Method for reducing alkyne into olefin by using water as hydrogen source

Abstract

The invention relates to the field of organic chemistry, in particular to a method for reducing alkyne into olefin by taking water as a hydrogen source, and the preparation method comprises the following steps: placing alkyne, a cobalt catalyst, a ligand, alkali, a boron reagent and water in an organic solvent, then reacting in an inert atmosphere at 100-120 DEG C, and after the reaction is finished, filtering, separating and purifying to obtain a finished product. The method has the advantages that all reactants are commercially available, easy to obtain and low in cost, the reaction condition is mild, the operation is simple, the stereoselectivity and the chemical selectivity are excellent, and the reaction yield is high, three reaction systems with different types of substrates are provided, olefin products with single configuration can be obtained with good to excellent yield, and the method is suitable for industrial production. The generation of another stereoisomer is completely avoided.

Description

Technical Field

[0001] The invention relates to the field of organic chemistry, in particular to a method for reducing alkynes to alkenes by using water as a hydrogen source. Background Art

[0002] The stereodivergent semihydrogenation reaction of alkynes plays an important role in organic synthesis. It can selectively obtain cis or trans alkenes, making them applicable to the preparation of bioactive molecules, natural products, drug molecules, etc. The classic Lindlar catalytic system is an important method for obtaining Z-alkenes. It is mostly used in the industrial preparation of cis alkenes, and can also be used to purify olefin products containing a small amount of alkynes. Although this method is simple and practical, it also has some problems, such as: isomerization of Z-alkenes to E-alkenes, excessive reduction of alkynes to alkanes rather than alkenes, and poor reproducibility. In addition, the reaction requires the addition of excess quinoline and the use of hydrogen as a hydrogen source, resulting in harmful waste and heavy metal residues in the product, which is dangerous and not conducive to sustainable development.

[0003] In recent years, methods for achieving hydrogen transfer using small molecule hydrogen sources have been widely developed, but most of them are based on precious metal catalytic systems, and most catalysts require multi-step synthesis, and the reaction system also faces problems such as a narrow substrate range. For example, Chinese invention patent 202110801019.6 discloses a method for selectively synthesizing cis- and trans-olefins by semi-reduction of alkynes using water as a hydrogen source catalyzed by precious metal palladium; Chinese invention patent 202110801026.6 discloses a method for selectively synthesizing cis- and trans-olefins by semi-reduction of alkynes catalyzed by iridium with water as a hydrogen source; In our previous research work, we developed a reaction system catalyzed by inexpensive metal nickel, using different bases for selective regulation to reduce alkynes to cis- and trans-olefins, respectively (Chinese invention application number is 2021 10289237.6), but a small amount of olefin isomers were inevitably produced in the product; in 2018, Liu Qiang's research group at Tsinghua University prepared Co catalysts modified with different ligands and applied them to the stereodivergent semi-hydrogenation of alkynes to alkenes, using ammonia borane as the hydrogen source, and the reaction stereoselectivity was 1:1->99:1 (J.Am.Chem.Soc.2016,138,8588-8594); Fan Baomin's research group developed a cobalt-catalyzed method for the semi-hydrogenation of alkynes to alkenes in 2019, using water as the hydrogen source and zinc powder as a reducing agent to assist the catalytic cycle, but its cis- and trans-selective stereoisomers were also generated (Chem.Commun.2019,55,5663-5666).

[0004] In summary, the semi-hydrogenation reaction of alkynes using water as the hydrogen source has made great progress in recent years, but there are still problems such as high catalyst cost, multiple synthesis steps and difficulty in avoiding stereoisomers. Summary of the invention

[0005] Preparing E-type and Z-type olefins with good yield and selectivity through selective regulation is an inevitable requirement for sustainable development, and is also a meaningful and challenging task. In order to solve the above problems, the present invention proposes a method for reducing alkynes to olefins using water as a hydrogen source, and through the selective regulation of different ligands, E-type and Z-type olefins are prepared with good yield and excellent selectivity.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for reducing alkynes to alkenes using water as a hydrogen source comprises the following steps:

[0008] Alkyne, cobalt catalyst, ligand, base, boron reagent and water are placed in an organic solvent, and then reacted at 100-120° C. in an inert atmosphere. After the reaction is completed, the product is filtered, separated and purified to obtain the finished product. The amount of the cobalt catalyst is 5%-10% of the molar amount of the alkyne, and the amount of the ligand is 11%-22% of the molar amount of the alkyne; the amount of the base is 2 times the molar amount of the alkyne, and the amount of the boron reagent is 1.5 times the molar amount of the alkyne; the amount of water is 2-3 times the molar amount of the alkyne, wherein the alkyne is a diaryl alkyne or an arylalkyl alkyne, and the structural formula of the alkyne is R 1 -≡-R 2 , R 1 and R 2 Any one of the following groups is selected: benzene ring, alkylbenzene, alkoxybenzene, halogenated benzene, ester benzene, carbonylbenzene, cyanobenzene, thienyl and pyridyl, and the ligand is 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-dicarboxylic acid methyl ester-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, biquinoline, 1,10-phenanthroline, 4,7-dimethoxy-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline At least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, tri-n-butylphosphine, tricyclohexylphosphine, tri-tert-butylphosphine, triphenylphosphine, trimethoxyphosphine, tri(4-methoxyphenyl)phosphine, tri(o-methylphenyl)phosphine, tri(2,6-dimethoxyphenyl)phosphine, 2-(di-tert-butylphosphinobiphenyl), tri(1-naphthyl)phosphine, 1,3-bis(diphenylphosphino)propane and diphenyl-2-pyridylmethane, preferably 2,9-dimethyl-1,10-phenanthroline and tri-tert-butylphosphine, and there are three reaction formulas in the present invention:

[0009]

[0010]

[0011] In formula (I), R 1 and R 2 Any one of the following groups: benzene ring, alkylbenzene, alkoxybenzene, halogenated benzene, ester group benzene, carbonyl benzene, cyanobenzene, thienyl and pyridyl; R in formula (II) 1 and R 2 Any one of the following groups: benzene ring, alkylbenzene, alkoxybenzene, halogenated benzene, ester group benzene, cyanobenzene, thienyl and pyridyl; R in formula (III) 1 Any one of the following groups: benzene ring, alkylbenzene, alkoxybenzene and halogenated benzene, R 2 Any one of the following groups is selected: chain alkyl, cycloalkyl and silane. The strategy of the present invention is that under the conditions of the cobalt catalyst, ligand, base, boron reagent and water, the boron reagent is used to activate water, and then combined with cobalt catalysis, B-Co-H species can be generated in situ to achieve hydrogen transfer. Under the control of different ligands, there is no over-hydrogenation product alkane, and E-type and Z-type olefins are generated with good yield and selectivity.

[0012] As a further embodiment of the present invention: the organic solvent is any one of tetrahydrofuran (THF), methanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), ethanol, tert-butanol, 1,4-dioxane, ether, acetonitrile, dichloromethane, isopropanol and n-hexane, preferably tetrahydrofuran (THF) and methanol.

[0013] As a further embodiment of the present invention: the cobalt catalyst is one or more of cobalt iodide, cobalt fluoride, cobalt chloride, cobalt acetate, octacarbonyl cobalt and cobalt (II) acetylacetonate, preferably cobalt chloride.

[0014] As a further embodiment of the present invention: the base is any one of potassium bicarbonate, potassium carbonate, cesium carbonate, potassium phosphate, potassium hydroxide, triethylenediamine, sodium trifluoroacetate, potassium formate, potassium tert-butoxide and DBU (1,8-diazabicycloundec-7-ene), preferably potassium bicarbonate.

[0015] As a further embodiment of the present invention, the boron reagent is one or more of biboric acid pinacol ester, tetrahydroxydiborane, biboric acid neopentyl glycol ester and pinacol borane, preferably biboric acid pinacol ester.

[0016] As a further solution of the present invention: filtration is performed by diatomaceous earth filtration, purification is performed by column chromatography or thin layer chromatography, the developing solvent used in the chromatography is petroleum ether or a mixture of petroleum ether and ethyl acetate, the molar ratio of petroleum ether to ethyl acetate is between 2:1-100:1, and the reaction time is 14-48h.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Using clean, green and easily available water as a hydrogen source is in line with the development concept of green chemistry and avoids the safety hazards caused by the use of hydrogen;

[0019] The reaction conditions are mild, and the catalysts, ligands, bases, boron reagents and organic solvents in the reaction conditions are all commercially available, without the need for further synthesis, and are relatively inexpensive. The reaction operation is simple and suitable for large-scale production;

[0020] The reaction has high yield, excellent stereoselectivity and no over-reduction product is generated.

[0021] In summary, the present invention has the advantages that all reactants are readily available and cheap, the reaction conditions are mild, the operation is simple, it has excellent stereoselectivity (only a single isomer is generated) and chemical selectivity (no excessive reduction product is generated), and the reaction yield is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the hydrogen spectrum of the olefin product obtained in Example 1 of the present invention.

[0023] Figure 2 This is the carbon spectrum of the olefin product obtained in Example 1 of the present invention.

[0024] Figure 3 This is the hydrogen spectrum of the olefin product obtained in Example 2 of the present invention.

[0025] Figure 4 This is the carbon spectrum of the olefin product obtained in Example 2 of the present invention.

[0026] Figure 5 This is the hydrogen spectrum of the olefin product obtained in Example 3 of the present invention.

[0027] Figure 6 This is the carbon spectrum of the olefin product obtained in Example 3 of the present invention.

[0028] Figure 7 This is the hydrogen spectrum of the olefin product obtained in Example 4 of the present invention.

[0029] Figure 8 This is the carbon spectrum of the olefin product obtained in Example 4 of the present invention.

[0030] Fig. 9 This is the hydrogen spectrum of the olefin product obtained in Example 5 of the present invention.

[0031] Fig.10 This is the carbon spectrum of the olefin product obtained in Example 5 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The method of the present invention has three reaction systems with different types of substrates, all of which can obtain single-configuration olefin products with good to excellent yields, and completely avoid the generation of another stereoisomer; the present invention uses the earth's abundant metal cobalt as a catalyst, combined with a boron reagent to activate water to achieve hydrogen transfer, and the reaction system does not generate over-hydrogenation products such as alkanes. All reactants are commercially available, the conditions are mild, the selectivity is good, and the yield is high. Compared with other methods of the same type, the present invention performs excellently and has good application prospects.

[0034] Example 1 Reduction of phenylacetylene to E-phenylethylene

[0035] Cobalt chloride (1.9 mg, 5% of the molar amount of alkyne), 2,9-dimethyl-1,10-phenanthroline (6.9 mg, 11% of the molar amount of alkyne), 1,2-diphenylacetylene (53.4 mg, 1.0 equiv.), potassium bicarbonate (60.0 mg, 2 times the molar amount of alkyne), and pinacol diboron (114.3 mg, 1.5 times the molar amount of alkyne) were weighed separately and added into a 25 mL sealed tube. The air in the reaction tube was then replaced with argon. Distilled water (10.8 μL, 2 times the molar amount of alkyne) and THF (2 ml) were added using a microsyringe under argon conditions. The reaction tube was sealed and reacted at 100°C for 14 h. After the reaction was stopped, the reaction solution was filtered with diatomaceous earth, the reaction solution was spin-dried, and the E-type olefin product was separated by column chromatography. The total yield of the reaction was calculated to be 75%, and the ratio of cis-trans olefins in the product was: Z / E=0 / 100 (Z / E is the ratio of cis-olefin to trans-olefin). The hydrogen spectrum and carbon spectrum of the olefin product were measured, and the measurement results are shown in Figure 1-Figure 2 ,from Figure 1 and Figure 2 The purity of the obtained compound can be seen in .

[0036]

[0037] E-phenylethylene: white solid, 1 H NMR (400MHZ, CDCl3) δ7.60 (d, J = 7.4HZ, 4H), 7.45 (t, J = 7.5HZ, 4H), 7.36 (d, J = 7.2HZ, 2H), 7.20 (s, 2H);

[0038] 13 C NMR (101 MHZ, CDCl3) δ 137.41, 128.77, 127.71, 126.61, where s is a singlet, d is a doublet, t is a triplet, q is a quartet, dd is two doublets, dt is two triplets, m is a multiplet, and J is the coupling constant.

[0039] Example 2 Reduction of phenylacetylene to Z-phenylethylene

[0040] Cobalt chloride (3.9 mg, 10% of the molar amount of alkyne), tri-tert-butylphosphine (13.3 mg, 22% of the molar amount of alkyne), 1,2-di-p-tolueneacetylene (61.9 mg, 1 times the molar amount of alkyne), potassium bicarbonate (60.0 mg, 2 times the molar amount of alkyne), and pinacol diboron (114.3 mg, 1.5 times the molar amount of alkyne) were weighed separately and added into a 25 mL sealed tube. The air in the reaction tube was then replaced with argon. Distilled water (16.2 μL, 3 times the molar amount of alkyne) and MeOH (methanol, 2 ml) were added using a microsyringe under argon conditions. The reaction tube was sealed and reacted at 100°C for 14 h. After the reaction was stopped, the reaction solution was filtered with diatomaceous earth, the reaction solution was spin-dried, and the Z-type olefin product was separated by column chromatography. The total yield of the reaction was calculated to be 52%. The ratio of cis- and trans-olefins in the product was: Z / E=100 / 0 (Z / E is the ratio of cis-olefin to trans-olefin). The hydrogen spectrum and carbon spectrum of the olefin product were measured. The results are shown in Figure 3-Figure 4 ,from Figure 3 and Figure 4 The purity of the obtained compound can be seen in .

[0041]

[0042] Z-phenylethylene: white solid, 1 H NMR(400MHZ, CDCl3)δ7.30–7.21(m,10H),6.64(s,2H);

[0043] 13 C NMR (101 MHZ, CDCl3) δ 137.22 (s), 130.23 (s), 128.85 (s), 128.18 (s), 127.06 (s), where s is a singlet, d is a doublet, t is a triplet, q is a quartet, dd is two doublets, dt is two triplets, m is a multiplet, and J is a coupling constant.

[0044] Example 31,2-Di-p-tolueneacetylene reduction to E-formula-1,2-di-p-toluenephenylethylene

[0045] Cobalt chloride (1.9 mg, 5% of the molar amount of alkyne), 2,9-dimethyl-1,10-phenanthroline (6.9 mg, 11% of the molar amount of alkyne), 1,2-di-p-tolueneacetylene (61.9 mg, 1 times the molar amount of alkyne), potassium bicarbonate (60.0 mg, 2 times the molar amount of alkyne), and pinacol diboron (114.3 mg, 1.5 times the molar amount of alkyne) were weighed separately and added into a 25 mL sealed tube. The air in the reaction tube was then replaced with argon. Distilled water (10.8 μL, 2 times the molar amount of alkyne) and THF (2 ml) were added using a microsyringe under argon conditions. The reaction tube was sealed and reacted at 100°C for 14 h. After the reaction was stopped, the reaction solution was filtered with diatomaceous earth, the reaction solution was spin-dried, and the E-type olefin product was separated by column chromatography. The total yield of the reaction was calculated to be 84%, and the ratio of cis-trans olefins in the product was: Z / E=0 / 100 (Z / E is the ratio of cis-olefin to trans-olefin). The hydrogen spectrum and carbon spectrum of the olefin product were measured, and the measurement results are shown in Figure 5-Figure 6 ,from Figure 5 and Figure 6 The purity of the obtained compound can be seen in .

[0046]

[0047] E-1,2-di-p-toluene: white solid, 1 H NMR (400MHZ, CDCl3) δ7.43 (d, J = 7.4HZ, 4H), 7.18 (d, J = 7.2HZ, 4H), 7.06 (s, 2H), 2.38 (s, 6H);

[0048] 13 C NMR (101 MHz, CDCl3) δ 137.31, 134.79, 129.43, 127.69, 126.37, 21.30, where s is a singlet, d is a doublet, t is a triplet, q is a quartet, dd is two doublets, dt is two triplets, m is a multiplet, and J is the coupling constant.

[0049] Example 41,2-Di-p-tolueneacetylene reduction to Z-1,2-di-p-toluenephenylethylene

[0050] Cobalt chloride (3.9 mg, 10% of the molar amount of alkyne), tri-tert-butylphosphine (13.3 mg, 22% of the molar amount of alkyne), 1,2-ditolueneacetylene (61.9 mg, 1 times the molar amount of alkyne), potassium bicarbonate (60.0 mg, 2.0 times the molar amount of alkyne), and pinacol diboron (114.3 mg, 1.5 times the molar amount of alkyne) were weighed separately and added into a 25 mL sealed tube. The air in the reaction tube was then replaced with argon. Distilled water (16.2 μL, 3 times the molar amount of alkyne) and MeOH (2 ml) were added using a microsyringe under argon conditions. The reaction tube was sealed and reacted at 100°C for 14 h. After the reaction was stopped, the reaction solution was filtered with diatomaceous earth, the reaction solution was spin-dried, and the Z-type olefin product was separated by column chromatography. The total yield of the reaction was calculated to be 65%, and the ratio of cis-trans olefins in the product was: Z / E=100 / 0 (Z / E is the ratio of cis-olefins to trans-olefins). The hydrogen spectrum and carbon spectrum of the olefin product were measured, and the measurement results are shown in Figure 7-Figure 8 ,from Figure 7 and Figure 8 The purity of the obtained compound can be seen in .

[0051]

[0052] Z-1,2-di-p-toluene: white solid, 1 H NMR (400MHZ, CDCl3) δ7.17 (d, J = 8.0HZ, 4H), 7.04 (d, J = 7.8HZ, 4H), 6.52 (s, 2H), 2.32 (s, 6H);

[0053] 13 C NMR (101 MHz, CDCl3) δ 136.70, 134.48, 129.49, 128.79, 21.21, where s is a singlet, d is a doublet, t is a triplet, q is a quartet, dd is two doublets, dt is two triplets, m is a multiplet, and J is the coupling constant.

[0054] Example 5 Reduction of tert-butylphenylacetylene to Z-tert-butylstyrene

[0055] Cobalt chloride (3.9 mg, 10% of the molar amount of alkyne), 2,9-dimethyl-1,10-phenanthroline (13.7 mg, 22% of the molar amount of alkyne), 1, tert-butylphenylacetylene (47.5 mg, 1 times the molar amount of alkyne), potassium bicarbonate (60.0 mg, 2 times the molar amount of alkyne), and pinacol diboron (114.3 mg, 1.5 times the molar amount of alkyne) were weighed separately and added into a 25 mL sealed tube. The air in the reaction tube was then replaced with argon. Distilled water (16.2 μL, 3 times the molar amount of alkyne) and MeOH (2 ml) were added using a microsyringe under argon conditions. The reaction tube was sealed and reacted at 100°C for 14 h. After the reaction was stopped, the reaction solution was filtered with diatomaceous earth, the reaction solution was spin-dried, and the Z-type olefin product was separated by column chromatography. The total yield of the reaction was calculated to be 60%, and the ratio of cis-trans olefins in the product was: Z / E=100 / 0 (Z / E is the ratio of cis-olefin to trans-olefin). The hydrogen spectrum and carbon spectrum of the olefin product were measured, and the measurement results are shown in Figure 9-10 ,from Fig. 9 and Fig.10 The purity of the obtained compound can be seen in .

[0056]

[0057] Tert-butylstyrene: colorless liquid, 1 H NMR (400MHZ, CDCl3) δ7.39 (d, J = 7.2HZ, 2H), 7.31 (t, J = 7.6HZ, 2H), 7.21 (t, J = 7.2HZ, 1H), 6.31 (d, J = 6.7HZ, 2H), 1.15 (s, 9H);

[0058] 13 C NMR (101 MHz, CDCl3) δ 141.82, 138.03, 128.45, 126.72, 126.00, 124.54, 77.32, 77.00, 76.68, 33.33, 29.58, where s is a singlet, d is a doublet, t is a triplet, q is a quartet, dd is two doublets, dt is two triplets, m is a multiplet, and J is a coupling constant.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for reducing alkynes to alkenes using water as a hydrogen source, characterized in that: The following steps are involved: Alkyne, cobalt catalyst, ligand, base, boron reagent and water are placed in an organic solvent, and then reacted at 100-120° C. in an inert atmosphere. After the reaction is completed, the product is filtered, separated and purified to obtain the finished product. The amount of the cobalt catalyst is 5%-10% of the molar amount of the alkyne, and the amount of the ligand is 11%-22% of the molar amount of the alkyne; the amount of the base is 2 times the molar amount of the alkyne, and the amount of the boron reagent is 1.5 times the molar amount of the alkyne; the amount of water is 2-3 times the molar amount of the alkyne, wherein the alkyne is a diaryl alkyne or an arylalkyl alkyne, and the structural formula of the alkyne is R 1 -≡-R 2 , R 1 and R 2 Any one of the following groups: benzene ring, alkylbenzene, alkoxybenzene, halogenated benzene, ester benzene, carbonylbenzene, cyanobenzene, thienyl and pyridyl, the ligand is 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-dicarboxylic acid methyl ester-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, biquinoline, 1,10-phenanthroline, 4,7-dimethoxy-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline At least one of phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, tri-n-butylphosphine, tricyclohexylphosphine, tri-tert-butylphosphine, triphenylphosphine, trimethoxyphosphine, tri(4-methoxyphenyl)phosphine, tri(o-methylphenyl)phosphine, tri(2,6-dimethoxyphenyl)phosphine, 2-(di-tert-butylphosphinobiphenyl), tri(1-naphthyl)phosphine, 1,3-bis(diphenylphosphino)propane and diphenyl-2-pyridylmethane.

2. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1, characterized in that: The organic solvent is any one of THF, methanol, DMF, DMA, ethanol, tert-butanol, 1,4-dioxane, ether, acetonitrile, dichloromethane, isopropanol and n-hexane.

3. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1 or 2, characterized in that: The cobalt catalyst is one or more of cobalt iodide, cobalt fluoride, cobalt chloride, cobalt acetate, octacarbonyl cobalt and cobalt (II) acetylacetonate.

4. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1, characterized in that: The base is any one of potassium bicarbonate, potassium carbonate, cesium carbonate, potassium phosphate, potassium hydroxide, triethylenediamine, sodium trifluoroacetate, potassium formate, potassium tert-butoxide and DBU.

5. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1, characterized in that: The boron reagent is one or more of pinacol borate, tetrahydroxydiborane, neopentyl glycol borate and pinacol borane.

6. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1, characterized in that: The filtration is performed by diatomaceous earth filtration, and the purification is performed by column chromatography or thin layer chromatography.

7. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 6, characterized in that: The developing solvent used in the chromatography is petroleum ether or a mixture of petroleum ether and ethyl acetate, and the molar ratio of petroleum ether to ethyl acetate is between 2:1-100:

1.

8. The method for reducing alkynes to alkenes using water as a hydrogen source according to claim 1, characterized in that: The reaction time is 14-48h.

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