An iodine-mediated method for alcohol reduction

Abstract

The present application provides an iodine-mediated alcohol reduction method, which relates to the field of organic chemistry; the method provided by the present application uses H2 as a reducing agent, hydroiodic acid (HI) as a catalyst to catalyze the deoxidization reduction of alcohol; the reaction process is as follows: alcohol, HI and solvent are mixed and put into a batch reaction kettle, H2 is introduced into the reaction kettle, heated to 100-300 DEG C and reacted for 1-24 h, a reduction reaction occurs to generate alkanes; the method is simple and environmentally friendly, the by-product is H2O, and there is no metal catalysis; and benzyl alcohol, linalool, allyl alcohol and derivatives of the three are used as substrates.

Description

Technical Field

[0001] This invention relates to the field of organic chemistry, and more specifically to an iodine-mediated method for the reduction of alcohols. Background Technology

[0002] Fossil fuels have long played a dominant role in the pharmaceutical, energy, and materials industries. Most organic compounds are derived from primary petrochemical products of fossil fuels and are typically low-functionality hydrocarbons such as benzene, alkenes, or alkanes. Therefore, research in organic synthesis has focused on the activation and functionalization of CH bonds. However, with the depletion of fossil fuels, alternative sustainable resources have become a research priority. Biomass is the only renewable carbon resource with the potential to replace fossil fuels as feedstock for various chemicals. Due to its complex functional group nature, the conversion of biomass into high-value chemicals requires the development of efficient defunctionalization methods, unlike petrochemicals. Because biomass contains multiple hydroxyl functional groups, the selective deoxygenation of alcohols is an important transformation in biomass chemical synthesis.

[0003] Several methods exist for the selective deoxygenation of alcohols, including free radical deoxygenation, transition metal catalysis, and red phosphorus reflux hydroiodic acid deoxygenation. In the free radical deoxygenation reaction, an intermediate thioester is first formed, and then reduced by a tin reagent. Transition metal catalysis utilizes transition metals such as Ni, Co, Ir, Pd, and Ru, which are commonly used to catalyze the reductive deoxygenation of alcohols. The red phosphorus reflux hydroiodic acid deoxygenation method is still used industrially. This method involves two steps: first, the hydroxyl group is converted into a more easily reduced alkyl iodide; second, the iodide is reduced by excess hydroiodic acid to obtain an alkane. This method has been subsequently improved: using HI as a catalytic amount, with red phosphorus or hypophosphite as a reducing agent, elemental iodine (I₂) is reduced to hydroiodic acid (HI). However, phosphorus is oxidized to phosphoric acid, and the resulting byproducts cause significant environmental pollution, and the catalyst is not recyclable. Currently, the most commonly used methods for reducing benzyl alcohol, linalool, allyl alcohol, benzyl alcohol derivatives, and allyl alcohol derivatives are free radical deoxygenation and transition metal catalysis. However, these methods have problems such as producing more byproducts, causing more serious environmental pollution, expensive catalysts, and metal residues.

[0004] Therefore, a new solution needs to be developed to improve the above problems. Summary of the Invention

[0005] This invention aims to provide an iodine-mediated alcohol reduction method. First, the alcohol reacts with the catalyst HI to produce iodoalkanes. Then, under high temperature and metal-free catalytic conditions, H2 is used as a reducing agent to reduce the iodoalkanes to produce alkanes and HI. The method provided by this invention has the advantages of being environmentally friendly, metal-free, and highly universal. Furthermore, this method is tolerant to benzyl alcohol, allyl alcohol, linalool, and their derivatives.

[0006] This invention provides an iodine-mediated alcohol reduction method, comprising the following steps:

[0007] In a hydrogen atmosphere, under the action of hydroiodic acid, an alcohol in a solvent undergoes a reduction reaction to produce an alkane; the alcohol includes at least one of benzyl alcohol, linalool, allyl alcohol, benzyl alcohol derivatives, linalool derivatives, and allyl alcohol derivatives.

[0008] Optionally, the derivative is a compound containing a benzyl alcohol or allyl alcohol structure formed by replacing atoms or groups of atoms in the molecule of benzyl alcohol or allyl alcohol with other atoms or groups of atoms, and is called a derivative of benzyl alcohol or allyl alcohol.

[0009] Optionally, the benzyl alcohol derivative includes 4-methylbenzyl alcohol, 4-isopropylbenzyl alcohol, and p-hydroxymethylbenzoic acid.

[0010] Optionally, the allyl alcohol derivative includes lactic acid, 2-octenol, and 2-hexenol.

[0011] Optionally, the method provided by the present invention consists of a two-step reaction:

[0012] First step reaction: The alcohol reacts with the catalyst HI to produce iodoalkane;

[0013] The second step of the reaction involves reducing iodoalkanes with H2 as a reducing agent under high temperature and metal-free catalytic conditions to produce alkanes and HI.

[0014] Optionally, the HI generated in the second step reaction can be used as a catalyst in the first step reaction.

[0015] Optionally, the concentration of alcohol in the reaction is 5-25 g / L.

[0016] Optionally, the concentration of hydroiodic acid in the reaction is 0.1-10 g / L.

[0017] Optionally, the solvent includes at least one of acetonitrile, n-hexane, n-heptane, n-octane, cyclohexane, and 2-methyltetrahydrofuran.

[0018] Optionally, the pressure of the hydrogen gas is 0.1-5 MPa.

[0019] Optionally, the reaction temperature is 100-300℃; the reaction time is 1-24h.

[0020] Optionally, the reaction byproduct is water.

[0021] Secondly, this invention provides an application of an iodine-mediated alcohol reduction method in biomass chemical synthesis.

[0022] The beneficial effects of this invention include:

[0023] (1) The preparation method provided by the present invention does not add a metal catalyst, thus avoiding metal contamination;

[0024] (2) The preparation method provided by the present invention has high substrate versatility and is applicable to one or more mixtures of benzyl alcohol, allyl alcohol, benzyl alcohol derivatives and allyl alcohol derivatives as substrates for reaction.

[0025] (3) The preparation method provided by the present invention is a free radical reaction, and the byproduct is H2O, which is environmentally friendly. Attached Figure Description

[0026] Figure 1 A schematic diagram of an iodine-mediated alcohol reduction method;

[0027] Figure 2 Q-TOF diagram of Tempo capturing toluene radicals to form new compounds;

[0028] Figure 3 Q-TOF fragment peak diagram for the capture of toluene radicals by Tempo to form new compounds. Detailed Implementation

[0029] The present invention will be further described in conjunction with the accompanying drawings and through the following embodiments.

[0030] On one hand, embodiments of the present invention provide an iodine-mediated alcohol reduction method, comprising the following steps:

[0031] In a hydrogen atmosphere, under the action of hydroiodic acid, an alcohol in a solvent undergoes a reduction reaction to produce an alkane; the alcohol includes at least one of benzyl alcohol, linalool, allyl alcohol, benzyl alcohol derivatives, linalool derivatives, and allyl alcohol derivatives.

[0032] Specifically, the derivatives are compounds containing the structure of benzyl alcohol or allyl alcohol formed by replacing atoms or groups of atoms in the molecules of benzyl alcohol or allyl alcohol with other atoms or groups of atoms, and are called derivatives of benzyl alcohol or allyl alcohol.

[0033] Specifically, the benzyl alcohol derivatives include 4-methylbenzyl alcohol, 4-isopropylbenzyl alcohol, and p-hydroxymethylbenzoic acid.

[0034] Specifically, the allyl alcohol derivatives include lactic acid, 2-octenol, and 2-hexenol.

[0035] In some embodiments, see Figure 1 The method provided by this invention consists of two steps:

[0036] First step reaction: The alcohol reacts with the catalyst HI to produce iodoalkane;

[0037] The second step of the reaction involves reducing iodoalkanes with H2 as a reducing agent under high temperature and metal-free catalytic conditions to produce alkanes and HI.

[0038] Specifically, Figure 1 The R group can be hydrogen, alkyl, or aryl.

[0039] Specifically, the HI generated in the second step reaction can then be used as a catalyst in the first step reaction.

[0040] In some embodiments, the concentration of alcohol in the reaction is 5-25 g / L.

[0041] In some embodiments, the concentration of hydroiodic acid in the reaction is 0.1-10 g / L.

[0042] In some embodiments, the solvent includes at least one selected from acetonitrile, n-hexane, n-heptane, n-octane, cyclohexane, and 2-methyltetrahydrofuran.

[0043] Specifically, the volume fraction of the solvent is 90 vol%.

[0044] In some embodiments, the pressure of the hydrogen gas is 0.1-5 MPa.

[0045] In some embodiments, the reaction temperature is 100-200°C; the reaction time is 1-12 hours.

[0046] In some embodiments, the reaction byproduct is water.

[0047] In some embodiments, an Agilent 7890B gas chromatograph with an Agilent HP-5 capillary column (30m*32μm*0.25μm) was used for quantitative analysis of the yield.

[0048] In some embodiments, a Thermo Scientific TRACE1310 gas chromatograph was used for qualitative analysis of the product, and the chromatographic column was a Thermo Scientific TG-MS capillary column (30m*32μm*0.25μm).

[0049] On the other hand, the present invention provides an application of an iodine-mediated alcohol reduction method in biomass chemical synthesis.

[0050] Example 1

[0051] Example 1 of the present invention provides an iodine-mediated alcohol reduction method, comprising the following steps:

[0052] 108.1 mg benzyl alcohol (1 mmol), 13.2 mg HI (0.1 mmol), and 10 mL n-hexane were added to a batch reactor, and 2 MPa H2 was introduced. The reaction was carried out at 160 °C for 10 h. Gas chromatography analysis showed that the product was toluene (0.95 mmol), with a molar yield of 95%.

[0053] Example 2

[0054] Example 2 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0055] 158.2 mg of 2-naphthalenemethanol (1 mmol), 13.2 mg of HI (0.1 mmol), and 20 mL of cyclohexane were added to a batch reactor, and H2 was introduced at 5 MPa. The reaction was carried out at 100 °C for 24 h. Gas chromatography analysis showed that the product was 2-methylnaphthalene (0.33 mmol), with a molar yield of 33%.

[0056] Example 3

[0057] Example 3 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0058] 150.2 mg of 4-isopropylbenzyl alcohol (1 mmol), 26.4 mg of HI (0.2 mmol), and 30 mL of n-heptane were added to a batch reactor, and 1 MPa of H2 was introduced. The reaction was carried out at 160 °C for 24 h. Gas chromatography analysis showed that the product was 4-isopropyltoluene (0.99 mmol), with a molar yield of 99%.

[0059] Example 4

[0060] Example 4 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0061] 154.2 mg linalool (1 mmol), 26.4 mg hydroiodic acid (0.2 mmol), and 30 mL of n-heptane solvent were added to a batch reactor, and hydrogen gas was introduced at 1 MPa. The mixture was heated at 140 °C for 6 h. After the reaction was completed, the product was analyzed by GC, and the molar yield of 3,7-dimethyl-1,6-dioctene was calculated to be 91%.

[0062] Example 5

[0063] Example 5 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0064] 122.2 g of 4-methylbenzyl alcohol (1 mmol), 132 mg of HI (0.5 mmol), and 30 mL of n-octane were added to a batch reactor, and 0.5 MPa of H2 was introduced. The reaction was carried out at 160 °C for 12 h. Gas chromatography analysis showed that the product was 4-methoxytoluene (0.97 mmol), with a molar yield of 97%.

[0065] Example 6

[0066] Example 6 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0067] 142.58 mg of 4-chlorobenzyl alcohol (1 mmol), 13.2 mg of HI (0.1 mmol), and 20 mL of 2-methyltetrahydrofuran were added to a batch reactor, and H2 was bubbled through at 5 MPa. The reaction was carried out at 180 °C for 10 h. Gas chromatography analysis showed that the product was 4-chlorotoluene (0.91 mmol), with a molar yield of 91%.

[0068] Example 7

[0069] Example 7 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0070] 166.17 mg of methyl 4-(hydroxymethyl)benzoate (1 mmol), 26.4 mg of HI (0.2 mmol), and 40 mL of 2-n-heptane were added to a batch reactor, and H2 was bubbled through at 0.5 MPa. The reaction was carried out at 200 °C for 12 h. Gas chromatography analysis showed that the product was methyl 4-methylbenzoate (0.89 mmol), with a molar yield of 89%.

[0071] Example 8

[0072] Example 8 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0073] 122.2 mg of 1-phenylethanol (1 mmol), 13.2 mg of HI (0.1 mmol), and 40 mL of 2-methyltetrahydrofuran were added to a batch reactor, and H2 was introduced at 3 MPa. The reaction was carried out at 200 °C for 24 h. Gas chromatography analysis showed that the product was ethylbenzene (0.85 mmol), with a molar yield of 85%.

[0074] Example 9

[0075] Example 9 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0076] 134.2 mg cinnamyl alcohol (1 mmol), 13.2 mg HI (0.1 mmol), and 20 mL cyclohexane were added to a batch reactor, and H2 was introduced at 3 MPa. The reaction was carried out at 140 °C for 1 h. Gas chromatography analysis showed that the product was trans-β-methylstyrene (0.95 mmol), with a molar yield of 95%.

[0077] Example 10

[0078] Example 10 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0079] 100.2 mg 2-hexenol (1 mmol), 13.2 mg HI (0.1 mmol), and 20 mL n-hexane were added to a batch reactor, and 1 MPa H2 was introduced. The reaction was carried out at 300 °C for 1 h. Gas chromatography analysis showed that the product was 2-hexene (0.3 mmol), with a molar yield of 30%.

[0080] Example 11

[0081] Example 11 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0082] 128.2 mg of 2-octenol (1 mmol), 13.2 mg of HI (0.1 mmol), and 30 mL of acetonitrile were added to a batch reactor, and 1 MPa of H2 was introduced. The reaction was carried out at 120 °C for 2 h. Gas chromatography analysis showed that the product was 2-octene (0.9 mmol), with a molar yield of 90%.

[0083] Example 12

[0084] Example 12 of the present invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0085] 900.1 mg lactic acid (10 mmol), 132 mg HI (1 mmol), and 20 mL n-hexane were added to a batch reactor, and H2 was introduced at 3 MPa. The reaction was carried out at 160 °C for 10 h. Gas chromatography analysis showed that the product was propionic acid (0.8 mmol), with a molar yield of 80%.

[0086] Example 13

[0087] Example 13 of this invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0088] 182.2 mg of benzyl alcohol (1 mmol), 6.6 mg of HI (0.05 mmol), and 10 mL of n-octane were added to a batch reactor, and H2 was introduced at 4 MPa. The reaction was carried out at 200 °C for 12 h. Gas chromatography analysis showed that the product was 2-phenylmethane (0.8 mmol), with a molar yield of 80%.

[0089] Example 14

[0090] Example 14 of this invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0091] 138.2 mg of p-phenylenediol (1 mmol), 13.2 mg of HI (0.1 mmol), and 30 mL of acetonitrile were added to a batch reactor, and H2 was introduced at 1 MPa. The reaction was carried out at 300 °C for 12 h. Gas chromatography analysis showed that the product was p-xylene (0.96 mmol), with a molar yield of 96%.

[0092] Example 15

[0093] Example 15 of this invention provides a method for iodine-mediated alcohol reduction, comprising the following steps:

[0094] 128.2 mg of 2,5-dimethylfuran (1 mmol), 26.4 mg of HI (0.2 mmol), and 30 mL of acetonitrile were added to a batch reactor, and H2 was bubbled through at 2 MPa. The reaction was carried out at 180 °C for 6 h. Gas chromatography analysis showed that the product was 2,5-dimethylfuran (0.92 mmol), with a molar yield of 92%.

[0095] Performance verification

[0096] The reaction mechanism of the present invention was verified by intermediate capture experiments, including the following steps:

[0097] S1. Monitoring of reaction intermediates:

[0098] Mechanistic studies were conducted using benzyl alcohol as a substrate, and benzyl iodine was observed to be the main intermediate. The reaction formula is shown below.

[0099]

[0100] S2, Hydrogen reduction of benzyl iodine:

[0101] Using benzyl iodine as a substrate and H2 as a reducing agent at 180℃, the yield of toluene was 99%, and the reaction formula is shown below;

[0102]

[0103] S3, Free Radical Capture:

[0104] With the addition of the free radical scavenger (Tempo), the yield of toluene was only 2%, as shown in the following reaction formula;

[0105]

[0106] Tempo was used to capture toluene radicals, and the formation of new compounds by Tempo-QTOF / MS was detected. The compounds were detected by QTOF positive ion mode scanning. 16 H 25 NO hydrogenation ([C 16 H 25 The predicted mass of NO+H+) was 248.2009, and the actual measured mass was 248.2009. Figure 2 As shown; the Q-TOF fragment peak diagram of Tempo capturing toluene radicals to form new compounds is shown below. Figure 3 As shown; this demonstrates that the reduction of benzyl iodine by H₂ is a free radical reaction;

[0107] Therefore, it is demonstrated that under the high-temperature conditions provided by this invention, H2 can reduce allyl iodine compounds without a metal catalyst.

[0108] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. An iodine-mediated alcohol reduction method, characterized in that, Includes the following steps: In a hydrogen atmosphere, under the action of hydroiodic acid, an alcohol in a solvent undergoes a reduction reaction to produce an alkane; the alcohol includes at least one of benzyl alcohol, linalool, allyl alcohol, benzyl alcohol derivatives, and allyl alcohol derivatives; the benzyl alcohol derivative includes at least one of 4-methylbenzyl alcohol, 4-isopropylbenzyl alcohol, and p-hydroxymethylbenzoic acid; the allyl alcohol derivative includes at least one of lactic acid, 2-octenol, and 2-hexenol; the concentration of hydroiodic acid in the reaction is 0.1-10 g / L; the solvent includes at least one of acetonitrile, n-hexane, n-heptane, n-octane, cyclohexane, and 2-methyltetrahydrofuran.

2. The method according to claim 1, characterized in that, The concentration of alcohol in the reaction is 5-25 g / L.

3. The method according to claim 1, characterized in that, The pressure of the hydrogen gas is 0.1-5 MPa.

4. The method according to claim 1, characterized in that, The reaction temperature is 100-300 ℃; the reaction time is 1-24 h.

5. The method according to claim 1, characterized in that, The reaction byproduct is water.

Images