A catalytic method for photocatalytic preparation of 2-furanacetic acid methyl ester compounds

Abstract

The application belongs to the field of catalytic method and catalyst technology, and particularly relates to a catalytic method for preparing 2-furan acetic acid methyl ester compounds by photocatalysis, which is based on a 1,4-carbonylation / cycloisomerization reaction of 1,3-alkyne with CO2 in a photocatalytic system, and CO2 is used as a carboxyl source; no photosensitizer is used; the method has high yield and good chemical selectivity; the reaction substrate range of the method is wide, and various functional groups such as methyl, methoxy, phenyl and halogen can be compatible with the reaction; 1,4-dihydropyridine compounds with different position substitutions on the phenyl group can also be compatible in the system and converted into target products. The reaction condition is mild, and the three-component coupling mode is used starting from simple and easily available substrate raw materials, so that the use of complex substrates is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of catalytic methods and catalysts, and particularly relates to a catalytic method for photocatalytic preparation of 2-furanacetic acid methyl ester compounds. BACKGROUND

[0002] Polysubstituted furan and its derivatives are an important class of heterocyclic compounds, whose core structure is a furan ring (a five-membered heterocyclic ring containing one oxygen atom) and multiple substituents (such as alkyl, aryl, halogen, carbonyl, etc.) are connected to the ring. This class of compounds has wide applications in the fields of organic synthesis, medicinal chemistry, material science, etc. Furanacetic acid is one of the polysubstituted furan compounds, which has a good active structure unit. For example, in the research of compounds for treating neurokinin-mediated diseases disclosed in US 2005 / 0256164 Al, it was found that the carboxylic acid fragment of a specific furanacetic acid fragment showed good activity.

[0003] The existing synthesis methods of polysubstituted furan and its derivatives mainly include: (1) direct functionalization of furan ring: introducing substituents on the existing furan ring through electrophilic substitution or metal-catalyzed coupling reaction; (2) construction of polysubstituted furan from non-furan precursors: such as Paal-Knorr synthesis method, which is to cyclize 1,4-diketone compounds under acidic conditions to generate furan; furfural (biomass derivative) is prepared into polysubstituted furan through oxidation, reduction or condensation reaction, such as the synthesis method of furanacetic acid ester compounds disclosed in invention patent CN112898247B, which is to use furfuryl alcohol compounds as raw materials, carbon monoxide gas as carbonyl source, ester compounds as additive, and perform carbonylation reaction in organic solvent under the action of catalyst to obtain furanacetic acid ester compounds. The catalyst is a combination of base, palladium metal salt and phosphine ligand. However, the above-mentioned methods have the problems of low selectivity and conversion rate; the use of noble metal palladium as catalyst is toxic to the environment and living organisms, and also has the problem of high cost; the use of carbon monoxide gas as carbonyl source is toxic, etc., which limits its application. In addition, the synthesis of furanacetic acid also faces the problems of single product structure and inability to construct polysubstituted furanacetic acid containing multiple functional groups, especially the green catalytic synthesis faces great challenges. Therefore, how to develop new and efficient synthesis methods has been the focus of attention of synthetic chemists.

[0004] In view of the above technical problems, the application provides a catalytic method for photocatalytic preparation of 2-furanacetic acid methyl ester compounds, which uses photocatalysis, utilizes light energy, and performs reaction at room temperature without high temperature, reduces greenhouse gas carbon dioxide to high-value carboxylic acid derivatives, significantly improves the conversion rate and selectivity of 2-furanacetic acid, develops a green and environmentally friendly preparation method, reduces pollution, and improves the efficiency of catalytic reaction and the preparation efficiency of 2-furanacetic acid methyl ester. SUMMARY

[0005] The application aims to provide a catalytic method for photocatalytic preparation of 2-furanacetic acid methyl ester compounds, comprising the following steps:

[0006]

[0007] wherein, R 1 is any one of t-butyl, phenyl, methyl; R 2 is any one of phenyl, 4-methoxyphenyl, 2-methoxyphenyl, 4-fluorophenyl, ester group; R 3 is any one of phenyl, 4-methylphenyl, 4-chlorophenyl, piperonyl, naphthyl, biphenyl;

[0008] (1) under an argon environment, 1,3-alkynyl compounds, 1,4-dihydropyridine compounds and a base are added into a Schlenk reaction tube, a solvent is added, and carbon dioxide gas is introduced;

[0009] (2) the reaction is stirred at room temperature under visible light until the 1,3-alkynyl compounds, 1,4-dihydropyridine compounds and the base added in step (1) disappear;

[0010] (3) after the reaction is completed, the reaction solution is acidified, the aqueous phase is extracted, the organic phases are combined and then washed, dried and concentrated under reduced pressure;

[0011] (4) the organic phase obtained in step (3) is dissolved in a mixed solution of dichloromethane and methanol, and a methylation reagent is added, and the reaction is carried out at room temperature, after the reaction is completed, the organic phase is concentrated under reduced pressure, filtered, and the target product is obtained.

[0012] Preferably, the base in step (1) is a carbonate, a formate, an alkoxy base or a hydroxide base.

[0013] Preferably, the carbonate in step (1) is cesium carbonate; the formate is one or more of cesium formate and potassium formate; the alkoxy salt is one or more of sodium methoxide, sodium tert-butoxide, lithium tert-butoxide or sodium tert-amylate; and the hydroxide base is potassium hydroxide.

[0014] Preferably, the solvent in step (1) is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, dichloromethane or toluene.

[0015] Preferably, the visible light in step (2) is 430-460 nm blue light, and the light source power is 1-100 W.

[0016] Preferably, the methylation reagent in step (4) is trimethylsilyl diazomethane.

[0017] Preferably, the ratio of dichloromethane to methanol in the mixed solution of dichloromethane and methanol in step (4) is 4:1.

[0018] Preferably, the reaction temperature in step (2) is 25-30°C and the reaction time is 24 hours.

[0019] The beneficial effects of this invention are as follows: This invention provides a photocatalytic method for the preparation of methyl furanoate compounds, based on the participation of CO2 in the 1,4-carbon acylation / cycloisomerization reaction of 1,3-enyne in the photocatalytic system, using CO2 as the carboxyl group source; it requires no photosensitizer; it has high yield and good chemoselectivity; the reaction substrate scope of this invention is broad, and various functional groups such as methyl, methoxy, phenyl, and halogens are compatible with this reaction; 1,4-dihydropyridine compounds with different substitutions at different positions on the phenyl group can also be compatible with the system and converted into the target product. The reaction conditions are mild, and it starts from simple and readily available substrate raw materials, adopting a three-component coupling method to avoid the use of complex substrates. Detailed Implementation

[0020] The following specific embodiments further illustrate the scope of protection of the present invention, but it should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0021] It should be noted that, unless otherwise specified, the methods described in the following embodiments are all conventional methods, and the reagents described are all commercially available.

[0022] In the following examples, trimethylsilyl diazomethane (TMSCHN2) is a safe and stable alternative to diazomethane (CH2N2), widely used in reactions such as methylation, cyclopropanation, and dipolar cycloaddition. Compared with highly toxic and explosive diazomethane, TMSCHN2 has advantages such as ease of handling, stable storage, and lower toxicity.

[0023] In the following examples, Ir[(ppy)2(dtbbpy)]PF6 is an important cationic iridium(III) complex that is widely used in organic optoelectronic materials (such as OLEDs, photocatalysis, and bioimaging) and photochemical research (such as photosensitization and photoredox catalysis).

[0024] In the following embodiments, Ir[(dF(CF3)ppy)2(dtbbpy)]PF6 is an iridium(III) complex modified with fluorine atoms and trifluoromethyl groups, belonging to cationic phosphorescent materials. It has advantages over traditional Ir(ppy)3 derivatives in photophysical properties, stability, and application range, especially in deep red / near-infrared luminescence, photocatalysis, and bioimaging.

[0025] In the following embodiments, the... fac -Ir(ppy)3 (tris(2-phenylpyridine)iridium) is the most classic green phosphorescent material among iridium(III) complexes and can be used as a photocatalyst.

[0026] In the following examples, the 4CzIPN is a typical thermally activated delayed fluorescence (TADF) material that achieves efficient reverse intersystem crossing (RISC) through a strong donor-acceptor (DA) structure of carbazole (Cz) and cyano (CN).

[0027] In the following examples, the Schlenk tube is a laboratory glass instrument designed specifically for anhydrous and oxygen-free operations, and is widely used in chemical reactions that are sensitive to air / moisture (such as organometallic synthesis, transition metal catalysis, free radical reactions, etc.).

[0028] Example 1

[0029] Under an argon atmosphere, 1-(4,4-dimethyl-3-methylpentan-1-ynyl)-4-methoxybenzene 1a (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3aa.

[0030]

[0031] The product test data are as follows:

[0032] Yellow oily substance, yield 75%.

[0033] 1 H NMR (400 MHz, CDCl3) δ 7.62 (d, J = 8.0 Hz, 2H), 7.37 – 7.34 (m,4H), 7.24 – 7.21 (m, 1H), 6.89 (d, J = 8.1 Hz, 2H), 6.59 (s, 1H), 5.31 (s,1H), 3.80 (s, 3H), 3.75 (s, 3H), 1.33 (s, 9H).

[0034] 13 C NMR (100 MHz, CDCl3) δ 171.4, 158.8, 151.4, 144.2, 132.6, 130.7,123.0, 129.0, 128.5, 127.0, 123.5, 113.8, 106.1, 55.2, 52.6, 49.9, 31.4,30.3.

[0035] Example 2

[0036] Under an argon atmosphere, 1-(4,4-dimethyl-3-methylpentan-1-ynyl)-4-fluorobenzene 1b (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3ba.

[0037]

[0038] The product test data are as follows:

[0039] Yellow solid, yield 52%.

[0040] 1 H NMR (400 MHz, CDCl3): δ 7.65 (d, J = 7.6 Hz, 2H), 7.45 – 7.38 (m,4H), 7.29 (d, J = 8.0 Hz, 1H), 7.10 – 7.06 (m, 2H), 6.60 (s, 1H), 5.38 (s,1H), 3.80 (s, 3H), 1.37 (s, 9H).

[0041] 13 C NMR (100 MHz, CDCl3): δ 171.0, 162.1 (d, J = 245.0 Hz), 151.6,143.6, 132.9, 132.6 (d, J = 4.0 Hz), 130.6, 130.5 (d, J = 8.0 Hz), 128.6,127.2, 123.5, 115.4 (d, J = 22.0 Hz), 106.2, 52.70, 49.8, 31.3, 30.3.

[0042] 19 F NMR (377 MHz, CDCl3): δ -115.2.

[0043] Example 3

[0044] Under an argon atmosphere, 1-(4,4-dimethyl-3-methylpentyl-1-ynyl)-2-methoxybenzene 1c (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3ca.

[0045]

[0046] The product test data are as follows:

[0047] Yellow solid, yield 70%.

[0048] 1 H NMR (400 MHz, CDCl3): δ 7.60 (d, J = 8.0 Hz, 2H), 7.35 – 7.31 (m,2H), 7.28 – 7.18 (m, 3H), 6.94 – 6.87 (m, 2H), 6.62 (s, 1H), 5.74 (s, 1H),3.85 (s, 3H), 3.74 (s, 3H), 1,29 (s, 9H).

[0049] 13 C NMR (100 MHz, CDCl3): δ 171.4, 156.4, 151.4, 143.8, 133.0, 130. 8, 129.8, 128. 6, 128.5, 127.0, 126.0, 123.4, 120.6, 110.2, 106.2, 55.4, 52.5,44.2, 31.1, 30.3.

[0050] Example 4

[0051] Under an argon atmosphere, 1-(4,4-dimethyl-3-methylpentyl-1-ynyl)-4-(4-ethylphenyl)benzene 1d (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3da.

[0052]

[0053] The product test data are as follows:

[0054] White solid, yield 70%.

[0055] 1 H NMR (400 MHz, CDCl3): δ 7.62 (d, J = 7.6 Hz, 2H), 7.56 (d, J = 8.4Hz, 2H), 7.51 – 7.46 (m, 4H), 7.36 – 7.33 (m, 2H), 7.26 – 7.20 (m, 3H), 6.60 (s, 1H), 5.40 (s, 1H), 3.76 (s, 3H), 2.68 (q, J = 7.6, 15.2 Hz, 2H), 1.34 (s,9H), 1.26 (t, J = 7.6 Hz, 3H).

[0056] 13C NMR (100 MHz, CDCl3): δ 171.2, 151.5, 143.8, 143.4, 140.2, 138.1,135.5, 132.9, 130.7, 129.3, 128.6, 128.2, 127.1, 127.0, 123.5, 106.2, 52.7,50.4, 31.4, 30.4, 28.5, 15.6.

[0057] Example 5

[0058] Under an argon atmosphere, 0.3 mmol of 4-methoxy-1-(non-1-en-3-yn-2-yl)benzene 1e, 0.2 mmol of ethyl 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a, and 0.6 mmol of cesium carbonate were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3ea.

[0059]

[0060] The product test data are as follows:

[0061] Yellow oily substance, yield 50%.

[0062] 1 H NMR (400 MHz, CDCl3): δ 7.69 (d, J = 7.2 Hz, 2H), 7.42 – 7.37 (m,4H), 7.28 – 7.24 (m, 1H), 6.97 (d, J= 8.8 Hz, 2H), 6.73 (s, 1H), 3.85 (s,3H), 3.73 (s, 3H), 2.13 – 1.97 (m, 2H), 1.26 – 1.19 (m, 6H), 0.81 – 0.78 (m,3H).

[0063] 13 C NMR (100 MHz, CDCl3): δ 172.5, 158.7, 152.4, 146.1, 130.6, 129.2,128.6, 127.3, 125.8, 125.4, 123.6, 114.1, 106.8, 55.3, 52.3, 43.6, 31.3,30.5, 26.9, 22.3, 13.9.

[0064] Example 6

[0065] Under an argon atmosphere, but-3-en-1-ynylbenzene 1f (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate ethyl ester 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and trimethylsilyldiazomethane (0.4 mmol) was added. The reaction was carried out at room temperature for 1 hour. After the reaction was completed, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3fa.

[0066]

[0067] The product test data are as follows:

[0068] Yellow oily substance, yield 51%.

[0069] 1 H NMR (400 MHz, CDCl3): δ 7.53 (d, J = 8.4 Hz, 2H), 7.34 (d,J = 8.0Hz, 2H), 7.29 – 7.22 (m, 5H), 7.16 – 7.12 (m, 1H), 6.50 (d, J = 3.6 Hz, 1H), 6.19 (d, J = 3.2 Hz, 1H), 5.01 (s, 1H), 3.66 (s, 3H).

[0070] 13 C NMR (100 MHz, CDCl3): δ 170.9, 153.6, 151.1, 136.0, 130.6, 128.7,128.6, 128.5, 127.8, 127.2, 123.6, 110.2, 105.7, 52.6, 51.4.

[0071] Example 7

[0072] Under an argon atmosphere, 1 g (0.3 mmol) of (3-methylbut-3-en-1-ynyl)benzene, 2a (0.2 mmol) of 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate, and 0.6 mmol of cesium carbonate were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1-20:1) to obtain the target product 3ga.

[0073]

[0074] The product test data are as follows:

[0075] Yellow oily substance, yield 59%.

[0076] 1 H NMR (400 MHz, CDCl3): δ 7.52 (d, J= 8.4 Hz, 2H), 7.33 (d, J = 8.4Hz, 2H), 7.28 – 7.24 (m, 4H), 7.22 – 7.18 (m, 1H), 7.15 – 7.12 (m, 1H), 6.40(s, 1H), 5.02 (s, 1H), 3.67 (s, 3H), 1.91 (s, 3H).

[0077] 13 C NMR (100 MHz, CDCl3): δ 171.0, 152.3, 145.4, 136.3, 130.7, 128.7,128.5, 127.5, 127.1, 123.6, 118.9, 108.7, 52.6, 49.4, 10.0.

[0078] Example 8

[0079] Under an argon atmosphere, 1-(but-3-en-1-ynyl)-4-methylbenzene 1 h (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1-20:1) to obtain 3 ha of the target product.

[0080]

[0081] The product test data are as follows:

[0082] Yellow oily substance, yield 53%.

[0083] 1 H NMR (400 MHz, CDCl3): δ 7.61 (d, J= 8.8 Hz, 2H), 7.36 – 7.30 (m,4H), 7.24 – 7.20 (m, 1H), 7.17 (d, J = 7.6 Hz, 2H), 6.58 (d, J = 3.2 Hz, 1H), 6.26 (d, J = 3.2 Hz, 1H), 5.06 (s, 1H), 3.75 (s, 3H), 2.34 (s, 3H).

[0084] 13 C NMR (100 MHz, CDCl3): δ 171.1, 153.6, 151.3, 137.6, 133.0, 130.7,129.4, 128.6, 128.4, 127.2, 123.6, 110.1, 105.7, 52.6, 51.0, 21.1.

[0085] Example 9

[0086] Under an argon atmosphere, (4-phenylbut-1-en-3-yn-2-yl)benzene 1i (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide gas. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1-20:1) to obtain the target product 3ia.

[0087]

[0088] The product test data are as follows:

[0089] Yellow oily substance, yield 65%.

[0090] 1H NMR (400 MHz, CDCl3): δ 7.69 (d, J = 8.4 Hz, 2H), 7.64 – 7.60 (m,4H), 7.48 – 7.43 (m, 4H), 7.39 – 7.35 (m, 3H), 7.32 – 7.28 (m, 1H), 6.64 (s,1H), 5.39 (s, 1H), 3.77 (s, 3H), 1.35 (s, 9H).

[0091] 13 C NMR (100 MHz, CDCl3): δ 171.2, 151.3, 144.0, 140.6, 139.6, 136.8,133.0, 129.7, 128.9, 128.8, 128.5, 127.4, 127.3, 127.2, 126.8, 123.9, 106.4,52.6, 50.7, 31.4, 30.4.

[0092] Example 10

[0093] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-4-[(2-methoxyphenyl)carbonyl]-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2b (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3jb.

[0094]

[0095] The product test data are as follows:

[0096] Yellow oily substance, yield 71%.

[0097] 1 H NMR (400 MHz, CDCl3): δ 7.78 – 7.76 (m, 2H), 7.40 (d, J = 8.4 Hz,2H), 7.34 – 7.31 (m, 2H), 7.28 – 7.17 (m, 2H), 7.00 – 6.96 (m, 1H), 6.92 (d, J = 8.4 Hz, 1H), 6.86 (s, 1H), 5.37 (s, 1H), 3.92 (s, 3H), 3.73 (s, 3H), 1.33(s, 9H).

[0098] 13 C NMR (100 MHz, CDCl3): δ 171.4, 155.2, 148.0, 143.0, 137.1, 132.8,129.0, 128.5, 127.8, 127.4, 126.0, 120.8, 119.7, 111.1, 110.8, 55.4, 52.7,50.7, 31.5, 30.4.

[0099] Example 11

[0100] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-4-[(3-methoxyphenyl)carbonyl]-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2c (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3jc.

[0101]

[0102] The product test data are as follows:

[0103] Yellow solid, yield 67%.

[0104] 1 H NMR (400 MHz, CDCl3): δ 7.41 (d, J = 8.4 Hz, 2H), 7.36 – 7.32 (m,2H), 7.30 – 7.20 (m, 3H), 7.13 (s, 1H), 6.78 (d, J = 8.0 Hz, 1H), 6.58 (s,1H), 5.35 (s, 1H), 3.83 (s, 3H), 3.74 (s, 3H), 1.32 (s, 9H).

[0105] 13 C NMR (100 MHz, CDCl3): δ 171.1, 159.7, 151.3, 143.9, 136.8, 132.9,132.0, 129.6, 128.9, 128.5, 127.4, 116.2, 112.7, 109.0, 106.5, 55.2, 52.6,50.7, 31.4, 30.3.

[0106] Example 12

[0107] Under an argon atmosphere, (4,4-dimethyl-3-methylpentyl-1-ynyl)benzene 1j (0.3 mmol), 4-(benzo[d][1,3]dioxanepentanyl-5-ylcarbonyl)-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2d (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3jd.

[0108]

[0109] The product test data are as follows:

[0110] Yellow oily substance, yield 60%.

[0111] 1 H NMR (400 MHz, CDCl3): δ 7.40 (d, J = 8.4 Hz, 2H), 7.36 – 7.32 (m,2H), 7.29 – 7.25 (m, 1H), 7.12 – 7.08 (m, 2H), 6.79 (d, J = 8.0 Hz, 1H), 6.44(s, 1H), 5.95 (s, 2H), 5.34 (s, 1H), 3.74 (s, 3H), 1.31 (s, 9H).

[0112] 13C NMR (100 MHz, CDCl3): δ 171.2, 151.3, 147.8, 146.8, 143.2, 136.9,132.8, 128.8, 128.5, 127.4, 125.3, 117.4, 108.5, 105.0, 104.4, 101.0, 52.6,50.6, 31.4, 30.3.

[0113] Example 13

[0114] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-2,6-dimethyl-4-[(4-methylphenyl)carbonyl]-1,4-dihydropyridine-3-carboxylate 2e (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to give the target product 3je.

[0115]

[0116] The product test data are as follows:

[0117] Yellow solid, yield 79%.

[0118] 1 H NMR (400 MHz, CDCl3): δ 7.55 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 7.2Hz, 2H), 7.40 – 7.36 (m, 2H), 7.33 – 7.29 (m, 1H), 7.19 (d, J= 7.6 Hz, 2H), 6.57 (s, 1H), 5.40 (ss, 1H), 3.78 (s, 3H), 2.38 (s, 3H), 1.36 (s, 9H).

[0119] 13 C NMR (100 MHz, CDCl3): δ 171.2, 151.7, 143.4, 136.9, 136.8, 132.7,129.2, 128.8, 128.4, 128.0, 127.3, 123.4, 105.3, 52.5, 50.6, 31.3, 30.3,21.2.

[0120] Example 14

[0121] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-2,6-dimethyl-4-[(4-phenylphenyl)carbonyl]-1,4-dihydropyridine-3-carboxylate 2f (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3jf.

[0122]

[0123] The product test data are as follows:

[0124] White solid, yield 57%.

[0125] 1 H NMR (400 MHz, CDCl3): δ 7.70 (d, J= 8.4 Hz, 2H), 7.64 – 7.60 (m,4H), 7.48 – 7.44 (m, 4H), 7.39 – 7.36 (m, 3H), 7.34 – 7.29 (m, 1H), 6.65 (s,1H), 5.40 (s, 1H), 3.78 (s, 3H), 1.36 (s, 9H).

[0126] 13 C NMR (100 MHz, CDCl3): δ 171.2, 151.3, 144.0, 140.6, 139.6, 136.8,133.0, 129.7, 128.9, 128.8, 128.5, 127.4, 127.3, 127.2, 126.8, 123.9, 106.4,52.6, 50.7, 31.4, 30.4.

[0127] Example 15

[0128] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2a (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide gas. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3ja.

[0129]

[0130] The product test data are as follows:

[0131] White solid, yield 79%.

[0132] 1H NMR (400 MHz, CDCl3) δ 7.61 (d, J = 8.4 Hz, 2H), 7.42 (d, J = 8.4Hz, 2H), 7.37 – 7.33 (m, 4H), 7.30 (d, J = 8.4 Hz, 1H), 7.24 – 7.20 (m, 1H), 6.59 (s, 1H), 5.36 (s, 1H), 3.75 (s, 3H), 1.33 (s, 9H).

[0133] 13 C NMR (100 MHz, CDCl3) δ 171.2, 151.6, 143.9, 136.9, 132.9, 130.8,129.0, 128.6, 128.5, 127.4, 127.1, 123.6, 106.2, 52.7, 50.8, 31.4, 30.4.

[0134] Example 16

[0135] Under an argon atmosphere, 1k (0.3 mmol) of 4-chloro-1-(non-1-en-3-yn-2-yl)benzene, 2a (0.2 mmol) of 4-phenylcarbonyl-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate, and 0.6 mmol of cesium carbonate were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1-20:1) to obtain the target product 3 kDa.

[0136]

[0137] The product test data are as follows:

[0138] Yellow oily substance, yield 67%.

[0139] 1 H NMR (400 MHz, CDCl3) δ 7.68 (d, J = 8.4 Hz, 2H), 7.43 – 7.37 (m,6H), 7.29 – 7.25 (m, 1H), 6.72 (s, 1H), 3.85 (dd, J = 8.8, 6.8 Hz, 1H), 3.73(s, 3H), 2.15 – 1.99 (m, 2H), 1.28 – 1.19 (m, 6H), 0.81 – 0.78 (m, 3H).

[0140] 13 C NMR (100 MHz, CDCl3) δ 172.2, 152.8, 146.7, 133.0, 131.8, 130.3,129.4, 128.9, 128.6, 127.5, 124.8, 123.7, 106.4, 52.3, 43.7, 31.3, 30.4,26.8, 22.3, 13.9.

[0141] Example 17

[0142] Under argon atmosphere, 1 g (0.3 mmol) of (4,4-dimethyl-3-methylpentan-1-ynyl)benzene, 2 g (0.2 mmol) of 4-[(4-chlorophenyl)carbonyl]-5-(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate, and 0.6 mmol of cesium carbonate were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain 3 j g of the target product.

[0143]

[0144] The product test data are as follows:

[0145] White solid, yield 61%.

[0146] 1 H NMR (400 MHz, CDCl3) δ 7.52 (d, J = 8.4 Hz, 2H), 7.41 – 7.29 (m,7H), 6.58 (s, 1H), 5.36 (s, 1H), 3.76 (s, 3H), 1.33 (s, 9H).

[0147] 13 C NMR (100 MHz, CDCl3) δ 171.1, 150.5, 144.2, 136.7, 133.1, 132.6,129.2, 128.84, 128.75, 128.5, 127.5, 124.8, 106.6, 52.6, 50.7, 31.3, 30.4.

[0148] Example 18

[0149] Under argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-4-[(4-methoxyphenyl)carbonyl]-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2h (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide gas. The reaction was stirred at room temperature under 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, the aqueous phase was extracted five times with ethyl acetate, the organic phases were combined, washed three times with saturated brine, and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3jh.

[0150]

[0151] The product test data are as follows:

[0152] White solid, yield 82%.

[0153] 1 H NMR (400 MHz, CDCl3) δ 7.44 (d, J = 8.4 Hz, 2H), 7.31(d, J = 7.2Hz, 2H), 7.25 – 7.21 (m, 2H), 7.17 – 7.14 (m, 1H), 6.77 (d, J = 8.8 Hz, 2H), 6.35 (s, 1H), 5.25 (s, 1H), 3.67 (s, 3H), 3.62 (s, 3H), 1.22 (s, 9H).

[0154] 13 C NMR (100 MHz, CDCl3) δ 171.2, 158.8, 151.5, 143.0, 137.0, 132.7,128.8, 128.4, 127.3, 124.9, 123.8, 113.9, 104.5, 55.1, 52.4, 50.6, 31.3,30.3.

[0155] Example 19

[0156] Under an argon atmosphere, (4,4-dimethyl-3-methylpentan-1-ynyl)benzene 1j (0.3 mmol), 5-(ethoxycarbonyl)-4-(furan-2-ylcarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylate 2i (0.2 mmol), and cesium carbonate (0.6 mmol) were added to a dry 10 mL Schlenk reaction tube. 3 mL of dimethyl sulfoxide was added, followed by three purgings with carbon dioxide gas. The reaction was stirred at room temperature under a 12 W 460 nm LED blue light for 24 h until the starting material disappeared. After the reaction was complete, the reaction solution was acidified with dilute hydrochloric acid, and the aqueous phase was extracted five times with ethyl acetate. The combined organic phases were washed three times with saturated brine and dried with anhydrous Na₂SO₄. The organic phase was then concentrated under reduced pressure. The organic phase was then dissolved in a 5 mL mixture of dichloromethane and methanol (dichloromethane:methanol = 4:1), and 0.4 mmol of trimethylsilyldiazomethane was added. The reaction was carried out at room temperature for 1 hour. After the reaction was complete, the organic phase was concentrated under reduced pressure and filtered through a silica gel column (PE:EA = 60:1 - 20:1) to obtain the target product 3ji.

[0157]

[0158] The product test data are as follows:

[0159] Yellow oily substance, yield 60%.

[0160] 1 H NMR (400 MHz, CDCl3) δ 7.39 – 7.31 (m, 5H), 7.29 – 7.24 (m, 1H), 6.50 – 6.48 (m, 2H), 6.42 – 6.41 (m, 1H), 5.35 (s, 1H), 3.73 (s, 3H), 1.31(s, 9H).

[0161] 13 C NMR (100 MHz, CDCl3) δ 171.0, 146.6, 144.5, 143.6, 141.5, 136.7,132.6, 128.8, 128.5, 127.4, 111.3, 106.2, 104.9, 52.6, 50.5, 31.3, 30.3.

[0162] Example 20

[0163] Following the method described in Example 15, the photocatalyst, alkali, or solvent were changed simultaneously or individually, and their effects on the yield were observed.

[0164]

[0165] Table 1 shows the comparison of product yields with changes in conditions.

[0166] Table 1 Screening of Reaction Conditions

[0167] seq. photocatalyst base solvent yield (%) 1 PC1 Cs2CO3 DMSO 59 2 PC1 HCOOCs DMSO 16 3 PC1 MeONa DMSO 27 4 PC1 LiO t Bu]]> DMSO 50 5 PC1 NaO t Bu]]> DMSO 55 6 PC1 Cs2CO3 DMA 45 7 PC1 Cs2CO3 NMP 49 8 PC1 Cs2CO3 CH3CN N.R. 9 PC2 Cs2CO3 DMSO 69 10 PC3 Cs2CO3 DMSO 33 11 PC4 Cs2CO3 DMSO 67 12 - Cs2CO3 DMSO 79 13 - - DMSO N.R. 14 a ]] - Cs2CO3 DMSO N.R.

[0168] Note: PC1 = Ir[(ppy)2dtbbpy]PF6, PC2 = Ir[(dF(CF3)ppy)2dtbbpy]PF6, PC3 = fac -Ir(ppy)3, PC4 = 4CzIPN, the NMR yields are shown in Table 1, with trimethoxybenzene as an internal standard. a No light exposure; other groups of photos are under blue light.

[0169] As shown in Table 1, the separation yield reached 79% under the reaction conditions of this invention. A series of control experiments demonstrated that light and alkali play indispensable roles in the reaction; the target product cannot be obtained without either. The reaction yield reached its highest level in the absence of a photosensitizer. The yield decreased with different alkalis, with strong alkalis showing better results than weak alkalis. The yield decreased with changing the solvent DMA, mainly due to residual feedstock. In summary, it can be seen that both 1,3-enyne compounds and 1,4-dihydropyridine compounds can synthesize methyl furanoate compounds with high yields and good chemoselectivity. Various functional groups, such as methyl, methoxy, phenyl, and halogen, are compatible with this reaction. 1,4-dihydropyridine compounds with different substitutions at different positions on the phenyl group can also be compatible with the system and converted into the target product.

[0170] In summary, this invention provides a photocatalytic method for the preparation of methyl furanoate compounds. It is based on the photocatalytic system where CO2 participates in the 1,4-carbon acylation / cycloisomerization reaction of 1,3-enyne, using CO2 as the carboxyl group source. It requires no photosensitizer, exhibits high yield and good chemoselectivity, and has a broad substrate scope, compatible with various functional groups such as methyl, methoxy, phenyl, and halogens. 1,4-dihydropyridine compounds with different substitutions at different positions on the phenyl group can also be compatible with the system and converted into the target product. The reaction conditions are mild, and the method uses a three-component coupling approach starting from simple and readily available substrates, avoiding the use of complex substrates.

Claims

1. A photocatalytic method for preparing methyl furanoate compounds, characterized in that, Includes the following steps: ； Among them, R 1 It is any one of tert-butyl, phenyl, and methyl; R 2 It is any one of phenyl, 4-methoxyphenyl, 2-methoxyphenyl, and 4-fluorophenyl; R 3 It is any one of phenyl, 4-methylphenyl, 4-chlorophenyl, piperyl, naphthyl, and biphenyl; (1) In an argon atmosphere, 1,3-enyne compounds, 1,4-dihydropyridine compounds and bases are added to a Schlenk reaction tube, a solvent is added, and carbon dioxide gas is introduced. (2) Stir the reaction at room temperature and under visible light until the 1,3-enyne compounds, 1,4-dihydropyridine compounds and base added in step (1) disappear; (3) After the reaction is complete, acidify the reaction solution, extract the aqueous phase, combine the organic phases, wash, dry, and concentrate under reduced pressure; (4) Dissolve the organic phase obtained in step (3) in a mixed solution of dichloromethane and methanol, add a methylating agent, react at room temperature, concentrate the organic phase under reduced pressure after the reaction is complete, filter, and obtain the target product; the base mentioned in step (1) is a carbonate, formate, alkoxy salt or hydroxide base; the carbonate is cesium carbonate; the formate is one or more of cesium formate and potassium formate; the alkoxy salt is one or more of sodium methoxide, sodium tert-butoxide, lithium tert-butoxide or sodium tert-pentoxide; the hydroxide base is potassium hydroxide; the methylating agent mentioned in step (4) is trimethylsilyldiazomethane.

2. The catalytic method as described in claim 1, characterized in that, The solvent in step (1) is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, dichloromethane or toluene.

3. The catalytic method as described in claim 1, characterized in that, The visible light mentioned in step (2) is 430-460 nm blue light, and the power of the light source is 1-100W.

4. The catalytic method according to claim 1, characterized in that, In step (4), the ratio of dichloromethane to methanol in the mixed solution of dichloromethane and methanol is 4:

1.

5. The catalytic method as described in claim 1, characterized in that, The reaction temperature in step (2) is 25-30℃ and the reaction time is 24 hours.

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