A method for preparing cyclohexanol by photocatalytic cyclohexene hydration reaction

Abstract

This invention discloses a method for preparing cyclohexanol by photocatalytic hydration of cyclohexene: under inert gas protection, cyclohexene (Formula II) and water undergo a hydration reaction in an organic solvent, catalyzed by a photocatalyst and a co-catalyst, and irradiated by a light source, to obtain cyclohexanol (Formula I); the photocatalyst is an acridine salt compound (Formula III). This method is highly atom-economical, produces no byproducts, is environmentally friendly, and has broad industrial application prospects. The single-pass yield of cyclohexanol prepared by the photocatalytic hydration reaction of this invention can reach over 30%, which is significantly higher than the yield of existing technologies.

Description

Technical Field

[0001] This invention relates to a method for preparing cyclohexanol by hydration reaction of cyclohexene and water under the action of a photocatalyst. Background Technology

[0002] Cyclohexanol is an important chemical intermediate, mainly used in the production of adipic acid, caprolactam, and polyamide 66, and is an indispensable intermediate for amide products. Simultaneously, due to the excellent solubility and low volatility of alcohols, cyclohexanol can also be widely used in non-amide products. In the coatings industry, cyclohexanol is commonly used as a solvent for paints, shellac, and varnishes; in the textile industry, it can be used as a dye solvent and as a matting agent for textiles and synthetic fiber fabrics. Furthermore, cyclohexanol can be used in disinfectants, fragrances, insecticides, fungicides, leather degreasing agents, and coating diluents. Traditional methods for preparing cyclohexanol mainly include the cyclohexane oxidation method and the phenol hydrogenation method. The phenol hydrogenation method is the most traditional method. However, due to the relatively complex process of phenol production and the significant difficulties in utilizing the byproduct acetone, very few companies now use this process (Tian Aiguo. Partial hydrogenation process for benzene to produce cyclohexanol [J]. Chemical Industry and Engineering Progress. 2003, 22, 529-533). The cyclohexane oxidation method is currently the main industrial method for producing cyclohexanol. It involves first hydrogenating benzene to cyclohexane, followed by catalytic oxidation to obtain cyclohexanol and cyclohexanone. However, this method also has some problems. The single-pass conversion rate of cyclohexane is only 5%-6%, and the selectivity is only 75%-80%. Furthermore, the post-treatment costs for reaction byproducts are relatively high. Moreover, the oxidation of cyclohexane using H₂O₂ introduces the risk of explosion in the reaction system (Suresh AK, Sridhar T, Potter O E. AIChE Journal. 1988, 34, 55-68.).

[0003] The cyclohexene hydration method is currently the most promising process for producing cyclohexanol, offering advantages over phenol hydrogenation and cyclohexane oxidation, including lower consumption, environmental friendliness, and cost. Asahi Kasei Corporation of Japan has industrialized the cyclohexene hydration process for producing cyclohexanol. Asahi Kasei independently developed the ZSM-5 silica-alumina molecular sieve as a catalyst, which is composed of a mixture of aluminum sulfate, sodium silicate, concentrated sulfuric acid, sodium chloride, and nitrogen-containing compounds. However, this process also has its limitations. Because the cyclohexene hydration reaction is strictly limited by thermodynamic equilibrium, the single-pass yield of cyclohexanol is only about 10%, significantly reducing the application value of this technology (Fukuoka Y.; Mitsui O.JP60104031A, 1985; Tojo M.; Fukuoka Y.JP61180735A, 1986.). In 2017, A.-W. Lei's group reported the photocatalytic anti-Markovnikov hydration of alkenes (ACS Catal. 2017, 7, 1432). While the literature reported the hydration of cyclododecene, it did not report the hydration of cyclohexene. We attempted the standard method described in the literature to hydrate cyclohexene, but found that no cyclohexanol was produced. Therefore, there is an urgent need to develop green, environmentally friendly, efficient, and highly selective methods for the synthesis of cyclohexanol. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing cyclohexanol, wherein cyclohexene and water undergo a hydration reaction under the action of a photocatalyst to prepare cyclohexanol.

[0005] The technical solution adopted in this invention is:

[0006] A method for preparing cyclohexanol by photocatalytic hydration reaction of cyclohexene, the method comprising: under the protection of an inert gas, cyclohexene of formula II and water are subjected to a hydration reaction in an organic solvent, under the catalysis of a photocatalyst and a co-catalyst, and under the irradiation of a light source, to obtain cyclohexanol of formula I;

[0007]

[0008] The reaction equation is shown below:

[0009]

[0010] The photocatalyst is an acridine salt compound represented by Formula III.

[0011]

[0012] In Equation III, R 1 R 2 Each can be independently hydrogen, methyl, methoxy, or halogen; R 3It is a C1-C10 alkyl group or a C6-C10 aryl group; R 4 It is a C1-C10 alkyl group or a C6-C10 aryl group; the complex anion X- is ClO4. - BF4 - ,Br - or PF6 - ;

[0013] The H on the C1 to C10 alkyl group is not substituted or is substituted by one or more substituents A, wherein the substituents A are halogens;

[0014] The H on the aryl group of C6 to C10 is not substituted or is substituted by one or more substituents B, wherein the substituents B are alkyl groups of C1 to C6;

[0015] Furthermore, R is preferred. 1 It is H, Br or methyl, more preferably H;

[0016] Preferred R 2 For H;

[0017] Preferred R 3 The alkyl, phenyl, or substituted phenyl group of C1 to C6 that is either unsubstituted or halogenated, wherein the substituent on the substituted phenyl group is a C1 to C4 alkyl group; more preferably, R 3 It is methyl, phenyl, 4-chlorobutyl or 5-chloropentyl; R 3 The most preferred option is 5-chloropentyl;

[0018] Preferred R 4 It is phenyl or 2,4,6-trimethylphenyl;

[0019] The most preferred photocatalyst is the compound shown in Formula III-1:

[0020]

[0021] The synthesis of the compounds shown in Formula III can be carried out with reference to: Huang, XY; Ding, R.; Mo, ZY; Xu, YL; Tang, HT; Wang, HS; Chen, YY; Pan, YMOrg. Lett. 2018, 20, 4819–4823.

[0022] The amount of the photocatalyst is 0.1%-100% of the amount of cyclohexene shown in Formula II, preferably 1-10%, more preferably 1-5%, and most preferably 3-4%.

[0023] The cocatalyst is any one of the following compounds: thiophene, p-methylthiophene, o-chlorothiophene, o-aminothiophene, diphenyl disulfide, 4,4'-dimethyldiphenyl disulfide, 4,4'-dichlorodiphenyl disulfide, bis(2-aminophenyl) disulfide, 4,4'-diaminodiphenyl disulfide, 4,4'-dimethoxydiphenyl disulfide; preferably 4,4'-dimethyldiphenyl disulfide or 4,4'-dichlorodiphenyl disulfide.

[0024] The amount of the co-catalyst is 1%-200% of the amount of cyclohexene shown in Formula II, preferably 10-20%.

[0025] The inert gas is typically nitrogen.

[0026] The organic solvent is any one of the following compounds: acetonitrile, methanol, dichloromethane, tetrahydrofuran, 1,4-dioxane, toluene, anisole; preferably acetonitrile.

[0027] The volumetric amount of the organic solvent used, expressed as the amount of cyclohexene represented by Formula II, is 1 to 100 mL / mmol, preferably 6 to 20 mL / mmol.

[0028] The light source is visible light or ultraviolet light, preferably blue light, and more preferably 30W blue light.

[0029] The hydration reaction is carried out at a temperature of 0–60°C, preferably 40–50°C, and the reaction time is 1–24 hours.

[0030] In this invention, water serves as both a reactant and a solvent; the volume of water used, calculated based on the amount of cyclohexene represented by Formula II, is 0.5–10 mL / mmol, preferably 0.5–2 mL / mmol. More preferably, the volume of water is 10% of the volume of the organic solvent.

[0031] In this invention, after the reaction is completed, the light source is stopped, and the resulting reaction solution is post-treated to obtain cyclohexanol as shown in Formula I. The post-treatment method of the reaction solution is generally as follows: the solvent is removed from the resulting reaction solution by evaporation, the residue is filtered, and the filtrate is distilled under reduced pressure to obtain cyclohexanol as shown in Formula I, with a purity of over 98%.

[0032] The solids obtained from filtration are photocatalysts and co-catalysts, which can be recycled.

[0033] The reaction of this invention can be carried out by stirring or by flow in a tubular reactor.

[0034] The principle of the photocatalytic hydration reaction for preparing cyclohexanol in this invention is as follows: the photocatalyst (Formula III) absorbs light from the ground state to the excited state. Under the action of the excited-state photocatalyst, cyclohexene (Formula II) generates a free radical cationic intermediate. Water, as a nucleophile, selectively adds to the free radical cationic intermediate. After the intermediate further loses a proton, it generates a hydroxyl-containing free radical intermediate. Finally, under the action of a co-catalyst, cyclohexanol as shown in Formula I is generated.

[0035] This invention overcomes the problems of complex operation steps and the need for explosive reaction raw materials in traditional cyclohexanol synthesis methods. This invention uses simple, inexpensive, and readily available chemical raw materials, cyclohexene and water, as raw materials. The photocatalyst and co-catalyst are solids, which can be separated into solid and liquid phases and recycled. This method has high atom economy, produces no by-products, is environmentally friendly, and has broad industrial application prospects. The single-pass yield of cyclohexanol prepared by the photocatalytic hydration reaction of this invention can reach over 30%, which is significantly improved compared to existing technologies. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0037] The photocatalyst in the examples was synthesized as follows: References: Huang, XY; Ding, R.; Mo, ZY; Xu, YL; Tang, HT; Wang, HS; Chen, YY; Pan, YMOrg. Lett. 2018, 20, 4819–4823.

[0038] Catalyst III-2

[0039] (1) N-phenyl-o-aminobenzoic acid (formula a, 18.56 g, 87 mmol) was suspended in concentrated sulfuric acid (45 mL), heated to 98 °C, and magnetically stirred. The reaction mixture was maintained at this temperature for 6 hours, and then carefully poured into a round-bottom flask containing water (200 mL). The mixture was heated to 105 °C for 0.5 hours. After cooling the reaction mixture to room temperature, it was filtered to obtain a green solid, which was then carefully poured into a round-bottom flask containing sodium carbonate (12.93 g, 122 mmol) and water (200 mL) and heated to 105 °C for 0.5 hours. After cooling the reaction mixture to room temperature, it was filtered and washed with water to give the green solid product acridinone (formula b, 12.58 g, yield 74%).

[0040] (2) At room temperature, KOH (240 mmol, 6 M, aq) was added to a solution of acridinone (formula b, 25.7 mmol, 5.02 g) and benzyltriethylammonium chloride (2.02 mmol, 0.375 g) in THF (50 mL). Then, iodomethane (111 mmol, 7.0 mL) was added dropwise at room temperature. The solution was stirred at room temperature for 20 hours. The mixture was extracted with chloroform (50 mL × 3). The combined organic layers were washed with water (100 mL) and brine (100 mL), dried over Na2SO4, and the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography, eluting with a petroleum ether:ethyl acetate:dichloromethane volume ratio of 2:1:0.1. The solvent was evaporated from the eluent to give the green solid N-methylacridinone (formula c, 4.45 g, yield 85%).

[0041] (3) At room temperature, a solution of NBS (3.738 g, 21 mmol) in 15 mL of DMF was added dropwise to a solution of N-methylacridone (III-c, 2.114 g, 10 mmol) in 50 mL of DMF. The reaction mixture was stirred at 80 °C for 24 hours. The reaction mixture was cooled to room temperature and quenched with water. The reaction mixture was filtered, and the residue was washed with a mixture of petroleum ether solvents to give 2,7-dibromo-10-methyl-acridone (formula d, 3.05 g, yield 83%).

[0042] (4) Dissolve 0.025 mol of trimethylbromobenzene (4.9772 g) in 20 mL of anhydrous THF and add a few drops to magnesium shavings (0.03 mol, 0.7200 g), along with one grain of iodine. Then, stir vigorously with a magnetic stirrer and heat the reaction with a hot air gun until the THF begins to reflux and the color of the reaction solution fades. Continue to add the trimethylbromobenzene solution. After heating and stirring under reflux for 3 hours, reserve approximately 1 M of the trimethylbromobenzene magnesium bromide solution for further use.

[0043] (5) The obtained approximately 1M magnesium bromide (20 mmol, 20 mL) solution was added dropwise to a suspension of 2,7-dibromo-10-methyl-acridone (formula d, 10 mmol, 3.6704 g) in anhydrous THF (1 M, 10 mL). The solution was stirred at room temperature for 24 hours, then the resulting mixture was cooled to 0 °C and H2O (10 mL) was added dropwise. Then, HBF4 (70%, 0.02 mol, 1.73 mL) was added. THF was removed under reduced pressure and the residue was dissolved in H2O and extracted with CH2Cl2 (4 × 30 mL). The organic phases were combined, washed with brine (30 mL), dried over anhydrous Na2SO4, and filtered. Finally, the solvent was removed under reduced pressure, the resulting solid was recrystallized, dissolved in a minimum volume of dichloromethane, and precipitated with diethyl ether. This procedure was repeated twice to obtain 2,7-dibromo-[Acr-Mes]. + BF4 - (Formula III-2, 5.7703 g, yield 88%).

[0044]

[0045]

[0046] Catalyst III-3: In step (5), 2,7-dibromo-10-methyl-acridone is replaced with N-methylacridone as shown in formula c, and HBF4 is replaced with HClO4 to obtain Acr as shown in formula III-3. + -MesClO4 -

[0047] Catalyst III-4: In step (2), iodomethane is replaced with bromobenzene to obtain N-phenyl acridine ketone as shown in formula c-1. In step (5), 2,7-dibromo-10-methyl-acridone is replaced with N-phenyl acridine ketone as shown in formula c-1, and HBF4 is replaced with HClO4 to obtain N-Ph-Acr as shown in formula III-4. + -MesClO4 -

[0048] Catalyst III-5: In step (1), N-phenyl-o-aminobenzoic acid is replaced with 5-methyl-2-(p-tolylamino)benzoic acid, and 2,7-dimethyl-10-methyl-acridone of formula c-2 is obtained through steps (1) and (2). In step (5), 2,7-dibromo-10-methyl-acridone is replaced with the compound shown in formula c-2, and HBF4 is replaced with HClO4, to obtain 2,7-dimethyl-Acr of formula III-5. + -MesClO4 -

[0049] Catalyst III-6: In step (2), iodomethane is replaced with 1-bromo-4-chlorobutane to obtain N-4-chlorobutane-acridone as shown in formula c-3; in step (4), trimethylbromobenzene is replaced with bromobenzene; and in step (5), 2,7-dibromo-10-methyl-acridone is replaced with the compound shown in formula c-3 to prepare N-(4-Cl-Bu)-Acr as shown in formula III-6. + -Ph BF4 -

[0050] Catalyst III-7: In step (2), iodomethane is replaced with 1-bromo-4-chlorobutane to obtain N-4-chlorobutane-acridone as shown in formula c-3. In step (5), 2,7-dibromo-10-methyl-acridone is replaced with the compound shown in formula c-3 to prepare N-(4-Cl-Bu)-Acr as shown in formula III-7. + -Mes BF4 -

[0051] Catalyst III-1: In step (2), iodomethane is replaced with 1-bromo-5-chloropentane to obtain N-4-chloropentane-acridone as shown in formula c-4. In step (5), 2,7-dibromo-10-methyl-acridone is replaced with the compound shown in formula c-4 to prepare N-(5-Cl-amyl)-Acr as shown in formula III-1. + -Mes BF4 -

[0052] Example 1: Preparation of cyclohexanol. The reaction formula is as follows:

[0053]

[0054] The specific preparation method is as follows:

[0055] Under a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and Acr were added sequentially to a clean Schlenk tube. + -MesClO4 - (0.012 mmol, 4 mol%), 4,4'-dichlorodiphenyl disulfide (0.03 mmol, 10 mol%), water (H₂O, 0.6 mL), and acetonitrile (CH₃CN, 6.0 mL) were sealed in a reaction tube; the reaction was carried out at 40 °C under 30 W blue light irradiation for 24 hours. Irradiation was then stopped, and the mixture was cooled; the reaction solution was filtered, and dodecane (internal standard) was added. The product structure was analyzed and the yield was calculated by gas chromatography, yielding 3.5%. Acr + -MesClO4 - The proton spectrum is as follows: 1H NMR (400MHz, CDCl3) δ8.83(2H,d,J=9.2Hz),8.42(2H,m),7.86(2H,d,J=8.5Hz),7.79(2H,m),7.16(2H,s),5.13(3H,s),2.48(3H,s),1.73(6H,s).

[0056] Example 2: Preparation of cyclohexanol

[0057] The reaction equation is as follows:

[0058]

[0059] The specific preparation method is as follows:

[0060] In a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and N-Ph-Acr were sequentially added to a clean Schlenk tube. + -MesClO4 - (0.009 mmol, 3 mol%), 4,4'-dichlorodiphenyl disulfide (0.06 mmol, 20 mol%), water (H₂O, 0.2 mL), and acetonitrile (CH₃CN, 2.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light irradiation at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 4.5%. N-Ph-Acr + -MesClO4 - The proton spectrum is as follows: 1 H NMR (400MHz, CDCl3) δ8.13(2H,m),7.94-7.88(5H,m),7.83-7.75(4H,m),7.63(2H,d,J=9.0Hz),7.18(2H,s),2.50(3H,s),1.88(6H,s).

[0061] Example 3: Preparation of cyclohexanol

[0062] The reaction equation is as follows:

[0063]

[0064] The specific preparation method is as follows:

[0065] Under a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and 2,7-dimethyl-Acr were sequentially added to a clean Schlenk tube. + -MesClO4 -(0.012 mmol, 4 mol%), 4,4'-dichlorodiphenyl disulfide (0.03 mmol, 10 mol%), water (H₂O, 0.6 mL), and acetonitrile (CH₃CN, 6.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light at 40 °C for 24 hours. After irradiation, the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 2.8%. 2,7-dimethyl-Acr + -MesClO4 - The proton spectrum is as follows: 1 H NMR (400MHz, CDCl3) δ8.66(2H,d,J=9.4Hz),8.18(2H,d,J=9.4Hz),7.48(2H,s),7.16(2H,s),5.05(3H,s),2.53(6H,s),2.50(3H,s),1.72(6H,s).

[0066] Example 4: Preparation of cyclohexanol

[0067] The reaction equation is as follows:

[0068]

[0069] The specific preparation method is as follows:

[0070] In a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and 2,7-dibromo-Acr were sequentially added to a clean Schlenk tube. + -Mes BF4 - (0.009 mmol, 3 mol%), diphenyl disulfide (0.06 mmol, 20 mol%), water (H₂O, 0.2 mL), and acetonitrile (CH₃CN, 2.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light irradiation at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 3.1%. 2,7-dibromo-Acr + -Mes BF4 - The proton spectrum is as follows: 1 H NMR (400MHz, CDCl3) δ8.72(2H,d,J=9.7Hz),8.40(2H,dd,J=2.1,9.7Hz),7.90(2H,d,J=2.1Hz),7.18(2H,s),5.09(3H,s),2.51(3H,s),1.75(6H,s).

[0071] Example 5: Preparation of cyclohexanol

[0072] The reaction equation is as follows:

[0073]

[0074] The specific preparation method is as follows:

[0075] In a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and N-(4-Cl-Bu)-Acr were sequentially added to a clean Schlenk tube. + -Ph BF4 - (0.009 mmol, 3 mol%), diphenyl disulfide (0.06 mmol, 20 mol%), water (H₂O, 0.2 mL), and acetonitrile (CH₃CN, 2.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light irradiation at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 1.4%. N-(4-Cl-Bu)-Acr + -PhClO4 - The proton and carbon spectra are as follows: 1 H NMR(400MHz, CDCl3)δ8.74(2H,d,J=9.3Hz),8.44(2H,m),8.01(2H,d,J=8.5Hz),7.80(2 H,m),7.73(3H,m),7.48(2H,m),5.56(2H,m),3.84(2H,t,J=5.7Hz),2.53-2.47(4H,m). 13 C NMR (100MHz, CDCl3) δ161.7,140.8,139.8,133.0,130.6,130.5,129.8,129.1,128.1,126.1,118.5,50.3,44.8,28.8,26.1.

[0076] Example 6: Preparation of cyclohexanol

[0077] The reaction equation is as follows:

[0078]

[0079] The specific preparation method is as follows:

[0080] In a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and N-(4-Cl-Bu)-Acr were sequentially added to a clean Schlenk tube. + -Mes BF4 -(0.009 mmol, 3 mol%), diphenyl disulfide (0.06 mmol, 20 mol%), water (H₂O, 0.2 mL), and acetonitrile (CH₃CN, 2.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light irradiation at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 6.7%. N-(4-Cl-Bu)-Acr + -Mes BF4 - The proton and carbon spectra are as follows: 8.78 (2H, d, J = 9.3 Hz), 8.46 (2H, m), 7.87 (2H, d, J = 7.5 Hz), 7.80 (2H, m), 7.17 (2H, s), 5.60 (2H, m), 3.86 (2H, t, J = 5.7 Hz), 2.52–2.38 (4H, m), 2.49 (3H, s), 1.73 (6H, s). 13 C NMR (100MHz, CDCl3) δ163.2,140.8,140.5,140.1,135.9,129.4,129.3,129.2,128.6,126.1,119.1,50.6,44.9,28.9,26.4,21.4,20.2.

[0081] Example 7: Preparation of cyclohexanol

[0082] The reaction equation is as follows:

[0083]

[0084] The specific preparation method is as follows:

[0085] In a nitrogen atmosphere, a magnetic stir bar, cyclohexene (II, 0.3 mmol, 1.0 equiv), and N-(5-Cl-Am)-Acr were sequentially added to a clean Schlenk tube. + -Mes BF4 - (0.009 mmol, 3 mol%), diphenyl disulfide (0.06 mmol, 20 mol%), water (H₂O, 0.2 mL), and acetonitrile (CH₃CN, 2.0 mL) were used in a sealed reaction tube. The reaction was carried out under 30 W blue light irradiation at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was identified and the yield was calculated by GC, yielding 7.3%. N-(5-Cl-Am)-Acr + -Mes BF4 - The proton and carbon spectra are as follows: 1H NMR (400MHz, CDCl3) δ8.74(2H,d,J=9.3Hz),8.48(2H,m),7.86(2H,d,J=8.3Hz),7.80(2H,m) ,7.16(2H,s),5.54(2H,m),3.62(2H,m),2.48(3H,s),2.33(2H,m),1.98(4H,m),1.72(6H,s). 13 C NMR (100MHz, CDCl3) δ163.0,140.8,140.0,135.9,129.3,128.6,126.1,119.0,51.1,45.0,32.0,28.6,23.9,21.4,20.2.

[0086] Example 8: Preparation of cyclohexanol

[0087] The reaction equation is as follows:

[0088]

[0089] The specific preparation method is as follows:

[0090] In a nitrogen atmosphere, cyclohexene (II, 0.75 mmol, 1.0 equiv) and N-(4-Cl-Bu)-Acr were added sequentially to a clean Schlenk tube. + -Mes BF4 - The reaction mixture consisted of 0.0225 mmol (3 mol%), 4,4'-dimethyl diphenyl disulfide (0.15 mmol, 20 mol%), water (H₂O, 0.6 mL), and acetonitrile (CH₃CN, 6 mL). The mixture was transferred from the reaction tube to a photoreactive flow reactor and reacted at 40°C under 30 W blue light irradiation for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was analyzed and the yield was calculated by GC, yielding 17.7%.

[0091] Example 9: Preparation of cyclohexanol

[0092] The reaction equation is as follows:

[0093]

[0094] The specific preparation method is as follows:

[0095] In a nitrogen atmosphere, cyclohexene (II, 0.75 mmol, 1.0 equiv) and N-(5-Cl-Am)-Acr were added sequentially to a clean Schlenk tube. + -Mes BF4 -(0.0225 mmol, 3 mol%), 4,4'-dimethyl diphenyl disulfide (0.15 mmol, 20 mol%), water (H₂O, 0.6 mL), and acetonitrile (CH₃CN, 6 mL) were added to a photoreactive flow reactor. The reaction mixture was incubated under 30 W blue light at 40 °C for 24 hours. Irradiation was then stopped, and the mixture was cooled. The product structure was analyzed and the yield was calculated by GC, yielding 30.4%.

[0096] Example 10: Preparation of cyclohexanol

[0097] The reaction equation is as follows:

[0098]

[0099] The specific preparation method is as follows:

[0100] In a nitrogen atmosphere, cyclohexene (II, 0.75 mmol, 1.0 equiv) and N-(5-Cl-Am)-Acr were added sequentially to a clean Schlenk tube. + -Mes BF4 - The reaction mixture (0.0225 mmol, 3 mol%), 4,4'-dichlorodiphenyl disulfide (0.15 mmol, 20 mol%), water (H₂O, 0.6 mL), and acetonitrile (CH₃CN, 6 mL) was transferred from the reaction tube to a photoreactive flow reactor. The reaction was carried out under 30 W blue light at 40 °C for 24 hours. After irradiation, the mixture was cooled. The product structure was analyzed and the yield was calculated by GC, yielding 33.2%. The resulting reaction solution was first purified by rotary evaporation to remove most of the solvent and cyclohexene, and then further purified by vacuum distillation to obtain cyclohexanol with a purity of over 98%.

Claims

1. A method for preparing cyclohexanol by photocatalytic cyclohexene hydration reaction, characterized in that... The method is as follows: Under inert gas protection, cyclohexene (represented by Formula II) and water undergo a hydration reaction in an organic solvent, catalyzed by a photocatalyst and a co-catalyst, and irradiated by a light source, to obtain cyclohexanol (represented by Formula I); the reaction formula is shown below: The co-catalyst is 4,4'-dimethyldiphenyl disulfide or 4,4'-dichlorodiphenyl disulfide; The photocatalyst is a compound represented by Formula III-1:

2. The method as described in claim 1, characterized in that... The amount of the photocatalyst is 0.1%-100% of the amount of cyclohexene shown in Formula II; the amount of the co-catalyst is 1%-200% of the amount of cyclohexene shown in Formula II.

3. The method as described in claim 1, characterized in that... The organic solvent is any one of the following compounds: acetonitrile, methanol, dichloromethane, tetrahydrofuran, 1,4-dioxane, toluene, and anisole.

4. The method as described in claim 1, characterized in that... The light source is visible light or ultraviolet light.

5. The method as described in claim 1, characterized in that... The hydration reaction is carried out at a temperature of 0–60°C for 1–24 hours.

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