Method for preparing carboxylic ester by catalyzing alkyne oxidative cracking

Abstract

The invention provides a method for preparing carboxylic ester by catalyzing alkyne oxidative cracking. According to the method, alkyne is taken as a substrate, oxygen is taken as an oxygen source, fatty alcohol (methanol, ethanol, propanol, isopropanol and butanol) is taken as an esterification reagent and solvent, and C-C triple bonds in alkyne molecules are subjected to oxidative cracking under the catalysis of nitrate (magnesium nitrate, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, aluminum nitrate and silver nitrate), nitric acid or NO2 and are converted into carboxylic ester. The reaction temperature is 60-100 DEG C, the reaction time is 2-30 hours, and the molar ratio of the substrate to nitrate in the catalytic reaction is 1: 0.2. Due to the fact that the catalytic reaction is high in selectivity, high in yield and few in by-product, the yield can reach 90% or above, and the method has the advantages of being high in atom utilization efficiency, economical, environmentally friendly and good in application prospect.

Description

Technical Field

[0001] The invention relates to a method for preparing carboxylic acid esters by using nitrate, nitric acid or NO2 to efficiently catalyze the oxidative cleavage of the C—C triple bond in alkynes, and belongs to the technical field of environmental functional catalytic production of chemicals. Background Art

[0002] Carboxylic acid esters are an important class of organic compounds with significant applications in organic synthesis, industrial and agricultural production, and pharmaceutical synthesis. Therefore, developing new, environmentally friendly methods for synthesizing carboxylic acid esters is a crucial challenge in modern organic synthesis. The inventors have provided a highly efficient method for synthesizing carboxylic acid esters by catalyzing the oxidative cleavage of alkynes. This method converts alkyne compounds into the corresponding carboxylic acid esters through oxidative cleavage of the C-C triple bond.

[0003] According to the different oxidants used, the preparation of carboxylic acid esters by oxidative cracking of alkynes can be divided into two categories: using strong oxidants (ozone, NaIO4, TBHP, OsO4, Oxone reagent, I (III) reagent, etc.) and using oxygen. In terms of using strong oxidants as oxygen sources, there are safety issues such as the toxicity of the oxidant itself and expensive cost issues, and an equivalent amount of waste will be generated, causing waste and increasing the cost of product separation, which does not meet the needs of sustainable development (J.Org.Chem.2014,79,2709-2715.). In terms of using oxygen as an oxygen source, it is generally necessary to use various expensive metals as catalysts (J.Am.Chem.Soc.2008,130,5030-5031.), and it is also limited in terms of reaction selectivity, etc., less than 80% (Org.Biomol.Chem.2022,20,8305-8312., Catal.Sci.Technol.2020,10,8458-8464.). Therefore, it is particularly important to develop new catalytic systems and use non-precious metal catalytic systems to achieve highly selective oxidative cracking of alkynes to prepare carboxylates under the condition of oxygen as an oxidant. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing carboxylic acid esters by catalytic oxidative cleavage of alkynes. The method uses nitrate, nitric acid or NO2 as a catalyst, oxygen as an oxidant, and fatty alcohol as an esterification reagent and solvent to achieve oxidative cleavage of the C-C triple bond in the alkyne and convert it into a carboxylic acid ester.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes, using alkynes as substrates, oxygen as an oxygen source, fatty alcohols as esterification reagents and solvents, and nitrates, nitric acid or NO2 as catalysts, to react and generate carboxylic acid ester compounds.

[0007] The alkynes include phenylacetylene, 4-ethynyltoluene, 3-ethynyltoluene, 2-ethynyltoluene, 4-tert-butylphenylacetylene, 4-fluorophenylacetylene, 4-chlorophenylacetylene, 4-bromophenylacetylene, 4-ethynylbenzonitrile, 4-ethynyl-α,α,α,-trifluorotoluene, 1-ethynyl-4-nitrobenzene, 4-methoxyphenylacetylene, 4-ethynylbenzyl alcohol, 4-ethynylbenzaldehyde, 4-methylformate phenylacetylene, 4-alkynylacetophenone, 2-ethynylnaphthalene, 4-ethynylbiphenyl, 5-alkynylbenzo[d][1,3]dioxole, 2-ethynylthiophene, phenylalkynyltrimethylsilane, 4-phenyl-3-butyn-2-one, methyl phenylpropiolate, 1-phenyl-1-hexyne, 1-heptyne or 6-dodecyne.

[0008] The catalyst includes nitrates such as magnesium nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, aluminum nitrate, and silver nitrate, as well as nitric acid and NO2.

[0009] The oxidant required for the oxidation reaction is oxygen, and the oxygen pressure is 1 MPa.

[0010] The selected fatty alcohols include methanol, ethanol, propanol, butanol, and isopropanol.

[0011] The reaction temperature is 60-160°C, preferably 140-160°C.

[0012] The reaction time is 2-30 hours, preferably 10-20 hours.

[0013] In the catalytic reaction, the molar ratio of the reaction substrate to the nitrate ion in the added catalyst is 1:0.2.

[0014] The amount of the reaction substrate used in the catalytic reaction ranges from 0.5 to 1 mmol.

[0015] The present invention discloses the following technical effects:

[0016] The present invention converts alkynes into carboxylic esters through oxidative cleavage of the C-C triple bond using nitrate, nitric acid, or NO2 as a catalyst, oxygen as an oxidant, and a fatty alcohol as an esterification agent and solvent. Due to the highly selective catalytic reaction, high yields and minimal byproducts, the product yield can reach over 90%.

[0017] This method is simple to operate, has high oxidation efficiency, good selectivity, high product yield, and low cost. Using oxygen as the oxygen source greatly improves the atomic utilization efficiency, conforms to the principles of economy, environmental protection, and sustainability, and has great application prospects. DETAILED DESCRIPTION

[0018] The following examples will help to understand the present invention, but the present invention is not limited thereto.

[0019] Example 1

[0020] 1 mmol of phenylacetylene, 0.1 mmol of zinc nitrate, and 8 mL of methanol were added sequentially to a 25 mL stainless steel autoclave, filled with 1 MPa of oxygen, and placed in a 140°C heating block with stirring for 10 hours. GC / GC-MS analysis of the reaction product revealed a 92% yield of methyl benzoate.

[0021] Example 2-18

[0022] Except for the different reaction conditions such as catalyst and dosage, solvent, reaction time, and reaction temperature, the catalyst activity evaluation was the same as in Example 1. The reaction conditions and catalytic reaction results are shown in Table 1. As can be seen from Table 1 and Example 1, phenylacetylene can be oxidatively cracked to produce methyl benzoate under the catalysis of various nitrates (Examples 1, 2-8), nitric acid (Example 9), and NO2 (Examples 10-12). Using different catalysts for catalytic conversion at the same reaction temperature and reaction time resulted in varying reaction speeds. By optimizing the reaction conditions (increasing the reaction temperature or extending the reaction time), the yield of the target product can be further improved (Examples 1-14). In addition, the selected fatty alcohol also has a significant impact on the reactivity of the corresponding benzoic acid ester obtained by catalytic conversion (Examples 1, 15-18).

[0023] We were able to achieve the oxidative cracking of alkynes to produce carboxylic acid esters using such a catalytic system of nitrate, nitric acid, and NO2. Although the yields varied, the data demonstrated catalytic activity. This fully demonstrates that the present method for catalyzing the oxidative cracking of alkynes to produce carboxylic acid esters is entirely feasible using alkynes as substrates, oxygen as the oxygen source, fatty alcohols (methanol, ethanol, propanol, butanol, isopropanol) as the esterification reagent and reaction solvent, and nitrate, nitric acid, or NO2 as the catalyst to produce carboxylic acid esters.

[0024] Table 1. Preparation of benzoic acid esters by oxidative cleavage of phenylacetylene.

[0025]

[0026] Examples 19-44

[0027] Except for the reaction substrate and its amount, reaction time, and reaction temperature, the other reaction conditions and reaction product yield evaluation were the same as in Example 1. Specifically, the reaction substrate amount used in Examples 19-38, 40-43 was 1 mmol, and the reaction substrate amount used in Examples 39 and 44 was 0.5 mmol. Other reaction temperatures, reaction times, reaction substrates used, and catalytic reaction results are shown in Table 2. As can be seen from Table 2, a variety of terminal alkynes and internal alkynes with different functional groups can be converted into the corresponding carboxylic acid esters, further demonstrating the universality of our catalytic system.

[0028] Table 2. Oxidative cleavage of various alkynes to carboxylates catalyzed by zinc nitrate.

[0029]

[0030]

[0031] In summary, the scheme described in this patent enables the targeted oxidation of alkynes to their corresponding carboxylic acid esters. By regulating the reaction conditions, most alkynes can achieve yields exceeding 90%. A few alkyne compounds with easily oxidizable functional groups, such as 4-ethynylbenzyl alcohol, can also achieve yields of 64%. Therefore, the present invention offers high oxidation efficiency, good selectivity, and high product yields. Furthermore, the use of oxygen as the oxygen source during the reaction is environmentally friendly and has promising application prospects.

Claims

1. A method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes, characterized in that: Using alkynes as substrates, oxygen as the oxygen source, and fatty alcohols as esterification reagents and solvents, under the catalysis of nitrates, nitric acid or NO2, the CC triple bond in the alkyne molecule undergoes oxidative cleavage and is converted into a carboxylic ester.

2. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: Alkyne compounds include phenylacetylene, 4-ethynyltoluene, 3-ethynyltoluene, 2-ethynyltoluene, 4-tert-butylphenylacetylene, 4-fluorophenylacetylene, 4-chlorophenylacetylene, 4-bromophenylacetylene, 4-ethynylbenzonitrile, 4-ethynyl-α,α,α,-trifluorotoluene, 1-ethynyl-4-nitrobenzene, 4-methoxyphenylacetylene, 4-ethynylbenzyl alcohol, 4-ethynylbenzaldehyde, 4-methylphenylacetylene carboxylate, 4-alkynylacetophenone, 2-ethynylnaphthalene, 4-ethynylbiphenyl, 5-alkynylbenzo[d][1,3]dioxole, 2-ethynylthiophene, phenylalkynyltrimethylsilane, 4-phenyl-3-butyn-2-one, methyl phenylpropiolate, 1-phenyl-1-hexyne, 1-heptyne or 6-dodecyne.

3. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The catalyst includes nitrates such as magnesium nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, aluminum nitrate, and silver nitrate, as well as nitric acid or NO2.

4. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The oxidant required for the oxidation reaction is oxygen, and the oxygen pressure is 1 MPa.

5. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The selected fatty alcohols include methanol, ethanol, propanol, butanol, and isopropanol.

6. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The reaction temperature is 60-160° C.; the reaction time is 2-30 hours.

7. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: In the catalytic reaction, the molar ratio of the reaction substrate to the nitrate ion in the added catalyst is 1:0.

2.

8. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The amount of the reaction substrate used in the catalytic reaction ranges from 0.5 to 1 mmol.

9. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The reaction temperature range is 140-160°C.

10. The method for preparing carboxylic acid esters by catalytic oxidative cracking of alkynes according to claim 1, wherein: The reaction time is 10-20h.

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