Method for preparing aza-2, 5-cyclohexadienone
By using inexpensive inorganic salt catalysts to prepare aza-2,5-cyclohexadienone in aqueous solvents, the high cost problem in existing technologies is solved, achieving low-cost and high-efficiency preparation of aza-2,5-cyclohexadienone, which is suitable for industrial production.
Patent Information
- Application Number
- CN202511167547.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-20
- Publication Date
- 2025-11-18
AI Technical Summary
Existing methods for preparing aza-2,5-cyclohexadienone require the use of expensive precious metals, chiral phosphoric acid, or complex photocatalytic systems, resulting in high costs.
Aza-2,5-cyclohexadienone was prepared by inexpensive and readily available inorganic salts as catalysts via intermolecular coupling reactions in water as a solvent, using substituted phenols and azo compounds as raw materials.
A low-cost method for preparing aza-2,5-cyclohexadienone was achieved, which is simple to operate, pollution-free, and has a high product yield, making it suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing aza-2,5-cyclohexadienone. Background Technology
[0002] Aza-2,5-cyclohexadienones are important intermediates in total synthesis and are also structural units widely found in agriculture, medicine, and many bioactive molecules. The structural formula of aza-2,5-cyclohexadienones is as follows:
[0003]
[0004] Currently, reported methods for preparing aza-2,5-cyclohexadienone include: 1) using the noble metal oxide Ag₂O as a catalyst and controlling the reaction temperature at 0℃; 2) using chiral phosphoric acid as a catalyst to convert phenol and azo precursors into aza-2,5-cyclohexadienone; and 3) utilizing photocatalysis, i.e., reacting the organic photocatalyst riboflavin tetraacetate, phenol, and azo precursors in a mixed solvent of acetonitrile and water under light irradiation to obtain aza-2,5-cyclohexadienone. While these synthetic methods can successfully prepare aza-2,5-cyclohexadienone, they require expensive noble metals, chiral phosphoric acid, or complex photocatalytic systems, resulting in high costs. Summary of the Invention
[0005] In view of this, the object of the present invention is to provide a method for preparing aza-2,5-cyclohexadienone. The method provided by the present invention uses inexpensive and readily available inorganic salts as catalysts to prepare aza-2,5-cyclohexadienone, resulting in low production costs.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] This invention provides a method for preparing aza-2,5-cyclohexadienone, comprising the following steps:
[0008] A mixture of substituted phenol, azo compound, inorganic salt and water was subjected to an intermolecular coupling reaction to yield aza-2,5-cyclohexadienone.
[0009] The substituted phenol has the structure shown in Formula I:
[0010]
[0011] In Formula I, R1 is a halogen, methoxy, or hydrogen, and R2 is an alkyl group;
[0012] The azo compound is an azodicarbonate;
[0013] The inorganic salts include one or more of the following: carbonates, bicarbonates, phosphates, dihydrogen phosphates, dihydrogen phosphates, chlorides, sulfates, sulfites, and silicates of alkali metal elements.
[0014] Preferably, the alkyl group includes methyl or ethyl.
[0015] Preferably, the azodicarbonate ester includes one or more of diethyl azodicarbonate, diisopropyl azodicarbonate, ditert-butyl azodicarbonate, and dibenzyl azodicarbonate.
[0016] Preferably, the molar ratio of the substituted phenol to the azo compound is 1:(1-2).
[0017] Preferably, the carbonate includes one or more of sodium carbonate, potassium carbonate, and cesium carbonate; the bicarbonate includes sodium bicarbonate; the phosphate includes potassium phosphate and / or sodium phosphate; the dihydrogen phosphate includes dipotassium hydrogen phosphate and / or disodium hydrogen phosphate; the dihydrogen phosphate includes potassium dihydrogen phosphate and / or sodium dihydrogen phosphate; the chloride includes sodium chloride; the sulfate includes sodium sulfate and / or potassium sulfate; the sulfite includes sodium sulfite and / or potassium sulfite; and the silicate includes sodium silicate.
[0018] Preferably, the molar ratio of the substituted phenol to the inorganic salt is 1:(0.1 to 1).
[0019] Preferably, the ratio of the substituted phenol to water is 3 mmol:(10-20) mL.
[0020] Preferably, the intermolecular coupling reaction is carried out at a temperature of 25–40°C for 4–24 hours.
[0021] Preferably, after the intermolecular coupling reaction is completed, the method further includes post-treatment of the resulting reaction solution, the post-treatment including:
[0022] The resulting reaction solution was extracted, and the resulting organic phase was successively dried, concentrated, and purified by thin-layer chromatography to obtain aza-2,5-cyclohexadienone; the extractant used in the extraction included one or more of dichloromethane, ethyl acetate, and methyl tert-butyl ether.
[0023] Preferably, the developing solvent used in the thin-layer chromatography purification is a mixture of a polar solvent and petroleum ether, wherein the polar solvent includes one or more of ethyl acetate, dichloromethane, and methanol; and the volume ratio of the polar solvent to petroleum ether is (1-3):5.
[0024] This invention provides a method for preparing aza-2,5-cyclohexadienone, comprising the following steps: mixing a substituted phenol, an azo compound, an inorganic salt, and water, and carrying out an intermolecular coupling reaction to obtain aza-2,5-cyclohexadienone; wherein the inorganic salt includes one or more of alkali metal carbonates, bicarbonates, phosphates, dihydrogen phosphates, dihydrogen phosphates, chlorides, sulfates, sulfites, and silicates. This invention uses inexpensive and readily available inorganic salts as catalysts to catalyze the molecular coupling reaction of substituted phenols and azo compounds to prepare aza-2,5-cyclohexadienone. This invention, under the catalysis of simple inorganic salts and using water as the reaction solvent, completes the preparation of aza-2,5-cyclohexadienone under mild conditions, low production cost, few byproducts, high product yield, high atom economy, and simple separation and purification. The method provided by this invention is simple to operate, pollution-free, meets the requirements of green chemistry development, and is suitable for industrial production. Detailed Implementation
[0025] This invention provides a method for preparing aza-2,5-cyclohexadienone, comprising the following steps:
[0026] A mixture of substituted phenol, azo compound, inorganic salt and water was subjected to an intermolecular coupling reaction to yield aza-2,5-cyclohexadienone.
[0027] The substituted phenol has the structure shown in Formula I:
[0028]
[0029] In Formula I, R1 is a halogen, methoxy, or hydrogen, and R2 is an alkyl group;
[0030] The azo compound is an azodicarbonate;
[0031] The inorganic salts include one or more of the following: carbonates, bicarbonates, phosphates, dihydrogen phosphates, dihydrogen phosphates, chlorides, sulfates, sulfites, and silicates of alkali metal elements.
[0032] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.
[0033] In this invention, the substituted phenol has the structure shown in Formula I, where R1 is a halogen, methoxy group or hydrogen, and the halogen is fluorine, chlorine or bromine; R2 is an alkyl group, and the alkyl group preferably includes methyl or ethyl.
[0034] In this invention, the substituted phenol may specifically be one or more of 2-fluoro-4-methylphenol, 2-chloro-4-methylphenol, 2-bromo-4-methylphenol, 2-bromo-4-ethylphenol, 3-fluoro-4-methylphenol, 3-chloro-4-methylphenol, 3-bromo-4-methylphenol, 4-methylphenol, and 4-ethylphenol.
[0035] In this invention, the azo compound is an azodicarbonate, which can be an aliphatic azodicarbonate or an aromatic azodicarbonate. Preferably, the azodicarbonate includes one or more of diethyl azodicarbonate, diisopropyl azodicarbonate, di-tert-butyl azodicarbonate, and dibenzyl azodicarbonate; the structural formula of the azodicarbonate is shown in Formula II, where R is preferably ethyl, isopropyl, tert-butyl, or benzyl.
[0036]
[0037] In this invention, the carbonate preferably includes one or more of sodium carbonate, potassium carbonate, and cesium carbonate; the bicarbonate preferably includes sodium bicarbonate; the phosphate preferably includes potassium phosphate and / or sodium phosphate; the dihydrogen phosphate preferably includes dipotassium hydrogen phosphate and / or disodium hydrogen phosphate; the dihydrogen phosphate preferably includes potassium dihydrogen phosphate and / or sodium dihydrogen phosphate; the chloride preferably includes sodium chloride; the sulfate preferably includes sodium sulfate and / or potassium sulfate; the sulfite preferably includes sodium sulfite and / or potassium sulfite; and the silicate preferably includes sodium silicate. In this invention, the inorganic salt, acting as a catalyst, possesses the characteristic of activating phenolic substrates and can catalyze the intermolecular coupling reaction between substituted phenols and azo compounds under mild conditions to generate aza-2,5-cyclohexadienone.
[0038] In this invention, water is used as the reaction solvent.
[0039] In this invention, the molar ratio of the substituted phenol to the azo compound is preferably 1:(1-2), more preferably 1:(1.2-1.8), and even more preferably 1:(1.2-1.5). In this invention, the molar ratio of the substituted phenol to the inorganic salt is preferably 1:(0.1-1), more preferably 1:(0.1-0.8), and even more preferably 1:(0.1-0.2). In this invention, the volume ratio of the substituted phenol to water is preferably 3 mmol:(10-20) mL, and can be 3 mmol:10 mL, 3 mmol:15 mL, or 3 mmol:20 mL.
[0040] The present invention preferably involves sequentially adding substituted phenol, azo compound, inorganic salt and water to a reaction vessel to carry out an intermolecular coupling reaction.
[0041] In this invention, the temperature of the intermolecular coupling reaction is preferably 25-40°C, but can be 30 or 35°C, and the time is preferably 4-24 hours, but can be 6, 8 or 10 hours.
[0042] In this invention, the reaction involved in the intermolecular coupling reaction is as follows (the compound represented by formula III in the reaction formula is aza-2,5-cyclohexadienone):
[0043]
[0044] Furthermore, when the substituted phenol is 2-fluoro-4-methylphenol and the azo compound is diethyl azodicarbonate, the specific reaction formula involved in the intermolecular coupling reaction is as follows:
[0045]
[0046] After the intermolecular coupling reaction is completed, the present invention preferably performs post-treatment on the resulting reaction solution, the post-treatment preferably including:
[0047] The resulting reaction solution was extracted, and the resulting organic phase was successively dried, concentrated, and purified by thin-layer chromatography to obtain aza-2,5-cyclohexadienone.
[0048] In this invention, the extractant used for extraction preferably includes one or more of dichloromethane, ethyl acetate, and methyl tert-butyl ether.
[0049] In this invention, the drying agent preferably includes anhydrous sodium sulfate and / or anhydrous magnesium sulfate.
[0050] The present invention does not have any particular limitation on the concentration method. Any concentration method known to those skilled in the art can be used to remove the solvent (extractant), such as vacuum distillation.
[0051] In this invention, the developing solvent used for thin-layer chromatography purification is preferably a mixed solvent of a polar solvent and petroleum ether. The polar solvent preferably includes one or more of ethyl acetate, dichloromethane, and methanol. The volume ratio of the polar solvent to petroleum ether is preferably (1-3):5, more preferably (1.5-2.5):5, and even more preferably (1.5-2):5.
[0052] This invention uses substituted phenols and azo compounds as raw materials, water as a reaction solvent, and inexpensive and readily available inorganic salts as catalysts to catalyze the molecular coupling reaction of substituted phenols and azo compounds to synthesize aza-2,5-cyclohexadienone. The production cost is low, the preparation conditions are mild, the atom economy is high, and the product yield is high.
[0053] To further illustrate the present invention, the method for preparing aza-2,5-cyclohexadienone provided by the present invention will be described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.
[0054] Example 1
[0055] Preparation of diethyl 2,5-cyclohexadienone-1-(3-fluoro-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate
[0056] 2-Fluoro-4-methylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(3-fluoro-1-methyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 82%).
[0057] Its structure was determined by proton and carbon NMR spectra. 1 H NMR(500MHz, CDCl3) δ7.17(d,J=20.3Hz,1H),6.86(dd,J=25.3,11.4Hz,1H),6.44(d,J=12.5Hz,1H),6.16 (dd,J=17.1,12.0Hz,1H),4.22-4.07(m,4H),1.30-1.25(m,3H),1.25-1.18(m,3H),1.14(t,J=7.2Hz,3H). 13 CNMR (126MHz, CDCl3) δ178.45,178.27,157.28,155.07,154.11,152.89,151.98,126.07,62.98,62.56,62.05,25.49,14.45.14.2.
[0058] Example 2
[0059] Preparation of diethyl 2,5-cyclohexadienone-1-(3-chloro-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate
[0060] 2-Chloro-4-methylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(3-chloro-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 83%).
[0061] Its structure was determined by proton and carbon NMR spectra. 1 H NMR (500MHz, CDCl3) δ7.10-6.56(m,3H),6.24(dd,J=11.6,9.9Hz,1H),4.30-4.04(m,4H),1.54(s,3H),1.33-1.21(m,3H),1.14(s,3H). 13 C NMR (126MHz, CDCl3) δ178.43,157.34,155.36,152.36,147.48,126.12,63.08,62.57,62.30,25.07,14.49,14.47.
[0062] Example 3
[0063] Preparation of diethyl 2,5-cyclohexadienone-1-(3-bromo-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid ester
[0064] 2-Bromo-4-methylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(3-bromo-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 85%).
[0065] Its structure was determined by proton and carbon NMR spectra. 1H NMR (500MHz, CDCl3) δ7.33-7.27(m,2H),6.88(dd,J=9.9,2.8Hz,1H),6.22(t,J=10.5Hz,1H),4.15(tdd ,J=25.1,19.9,11.2Hz,4H),1.49(d,J=2.9Hz,3H),1.25(dt,J=10.9,4.1Hz,3H),1.11(t,J=6.8Hz,3H). 13 C NMR (126MHz, CDCl3) δ178.24,157.31,155.04,152.14,152.02,125.41,123.03,64.07,62.98,62.93,24.73,14.44,14.15.
[0066] Example 4
[0067] Preparation of diethyl 2,5-cyclohexadienone-1-(2-chloro-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid ester
[0068] 3-Chloro-4-methylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(2-chloro-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 80%).
[0069] Its structure was determined by proton and carbon NMR spectra. 1 H NMR (500MHz, CDCl3) δ6.94-6.80(m,2H),6.36-6.28(m,1H),6.18-6.09(m,1H),4.22(q,J=7.2Hz,4H),1.48(s,3H),1.18(m,6H). 13 CNMR (126MHz, CDCl3) δ184.03,171.28,155.35,152.48,152.36,127.98,126.26,64.19,63.66,62.73,62.57,62.30,60.49,24.99,14.49,14.21.
[0070] Example 5
[0071] Preparation of diethyl 2,5-cyclohexadienone-1-(3-bromo-1-ethyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid ester
[0072] 2-Bromo-4-ethylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(3-bromo-1-ethyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 85%).
[0073] Its structure was determined by proton and carbon NMR spectra. 1 H NMR(500MHz, CDCl3)δ7.24-7.12(m,1H),6.78(dd,J=22.1,13.5Hz,2H),6.36(dd,J=10.0,5.6Hz,1H), 4.23-4.09(m,4H),1.98(d,J=7.5Hz,2H),1.30-1.26(m,3H),1.21-1.15(m,3H),0.83(t,J=7.4Hz,3H). 13 C NMR (126MHz, CDCl3) δ178.64,157.35,155.33,150.48,150.38,150.20,150.08,127 .31,124.07,67.01,64.26,63.19,62.82,62.67,62.40,29.38,14.54,14.30,8.20.
[0074] Example 6
[0075] Preparation of diisopropyl 2,5-cyclohexadienone-1-(1-ethyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid diisopropyl ester
[0076] 4-Ethylphenol (0.3 mmol), diisopropyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain 1-(1-ethyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid diisopropyl ester (yield 50%).
[0077] Its structure was determined by proton and carbon NMR spectra. 1 H NMR (400MHz, CDCl3) δ7.15(dd,J=10.3,3.1Hz,1H),6.83(d,J=9.2Hz,2H),6.27(ddd,J=10.3,5.8,2.0Hz,2H),4.93 (dt,J=30.4,6.3Hz,2H),2.04-1.89(m,2H),1.29(dd,J=6.5,3.2Hz,6H),1.21-1.16(m,6H),0.82(t,J=7.5Hz,3H). 13 C NMR (101MHz, CDCl3) δ185.86,156.96,155.01,150.28,128.75,128.64,70.89,70.34,64.31,29.36,22.06,21.95,21.89,21.83,8.08.
[0078] Example 7
[0079] Preparation of diethyl 2,5-cyclohexadienone-1-(1-ethyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid ester
[0080] 4-Ethylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium carbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(1-ethyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 80%).
[0081] Its structure was determined by proton and carbon NMR spectra. 1 H NMR (400MHz, CDCl3) δ7.40-6.73(m,3H),6.36-6.16(m,2H),4.25-4.08(m,4H),1.97( t,J=7.7Hz,2H),1.28(d,J=6.4Hz,3H),1.19(d,J=6.8Hz,3H),0.81(d,J=7.1Hz,3H). 13 C NMR (101MHz, CDCl3) δ185.84,157.26,155.45,150.31,150.28,150.10,150.01,149.98,129.07,129.03, 129.03,128.94,128.84,128.78,128.72,64.46,62.79,62.52,62.44,29.24,14.48,14.32,14.23,8.03.
[0082] Example 8
[0083] Preparation of diethyl 2,5-cyclohexadienone-1-(3-bromo-1-methyl-4-oxocyclohex-2,5-dien-1-yl)hydrazine-1,2-dicarboxylic acid ester
[0084] 2-Bromo-4-methylphenol (0.3 mmol), diethyl azodicarbonate (0.45 mmol), sodium bicarbonate (0.03 mmol), and water (1 mL) were added sequentially to a 5 mL reaction vessel. The mixture was stirred at 30 °C for 6 h. Ethyl acetate was added to the resulting reaction solution for extraction (the volume ratio of reaction solution to ethyl acetate was 1:2). The resulting organic phase was dried over anhydrous sodium sulfate, and the organic solvent (ethyl acetate) was removed by vacuum distillation. Thin-layer chromatography was then performed (the developing solvent was ethyl acetate and petroleum ether in a volume ratio of 1:3) to obtain diethyl 1-(3-bromo-1-methyl-4-oxocyclohexyl-2,5-dien-1-yl)hydrazine-1,2-dicarboxylate (yield 72%).
[0085] Its structure was determined by proton and carbon NMR spectra. 1 H NMR (500MHz, CDCl3) δ7.33-7.27(m,2H),6.88(dd,J=9.9,2.8Hz,1H),6.22(t,J=10.5Hz,1H),4.15(tdd ,J=25.1,19.9,11.2Hz,4H),1.49(d,J=2.9Hz,3H),1.25(dt,J=10.9,4.1Hz,3H),1.11(t,J=6.8Hz,3H). 13C NMR (126MHz, CDCl3) δ178.24,157.31,155.04,152.14,152.02,125.41,123.03,64.07,62.98,62.93,24.73,14.44,14.15.
[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing aza-2,5-cyclohexadienone, characterized in that, Includes the following steps: A mixture of substituted phenol, azo compound, inorganic salt and water was subjected to an intermolecular coupling reaction to yield aza-2,5-cyclohexadienone. The substituted phenol has the structure shown in Formula I: In Formula I, R1 is a halogen, methoxy, or hydrogen, and R2 is an alkyl group; The azo compound is an azodicarbonate; The inorganic salts include one or more of the following: carbonates, bicarbonates, phosphates, dihydrogen phosphates, dihydrogen phosphates, chlorides, sulfates, sulfites, and silicates of alkali metal elements.
2. The method according to claim 1, characterized in that, The alkyl group includes methyl or ethyl.
3. The method according to claim 1, characterized in that, The azodicarbonate esters include one or more of diethyl azodicarbonate, diisopropyl azodicarbonate, ditert-butyl azodicarbonate, and dibenzyl azodicarbonate.
4. The method according to any one of claims 1 to 3, characterized in that, The molar ratio of the substituted phenol to the azo compound is 1:(1-2).
5. The method according to claim 1, characterized in that, The carbonate includes one or more of sodium carbonate, potassium carbonate, and cesium carbonate; the bicarbonate includes sodium bicarbonate; the phosphate includes potassium phosphate and / or sodium phosphate; the dihydrogen phosphate includes dipotassium hydrogen phosphate and / or disodium hydrogen phosphate; the dihydrogen phosphate includes potassium dihydrogen phosphate and / or sodium dihydrogen phosphate; the chloride includes sodium chloride; the sulfate includes sodium sulfate and / or potassium sulfate; the sulfite includes sodium sulfite and / or potassium sulfite; and the silicate includes sodium silicate.
6. The method according to claim 1 or 5, characterized in that, The molar ratio of the substituted phenol to the inorganic salt is 1:(0.1~1).
7. The method according to claim 1, characterized in that, The ratio of the substituted phenol to water is 3 mmol:(10-20) mL.
8. The method according to claim 1, characterized in that, The intermolecular coupling reaction is carried out at a temperature of 25–40 °C for 4–24 h.
9. The method according to claim 1 or 8, characterized in that, After the intermolecular coupling reaction is completed, the method further includes post-treatment of the resulting reaction solution, the post-treatment including: The resulting reaction solution was extracted, and the resulting organic phase was successively dried, concentrated, and purified by thin-layer chromatography to obtain aza-2,5-cyclohexadienone; the extractant used in the extraction included one or more of dichloromethane, ethyl acetate, and methyl tert-butyl ether.
10. The method according to claim 9, characterized in that, The developing solvent used in the thin-layer chromatography purification is a mixture of a polar solvent and petroleum ether. The polar solvent includes one or more of ethyl acetate, dichloromethane, and methanol. The volume ratio of the polar solvent to petroleum ether is (1-3):5.