A synthetic method for preparing 6-methoxydihydropyranone from substituted 2,5-dihydrofurfuryl alcohol in one step

Abstract

The application belongs to the technical field of chemical synthesis method, and discloses a kind of synthesis method for preparing 6-methoxydihydropyranone from substituted 2,5-dihydrofuran methanol in one step.Under the catalysis of acid, the yield of 6-methoxydihydropyranone prepared from substituted 2,5-dihydrofuran methanol in one step reaches 92%.The preparation method provided by the application has the characteristics of simple operation, low preparation cost, environmental friendliness, high yield and the like.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis methods. The invention relates to a one-step synthesis method for preparing 6-methoxydihydropyranone from substituted 2,5-dihydrofuran methanol. Background Technology

[0002] The 2H-pyran-3(6H)-one structure is an intermediate in the synthesis of sugars, steroids, antibiotics, foods, metabolic intermediates, natural products, and compounds with potential biological activity. Chemical or electrochemical oxidation using substituted furanol as a starting material is one of the important methods for preparing dihydropyranones. The electrochemically prepared substituted 2,5-dialkoxydihydrofuranol can be converted to 6-alkoxy-substituted dihydropyranones in one or more steps via the following three main routes (Scheme 1):

[0003] One method involves using excess formic acid as a catalyst and methanol as a solvent to prepare 6-methoxy-substituted dihydropyranone from substituted 2,5-dimethoxydihydrofuran in a single step (0.6 mol feed, 400 mL formic acid). The use of a large excess of acid and the product's sensitivity to acid limit the application of this method. (US4342697)(Scheme 1, Eq.1)

[0004] Secondly: Under the action of acid, the substituted 2,5-dimethoxydihydrofuran methanol is first hydrolyzed and rearranged to generate a 6-hydroxy-substituted dihydropyranone, and then the following solutions are used: trimethyl orthoformate / anhydrous magnesium sulfate (Chem. Lett. 495-498, 1976) (Scheme 1, Eq. 2); triethyl orthoformate / anhydrous tin tetrachloride (Tetrahedron Lett. 1363-1364, 1976) (Scheme 1, Eq. 3); trimethyl orthoformate / boron trifluoride ether (Tetrahedron Lett. 605-608, 1990) (Scheme 1, Eq. 4); Ag2O / CH3I (J. Org. Chem., 2018, 2018(2): 196-208.) (Scheme 1, Eq. 4); Ag2O / CH3I (J. Org. Chem., 2018, 2018(2): 196-208.) (Scheme 1, Eq. 2). Etherification was carried out using either iridium catalyst (Adv.Synth.Catal.,2017,360(3):595-599)(Scheme 1, Eq.6) or a noble metal iridium catalyst (Adv.Synth.Catal.,2017,360(3):595-599)(Scheme 1, Eq.6).

[0005] Thirdly: the 6-hydroxyl-substituted dihydropyranone is acylated to ester or carbonate and then reacted with alcohol in the presence of metal compounds. This method requires a noble metal palladium catalyst (J.Am.Chem.Soc.,2003,125(41):12406-12407)(Scheme 1, Eq.7).

[0006]

[0007] The first method is limited by the use of excessive acid and the product's sensitivity to acid. The second method requires two steps, necessitating large amounts of drying agents or sensitive reagents (such as tin tetrachloride and boron trifluoride diethyl ether), and uses expensive raw materials (iodophors) or precious metal catalysts (iridium complexes). The third method requires three steps and a precious metal palladium catalyst. Therefore, developing an efficient and green method for the one-step preparation of 6-methoxydihydropyranone from 2,5-dihydrofuran-methanol has significant potential applications. Summary of the Invention

[0008] To overcome the shortcomings of existing methods, this invention provides a one-step synthetic method for preparing 6-methoxydihydropyranone from substituted 2,5-dihydrofuran methanol. Under acid catalysis, the yield of 6-methoxydihydropyranone obtained from 2,5-dihydrofuran methanol in one step reaches 92%. The preparation method provided by this invention has the advantages of simple operation, low preparation cost, environmental friendliness, and high yield.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A method for synthesizing 6-methoxydihydropyranone from 2,5-dihydrofuran methanol in one step, specifically: 2,5-dihydrofuran methanol (I) having the structure shown in general formula I is used to prepare 6-methoxydihydropyranone (II) having the structure shown in general formula II in the presence of a catalytic amount of acid in the next step.

[0011]

[0012] Wherein R is any one of C1-C8 alkyl, C6-C20 alkylphenyl, alkoxyphenyl, halophenyl, naphthoxyphenyl, trifluoromethylphenyl, or disubstituted or trisubstituted phenyl groups on the above benzene ring at different positions;

[0013] Where R 1 It is a C1-C3 alkyl group.

[0014] Furthermore, the solvent is any one or a mixture of two or more of the following: acetonitrile, nitromethane, dimethyl sulfoxide, N-methylpyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, ethyl acetate, dioxane, acetone, 1,2-dichloroethane, tetrahydrofuran, dichloromethane, chloroform, diethyl ether, benzene, toluene, hexane, and petroleum ether.

[0015] Furthermore, the acid is any one of trifluoromethanesulfonic acid, perchloric acid, sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, methanesulfonic acid, phenylphosphonic acid, diphenylphosphonic acid, and binaphthol phosphate.

[0016] Furthermore, if the acid is an aqueous solution, the concentration range is between 1 mol / L and 12.5 mol / L.

[0017] Furthermore, the amount of acid used is 0.01 to 0.80 equivalents of the raw materials used.

[0018] Furthermore, the reaction temperature range is between -20℃ and 100℃.

[0019] This invention employs the following specific synthetic method to prepare 6-methoxydihydropyranone: 1 mmol of a dihydrofuran-methanol compound, 0.01–0.80 equivalents of an acid catalyst, dissolved in 0.1–10 mL of organic solvent, and reacted at -20–100 °C for 1–600 minutes until the reaction was complete. The resulting mixture was neutralized with saturated sodium bicarbonate, the solvent was evaporated to dryness, and a sample was taken for NMR analysis.

[0020] Unless otherwise stated, the terms used herein have the following meanings.

[0021] As used herein, the term "alkyl" includes both straight-chain alkyl and branched-chain alkyl. When referring to a single alkyl group such as "methyl," it specifically refers to a straight-chain alkyl group; when referring to a single branched alkyl group such as "isopropyl," it specifically refers to a branched-chain alkyl group. For example, "alkyl groups below C4" includes methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl, etc. Similar rules apply to other groups used in this specification.

[0022] The term "halogen" as used in this article includes fluorine, chlorine, bromine, and iodine.

[0023] The following lists the structures of specific compounds 1 to 13 prepared in this invention, represented by general formula II, but the invention is not limited to these compounds.

[0024]

[0025] The advantages of this invention compared to the prior art are:

[0026] The synthesis method provided by this invention, under acid catalysis, achieves a one-step yield of 92% for the preparation of 6-methoxydihydropyranone by replacing 2,5-dihydrofuran-methanol. The preparation method provided by this invention is characterized by its simple operation, low preparation cost, environmental friendliness, and high yield. Attached Figure Description

[0027] Figure 1 :NMR image of 2-ethyl-6-methoxy-2H-pyran-3(6H)-one. Detailed Implementation

[0028] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Unless otherwise specified, the test methods described in the following embodiments are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0029] Example 1

[0030] Accurately weighed α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol (100 mg, 0.53 mmol), 5 mL tetrahydrofuran, and 1 mol / L sulfuric acid aqueous solution (53 μL, 0.053 mmol, 0.1 equivalent) were added sequentially to a 10 mL reaction flask. The mixture was sealed and stirred at 30 °C for 72 hours. After the reaction was completed, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was dried and characterized by NMR. The yield Y = 59%.

[0031] Example 2

[0032] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L perchloric acid aqueous solution, the reaction was carried out for 96 hours, and the yield Y = 23%.

[0033] Example 3

[0034] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L hydrochloric acid aqueous solution, the reaction was carried out for 88 hours, and the yield Y = 63%.

[0035] Example 4

[0036] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L methanesulfonic acid aqueous solution, the reaction was carried out for 40 hours, and the yield Y = 59%.

[0037] Example 5

[0038] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L p-toluenesulfonic acid aqueous solution, the reaction was carried out for 56 hours, and the yield Y = 54%.

[0039] Example 6

[0040] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L dodecylbenzenesulfonic acid aqueous solution, the reaction was carried out for 56 hours, and the yield Y = 52%.

[0041] Example 7

[0042] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L phenyl phosphoric acid aqueous solution, the reaction proceeded for 40 hours, and the yield Y = 69%.

[0043] Example 8

[0044] The difference between this embodiment and Example 1 is that the reaction acid catalyst was changed from a 1 mol / L sulfuric acid aqueous solution to a 1 mol / L phosphoric acid aqueous solution, the reaction was carried out for 72 hours, and the yield Y = 80%.

[0045] Example 9

[0046] The difference between this embodiment and Example 8 is that the reaction acid catalyst was changed from a 1 mol / L aqueous phosphoric acid solution to a 2 mol / L aqueous phosphoric acid solution, the reaction was carried out for 6 hours, and the yield Y = 82%.

[0047] Example 10

[0048] The difference between this embodiment and Example 8 is that the reaction acid catalyst was changed from a 1 mol / L aqueous phosphoric acid solution to a 4 mol / L aqueous phosphoric acid solution, the reaction was carried out for 1.5 hours, and the yield Y = 85%.

[0049] Example 11

[0050] The difference between this embodiment and Example 8 is that the reaction acid catalyst was changed from a 1 mol / L aqueous phosphoric acid solution to a 6 mol / L aqueous phosphoric acid solution, the reaction was carried out for 20 minutes, and the yield Y = 81%.

[0051] Example 12

[0052] The difference between this embodiment and Example 8 is that the reaction acid catalyst was changed from a 1 mol / L aqueous phosphoric acid solution to an 8 mol / L aqueous phosphoric acid solution, the reaction was carried out for 10 minutes, and the yield Y = 80%.

[0053] Example 13

[0054] The difference between this embodiment and Example 10 is that the amount of the reaction acid catalyst is changed from 0.1 equivalent to 0.2 equivalent, the reaction is carried out for 25 minutes, and the yield Y = 89%.

[0055] Example 14

[0056] The difference between this embodiment and Example 10 is that the amount of the reaction acid catalyst is changed from 0.1 equivalents to 0.4 equivalents, the reaction is carried out for 30 minutes, and the yield Y = 71%.

[0057] Example 15

[0058] The difference between this embodiment and Example 10 is that the amount of the reaction acid catalyst is changed from 0.1 equivalents to 0.6 equivalents, the reaction is carried out for 30 minutes, and the yield Y = 70%.

[0059] Example 16

[0060] The difference between this example and Example 13 is that the reaction solvent was changed from tetrahydrofuran to ethyl acetate, the reaction was carried out for 25 minutes, and the yield Y = 69%.

[0061] Example 17

[0062] The difference between this embodiment and Example 13 is that the reaction solvent was changed from tetrahydrofuran to dichloromethane, the reaction was carried out for 60 minutes, and the yield Y = 62%.

[0063] Example 18

[0064] The difference between this embodiment and Example 13 is that the reaction solvent was changed from tetrahydrofuran to toluene, the reaction was carried out for 25 minutes, and the yield Y = 73%.

[0065] Example 19

[0066] The difference between this example and Example 13 is that the reaction solvent was changed from tetrahydrofuran to acetonitrile, the reaction was carried out for 4 hours, and the yield Y = 71%.

[0067] Example 20

[0068] The difference between this example and Example 13 is that the reaction solvent was changed from tetrahydrofuran to n-hexane, the reaction was carried out for 3.5 hours, and the yield Y = 73%.

[0069] Example 21

[0070] The difference between this example and Example 13 is that the reaction solvent was changed from tetrahydrofuran to 1,2-dichloroethane, the reaction was carried out for 16 hours, and the yield Y = 68%.

[0071] Example 22

[0072] The difference between this embodiment and Example 13 is that the reaction temperature was changed from 30°C to 20°C, the reaction was carried out for 2 hours, and the yield Y = 83%.

[0073] Example 23

[0074] The difference between this embodiment and Example 13 is that the reaction temperature was changed from 30°C to 40°C, the reaction was carried out for 6 minutes, and the yield Y = 81%.

[0075] Example 24

[0076] The difference between this embodiment and Example 13 is that the reaction temperature is changed from 30°C to 50°C, the reaction is carried out for 2 minutes, and the yield Y = 80%.

[0077] Example 25

[0078] The difference between this embodiment and Example 13 is that the reaction temperature was changed from 30°C to 80°C, the reaction was carried out for 1 minute, and the yield Y = 78%.

[0079] Example 26

[0080] The difference between this embodiment and Example 13 is that the reaction concentration was changed from 20 mg / ml to 10 mg / ml, the reaction was carried out for 25 minutes, and the yield Y = 83%.

[0081] Example 27

[0082] The difference between this embodiment and Example 13 is that the reaction concentration was changed from 20 mg / ml to 30 mg / ml, the reaction was carried out for 25 minutes, and the yield Y = 92%.

[0083] Example 28

[0084] The difference between this embodiment and Example 13 is that the reaction concentration was changed from 20 mg / ml to 50 mg / ml, the reaction was carried out for 25 minutes, and the yield Y = 75%.

[0085] Example 29

[0086] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with α-methyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol, and the yield Y = 90%. The NMR data are as follows: 1 HNMR(400MHz,Chloroform-d)δ1.40(d,J=6.7Hz,3H),3.53(s,3H),4.54(q,J=6. 8Hz,1H),5.08(d,J=3.5Hz,1H),6.05–6.10(m,1H),6.84(dd,J=10.2,3.5Hz,1H).

[0087] Example 30

[0088] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with α-propyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol, and the yield Y = 83%. The NMR data are as follows: 1HNMR(500MHz,Chloroform-d)δ0.96(t,J=7.4Hz,3H),1.38-2.00(m,4H),3.54(d,J=4.3Hz,3H),4.23(dd d,J=169.5,8.8,3.9Hz,1H),5.08–5.25(m,1H),6.05–6.18(m,1H),6.85(ddd,J=18.8,10.3,2.7Hz,1H).

[0089] Example 31

[0090] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with α-isopropyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol, and the yield Y = 82%. The NMR data are as follows: 1 H NMR(400MHz,Chloroform-d)δ0.89(d,J=6.8Hz,3H),1.07(d,J=7.1Hz,3H),2.39–2.53(m,1H),3.51(s,3H) ,4.25(d,J=2.9Hz,1H),5.13(d,J=3.4Hz,1H),6.08(dd,J=10.1,0.7Hz,1H),6.84(dd,J=10.1,3.5Hz,1H).

[0091] Example 32

[0092] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with α-tert-butyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol, and the yield Y = 85%. The NMR data are as follows: 1 HNMR (400MHz, Chloroform-d) δ1.02(s,9H),3.44(s,3H),3.97(s,1H),5.03(d,J=3.5Hz,1H),5.93(d,J=10.1Hz,1H),6.69(dd,J=10.1,3.4Hz,1H).

[0093] Example 33

[0094] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(4-methoxyphenyl)ethanol, and the yield Y = 62%. The data are as follows: 1HNMR(600MHz,Chloroform-d)δ3.52(d,J=0.9Hz,3H),3.81(d,J=0.8Hz,3H),5.08(s,1H),5.42(d,J=1.4Hz ,1H),6.28(dd,J=10.4,1.5Hz,1H),6.89(dd,J=8.3,2.8Hz,1H),6.95–7.03(m,3H),7.29(t,J=7.9Hz,1H).

[0095] Example 34

[0096] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(3,5-dimethylphenyl)ethanol, and the yield Y = 76%. The data are as follows: 1 H NMR (600MHz, Chloroform-d) δ2.32(d,J=3.6Hz,6H),3.52(d,J=1.3Hz,3H),5.01(s,1H),5.39–5.42(m,1H),6.28(d,J=10.4Hz,1H),6.97–7.00(m,4H).

[0097] Example 35

[0098] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(phenyl)ethanol, and the yield Y = 80%. The data are as follows: 1 HNMR(600MHz,Chloroform-d)δ3.56(d,J=1.4Hz,3H),5.26(d,J=3.6Hz,1H),5.43(d,J=0 .9Hz,1H),6.20(d,J=10.3Hz,1H),6.96(ddd,J=10.3,3.5,1.4Hz,1H),7.34–7.42(m,5H).

[0099] Example 36

[0100] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(4-isopropylphenyl)ethanol, and the yield Y = 64%. The data are as follows: 1H NMR(600MHz,Chloroform-d)δ1.25(d,J=6.8Hz,6H),2.86–2.96(m,1H),3.55(s,3H),5.24(d,J=3 .5Hz,1H),5.41(s,1H),6.20(d,J=10.3Hz,1H),6.94(dd,J=10.3,3.5Hz,1H),7.24–7.30(m,4H).

[0101] Example 37

[0102] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(4-tert-butylphenyl)ethanol, and the yield Y = 78%. The data are as follows: 1 HNMR(600MHz,Chloroform-d)δ1.32(s,9H),3.50(s,3H),5.08(d,J=1.1Hz,1H),5.41(d,J=1.5Hz,1H ),6.28(dd,J=10.3,1.7Hz,1H),6.99(dd,J=10.4,1.6Hz,1H),7.31–7.34(m,2H),7.39–7.42(m,2H).

[0103] Example 38

[0104] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(2-trifluoromethylphenyl)ethanol, and the yield Y = 62%. The data are as follows: 1 HNMR(600MHz,Chloroform-d)δ3.56(s,3H),5.27(dd,J=3.6,0.5Hz,1H),5.43(s,1H),6.19(dd,J=10.2,0.8Hz,1H),6.96(dd,J=10.3,3. 5Hz,1H),7.05(tdd,J=8.4,2.7,1.0Hz,1H),7.12(dt,J=9.7,2.1Hz,1H),7.17(ddt,J=7.7,1.6,0.8Hz,1H),7.36(td,J=8.0,5.8Hz,1H).

[0105] Example 39

[0106] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(4-trifluoromethylphenyl)ethanol, and the yield Y = 52%. The data are as follows: 1 HNMR R(600MHz,Chloroform-d)δ3.57(s,3H),5.29(d,J=3.5Hz,1H),5.50(s,1H),6.21(dd,J=10. 3,0.8Hz,1H),6.98(dd,J=10.3,3.5Hz,1H),7.50–7.57(m,2H),7.65(dd,J=8.7,0.7Hz,2H).

[0107] Example 40

[0108] The difference between this example and Example 27 is that the reactant α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is replaced with (2,5-dimethoxy-2,5-dihydrofuran-2-yl)(4-trifluoromethylphenyl)ethanol, and the yield Y = 42%. The data are as follows: 1 HNMR(600MHz,Chloroform-d)δ3.56(d,J=1.4Hz,3H),5.27(d,J=3.5Hz,1H),5.41(s,1H),6.19(d,J=10.3 Hz,1H),6.96(ddd,J=10.3,3.5,1.4Hz,1H),7.27(dt,J=5.9,1.4Hz,1H),7.29–7.36(m,2H),7.40(s,1H).

[0109] Compare with Example 1:

[0110] Accurately weighed α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furan methanol (100 mg, 0.53 mmol), 5 mL methanol, and 1 mol / L phosphoric acid aqueous solution (53 μL, 0.053 mmol, 0.1 equivalent) were added sequentially to a 10 mL reaction flask. The mixture was sealed and stirred at 30 °C for 1 hour. After the reaction was completed, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was dried and characterized by NMR. The yield Y = 4%.

[0111] Compare with Example 2:

[0112] The difference between this comparative example and Comparative Example 1 is that the 1 mol / L phosphoric acid aqueous solution was replaced with 4.75 mmol / g sulfonic acid resin, and the yield Y = 14%.

[0113] Compare with Example 3:

[0114] The difference between this comparative example and Comparative Example 1 is that the 1 mol / L phosphoric acid aqueous solution was replaced with formic acid, the amount of acid used was 0.8 equivalents, the reaction was carried out for 24 hours, and the yield Y = 4%.

[0115] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for the one-step preparation of 6-methoxydihydropyranone from substituted 2,5-dihydrofuran-methanol, characterized in that, Accurately weighed 100 mg of α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol dissolved in tetrahydrofuran was added sequentially to a 10 ml reaction flask, resulting in a substrate concentration of 30 mg / ml. 0.2 equivalents of 4 mol / L phosphoric acid aqueous solution were added, and the mixture was sealed and stirred at 30 °C for 25 minutes. After the reaction was completed, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was then dried to obtain... The α-ethyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol structure is as follows: Where R1 is methyl and R is ethyl.

2. A method for the one-step preparation of 6-methoxydihydropyranone from substituted 2,5-dihydrofuran-methanol, characterized in that, Accurately weighed 100 mg of α-methyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol dissolved in tetrahydrofuran was added sequentially to a 10 ml reaction flask, resulting in a substrate concentration of 30 mg / ml. 0.2 equivalents of 4 mol / L phosphoric acid aqueous solution was added, and the mixture was sealed and stirred at 30 °C for 25 minutes. After the reaction was complete, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was then dried to obtain... The α-methyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol structure is as follows: ; where R1 is methyl and R is methyl.

3. A method for the one-step preparation of 6-methoxydihydropyranone from substituted 2,5-dihydrofuran-methanol, characterized in that, Accurately weighed 100 mg of α-propyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol dissolved in tetrahydrofuran was added sequentially to a 10 ml reaction flask, resulting in a substrate concentration of 30 mg / ml. 0.2 equivalents of 4 mol / L phosphoric acid aqueous solution was added, and the mixture was sealed and stirred at 30 °C for 25 minutes. After the reaction was complete, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was then dried to obtain... The α-propyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol structure is as follows: ; where R1 is methyl and R is propyl.

4. A method for the one-step preparation of 6-methoxydihydropyranone from substituted 2,5-dihydrofuran-methanol, characterized in that, Accurately weighed 100 mg of α-isopropyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol dissolved in tetrahydrofuran was added sequentially to a 10 ml reaction flask, resulting in a substrate concentration of 30 mg / ml. 0.2 equivalents of 4 mol / L phosphoric acid aqueous solution was added, and the mixture was sealed and stirred at 30 °C for 25 minutes. After the reaction was complete, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was then dried to obtain... The structure of the α-isopropyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is as follows: ; where R1 is methyl and R is isopropyl.

5. A method for the one-step preparation of 6-methoxydihydropyranone from substituted 2,5-dihydrofuran-methanol, characterized in that, Accurately weighed 100 mg of α-tert-butyl-2,5-dihydro-2,5-dimethoxy-2-furan-methanol dissolved in tetrahydrofuran was added sequentially to a 10 ml reaction flask, resulting in a substrate concentration of 30 mg / ml. 0.2 equivalents of 4 mol / L phosphoric acid aqueous solution were added, and the mixture was sealed and stirred at 30 °C for 25 minutes. After the reaction was completed, the reaction solution was neutralized with saturated sodium bicarbonate aqueous solution at low temperature to terminate the reaction. The organic phase was then dried to obtain the desired product. The structure of the α-tert-butyl-2,5-dihydro-2,5-dimethoxy-2-furanethanol is as follows: ; where R1 is methyl and R is tert-butyl.

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