Method for preparing silanol through selective oxidation of hydrosilane under catalysis of nano-porous palladium copper

Abstract

The invention belongs to the technical field of organic synthesis, industrial intermediates and related chemistry, and discloses a method for preparing silanol through selective oxidation of hydrosilane under the catalysis of nano-porous palladium-copper. The corresponding silanol is selectively prepared by taking hydrosilane as a raw material, a nano-porous palladium-copper catalyst as a catalyst and hydrogen peroxide as an oxidizing agent. Cheap hydrosilane is selected as a raw material in the reaction, hydrogen peroxide is used as an oxidizing agent, the silanol is synthesized by adopting a one-pot method, separation of an intermediate product is not needed, and tedious separation and purification steps are avoided. The product selectivity is high, the operation and post-treatment are simple, the catalyst activity is high, the property is stable, the reproducibility is good, the catalytic effect is not obviously reduced after repeated use, and industrialization is possible.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, industrial intermediates and related chemical technologies, and relates to a method for preparing silanol by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper. Background Art

[0002] Organosilicon compounds have attracted great interest due to their wide range of applications in industry and academia. In particular, silanols have been used industrially to produce silicon-based polymer materials, for derivatization of functional groups, and as nucleophiles in metal-catalyzed cross-coupling reactions in organic synthesis. Organosiliconols have also been identified as challenging bioactive substances in experimental pharmacology, and have been used in catalysis due to their anion recognition ability.

[0003] There are currently four methods for the synthesis of silanols. First, they can be obtained by acid-base hydrolysis of chloro or alkoxysilanes. However, this method requires strict monitoring of the reaction conditions, especially the pH value, because if the required conditions are not present, the silanols will easily condense to form the corresponding disiloxanes. The third method is to oxidize the Si-H groups to Si-OH groups using various oxidants, but in most cases, expensive, toxic or harmful oxidants are used, such as silver (I) salts, osmium oxide, hydroperoxides, permanganates, dioxananes, oxazolidinones, ozone or various organic catalysts. These processes also produce a large amount of disiloxanes as by-products. The fourth synthesis method, transition metal catalysis, effectively solves the problems existing in the above synthesis methods. That is, a set of diverse catalytic conditions is adopted to minimize the formation of by-products. Among the various metals used, Rh, Cu, Re, Pd, Ir, and W have been shown to be effective in oxidizing silane [see: (a) Dimitris Limnios and Christoforos G. Kokotos, ACS Catal. 2013, 3, 10, 2239–2243.]. And among the choices of transition metal catalysts, nanoporous catalysts have been widely studied due to their unique properties.

[0004] Nanoporous palladium copper material is a new type of nanostructured catalyst, which is composed of nanoscale pores, has a large specific surface area, excellent electrical and thermal conductivity, and non-toxic properties. It can show completely different physical and chemical properties from bulk metals and is a research hotspot in the field of catalysis. Nanoporous palladium copper (PdCuNPore) catalyst has the advantages of low price, simple preparation, high catalytic activity, high chemical selectivity, stable properties, and easy recycling. Summary of the invention

[0005] The present invention provides a method for preparing silanol, which uses cheap hydrosilane as a raw material, hydrogen peroxide as an oxidant, and synthesizes silanol by a one-pot method, does not require separation of intermediate products, and avoids cumbersome separation and purification steps. The selected catalyst has the advantages of high activity, stable properties, low price, high chemical selectivity, etc., and the catalytic activity is not significantly reduced after repeated use.

[0006] The technical solution of the present invention:

[0007] A method for preparing silanols by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper, using hydrosilane as a raw material, nanoporous palladium copper (PdCuNPore) as a catalyst, and hydrogen peroxide as an oxidant, selectively adding hydrosilane in a solvent to prepare the corresponding silanol, the synthesis route is as follows:

[0008]

[0009] R 1 Selected from hydrogen, alkyl, methoxy, substituted phenyl;

[0010] R 2 Selected from alkyl, methoxy, substituted phenyl;

[0011] R 3 Selected from alkyl, methoxy, substituted phenyl;

[0012] R 1 , R 2 , R 3 Same or different;

[0013] The nanoporous palladium copper catalyst has a pore size of 1 nm to 50 nm, the molar ratio of hydrosilane to the nanoporous palladium copper catalyst is 1:0.1; the molar ratio of hydrosilane to hydrogen peroxide is 1:2; the reaction temperature is 20-80°C; and the reaction time is 6-48h.

[0014] The solvents include dichloromethane, ethyl acetate, methanol, ethanol, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, dimethylacetamide, 1,4-dioxane, etc. The molar concentration of hydrosilane in the solvent is 0.13 mmol / mL.

[0015] The separation method uses a column chromatography method, using a silica gel column as a chromatography column, and the developing solvent is generally a mixed solvent of polar and non-polar solvents, such as ethyl acetate-petroleum ether, ethyl acetate-n-hexane.

[0016] The nanoporous palladium copper catalyst is obtained by chemically corroding and dealloying a Pd-Cu-Al alloy. The atomic ratio of Cu, Pd and Al in the nanoporous palladium copper catalyst is 19:1:80 or 19.9:0.1:80.

[0017] The beneficial effects of the present invention are that the reaction adopts a one-pot process, avoiding the separation and treatment of intermediate products, being simple and efficient, having high product selectivity, being simple in operation and post-treatment, having good catalyst reproducibility, and having no significant reduction in catalytic effect after repeated use, thus providing the possibility for its industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Example 1, dimethylphenylsilanol 1 H NMR spectrum.

[0019] Figure 2 Example 2, methyl diphenyl silanol 1 H NMR spectrum.

[0020] Figure 3 Example 3, triphenylsilanol 1 H NMR spectrum.

[0021] Figure 4 Example 4, benzyl dimethyl silanol 1 H NMR spectrum.

[0022] Figure 5 Example 5, dimethyl (p-benzyl) silanol 1 H NMR spectrum.

[0023] Figure 6 Example 6, (4-methoxyphenyl) dimethylsilanol 1 H NMR spectrum.

[0024] Figure 7 Example 7, (4-tert-butylphenyl) dimethylsilanol 1 H NMR spectrum.

[0025] Figure 8 Example 8, (4-bromophenyl)dimethylsilanol 1 H NMR spectrum.

[0026] Fig. 9 Example 9, (4-chlorophenyl) dimethylsilanol 1 H NMR spectrum.

[0027] Fig.10 Example 10, (4-thiomethylphenyl)dimethylsilanol 1 H NMR spectrum.

[0028] Fig.11 Scanning electron micrograph of the newly prepared nanoporous palladium copper. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0030] The method for preparing silanols of the present invention has a maximum selectivity and a separation yield of 100% and 99% respectively, the selected catalyst has good catalytic reaction reproducibility, the operation and post-treatment are simple, and the catalytic effect is not significantly reduced after repeated use, which provides favorable conditions for its industrial production.

[0031] The present invention is further described below in conjunction with specific embodiments. Simple replacements or improvements made by those skilled in the art to the present invention are all within the technical solution protected by the present invention.

[0032] Example 1: Synthesis of dimethylphenylsilanol

[0033] To an acetonitrile (1.5 mL) solvent containing a PdCuNPore (10 mol%) catalyst, add the substrate dimethylphenylsilane (31 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 30 ° C for 6 h. Silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) is used to obtain dimethylphenylsilanol with an isolation yield of 93%.

[0034]

[0035] Colorless liquid: 1 H NMR (400MHz, Chloroform-d) δ7.51 (d, J=6.0Hz, 4H), 7.29 (dt, J=13.9, 6.8Hz, 6H), 2.72 (s, 1H), 0.55 (s, 3H).

[0036] Example 2: Synthesis of methyldiphenylsilanol

[0037] Methyldiphenylsilane (40 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol) were added to tetrahydrofuran (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, and the mixture was placed on a magnetic stirrer and reacted at 30 °C for 12 h. Methyldiphenylsilanol was obtained by silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) with an isolation yield of 74%.

[0038]

[0039]

[0040] Colorless liquid; 1H NMR (400MHz, Chloroform-d) δ7.51 (d, J = 6.0Hz, 4H), 7.37–7.24 (m, 5H), 2.72 (s, 1H), 0.55 (s, 3H).

[0041] Example 3: Synthesis of triphenylsilanol

[0042] To a tetrahydrofuran (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate triphenylsilane (52 mg, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 50 ° C for 24 h. Silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) is used to obtain triphenylsilanol with an isolation yield of 60%.

[0043]

[0044] White solid: 1 H NMR (400MHz, Chloroform-d) δ7.58–7.46(m,6H),7.37–7.30(m,3H),7.30–7.23(m,6H),2.75(s,1H).

[0045] Example 4: Synthesis of benzyldimethylsilanol

[0046] To an acetonitrile (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate benzyldimethylsilane (32 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 45 ° C for 8 h, and obtain benzyldimethylsilanol by silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) with an isolation yield of 99%.

[0047]

[0048] Colorless liquid; 1 H NMR (400MHz, Chloroform-d) δ7.13(t,J=7.2Hz,2H),6.98(dd,J=18.2,7.1Hz,3H),2.08(s,2H),1.62(s,1H),0.04(s,6H).

[0049] Example 5: Synthesis of dimethyl (p-benzyl) silanol

[0050] To an ethyl acetate (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate dimethyl (P-benzyl) silane (33 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 30 ° C for 18 h. Silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) is used to obtain dimethyl (P-benzyl) silanol with an isolation yield of 85%.

[0051]

[0052] Colorless liquid; 1 H NMR (400MHz, Chloroform-d) δ7.50(d,J=7.8Hz,2H),7.22(d,J=7.2Hz,2H),2.37(s,3H),2.06(s,1H),0.40(s,6H).

[0053] Example 6: Synthesis of (4-methoxyphenyl)dimethylsilanol

[0054] To the N,N-dimethylformamide (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate (4-methoxyphenyl)dimethylsilane (33 mg, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 50 ° C for 32 h, and silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) to obtain (4-methoxyphenyl)dimethylsilanol with an isolation yield of 79%.

[0055]

[0056] Colorless liquid; 1 H NMR(400MHz,Chloroform-d)δ7.53(d,J=8.5Hz,2H),6.93(d,J=8.6Hz,2H),3.82(s,3H),2.16(s,1H),0.38(s,6H) .

[0057] Example 7: Synthesis of (4-tert-butylphenyl)dimethylsilanol

[0058] To a tetrahydrofuran (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate (4-tert-butylphenyl)dimethylsilane (43 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 80 ° C for 10 h, and silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) to obtain (4-tert-butylphenyl) dimethylsilanol with an isolation yield of 95%.

[0059]

[0060] White solid; 1 H NMR (400MHz, Chloroform-d) δ7.59–7.53(m,2H),7.47–7.42(m,2H),1.36(s,9H),0.41(s,6H).

[0061] Example 8: Synthesis of (4-bromophenyl)dimethylsilanol

[0062] To an acetonitrile (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate (4-bromophenyl)dimethylsilane (43 mg, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 30 ° C for 11 h. Silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) is used to obtain (4-bromophenyl)dimethylsilanol with an isolation yield of 89%.

[0063]

[0064] Colorless liquid; 1 H NMR (400MHz, Chloroform-d) δ7.50 (d, J = 8.2Hz, 2H), 7.41 (d, J = 8.2Hz, 2H), 0.36 (s, 6H).

[0065] Example 9: Synthesis of (4-chlorophenyl)dimethylsilanol

[0066] To an ethyl acetate (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate (4-chlorophenyl)dimethylsilane (34 μL, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 60 ° C for 15 h. Silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) is used to obtain (4-chlorophenyl)dimethylsilanol with an isolation yield of 87%.

[0067]

[0068] Colorless liquid: 1 H NMR (400MHz, Chloroform-d) δ7.52 (d, J = 8.3 Hz, 2H), 7.36 (d, J = 8.3 Hz, 2H), 0.40 (s, 6H).

[0069] Example 10: Synthesis of (4-thiomethylphenyl)dimethylsilanol

[0070] To a tetrahydrofuran (1.5 mL) solvent containing PdCuNPore (10 mol%) catalyst, add substrate (4-thiomethylphenyl)dimethylsilane (36 mg, 0.2 mmol) and hydrogen peroxide (43 μL, 0.4 mmol), place on a magnetic stirrer and react at 60 ° C for 12 h, and silica gel column chromatography (developing solvent, petroleum ether: ethyl acetate) to obtain (4-thiomethylphenyl)dimethylsilanol with an isolation yield of 80%.

[0071]

[0072] Colorless liquid: 1 H NMR (400MHz, Chloroform-d) δ7.37–7.29 (m, 2H), 7.10 (d, J = 8.2Hz, 2H), 2.33 (s, 3H), 0.23 (s, 6H).

[0073] In summary, when PdCuNPore is used as a catalyst, the reaction system has high chemical selectivity, no condensation occurs, and it only stays at the silanol product stage without over-oxidation, thereby obtaining the corresponding silanol compounds, and other groups remain in their original positions without change. Therefore, PdCuNPore is a catalyst with stable catalytic performance, excellent selectivity, easy recovery, and broad application prospects.

Claims

1. A method for preparing silanols by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper. It is characterized in that Using hydrosilane as raw material, nanoporous palladium copper as catalyst, hydrogen peroxide as oxidant, selectively adding hydrogen to silane in solvent to prepare corresponding silanol, the synthesis route is as follows: R 1 Selected from hydrogen, alkyl, methoxy, substituted phenyl; R 2 Selected from alkyl, methoxy, substituted phenyl; R 3 Selected from alkyl, methoxy, substituted phenyl; R 1 , R 2 , R 3 Same or different; Wherein, the molar ratio of hydrosilane to nanoporous palladium copper catalyst is 1:0.1; The molar ratio of hydrosilane to hydrogen peroxide is 1:2; The molar concentration of hydrosilane in the solvent is 0.13 mmol / mL; The reaction temperature is 20-80°C; the reaction time is 6-48h.

2. The method for preparing silanols by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper according to claim 1, It is characterized in that The nanoporous palladium copper catalyst has a pore size between 1nm and 50nm.

3. The method for preparing silanols by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper according to claim 1, It is characterized in that The solvent is dichloromethane, ethyl acetate, methanol, ethanol, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, dimethylacetamide or 1,4-dioxane.

4. The method for preparing silanols by selective oxidation of hydrosilane catalyzed by nanoporous palladium copper according to claim 1, It is characterized in that The nanoporous palladium copper catalyst is obtained by chemically corroding and dealloying a Pd-Cu-Al alloy. The atomic ratio of Cu, Pd and Al in the nanoporous palladium copper catalyst is 19:1:80 or 19.9:0.1:80.

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