A method for esterifying carboxylic acids

Abstract

The application discloses a carboxylic acid esterification method, which uses alcohol compounds and carboxylic acid compounds as raw materials, uses alkaline substances as additives, uses organic solvents as reaction solvents, and carries out reactions under the conditions of sulfur hexafluoride, a photocatalyst and light to obtain ester compounds. In the method, SF6 is activated under the photocatalytic condition, and the esterification reaction of carboxylic acid is realized by using the decomposition products of SF6, so that the ester compounds are obtained; wherein the decomposition products of SF6 are used as condensation reagents, the method effectively activates the greenhouse gas SF6, and fully utilizes the decomposition products of SF6 to realize the esterification of carboxylic acid, so that the SF6 is changed from waste to treasure; the raw materials required by the method are simple and easy to obtain, the reaction condition is simple, green and energy-saving, and the method has high application value.

Description

Technical Field

[0001] This invention relates to the field of organic intermediate synthesis technology, and more specifically to a carboxylic acid esterification method. Background Technology

[0002] Ester groups, as common functional groups, are widely present in many drug molecules. They not only increase the lipophilicity of drugs but are also essential structure-activity groups in many drug molecules. Ester compounds are also an important class of chemical products in the chemical industry and indispensable in our daily lives. Ester compounds are also important solvents, playing a significant role in the dissolution of cellulose, and hold a vital position in the fields of food additives and flavorings. Therefore, promoting the condensation esterification reaction of alcohols and carboxylic acids has significant practical value. Currently, esterification methods include:

[0003] Method 1: The Fischer-Speier esterification reaction, as the most classic esterification reaction, involves a reversible reaction between a carboxylic acid and an alcohol under the action of an acidic catalyst (sulfuric acid, sulfonic acid, phosphoric acid, hydrochloric acid, etc.) to produce ester compounds. Because it is a reversible reaction, it often requires the addition of an excess of one of the raw materials, or the use of a Dean-Stark apparatus to remove water.

[0004]

[0005] This method uses an acidic catalyst, which is characterized by high catalytic activity, low cost, and ease of preparation. However, its disadvantages include low yields and wasted raw materials in secondary and tertiary alcohol esterification (or the need for additional equipment for dehydration).

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

[0007]

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

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

[0010]

[0011] The advantages of this reaction system are that it is simple to operate, non-toxic, widely applicable, relatively mild under mild conditions, and has a high yield; however, the post-processing is complicated, and the excess of reactant alcohol results in a great deal of waste.

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

[0013] Furthermore, SF6 is a colorless, odorless, non-toxic, non-flammable, and non-corrosive gas at normal temperature and pressure. It is an inert gas with high stability, not decomposing even at high temperatures of 500-600℃, and does not react with acids, alkalis, or water. It is also an insulating gas with excellent insulating properties. This gas can adsorb free electrons in an electric field, effectively reducing ionization collisions in the gas, thus achieving an insulating effect and being used to extinguish high-voltage arcs. Therefore, SF6 is widely used in the power sector. However, SF6 has a powerful greenhouse effect, with a global warming potential 23,900 times that of CO2. Secondly, because SF6 is a synthetic gas with relatively stable chemical properties, it is extremely difficult to decompose, and its natural lifespan in the atmosphere can reach over three thousand years. With continuous accumulation in the atmosphere, its greenhouse effect continues to intensify. SF6 is currently subject to strict emission restrictions, and the disposal of large quantities of SF6 stored in the power sector faces difficulties.

[0014] SF6 itself has great potential for utilization. An SF6 molecule contains one sulfur atom and six fluorine atoms. The decomposition products of SF6 contain high-valence 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 this invention is how to synthesize ester compounds in a simple and safe way.

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

[0017] A method for carboxylic acid esterification, which uses alcohols and carboxylic acids as raw materials, an alkaline substance as an additive, and an organic solvent as a reaction solvent, and reacts under the conditions of sulfur hexafluoride, a photocatalyst, and light irradiation to obtain ester compounds.

[0018] This invention is a widely applicable carboxylic acid esterification method. This method is suitable for synthesizing various ester compounds and their derivatives. It has good tolerance to aryl carboxylic acids, alkyl carboxylic acids, substituted alkyl carboxylic acids, and heteroaryl carboxylic acids. Therefore, there are no particularly strict limitations 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 as follows: 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, benzylenyl, and benzofuranyl.

[0021] Preferably, the substituents in the substituted aryl and substituted alkyl groups are all C1-C. 20 Alkyl, C2-C 20 alkenyl, C1-C 20 Hydroxyl groups, C6-C 20 aryl, 5-10 membered heteroaryl containing one or more of 1-3 O, N, S heteroatoms, C2-C 30 The ester group, the number of carbon atoms is 2-20 and contains one or more of the following heteroatoms: cycloalkyl, trifluoromethyl, halogen, dimethylamino, cyano, amino, and carboxyl.

[0022] Preferably, the substituted aryl group is one of substituted phenyl, substituted pyrazolyl, substituted benzyl, substituted biphenyl, or substituted benzylene.

[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 as follows: 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, isoamyl alcohol, benzyl alcohol, and methanol.

[0027] Preferably, the photocatalyst is one or a mixture of two of organic photocatalysts or transition metal photocatalysts.

[0028] Preferably, the organic photocatalyst is 4CZIPN or Mes-Acr. + ClO4 — Mes-Acr-Me + ClO4 - One or more of the following mixtures.

[0029] Preferably, the transition metal photocatalyst is one or a mixture of two of Ir[dF(CF3)ppy]2(dtbbpy)PF6 and 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, more preferably N,N-diisopropylethylamine. The ester yield is highest when the base is N,N-diisopropylethylamine.

[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, the sulfur hexafluoride gas pressure is 1 atm during the reaction. The yield of ester compounds is highest when the gas pressure is 1 atm.

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

[0043] Preferably, the reaction is carried out at room temperature for 20 hours.

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

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

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

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

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

[0049] The present invention also proposes an ester compound prepared by the aforementioned carboxylic acid esterification method.

[0050] In this invention, alcohols and carboxylic acids undergo an esterification reaction, the reaction formula of which is as follows:

[0051]

[0052] The advantages of this invention are:

[0053] This invention uses readily available alcohols and carboxylic acids as reaction substrates, commercially available Ir[dF(CF3)ppy]2(dtbbpy)PF6 as a photocatalyst, and inexpensive and readily available basic substances such as N,N-diisopropylethylamine as additives. Esters are synthesized simply and efficiently under SF6 gas and room temperature light irradiation. Compared with other methods for synthesizing esters, this invention offers mild reaction conditions, uses readily available and inexpensive raw materials (including alcohols, carboxylic acids, and N,N-diisopropylethylamine), and is cost-effective, environmentally friendly, and industrially applicable. This method effectively activates and utilizes SF6, a greenhouse gas, fully leveraging the decomposition products of SF6 to achieve the esterification reaction of carboxylic acids, turning SF6 waste into a valuable resource.

[0054] This invention is applicable to a variety of carboxyl-containing compounds. After simple substrate exploration, we directly applied this reaction to drug synthesis.

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

[0056] This invention provides a carboxylic acid esterification reaction that uses readily available raw materials, is simple and safe to operate, and is green and energy-saving. Furthermore, SF6 is activated under photocatalytic conditions, and its decomposition products are used in the carboxylic acid esterification reaction, applying them to the synthesis of practical and in-demand ester compounds. Attached Figure Description

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

[0058] Figure 2 The carbon NMR spectrum of ethyl benzoate described in Example 1 of this invention;

[0059] Figure 3 The 1H NMR spectrum of ethyl 4-vinylbenzoate described in Example 2 of this invention;

[0060] Figure 4 The carbon NMR spectrum of ethyl 4-vinylbenzoate described in Example 2 of this invention;

[0061] Figure 5 The 1H NMR spectrum of ethyl 2-iodobenzoate described in Example 3 of this invention;

[0062] Figure 6 The carbon NMR spectrum of ethyl 2-iodobenzoate described in Example 3 of this invention;

[0063] Figure 7 The 1H NMR spectrum of ethyl 4-(dimethylamino)benzoate described in Example 4 of this invention;

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

[0065] Figure 9 The 1H NMR spectrum of ethyl 4-methoxybenzoate described in Example 5 of this invention;

[0066] Figure 10 The carbon NMR spectrum of ethyl 4-methoxybenzoate described in Example 5 of this invention;

[0067] Figure 11 The 1H NMR spectrum of ethyl 4-bromobenzoate described in Example 6 of this invention;

[0068] Figure 12 The carbon NMR spectrum of ethyl 4-bromobenzoate described in Example 6 of this invention;

[0069] Figure 13 The 1H NMR spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of this invention;

[0070] Figure 14 The carbon NMR spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of this invention;

[0071] Figure 15 The NMR fluorine spectrum of ethyl 4-trifluoromethylbenzoate described in Example 7 of this invention;

[0072] Figure 16 The 1H NMR spectrum of ethyl 4-cyanobenzoate described in Example 8 of this invention;

[0073] Figure 17 The carbon NMR spectrum of ethyl 4-cyanobenzoate described in Example 8 of this invention;

[0074] Figure 18 The 1H NMR spectrum of methyl 3-carboxylate and ethyl benzoate described in Example 9 of this invention;

[0075] Figure 19 The carbon NMR spectrum of methyl 3-carboxylate and ethyl benzoate as described in Example 9 of this invention;

[0076] Figure 20 The 1H NMR spectrum of ethyl 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylate described in Example 10 of this invention;

[0077] Figure 21 The carbon NMR spectrum of ethyl 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylate described in Example 10 of this invention;

[0078] Figure 22 The 1H NMR spectrum of ethyl 4-biphenylacetate as described in Example 11 of this invention;

[0079] Figure 23 The carbon NMR spectrum of ethyl 4-biphenylacetate as described in Example 11 of this invention;

[0080] Figure 24 The 1H NMR spectrum of the 2-(naphthyl-1-yl)ethyl[1,1'-biphenyl]-4-carboxylic acid ester described in Example 12 of this invention;

[0081] Figure 25 The carbon NMR spectrum of 2-(naphthyl-1-yl)ethyl[1,1'-biphenyl]-4-carboxylic acid ester described in Example 12 of this invention;

[0082] Figure 26 The 1H NMR spectrum of isopropyl [1,1'-biphenyl]-4-carboxylic acid described in Example 13 of this invention;

[0083] Figure 27 The carbon NMR spectrum of isopropyl [1,1'-biphenyl]-4-carboxylic acid as described in Example 13 of this invention;

[0084] Figure 28 The 1H NMR spectrum of isoamyl (Z)-3-(4-methoxyphenyl)acrylate described in Example 14 of this invention;

[0085] Figure 29 The carbon NMR spectrum of isoamyl (Z)-3-(4-methoxyphenyl)acrylate described in Example 14 of this invention;

[0086] Figure 30 The 1H NMR spectrum of isoamyl (E)-3-(4-methoxyphenyl)acrylate described in Example 14 of this invention;

[0087] Figure 31 The carbon NMR spectrum of isoamyl (E)-3-(4-methoxyphenyl)acrylate described in Example 14 of this invention;

[0088] Figure 32 The 1H NMR spectrum of benzyl benzoate described in Example 15 of this invention;

[0089] Figure 33 The carbon NMR spectrum of benzyl benzoate described in Example 15 of this invention;

[0090] Figure 34 The 1H NMR spectrum of dimethyl phthalate described in Example 16 of this invention;

[0091] Figure 35 This is the carbon NMR spectrum of dimethyl phthalate described in Example 16 of the present invention. Detailed Implementation

[0092] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0093] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0094] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0095] In this invention, "ester compounds" has the meaning commonly understood by those skilled in the art, namely, substances containing ester groups.

[0096] In this invention, "alcohols" has the meaning commonly understood by those skilled in the art, namely, compounds containing hydroxyl groups attached to carbon atoms of alkyl groups, such as methanol, ethanol, or various substituted derivatives thereof.

[0097] In this invention, "carboxylic acid compounds" has the meaning commonly understood by those skilled in the art, namely, compounds containing a carboxyl group attached to a carbon atom of an aromatic group or alkyl group, such as benzoic acid, 4-biphenylacetic acid, or various substituted derivatives thereof.

[0098] All raw materials used in the following specific examples are commercially available, and each reagent is purified using methods known in the art when necessary.

[0099] 1 H NMR and 13 All C NMR measurements were performed using a Bruker Avance 400 spectrometer. The test temperature was room temperature, and the solvent was deuterated chloroform. (Reference selection follows.) 1 ¹H NMR: CHCl₃ was 7.260 ppm; 13 C NMR: CHCl3 was 77,000 ppm.

[0100] In the following Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%), 0.5 mol% refers to the molar number of Ir[dF(CF3)ppy]2(dtbbpy)PF6 accounting 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 equivalent) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equivalent) and diisopropylethylamine (434.6 μL, 5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl benzoate (56.3 mg, 75% yield) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0104] The 1H NMR and 1C NMR spectra of the product ethyl benzoate are as follows: Figure 1-2 As shown, the specific data is 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 vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, 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), yielding 71%.

[0108] The 1H NMR and 1C NMR spectra of the product ethyl 4-vinylbenzoate are as follows: Figure 3-4 As shown, the specific data is 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] 124.0 mg of 2-iodobenzoic acid (1 equivalent) and 2.8 mg of Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, 291.8 μL of ethanol (10 equivalent) and 434.6 μL of diisopropylethylamine (5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, 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), yielding 87%.

[0112] The 1H NMR and 1C NMR spectra of the product ethyl 2-iodobenzoate are as follows: Figure 5-6 As shown, the specific data is 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 vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl 4-(dimethylamino)benzoate was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1) in 53.1 mg (yield 55%).

[0116] The 1H NMR and 1C NMR spectra of the product ethyl 4-(dimethylamino)benzoate are as follows: Figure 7-8 As shown, the specific data is 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 equivalent) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equivalent) and diisopropylethylamine (434.6 μL, 5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl 4-methoxybenzoate (60.3 mg, 67% yield) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0120] The 1H NMR and 1C NMR spectra of the product ethyl 4-methoxybenzoate are as follows: Figure 9-10 As shown, the specific data is 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 vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl 4-bromobenzoate (91.2 mg, 80% yield) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0124] The 1H NMR and 1C NMR spectra of the product ethyl 4-bromobenzoate are as follows: Figure 11-12 As shown, the specific data is 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 vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl 4-trifluoromethylbenzoate (95.9 mg, 88% yield) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0128] The NMR spectra, NMR spectra, and NMR spectra of the product ethyl 4-trifluoromethylbenzoate are as follows: Figure 13-15 As shown, the specific data is 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-Cyanobenzic 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 vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equiv.) and diisopropylethylamine (434.6 μL, 5 equiv.) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and ethyl 4-cyanobenzate (85.8 mg, 98%) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0132] The 1H NMR and 1C NMR spectra of the product ethyl 4-cyanobenzoate are as follows: Figure 16-17 As shown, the specific data is 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 methyl 3-carboxylate and ethyl benzoate

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

[0136] The 1H NMR and 1C NMR spectra of the product methyl 3-carboxylate and ethyl benzoate are as follows: Figure 18-19 As shown, the specific data is 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 ethyl 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylate

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

[0140] The 1H NMR and 1C NMR spectra of the product 1-(pyridin-3-yl)-1H-pyrazole-4-carboxylic acid ethyl ester are as follows: Figure 20-21 As shown, the specific data is 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] Example 11

[0142] Synthesis of Ethyl 4-biphenyl

[0143] 4-Biphenylacetic acid (106.1 mg, 1 equivalent) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, ethanol (291.8 μL, 10 equivalent) and diisopropylethylamine (434.6 μL, 5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, 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), yielding 86%.

[0144] The 1H NMR and 1C NMR spectra of the product ethyl 4-biphenyl are as follows: Figure 22-23 As shown, the specific data is 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-carboxylic acid ester

[0147] 4-Phenylacetic acid (99.0 mg, 1 equiv.), 1-naphthylethanol (861.1 mg, 10 equiv.), and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, followed by the addition of 3.0 mL of anhydrous tetrahydrofuran and bubbling for 3 minutes. Then, diisopropylethylamine (434.6 μL, 5 equiv.) was added, and the reaction mixture was stirred for 20 hours under a 15 W blue LED light source at 465 nm. After the reaction was complete, the organic solvent was removed under vacuum, and 160.2 mg of 2-(naphthyl-1-yl)ethyl[1,1'-biphenyl]-4-carboxylic acid ester (91%) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0148] The 1H NMR and 1C NMR spectra of the product 2-(naphth-1-yl)ethyl[1,1'-biphenyl]-4-carboxylic acid ester are as follows: Figure 24-25 As shown, the specific data is 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] Example 13

[0150] Synthesis of [1,1'-biphenyl]-4-carboxylic acid isopropyl ester

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

[0152] The 1H NMR and 1C NMR spectra of the product [1,1'-biphenyl]-4-carboxylic acid isopropyl ester are as follows: Figure 26-27 As shown, the specific data is 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] Example 14

[0154] Synthesis of isoamyl 3-(4-methoxyphenyl)acrylate

[0155] 4-Methoxycinnamic acid (89.1 mg, 1 equivalent) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, isoamyl alcohol (544.8 μL, 10 equivalent) and diisopropylethylamine (434.6 μL, 5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, 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% and a Z:E ratio of 3.7:1.

[0156] The 1H NMR and 1C NMR spectra of the product (Z)-3-(4-methoxyphenyl)acrylate are as follows: Figures 28-29 As shown, the specific data is 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 1H NMR and 1C NMR spectra of the product (E)-3-(4-methoxyphenyl)acrylate are as follows: Figures 30-31 As shown, the specific data is 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] Example 15

[0159] Synthesis of benzyl benzoate

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

[0161] The 1H NMR and 1C NMR spectra of the product benzyl benzoate are as follows: Figures 32-33 As shown, the specific data is 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 equivalent) and Ir[dF(CF3)ppy]2(dtbbpy)PF6 (2.8 mg, 0.5 mol%) were added to a 12 mL headspace vial with a PTFE gasket. After evacuation, an SF6 balloon was inserted, and 3.0 mL of anhydrous tetrahydrofuran was added, followed by bubbling for 3 minutes. Then, methanol (202.5 μL, 10 equivalent) and diisopropylethylamine (434.6 μL, 5 equivalent) were added. The reaction system was irradiated under a 15 W blue LED light source at 465 nm and stirred for 20 hours. After the reaction was complete, the organic solvent was removed under vacuum, and dimethyl phthalate (52.2 mg, 60%) was obtained by silica gel column chromatography (petroleum ether:ethyl acetate volume ratio = 20:1).

[0165] The hydrogen NMR and carbon NMR spectra of the product dimethyl phthalate are as follows: Figures 34-35 As shown, the specific data is 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, the gas was irradiated and stirred at room temperature under SF6 gas at one atmosphere.

[0167] Example 17

[0168] Following the method of Example 1, using 1 and 2 as raw materials, the reaction conditions were changed and carried out according to the following formula. The changed conditions are shown in the table below. The remaining steps are the same as in Example 1. The yields are shown in the table below.

[0169]

[0170] 1 Standard conditions 98 2 2 (3 equivalent) 62 3 2 (5 equivalents) 70 4 2 (8 equivalents) 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 25W 365nm 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 (0.5 mmol, 1.0 equiv.), 2 (5.0 mmol, 10 equiv.), photocatalyst was Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.0025 mmol, 0.5 mol%), diisopropylethylamine (2.5 mmol, 5.0 equiv.), 1 atm of SF6 (balloon), solvent was tetrahydrofuran. The reaction system was irradiated under a 15W 465nm blue LED light source and stirred for 20 hours. The yield was then separated.

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

[0173] The structural formulas and yields of the products from each embodiment are shown in the table below:

[0174]

[0175]

[0176]

[0177] As shown in Examples 1-16, this invention uses readily available alcohols and carboxylic acids as reaction substrates, commercially available Ir[dF(CF3)ppy]2(dtbbpy)PF6 as a photocatalyst, and inexpensive and readily available N,N-diisopropylethylamine as a base. Under SF6 gas at one atmosphere, at room temperature, and using 15W 465nm blue light as the light source, ester compounds are synthesized simply and efficiently. This method exhibits good tolerance to aryl and heteroaryl carboxylic acids, as well as aliphatic carboxylic acids. Replacing the alcohol with other primary alcohols also yields good results, and secondary alcohols also show good reactivity. Therefore, there are no particularly strict limitations on the number and type of substituents in alcohols and carboxylic acids. Consequently, there are also no particularly strict limitations on the number and type of substituents in ester compounds and their derivatives. Therefore, this is a general synthetic method for ester compounds that is mild, simple to operate, and easy to industrially promote. Furthermore, this method effectively activates and utilizes SF6, a greenhouse gas, fully utilizing the decomposition products of SF6 to achieve the esterification reaction of carboxylic acids, turning SF6 waste into a valuable resource.

[0178] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for carboxylic acid esterification, characterized in that: It uses alcohols and carboxylic acids as raw materials, alkaline substances as additives, and organic solvents as reaction solvents, and reacts them under sulfur hexafluoride, photocatalyst, and light irradiation conditions to obtain ester compounds; the photocatalyst is one or a mixture of two of organic photocatalysts or transition metal photocatalysts; the organic photocatalyst is 4CZIPN or Mes-Acr. + ClO4 — Mes-Acr-Me + ClO4 - The light source is one or a mixture of the following: the transition metal photocatalyst is one or a mixture of two of Ir[dF(CF3)ppy]2(dtbbpy)PF6 and Ir(dtbbpy)ppy2PF6; the wavelength of the light source is 365~480nm.

2. The carboxylic acid esterification method according to claim 1, characterized in that: The structural formula of the carboxylic acid compound is as follows: , where 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, benzylenyl, and benzofuranyl.

4. The carboxylic acid esterification method according to claim 2, characterized in that: The substituents in the substituted aryl and substituted alkyl groups are all C1-C. 20 Alkyl, C2-C 20 alkenyl, C1-C 20 Hydroxyl groups, C6-C 20 aryl, 5-10 membered heteroaryl containing one or more of 1-3 O, N, S heteroatoms, C2-C 30 The ester group, the number of carbon atoms is 2-20 and contains one or more of the following heteroatoms: cycloalkyl, trifluoromethyl, halogen, dimethylamino, cyano, amino, and carboxyl.

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

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 as follows: 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, isoamyl alcohol, benzyl alcohol, and methanol.

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

11. The carboxylic acid esterification method according to claim 10, characterized in that: The organic base is N,N- Diisopropylethylamine.

12. The carboxylic acid esterification method according to claim 1, characterized in that: The molar ratio of the alcohols to the carboxylic acids is 1:1 to 20:

1.

13. 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.

14. 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.

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

16. The carboxylic acid esterification method according to claim 1, characterized in that: The reaction temperature is 0~50℃, and the reaction time is 5~48h.

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

18. The carboxylic acid esterification method according to any one of claims 1-17, characterized in that: The ratio of the carboxylic acid compound to the reaction solvent is 0.5~0.1 mmol: 1 mL.

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