spectrum of 3-methylformate ethyl benzoate described in Example 9 of the present invention;

[0075] Fig.19 This is the NMR carbon spectrum of 3-methyl formate ethyl benzoate described in Example 9 of the present invention;

[0076] Fig. 20 This is the H NMR spectrum of ethyl 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylate described in Example 10 of the present invention;

[0077] Fig.21 This is the NMR carbon spectrum of 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid ethyl ester described in Example 10 of the present invention;

[0078] Fig. 22 This is the H NMR spectrum of ethyl 4-biphenylacetate described in Example 11 of the present invention;

[0079] Fig.23 This is the carbon NMR spectrum of ethyl 4-biphenylacetate described in Example 11 of the present invention;

[0080] Fig.24 This is the H NMR spectrum of 2-(naphthalen-1-yl)ethyl[1,1'-biphenyl]-4-carboxylate described in Example 12 of the present invention;

[0081] Fig.25 This is the carbon NMR spectrum of 2-(naphthalen-1-yl)ethyl[1,1'-biphenyl]-4-carboxylate described in Example 12 of the present invention;

[0082] Fig.26 is the H NMR spectrum of [1,1'-biphenyl]-4-carboxylic acid isopropyl ester described in Example 13 of the present invention;

[0083] Fig. 27 is the NMR carbon spectrum of [1,1'-biphenyl]-4-carboxylic acid isopropyl ester described in Example 13 of the present invention;

[0084] Fig.28 This is the H NMR spectrum of (Z)-3-(4-methoxyphenyl)acrylate described in Example 14 of the present invention;

[0085] Fig.29 This is the NMR carbon spectrum of (Z)-3-(4-methoxyphenyl)acrylate described in Example 14 of the present invention;

[0086] Fig.30 This is the H NMR spectrum of (E)-3-(4-methoxyphenyl)acrylate described in Example 14 of the present invention;

[0087] Fig.31 This is the NMR carbon spectrum of (E)-3-(4-methoxyphenyl)acrylate described in Example 14 of the present invention;

[0088] Fig.32 is the H NMR spectrum of benzyl benzoate described in Example 15 of the present invention;

[0089] Fig.33 is the NMR carbon spectrum of benzyl benzoate described in Example 15 of the present invention;

[0090] Fig.34 is the H NMR spectrum of dimethyl phthalate described in Example 16 of the present invention;

[0091] Fig.35 This is the carbon NMR spectrum of dimethyl phthalate described in Example 16 of the present invention. DETAILED DESCRIPTION

[0092] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. 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.

[0093] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0094] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0095] In the present invention, "ester compound" has the meaning commonly understood by those skilled in the art, that is, a substance containing an ester group.

[0096] In the present invention, "alcohol compounds" have the meaning commonly understood by those skilled in the art, that is, compounds containing a hydroxyl group connected to a carbon atom on an alkyl group, such as methanol, ethanol or various substituted derivatives thereof.

[0097] In the present invention, "carboxylic acid compounds" have the meaning commonly understood by those skilled in the art, i.e., compounds containing a carboxyl group connected to a carbon atom on an aromatic group or an alkyl group, such as benzoic acid, 4-biphenylacetic acid or various substituted derivatives thereof.

[0098] The raw materials used in the following specific examples are all commercially available, and each reagent is purified by means known in the art before use when necessary.

[0099] 1 H NMR and 13 C NMR was measured using a Bruker Avance 400 spectrometer. The test temperature was room temperature, the solvent was deuterated chloroform, and the reference was selected: 1 H NMR: CHCl3 7.260 ppm; 13 C NMR: CHCl3: 77.000 ppm.

[0100] The 0.5 mol% in the following Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) means that the molar number of Ir[dF(CF3)ppy]2(dtbbpy)PF6 accounts for 0.5% of the molar number of the carboxylic acid compound raw material.

[0101] Example 1

[0102] Synthesis of Ethyl Benzoate

[0103] Benzoic acid (61.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 56.3 mg of ethyl benzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 75%.

[0104] The H NMR and C NMR spectra of the product ethyl benzoate are as follows Figure 1-2 The specific data are as follows: 1H NMR (400MHz, CDCl3) δ8.06–8.04(m,2H),7.57–7.53(m,1H),7.45–7.41(m,2H),4.38(q,J=7.2Hz,2H),1.38(t,J=7.2Hz,3H)ppm. 13 C NMR (101MHz, CDCl3) δ166.6,132.7,130.4,129.5,128.3,60.9,14.3ppm.

[0105] Example 2

[0106] Synthesis of Ethyl 4-Vinylbenzoate

[0107] 4-vinylbenzoic acid (74.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 62.5 mg of ethyl 4-vinylbenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 71%.

[0108] The H NMR and C NMR spectra of the product 4-vinylbenzoic acid ethyl ester are as follows Figure 3-4 The specific data are as follows: 1 HNMR(400MHz, CDCl3)δ8.00–7.99(m,2H),7.46–7.44(m,2H),6.77–6.70(m,1H),5.85(d, J=17.2Hz,1H),5.37(d,J=11.2Hz,1H),4.36(q,J=6.8Hz,2H),1.39(t,J=7.2Hz,3H)ppm. 13 CNMR (101MHz, CDCl3) δ166.3,141.7,136.0,129.7,129.5,126.0,116.3,60.8,14.3ppm.

[0109] Example 3

[0110] Synthesis of Ethyl 2-Iodobenzoate

[0111] 2-Iodobenzoic acid (124.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were then added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 120.1 mg of ethyl 2-iodobenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 87%.

[0112] The H NMR and C NMR spectra of the product 2-iodobenzoic acid ethyl ester are as follows Figure 5-6 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ7.97–7.90(m,1H),7.78–7.72(m,1H),7.40–7.32(m,1H),7.14–7.06(m,1H),4.41–4.32(m,2H),1.41–1.33(m,3H)ppm. 13 C NMR (101MHz, CDCl3) δ166.5,141.1,135.3,132.4,130.7,127.8,93.9,61.6,14.1ppm.

[0113] Example 4

[0114] Synthesis of Ethyl 4-(Dimethylamino)benzoate

[0115] 4-(N,N-dimethylamino)benzoic acid (82.5 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 53.1 mg of ethyl 4-(dimethylamino)benzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 55%.

[0116] The H NMR and C NMR spectra of the product 4-(dimethylamino)benzoic acid ethyl ester are as follows Figure 7-8 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ7.92–7.90(m,2H),6.65–6.63(m,2H),4.32(q,J=6.8Hz,2H),3.03(s,6H),1.36(t,J=7.2Hz,3H)ppm. 13 C NMR (101MHz, CDCl3) δ167.0,153.2,131.2,117.2,110.6,60.1,40.0,14.4ppm.

[0117] Example 5

[0118] Synthesis of Ethyl 4-Methoxybenzoate

[0119] 4-Methoxybenzoic acid (76.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 60.3 mg of ethyl 4-methoxybenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 67%.

[0120] The H NMR and C NMR spectra of the product 4-methoxybenzoic acid ethyl ester are as follows Figure 9-10 The specific data are as follows: 1 HNMR (400MHz, CDCl3) δ8.00–7.98(m,2H),6.92–6.89(m,2H),4.33(q,J=6.8Hz,2H),3.85(s,3H),1.37(t,J=6.8Hz,3H)ppm. 13 C NMR (101MHz, CDCl3) δ166.3,163.2,131.5,122.8,113.5,60.6,55.3,14.3ppm.

[0121] Example 6

[0122] Synthesis of Ethyl 4-Bromobenzoate

[0123] 4-Bromobenzoic acid (100.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 91.2 mg of ethyl 4-bromobenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 80%.

[0124] The H NMR and C NMR spectra of the product 4-bromobenzoic acid ethyl ester are as follows Figure 11-12 The specific data are as follows: 1 HNMR (400MHz, CDCl3) δ7.87–7.83(m,2H),7.54–7.48(m,2H),4.37–7.29(m,2H),1.38–1.32(m,3H)ppm. 13 C NMR (101MHz, CDCl3) δ165.7,131.5,130.9,129.2,127.7,61.1,14.1ppm.

[0125] Example 7

[0126] Synthesis of Ethyl 4-Trifluoromethylbenzoate

[0127] 4-Trifluoromethylbenzoic acid (95.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 95.9 mg of ethyl 4-trifluoromethylbenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 88%.

[0128] The H NMR, C NMR and F NMR spectra of the product 4-trifluoromethylbenzoic acid ethyl ester are as follows Figure 13-15 The specific data are as follows: 1H NMR (400MHz, CDCl3) δ8.15–8.15(m,2H),7.69–7.67(m,2H),4.40(q,J=7.2Hz,2H),1.40(t,J=7.1Hz,3H)ppm. 13 C NMR (100MHz, CDCl3) δ = 165.3, 134.3 (q, J = 32.7Hz), 133.7, 129.9, 125.3 (q, J = 3.8Hz), 123.6 (q, J = 273.6Hz), 61.5, 14.2ppm. 19 FNMR (376MHz,CDCl3)δ-63.5ppm.

[0129] Example 8

[0130] Synthesis of Ethyl 4-Cyanobenzoate

[0131] 4-Cyanobenzoic acid (73.5 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 85.8 mg of ethyl 4-cyanobenzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 98%.

[0132] The H NMR and C NMR spectra of the product 4-cyanobenzoic acid ethyl ester are as follows Figure 16-17 The specific data are as follows: 1 HNMR (400MHz, CDCl3) δ8.12–8.10(m,2H),7.72–7.70(m,2H),4.38(q,J=7.2Hz,2H),1.38(t,J=7.2Hz,3H)ppm. 13 C NMR (101MHz, CDCl3) δ164.8,134.1,132.0,129.9,117.9,116.1,61.7,14.1ppm.

[0133] Example 9

[0134] Synthesis of 3-Methylformylbenzoate

[0135] Monomethyl isophthalate (90.1 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 84.2 mg of 3-methyl benzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 81%.

[0136] The H NMR and C NMR spectra of the product 3-methyl formate ethyl benzoate are as follows Figure 18-19 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ8.63(s,1H),8.20–8.15(m,2H),7.50–7.45(m,1H),4.39–4.33(m,2H),3.91–3.90(m,3H),1.39–1.35(m,3H)ppm. 13 C NMR (101MHz, CDCl3) δ166.1,165.6,133.6,133.5,130.8,130.5,130.4,128.4,61.2,52.2,14.2ppm.

[0137] Example 10

[0138] Synthesis of 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid ethyl ester

[0139] 1-(Pyridin-3-yl)-1H-pyrazole-4-carboxylic acid (94.6 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid ethyl ester 89.0 mg was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 82%.

[0140] The H NMR and C NMR spectra of the product 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid ethyl ester are as follows Figure 20-21 The specific data are as follows: 1 H NMR(400MHz, CDCl3)δ8.96(d,J=2.4Hz,1H),8.54–8.53(m,1H),8.44(s,1H),8.06(s,1H) ,8.02–7.99(m,1H),7.38–7.34(m,1H),4.27(q,J=6.8Hz,2H),1.30(t,J=7.2Hz,3H)ppm. 13 C NMR (101MHz, CDCl3) δ162.3,148.4,142.6,140.7,135.7,130.0,126.8,123.8,117.5,60.4,14.2ppm.

[0141] Embodiment 11

[0142] Synthesis of ethyl 4-biphenylacetate

[0143] 4-Biphenylacetic acid (106.1 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 103.2 mg of ethyl 4-biphenylacetate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 86%.

[0144] The H NMR and C NMR spectra of the product 4-biphenylacetic acid ethyl ester are as follows Figure 22-23 The specific data are as follows: 1 HNMR (400MHz, CDCl3) δ7.66–7.61(m,4H),7.51–7.38(m,5H),4.26–4.21(m,2H),3.72(s,2H),1.35–1.31(m,3H)ppm. 13C NMR (101MHz, CDCl3) δ171.4,140.6,139.8,133.0,129.5,128.6,127.1,127.1,126.9,60.7,40.8,14.0ppm.

[0145] Example 12

[0146] Synthesis of 2-(Naphthyl-1-yl)ethyl[1,1'-biphenyl]-4-carboxylate

[0147] 4-Phenylbenzoic acid (99.0 mg, 1 equiv.), 1-naphthylethanol (861.1 mg, 10 equiv.), Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, evacuated, and an SF6 balloon was inserted, then 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, diisopropylethylamine (434.6 μL, 5 equiv.) was added, and the reaction system was placed under 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 160.2 mg of 2-(naphthalene-1-yl)ethyl[1,1'-biphenyl]-4-carboxylate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 91%.

[0148] The H-NMR and C-NMR spectra of the product 2-(naphthalen-1-yl)ethyl[1,1'-biphenyl]-4-carboxylate are as follows Figure 24-25 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ8.26–8.24(m,1H),8.15–8.13(m,2H),7.94–7.92(m,1H),7.84–7.82(m ,1H),7.70–7.61(m,5H),7.58–7.42(m,6H),4.74(t,J=7.6Hz,2H),3.62(t,J=7.2Hz,2H)ppm. 13 C NMR (101MHz, CDCl3) δ166.4,145.5,139.9,133.8,133.7,132.0,130.1,128.9,128.8, 128.8,128.1,127.4,127.2,127.0,126.9,126.2,125.6,125.5,123.6,64.9,32.3ppm.

[0149] Embodiment 13

[0150] Synthesis of Isopropyl [1,1'-Biphenyl]-4-Carboxylate

[0151] 4-Phenylbenzoic acid (99.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Isopropanol (382.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were then added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 73.2 mg of [1,1'-biphenyl]-4-carboxylic acid isopropyl ester was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 61%.

[0152] The H-NMR and C-NMR spectra of the product [1,1'-biphenyl]-4-carboxylic acid isopropyl ester are as follows Figure 26-27 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ8.12(d,J=8.4Hz,2H),7.67–7.62(m,4H),7.50–7.38(m,3H),5.34–5.25(m,1H),1.40(d,J=6.8Hz,6H)ppm. 13 C NMR (101MHz, CDCl3) δ166.0,145.4,140.1,130.0,129.6,128.9,128.0,127.2,127.0,68.3,21.9ppm.

[0153] Embodiment 14

[0154] Synthesis of Isoamyl 3-(4-Methoxyphenyl) Acrylate

[0155] 4-Methoxycinnamic acid (89.1 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and after evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Subsequently, isoamyl alcohol (544.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 80.6 mg of 3-(4-methoxyphenyl) acrylate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 65%, Z:E = 3.7:1.

[0156] The H-NMR and C-NMR spectra of the product (Z)-3-(4-methoxyphenyl) acrylate are as follows: Figure 28-29 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ7.70–7.68(m,2H),6.89–6.83(m,3H),5.83(d,J=12.8Hz,1H),4.16( t,J=6.8Hz,2H),3.83(s,3H),1.76–1.62(m,1H),1.59–1.51(m,2H),0.92–0.90(m,6H)ppm. 13 C NMR (101MHz, CDCl3) δ166.6,160.3,143.2,132.1,127.4,117.2,113.3,62.8,55.3,37.2,25.0,22.4ppm.

[0157] The H NMR and C NMR spectra of the product (E)-3-(4-methoxyphenyl)acrylate are as follows: Figure 30-31 The specific data are as follows: 1 H NMR(400MHz, CDCl3)δ7.63(d,J=16.0Hz,1H),7.48–7.46(m,2H),6.90–6.88(m,2H),6.30(d,J=16.0Hz ,1H),4.22(t,J=6.8Hz,2H),3.82(s,3H),1.79–1.69(m,1H),1.61–1.56(m,2H),0.95–0.94(m,6H)ppm. 13C NMR (101MHz, CDCl3) δ167.4,161.2,144.2,129.6,127.1,115.6,114.2,63.0,55.3,37.4,25.0,22.4ppm.

[0158] Embodiment 15

[0159] Synthesis of Benzyl Benzoate

[0160] Benzoic acid (61.0 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Benzyl alcohol (519.9 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were then added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 70.0 mg of benzyl benzoate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 66%.

[0161] The H NMR and C NMR spectra of the product benzyl benzoate are as follows Figure 32-33 The specific data are as follows: 1 H NMR (400MHz, CDCl3) δ8.21–8.19(m,2H),7.59–7.38(m,8H),5.45(s,2H)ppm. 13 C NMR (101MHz, CDCl3) δ165.9,135.8,132.7,129.8,129.4,128.3,128.0,127.9,127.8,66.3ppm.

[0162] Example 16

[0163] Synthesis of Dimethyl Phthalate

[0164] Phthalic acid (83.1 mg, 1 equiv.) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace glass vial with a PTFE gasket, and a SF6 balloon was inserted after vacuuming. 3.0 mL of anhydrous tetrahydrofuran was added and bubbled for 3 minutes. Methanol (202.5 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were then added, and the reaction system was placed under a 15 W 465 nm blue LED light source and stirred for 20 hours. After the reaction was completed, the organic solvent was removed under vacuum, and 52.2 mg of dimethyl phthalate was obtained by silica gel column chromatography (petroleum ether: ethyl acetate volume ratio = 20:1), with a yield of 60%.

[0165] The H-NMR and C-NMR spectra of the product dimethyl phthalate are as follows: Figure 34-35 The specific data are as follows: 1 HNMR (400MHz, CDCl3) δ7.67–7.64(m,2H),7.48–7.45(m,2H),3.84(s,6H)ppm. 13 CNMR(101MHz,CDCl3)δ167.8,131.6,130.9,128.6,52.4ppm.

[0166] In the above embodiments, irradiation and stirring were performed at room temperature under SF6 gas at one atmosphere pressure.

[0167] Embodiment 17

[0168] According to the method of Example 1, 1 and 2 are used as raw materials, and the reaction conditions are changed to react as follows. The changed conditions are shown in the following table. The remaining steps are the same as in Example 1. The yields are shown in the following table:

[0169]

[0170] Serial number Conditions Yield (%) 1 Standard conditions 98 2 2(3equiv.) 62 3 2(5equiv.) 70 4 2(8equiv.) 85 5 The solvent is dichloromethane 62 6 The solvent is acetonitrile 48 7 The solvent is N,N-dimethylformamide 8 8 The photocatalyst is 4CzIPN 56 9 <![CDATA[The photocatalyst is Mes-Acr-Me + ClO4 - > 18 10 <![CDATA[The photocatalyst is Mes-Acr-Me + ClO4 - and irradiated under a 25 W 365 nm ultraviolet lamp]]> 70 11 No light source ND 12 <![CDATA[No SF6]]> ND 13 No diisopropylethylamine Trace 14 <![CDATA[Without Ir[dF(CF3)ppy]2(dtbbpy)PF6]]> ND

[0171] Standard conditions: 1 (0.5mmol, 1.0equiv.), 2 (5.0mmol, 10equiv.), photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.0025mmol, 0.5mol%), diisopropylethylamine (2.5mmol, 5.0equiv.), 1atm ofSF6 (balloon), solvent tetrahydrofuran, the reaction system was irradiated under a 15W 465nm blue LED light source and stirred for 20 hours, the isolated yield;

[0172] ND in the table means no product was generated.

[0173] The structural formula and yield of each embodiment product are as follows:

[0174]

[0175]

[0176]

[0177] As can be seen from Examples 1-16, the present invention uses easily available alcohol and carboxylic acid compounds as reaction substrates, commercially available Ir[dF(CF3)ppy]2(dtbbpy)PF6 as a photocatalyst, and cheap and easily available N,N-diisopropylethylamine as a base. Under an atmospheric pressure of SF6 gas, at room temperature, 15W of 465nm blue light is used as a light source to simply and efficiently synthesize ester compounds. The method has good tolerance to aromatic carboxylic acids, heteroaromatic carboxylic acids, and aliphatic carboxylic acids. The effect of replacing alcohol with other primary alcohols is still very good, and secondary alcohols also have good reactivity. Therefore, there are actually no particularly strict restrictions on the number and type of substituents in alcohols and carboxylic acids. Furthermore, there are no particularly strict restrictions on the number and type of substituents in ester compounds and their derivatives. Therefore, it is a general method for synthesizing ester compounds with mild conditions, simple operation, and easy industrial promotion. In addition, the method effectively activates and utilizes SF6, a greenhouse gas, and makes full use of SF6 decomposition products to realize the esterification reaction of carboxylic acids, turning SF6 into treasure.

[0178] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carboxylic acid esterification method, characterized in that: The method uses alcohol compounds and carboxylic acid compounds as raw materials, alkaline substances as additives, and organic solvents as reaction solvents, and performs a reaction under the conditions of sulfur hexafluoride, a photocatalyst and light to obtain ester compounds.

2. The carboxylic acid esterification method according to claim 1, characterized in that: The structural formula of the carboxylic acid compound is Wherein, R is one of aryl or substituted aryl, alkyl or substituted alkyl.

3. The carboxylic acid esterification method according to claim 2, characterized in that: The aryl group is one of biphenyl, phenyl, pyrazolyl, benzyl, benzalkenyl and benzofuranyl.

4. The carboxylic acid esterification method according to claim 2, characterized in that: The substituents in the substituted aryl and substituted alkyl are all C1-C 20 Alkyl, C2-C 20 Alkenyl, C1-C 20 Hydrocarbyloxy, C6-C 20 Aryl, 5-10 membered heteroaryl containing 1-3 O, N, S heteroatoms or one or more thereof, C2-C 30 The invention further comprises one of an ester group, a cycloalkyl group having 2 to 20 carbon atoms and containing 1 to 5 one or more heteroatoms of O, N, and S, a trifluoromethyl group, a halogen group, a dimethylamino group, a cyano group, an amino group, and a carboxyl group.

5. The carboxylic acid esterification method according to claim 4, characterized in that: The substituted aryl group is one of a substituted phenyl group, a substituted pyrazolyl group, a substituted benzyl group, a substituted biphenyl group, and a substituted benzalkenyl group.

6. The carboxylic acid esterification method according to claim 2, characterized in that: The substituted alkyl group is a substituted methyl group.

7. The carboxylic acid esterification method according to claim 1, characterized in that: The carboxylic acid compound is one of 4-phenylbenzoic acid, benzoic acid, 4-vinylbenzoic acid, 2-iodobenzoic acid, 4-(N,N-dimethylamino)benzoic acid, 4-methoxybenzoic acid, 4-bromobenzoic acid, 4-trifluoromethylbenzoic acid, 4-cyanobenzoic acid, monomethyl isophthalate, 1-benzofuran-5-carboxylic acid, 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid, p-methoxyphenylacetic acid, 4-biphenylacetic acid, 4-methoxycinnamic acid, and phthalic acid.

8. The carboxylic acid esterification method according to claim 1, characterized in that: The structural formula of the alcohol compound is Wherein, R1 and R2 are respectively one of H, alkyl or substituted alkyl, and aryl or substituted aryl.

9. The carboxylic acid esterification method according to claim 1, characterized in that: The alcohol compound is one of ethanol, 1-naphthylethanol, isopropanol, diethylaminoethanol, isopentanol, benzyl alcohol and methanol.

10. The carboxylic acid esterification method according to claim 1, characterized in that: The photocatalyst is an organic photocatalyst or a transition metal photocatalyst, or a mixture of the two.

11. The carboxylic acid esterification method according to claim 10, characterized in that: The organic photocatalyst is 4CZIPN, Mes-Acr + ClO4 — 、Mes-Acr-Me + ClO4 - A mixture of one or more of.

12. The carboxylic acid esterification method according to claim 10, characterized in that: The transition metal photocatalyst is one of Ir[dF(CF3)ppy]2(dtbbpy)PF6 and Ir(dtbbpy)ppy2PF6 or a mixture of the two.

13. The carboxylic acid esterification method according to claim 1, characterized in that: The alkaline substance is an organic base.

14. The carboxylic acid esterification method according to claim 13, characterized in that: The organic base is N,N-diisopropylethylamine.

15. The carboxylic acid esterification method according to claim 1, characterized in that: The wavelength of the light source is 365-480nm.

16. The carboxylic acid esterification method according to claim 1, characterized in that: The molar ratio of the alcohol compound to the carboxylic acid compound is 1:1 to 20:

1.

17. The carboxylic acid esterification method according to claim 1, characterized in that: The molar ratio of the alkaline substance to the carboxylic acid compound is 1:1 to 10:

1.

18. The carboxylic acid esterification method according to claim 1, characterized in that: The molar ratio of the photocatalyst to the carboxylic acid compound is 0.010:1 to 0.002:

1.

19. The carboxylic acid esterification method according to claim 1, characterized in that: During the reaction, the pressure of sulfur hexafluoride gas was 1 atm.

20. The carboxylic acid esterification method according to claim 1, characterized in that: The reaction temperature is 0-50°C and the reaction time is 5-48h.

21. The carboxylic acid esterification method according to claim 1, characterized in that: The reaction solvent is a mixture of one or more of tetrahydrofuran, acetonitrile, dichloromethane and N,N-dimethylformamide.

22. The carboxylic acid esterification method according to any one of claims 1 to 21, characterized in that: The usage ratio of the carboxylic acid compound and the reaction solvent is 0.5-0.1 mmol:1 mL.

23. An ester compound, characterized in that: The method is prepared by the carboxylic acid esterification method according to any one of claims 1 to 22.

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