A method for preparing acetal compounds promoted by visible light

Abstract

The present invention relates to the technical field of organic synthetic chemistry, and specifically to a method for preparing acetal compounds using visible light. The method uses alcohol and vinyl ether as reaction raw materials, conducts a stirring reaction under certain temperature conditions and irradiation with a light source, and obtains an acetal compound. The method employs simple reaction conditions and, for the first time, achieves the alkylation reaction of a hydroxyl compound in the absence of a photocatalyst. The method has the advantages of being environmentally friendly, having mild conditions, being easy to operate, having high atom economy, and having a wide range of substrate applicability. The method also provides a convenient means for constructing acetal compounds with potential biological activity and pharmacological effects.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthetic chemistry, and in particular to a method for preparing acetal compounds promoted by visible light. Background Art

[0002] Acetals are an important class of organic compounds. Due to their distinctive odor, they are used as cosmetic flavoring agents and food additives, and can also be added to biodiesel fuel as an antifreeze agent. In organic synthesis, acetals are often used as important intermediates for carbonyl protection. Therefore, the synthesis of acetal compounds has always been a key research topic in organic chemistry and related industries. The classic acetal synthesis method generally involves the reaction of an aldehyde with an alcohol under acid catalysis to form the acetal.

[0003] Hydroetherification of alkenes is also one of the most direct and efficient methods for preparing acetal compounds. This type of reaction can directly produce acetals from readily available alcohols and olefins in a single step. For example, Williams et al. used Al(OTf)3 as a catalyst to hydroetherify hydroxyl compounds with olefins to produce acetals (Tetrahedron, 2010, 4573-4576). Bonnet-Delpon et al. discovered that hexafluoroisopropanol can be hydroetherified with dihydrofuran to produce fluoroacetals (Adv. Synth. Catal. 2006, 348, 118–124).

[0004] Visible light is a clean, pollution-free energy source, and visible-light-promoted organic synthesis reactions have seen significant development in recent years. However, literature research indicates that methods for synthesizing acetals through the visible-light-promoted hydroetherification of alcohols and olefinic ethers without a catalyst have yet to be reported. This application provides a novel method for synthesizing acetal compounds using visible-light-promoted reactions without the use of a photocatalyst. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing acetal compounds promoted by visible light, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing an acetal compound promoted by visible light, comprising the following steps:

[0007] In an organic solvent, an alcohol having a structure represented by formula (I) and an ether having a structure represented by formula (II) are used as reaction raw materials. The reaction is carried out under visible light irradiation and stirred in an open state at room temperature. After the reaction is completed, the reaction solution is decompressed to remove the solvent to obtain a crude product. The crude product is purified by column chromatography to obtain an acetal compound having a structure represented by formula (III). The reaction equation is shown below:

[0008]

[0009] Wherein, the compound of formula (I) is a hydroxy compound, the substituent R is a C1-C20 straight-chain or branched hydrocarbon group, a C3-C8 cyclic hydrocarbon group, a phenyl group, a furanyl group, a thienylmethyl group, a naphthylmethyl group, or a benzyl group substituted with one or more substituents, and the substituent is an alkoxy group, an alkyl group, a cyano group, a nitro group, a trifluoromethyl group, a trifluoromethoxy group, a carboxyl group, an amino group, or a formyl group;

[0010] The compound of formula (II) is an open-chain vinyl ether or 2,3-dihydrofuran, 3,4-dihydropyran; the substituent R' is a C1-C20 hydrocarbon group, a C4-C7 cycloalkyl group, a benzyl group, or a phenyl group substituted with one or more substituents, wherein the substituent is an alkoxy group, an alkyl group, a trifluoromethyl group, a nitro group, a halogen group, or an amide group;

[0011] Preferably, the molar ratio of the alcohol of the structure represented by formula (I) to the enol of the structure represented by formula (II) is 1:1-1:2, preferably 1:2.

[0012] Preferably, the organic solvent is any one of dichloromethane, dichloroethane, chloroform, carbon tetrachloride and nitromethane, preferably carbon tetrachloride.

[0013] Preferably, the visible light is any one of sunlight, mercury lamp, fluorescent lamp, tungsten lamp, and LED lamp, preferably LED lamp.

[0014] Preferably, the reaction time is 10 h to 30 h.

[0015] Preferably, after the reaction is completed, the reaction solution is concentrated under reduced pressure, and the concentrate is separated by column chromatography using a mixture of petroleum ether and ethyl acetate as an eluent, wherein the volume ratio of petroleum ether:ethyl acetate is (1-60):1, the eluate is collected, and the solvent is rotary evaporated to obtain the acetal compound represented by formula (III).

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention uses cheap and readily available alcohols and olefin ethers as raw materials, does not require a photocatalyst, has low cost, high reaction efficiency, does not involve metals and oxidants, and is green and environmentally friendly.

[0018] 2. The present invention can obtain the target product in just one step, with high yield, good functional group compatibility, and simple post-processing. The obtained product is an important drug and organic synthesis intermediate. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] The present invention provides the following technical solution: a method for preparing an acetal compound promoted by visible light, comprising the following steps:

[0021] In an organic solvent, an alcohol having a structure represented by formula (I) and an ether having a structure represented by formula (II) are used as reaction raw materials. The reaction is carried out under visible light irradiation and stirred in an open state at room temperature. After the reaction is completed, the reaction solution is decompressed to remove the solvent to obtain a crude product. The crude product is purified by column chromatography to obtain an acetal compound having a structure represented by formula (III). The reaction equation is shown below:

[0022]

[0023] Wherein, the compound of formula (I) is a hydroxy compound, the substituent R is a C1-C20 straight-chain or branched hydrocarbon group, a C3-C8 cyclic hydrocarbon group, a phenyl group, a furanyl group, a thienylmethyl group, a naphthylmethyl group, or a benzyl group substituted with one or more substituents, and the substituent is an alkoxy group, an alkyl group, a cyano group, a nitro group, a trifluoromethyl group, a trifluoromethoxy group, a carboxyl group, an amino group, or a formyl group;

[0024] The compound of formula (II) is an open-chain vinyl ether or 2,3-dihydrofuran, 3,4-dihydropyran; the substituent R' is a C1-C20 hydrocarbon group, a C4-C7 cycloalkyl group, a benzyl group, or a phenyl group substituted with one or more substituents, wherein the substituent is an alkoxy group, an alkyl group, a trifluoromethyl group, a nitro group, a halogen group, or an amide group.

[0025] Example 1

[0026] The reaction equation is shown below:

[0027]

[0028] Under open conditions, benzyl alcohol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 15:1) to obtain 83 mg of the target compound with a yield of 93%.

[0029] The NMR spectrum data of the obtained product are: 1H NMR (400MHz, CDCl3): δ7.82–6.60(m,5H),5.22(dd,J=3.9,2.2Hz,1H),4.72(d,J=11.8Hz,1H),4. 48(d,J=11.8Hz,1H),4.07–3.77(m,2H),2.10–1.99(m,1H),1.98–1.92(m,2H),1.92–1.78(m,1H); 13 C NMR (100MHz, CDCl3): δ138.4,128.4,127.9,127.5,103.1,68.8,67.1,32.4,23.5.

[0030] Example 2

[0031] The reaction equation is shown below:

[0032]

[0033] Under open conditions, 4-fluorobenzyl alcohol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 10:1) to obtain 93 mg of the target compound with a yield of 95%.

[0034] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.37–7.26(m,2H),7.02(t,J=8.7Hz,2H),5.20(t,J=3.1Hz,1H),4.67(d,J=11.7Hz ,1H),4.43(d,J=11.7Hz,1H),4.00–3.87(m,2H),2.12–1.98(m,1H),1.98–1.89(m,2H),1.90–1.79(m,1H); 13 C NMR (100 MHz, CDCl3):

[0035] δ162.3(d,J C-F =245.2Hz),134.1(d,J C-F =3.2Hz),129.6(d,J C-F =

[0036] 8.1Hz),115.2(d,J C-F=21.3Hz),103.1,68.1,67.1,32.4,23.5; 19 FNMR (376MHz, CDCl3): δ-115.2.

[0037] Example 3

[0038] The reaction equation is shown below:

[0039]

[0040] Under open conditions, 4-chlorobenzyl alcohol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 15:1) to obtain 95 mg of the target compound with a yield of 90%.

[0041] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.30(d,J=8.5Hz,2H),7.26(d,J=8.5Hz,2H),5.19(t,J=3.1Hz,1H),4.67(d,J=12.1H z,1H),4.43(d,J=12.1Hz,1H),4.00–3.83(m,2H),2.09–2.00(m,1H),1.95–1,92(m,2H),1.90–1.79(m,1H); 13 C NMR (100MHz, CDCl3): δ136.9,133.2,129.1,128.5,103.2,68.0,67.1,32.4,23.5.

[0042] Example 4

[0043] The reaction equation is shown below:

[0044]

[0045] Under open conditions, 4-methylbenzyl alcohol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 15:1) to obtain 85 mg of the target compound with a yield of 89%.

[0046] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.23(d,J=7.6Hz,2H),7.14(d,J=7.7Hz,2H),5.29–5.02(m,1H),4.67(d,J=11.6Hz,1H),4 .43(d,J=11.6Hz,1H),4.09–3.79(m,2H),2.33(s,3H),2.09–1.98(m,1H),1.96–1.89(m,2H),1.88–1.79(m,1H); 13 CNMR (100MHz, CDCl3): δ137.2, 135.3, 129.1, 128.0, 103.0, 68.7, 67.0, 32.4, 23.5, 21.2.

[0047] Example 5

[0048] The reaction equation is shown below:

[0049]

[0050] Under open conditions, benzhydrol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 10:1) to obtain 108 mg of the target compound with a yield of 85%.

[0051] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.39–7.16(m,10H),5.77(s,1H),5.17(d,J=4.3Hz,1H),4.10–3.76(m,2H),2.23–1.97(m,2H),1.98–1.73(m,2H);13 CNMR (100MHz, CDCl3): δ143.0,141.5,128.5,128.2,127.8,127.6,127.1,126.9,101.2,78.5,67.1,32.4,23.5.

[0052] Example 6

[0053] The reaction equation is shown below:

[0054]

[0055] Under open conditions, 2-thiophene methanol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 20:1) to obtain 83 mg of the target compound with a yield of 90%.

[0056] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.25–7.15(m,1H),6.94(d,J=3.4Hz,1H),6.91–6.88(m,1H),5.17(t,J=3.1Hz,1H),4.76(d, J=12.4Hz,1H),4.61(d,J=12.4Hz,1H),3.94–3.81(m,2H),2.02–1.91(m,1H),1.89–1.84(m,2H),1.81–1.72(m,1H); 13 C NMR (100MHz, CDCl3): δ141.0,126.7,126.4,125.8,102.6,67.2,63.1,32.3,23.4.

[0057] Example 7

[0058] The reaction equation is shown below:

[0059]

[0060] Under open conditions, 2-naphthylmethanol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent by rotary evaporation, and the residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 20:1) to obtain 104 mg of the target compound with a yield of 91%.

[0061] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ8.01(d,J=8.2Hz,1H),7.78–7.72(d,J=8.2Hz,1H),7.69(d,J=8.2Hz,1H),7.48–7.27(m,4H),5.22–5.19(m,1H), 5.14(d,J=11 .7Hz,1H),4.74(d,J=11.8Hz,1H),3.93(td,J=7.9,6.1Hz,1H),3.84(td,J =7.8,5.7Hz,1H),2.09–1.87(m,1H),1.89–1.81(m,2H),1.78–1.70(m,1H); 13 C NMR (100MHz, CDCl3): δ133.8,133.7,131.9,128.6,128.5,126.7,126.2,125.8,125.4,124.1,103.2,67.3,67.3,32.5,23.6.

[0062] Example 8

[0063] The reaction equation is shown below:

[0064]

[0065] Under open conditions, phenol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 25:1) to obtain 66 mg of the target compound with a yield of 80%.

[0066] The NMR spectrum data of the obtained product are: 1H NMR (400MHz, CDCl3): δ7.34–7.20(m,5H),4.89(t,J=7.2Hz,1H),4.17–4.03(m,1 H),4.00–3.83(m,1H),2.36–2.25(m,1H),2.02–1.93(m,2H),1.84–1.72(m,1H); 13 C NMR (101 MHz, CDCl3): δ 13 C NMR (100MHz, CDCl3) δ143.7,128.4,127.5,125.9,80.8,69.0,34.9,26.2.

[0067] Example 9

[0068] The reaction equation is shown below:

[0069]

[0070] Under open conditions, cinnamyl alcohol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 15:1) to obtain 87 mg of the target compound with a yield of 85%.

[0071] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.39(d,J=7.2Hz,2H),7.31(t,J=7.5Hz,2H),7.28–7.15(m,1H),6.61(d,J=15.9Hz,1H),6.35–6.25(m,1H),5.23(t,J=3.1 Hz,1H),4.34(dd,J=12.7,5.7Hz,1H),4.12(dd,J=12.8,6.6Hz,1H),3.9 9–3.85(m,2H),2.12–1.97(m,1H),1.98–1.92(m,2H),1.91–1.78(m,1H); 13 C NMR (100MHz, CDCl3): δ136.8,132.4,128.5,127.6,126.5,126.0,103.2,67.6,67.1,32.4,23.5.

[0072] Example 10

[0073]

[0074] Under open conditions, β-citronellol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 15:1) to obtain 93 mg of the target compound with a yield of 82%.

[0075] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ5.04–5.00(m,2H),3.85–3.76(m,2H),3.67–3.58(m,1H),3.36–3.27(m,1H),1.95–1.76(m ,6H),1.61(s,3H),1.53(s,3H),1.50–1.44(m,2H),1.32–1.26(m,2H),1.14–1.02(m,1H),0.82(d,J=6.5Hz,3H); 13 CNMR (100MHz, CDCl3): δ131.1,124.8,103.9,66.8,65.5,37.3,36.6,32.4,29.6,25.8,25.5,23.5,19.4,17.7.

[0076] Example 11

[0077] The reaction equation is shown below:

[0078]

[0079] Under open conditions, n-heptanol (0.5 mmol), 2,3-dihydrofuran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 30:1) to obtain 77 mg of the target compound with a yield of 83%.

[0080] The NMR spectrum data of the obtained product are: 1H NMR (400MHz, CDCl3): δ5.11-5.03(m,1H),3.91-3.76(m,2H),3.62(dt,J=9.5,6.8Hz,1H),3.30( dt,J=9.5,6.6Hz,1H),2.09-1.70(m,4H),1.69-1.43(m,2H),1.38-1.16(m,8H),0.85(t,J=6.6l Hz,3H); 13 C NMR (100MHz, CDCl3): δ103.6,67.0,66.4,32.0,31.5,29.3,28.7,26.1,23.1,22.5,13.9.

[0081] Example 12

[0082] The reaction equation is shown below:

[0083]

[0084] Under open conditions, benzyl alcohol (0.5 mmol), 3,4-dihydropyran (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 25:1) to obtain 87 mg of the target compound with a yield of 91%.

[0085] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.41-7.36(m,4H),7.35-7.27(m,1H),4.82(d,J=12.0Hz,1H),4.75(t,J=3.6Hz,1H),4.53(d,J= 12.0Hz,1H),3.93(dd,J=11.6,8.7Hz,1H),3.61-3.52(m,1H),1.95-1.84(m,1H),1.79-1.71(m,1H),1.70-1.50(m,4H); 13 C NMR (100MHz, CDCl3): δ138.5, 128.5, 128.0, 127.6, 97.9, 69.1, 62.2, 30.9, 25.6, 19.7.

[0086] Example 13

[0087] The reaction equation is shown below:

[0088]

[0089] Under open conditions, benzyl alcohol (0.5 mmol), benzyl vinyl ether (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 20:1) to obtain 106 mg of the title compound with a yield of 88%.

[0090] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.40-7.29(m,10H),4.91(q,J=5.5Hz,1H,),4.69(d,J=11.5Hz,2H),4.57(d,J=11.7Hz,2H),1.37(d,J=5.5Hz,3H,); 13 C NMR (100MHz, CDCl3): δ140.0,129.6,128.9,128.5,100.3,68.2,20.6.

[0091] Example 14

[0092] The reaction equation is shown below:

[0093]

[0094] Under open conditions, benzyl alcohol (0.5 mmol), n-butyl vinyl ether (1 mmol), and carbon tetrachloride (2 ml) were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED light was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was removed from the solvent using a rotary evaporator. The residue was purified using a silica gel column (silica gel specification: 200-300 mesh, eluent: petroleum ether / ethyl acetate = 20:1) to obtain 88 mg of the title compound with a yield of 85%.

[0095] The NMR spectrum data of the obtained product are: 1 H NMR (400MHz, CDCl3): δ7.36-7.23(m,5H),4.82(q,J=5.5Hz,1H),4.67(d,J=11.6Hz,1H),4.53(d,J=11.6Hz,1H),3.64-3.61(m,1H),3.48-3.46(m,1H); 13C NMR (100MHz, CDCl3): δ138.4,128.4,127.4,127.5,99.0,66.9,64.7,31.9,19.8,19.4,13.8.

[0096] In summary, the present invention uses cheap and readily available alcohols and olefin ethers as raw materials and does not require the use of a photocatalyst; the reaction conditions are relatively mild and the operation is simple; the cost is low and the reaction efficiency is high; the atomic utilization rate of the present invention is 100%, which conforms to the concept of "green chemistry"; the present invention can obtain the target product in just one step, with high yield, good functional group compatibility, simple post-processing, and good application potential.

[0097] Anything not described in detail in the present invention is well known to those skilled in the art.

[0098] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of benzyl alcohol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 15:1 to obtain 83 mg of the target compound.

2. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of 4-fluorobenzyl alcohol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 10:1 to obtain 93 mg of the target compound.

3. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of 4-chlorobenzyl alcohol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 15:1 to obtain 95 mg of the target compound.

4. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of 4-methylbenzyl alcohol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was completed, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 15:1 to obtain 85 mg of the target compound.

5. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of benzhydrol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 10:1 to obtain 108 mg of the target compound.

6. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of 2-thiophene methanol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 20:1 to obtain 83 mg of the target compound.

7. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of 2-naphthylmethanol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition was complete, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 20:1 to obtain 104 mg of the target compound.

8. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of phenol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was completed, the organic phase was subjected to a rotary evaporation to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 25:1 to obtain 66 mg of the target compound.

9. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of cinnamyl alcohol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was completed, the organic phase was subjected to a rotary evaporation to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 15:1 to obtain 87 mg of the target compound.

10. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of β-citronellol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was completed, the organic phase was subjected to a rotary evaporator to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 15:1 to obtain 93 mg of the target compound.

11. A method for preparing acetal compounds promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of n-heptanol, 1 mmol of 2,3-dihydrofuran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was completed, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 30:1 to obtain 77 mg of the target compound.

12. A method for preparing an acetal compound promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of benzyl alcohol, 1 mmol of 3,4-dihydropyran, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent, and the residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 25:1 to obtain 87 mg of the target compound.

13. A method for preparing an acetal compound promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of benzyl alcohol, 1 mmol of benzyl vinyl ether, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 20:1 to obtain 106 mg of the target compound.

14. A method for preparing an acetal compound promoted by visible light, characterized in that: The reaction equation is shown below: Under open conditions, 0.5 mmol of benzyl alcohol, 1 mmol of n-butyl vinyl ether, and 2 ml of carbon tetrachloride were added to a 20 ml test tube equipped with a magnetic stirrer. After the addition, a blue LED lamp was placed 2 cm away from the test tube. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction was complete, the organic phase was subjected to a rotary evaporation to remove the solvent. The residue was purified using a silica gel column with a silica gel specification of 200-300 mesh and an eluent of petroleum ether / ethyl acetate = 20:1 to obtain 88 mg of the target compound.

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