CN103214392A - Synthetic method of N-benzylideneaniline compound - Google Patents

Abstract

The invention discloses a method for synthesizing N-benzylidene aniline compounds: nitrobenzene compounds represented by formula I and benzyl alcohol are used in a solvent-free condition or in a reaction solvent under the action of a loaded noble metal catalyst. Adding an inorganic base, stirring and reacting at 50-240°C under a nitrogen atmosphere, and reacting for 1-30 hours, the reaction solution is post-treated to prepare the N-benzylidene aniline compound shown in formula II; the supported noble metal The catalyst comprises a carrier and an active component loaded on the carrier, the active component is a noble metal, and the noble metal is palladium, ruthenium, gold, silver, iridium, platinum or rhodium. The noble metal catalyst prepared by the present invention has high activity and stability and good selectivity; the conversion rate of nitrobenzene compounds is 100%, and the selectivity of N-benzylidene aniline compounds can be greater than 95%; the preparation of the catalyst does not pollute environment.

Description

A kind of synthetic method of N-benzylidene aniline compound

(1) Technical field

The invention relates to a method for synthesizing N-benzylidene aniline compounds by a one-pot method of nitrobenzene compounds and benzyl alcohol, especially under the action of a loaded noble metal catalyst, nitrobenzene compounds and benzyl alcohol in alkaline conditions A method for synthesizing N-benzylidene aniline compounds in one pot with benzyl alcohol.

(2) Background technology

N-benzylidene aniline compounds (benzylidene aniline compounds) are an important class of organic synthesis intermediates, which are mainly used in the synthesis of anti-anxiety, sedative and hypnotic drugs, penicillin antibiotics and anti-parasitic drugs in medicine wait. In the production of pesticides, it is mainly used to produce amide herbicides and organophosphorus insecticides. In terms of food and feed additives, it can be applied to the production of amino acid compounds.

The traditional synthesis method of N-benzylidene aniline compounds is the direct condensation of aniline compounds and benzaldehyde. Although this method is very simple, the price of aniline compounds and benzaldehyde as raw materials is much higher than that of nitrobenzene compounds and benzyl alcohol, and aniline compounds are unstable and highly toxic. Some researchers used benzyl alcohol instead of benzaldehyde to condense with aniline compounds to generate N-benzylidene aniline compounds. For example, Kwon et al prepared a series of palladium catalysts supported by different carriers for the condensation reaction of aniline and benzyl alcohol. The reaction time was 20 hours. When the catalyst was 5.0% Pd/C, the yield of N-benzylidene aniline was only 19%. When being 3.5%Pd/Al ₂ O ₃ , N-benzylidene aniline productive rate is 42% (Kwon M, Kim S, Park S, et al.One-Pot Synthesis of Imines and Secondary Amines byPd-Catalyzed Coupling of Benzyl Alcohols and Primary Amines. J. Org. Chem., 2009, 74(7): 2877-2879). The method yield is very low. There is also the substitution of aniline with nitrobenzene, and catalytic hydrogenation reaction with benzaldehyde. For example, Santos et al. reported that Au/ _TiO2 was used for the catalytic hydrogenation of nitrobenzene and benzaldehyde, and the conversion rate of nitrobenzene was 94%, and the selectivity of N-benzylidene aniline was 93% (Santos L L, Sern P, Corma A. Chemoselective Synthesis of Substituted Imines, Secondary Amines, and β-AminoCarbonyl Compounds from Nitroaromatics through Cascade Reactions on Gold Catalysts. Chem. Eur., 2009, 15(33): 8196-8203). This method has a high yield of the target product, but hydrogen addition is needed as a hydrogen source during the reaction. In recent years, Tang et al. reported the research on the one-pot reaction of nitrobenzene and benzyl alcohol. Using Au/TiO ₂ as the catalyst, the conversion rate of nitrobenzene was 100% after 14 hours of reaction, and N-benzyl was produced with high selectivity. Aniline—the further reduction product of N-benzylideneaniline (Tang C H, He L, Liu Y M, et al.Direct One-Pot Reductive N-Alkylation of Nitroarenes by using Alcoholswith Supported Gold Catalysts.Chem.Eur.J. 2011, 17:7172-7177). Compared with the above-mentioned method, the method is simpler, lower in cost, does not need hydrogen in the reaction process, and is safe in operation. But N-benzylaniline compounds are easy to be further reduced to generate N-benzylaniline compounds.

(3) Contents of the invention

The object of the present invention is to provide a method for synthesizing N-benzylidene aniline compounds with simple process, low cost, safety, environmental friendliness, high conversion rate and selectivity.

The technical scheme that the present invention adopts is as follows:

A kind of synthetic method of the N-benzylidene aniline compound shown in formula II, described method is: with the nitrobenzene compound shown in formula I and benzyl alcohol under solvent-free condition or in reaction solvent, under loading Under the action of a type noble metal catalyst, add an inorganic base, under a nitrogen atmosphere, stir and react at a temperature of 50-240 ° C, after reacting for 1-30 hours, the reaction solution is post-treated to prepare the N-benzylidene aniline compound shown in formula II The ratio of the amount of nitrobenzene compounds represented by the formula I to benzyl alcohol is 1:2-30, preferably 1:5-30, more preferably 1:7-13; the reaction solvent is Toluene, methanol, ethanol, acetonitrile, acetone or water, preferably toluene;

In the formula I or II, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently hydrogen, halogen, methyl, ethyl, methoxy, ethoxy, formyl or vinyl, The halogen is fluorine, chlorine, bromine or iodine;

Further, preferably all of R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are hydrogen, or preferably one substituent in R ₁ to R ₅ is methyl or halogen, and the rest of the substituents are hydrogen; or preferably R ₁ to R 5 are hydrogen. Two substituents in _R5 are halogen and the remaining substituents are hydrogen. More preferably formula I is nitrobenzene, o-nitrotoluene or 3,5-dichloronitrobenzene.

The supported noble metal catalyst includes a carrier and an active component loaded on the carrier, the carrier is SiO ₂ , Al ₂ O ₃ , activated carbon, porous carbon material, TiO ₂ , ZrO ₂ or molecular sieve, preferably SiO ₂ or Porous carbon material; the active component is a noble metal, and the noble metal is palladium, ruthenium, gold, silver, iridium, platinum or rhodium, preferably palladium or ruthenium. The loading amount of the noble metal is 0.5-10.0% based on the mass of the carrier, preferably 2-5%;

The supported noble metal catalyst may also include a carrier and an active component and a cocatalyst loaded on the carrier, and the cocatalyst is one of alkali metal oxides, alkaline earth metal oxides, rare earth element oxides, non-noble metals or A combination of two or more; the non-noble metal is nickel, copper, cobalt or molybdenum, the alkali metal oxide is preferably sodium oxide, potassium oxide, and the alkaline earth metal oxide is preferably calcium oxide, barium oxide or magnesium oxide The rare earth element oxide is preferably cerium oxide, lanthanum oxide or samarium oxide; the cocatalyst is more preferably lanthanum oxide; %, where 0 means that it is infinitely close to 0 but not 0.

Further, the supported noble metal catalyst of the present invention is preferably composed of a carrier and an active component loaded on the carrier, the active component is a noble metal, and the loading amount of the noble metal is 0.5-10.0% based on the mass of the carrier, preferably 2 to 5%.

Or the supported noble metal catalyst is composed of a carrier and an active component loaded on the carrier and a cocatalyst, the active component is a noble metal, and the loading amount of the noble metal is 0.5 to 10.0% based on the mass of the carrier, and the cocatalyst It is one or a combination of two or more of alkali metal oxides, alkaline earth metal oxides, rare earth element oxides, and non-noble metals; the non-noble metals are nickel, copper, cobalt or molybdenum, and the alkali metal oxides are preferably It is sodium oxide, potassium oxide, and the alkaline earth metal oxide is preferably calcium oxide, barium oxide or magnesium oxide; the rare earth element oxide is preferably cerium oxide, lanthanum oxide or samarium oxide; The quality of the mass is calculated as 0 to 20%, where 0 means that it is infinitely close to 0 but not 0.

The inorganic base of the present invention is preferably sodium bicarbonate, sodium carbonate, potassium carbonate, potassium hydroxide, sodium hydroxide or ammonia water, preferably potassium hydroxide or sodium hydroxide, most preferably potassium hydroxide.

The reaction of the present invention can be carried out under solvent-free conditions or in a reaction solvent, that is, under solvent-free conditions without adding a reaction solvent.

The mass ratio of the inorganic base to the nitrobenzene compound represented by formula I is usually 0.05-2:1, preferably 0.1-0.3:1.

The mass ratio of the supported noble metal catalyst to the nitrobenzene compound represented by formula I is 0.01-0.3:1, preferably 0.1-0.3:1.

The mass ratio of the nitrobenzene compound represented by the formula I to the reaction solvent is 1:5-35, preferably 1:15-25.

The post-treatment method of the reaction liquid is as follows: after the reaction is completed, the reaction liquid is filtered, the filtrate is evaporated to remove the solvent, and then recrystallized with an aqueous ethanol solution with a volume concentration of 20% to 70% to obtain the N-benzylidene aniline compound shown in formula II .

The reaction temperature of the present invention is preferably 160-180°C.

The reaction time is preferably 16-26 hours, more preferably 16-22 hours.

Specifically, it is preferred that the method of the present invention be carried out according to the following steps: according to the ratio of the amount of nitrobenzene compounds to benzyl alcohol is 1:5-30, the mass ratio of nitrobenzene compounds to the reaction solvent is 1:5 ～35, the quality of the inorganic base is 0.05～2.0 times of the mass of the nitrobenzene compound, the consumption of the supported noble metal catalyst is 0.01～0.3 times of the mass of the nitrobenzene compound, and the nitrobenzene compound, benzyl alcohol, reaction Solvent and inorganic base are added to the reactor, the air in the reactor is replaced by nitrogen gas and the nitrogen atmosphere is maintained, the temperature is kept at 50-240°C, and the reaction is stirred for 1-30 hours. N-benzylidene aniline compounds represented by formula II were obtained by recrystallization from 70% ethanol aqueous solution.

The supported noble metal catalyst of the present invention can be made by impregnation method, specifically:

(1) When the supported noble metal catalyst is composed of a carrier and an active component loaded on the carrier, the preparation method is as follows: according to the loading amount of the noble metal, the weight of the carrier is 0.5-10.0%, and the amount of the loaded noble metal element and other substances is calculated. Theoretical amount of the soluble noble metal salt, take the theoretical amount of soluble noble metal salt and dissolve in water to make noble metal impregnating solution, the soluble noble metal salt is usually noble metal nitrate, noble metal chloride, noble metal acetate or noble metal sulphate, will The carrier is completely submerged in the precious metal impregnation solution, impregnated at 15-35°C (preferably 20-30°C) for 2-8 hours, and then adding excess reducing agent, the ratio of the amount of reducing agent to precious metal is usually 2 ～8:1, preferably 4～6:1, the reducing agent is usually sodium borohydride, potassium borohydride, sodium citrate, hydrazine hydrate or polyhydric alcohol, then stir at room temperature for 2～8 hours, suction filtration, filter cake Washing with redistilled water until there is no acid radical anion in the filtrate, and finally drying in vacuum at 60-150°C for 2-12 hours to prepare the supported noble metal catalyst.

(2) When the supported noble metal catalyst is composed of a carrier, an active component loaded on the carrier and a co-catalyst, the preparation method is: according to the loading amount of the co-catalyst, it is 0-20% based on the mass of the carrier, and the calculation and co-catalyst The theoretical amount of the soluble metal salt of the metal element and other substances, weigh the theoretical amount of the soluble metal salt and dissolve it in water to make the auxiliary agent impregnating solution, completely immerse the carrier in the auxiliary agent impregnating solution, and set the temperature at 15-350°C ( (preferably 20-30°C) for 2-8 hours, then dry all the additive impregnating liquid and the carrier at 80-150°C for 2-12 hours, and then bake at 400-800°C for 2-8 hours to get the support. Catalyst intermediates for catalysts;

According to the loading amount of the noble metal is 0.5-10.0% by weight of the carrier, calculate the theoretical amount of the soluble noble metal salt with the amount of loaded noble metal elements and other substances, weigh the theoretical amount of the soluble noble metal salt and dissolve it in water to make a noble metal impregnation solution, The soluble noble metal salt is usually noble metal nitrate, noble metal chloride, noble metal acetate or noble metal sulfate, and the catalyst intermediate loaded with co-catalyst is completely immersed in the noble metal impregnation solution, at 15 ~ 35 ° C (preferably 20 ~ 30°C) for 2 to 8 hours, and then add excess reducing agent, the ratio of the reducing agent to the amount of noble metal is usually 2 to 8:1, preferably 4 to 6:1, and the reducing agent is usually Sodium borohydride, potassium borohydride, sodium citrate, hydrazine hydrate or polyols, then stirred at room temperature for 2 to 8 hours, suction filtered, and the filter cake was washed with distilled water until there were no acid anions in the filtrate, and finally at 60 to 150°C Vacuum drying for 2-12 hours to prepare the supported noble metal catalyst.

The preparation of supported catalysts by impregnation is a method well known to those skilled in the art.

The supported noble metal catalyst of the present invention can also be prepared by hydrogen reduction:

(i) When the supported noble metal catalyst is composed of a carrier and an active component loaded on the carrier, the preparation method is as follows: according to the loading amount of the noble metal, the weight of the carrier is 0.5 to 10.0%, and the amount of the loaded noble metal element and other substances is calculated. Theoretical amount of the soluble noble metal salt, take the theoretical amount of soluble noble metal salt and dissolve in water to make noble metal impregnating solution, the soluble noble metal salt is usually noble metal nitrate, noble metal chloride, noble metal acetate or noble metal sulphate, will The carrier is completely immersed in the precious metal impregnation solution, impregnated at 15-35°C (preferably 20-30°C) for 2-8 hours, dried at 80-150°C for 2-12 hours, and then calcined at 400-800°C for 2-8 hours , and finally reducing by introducing a reducing gas at 300-700° C. for 1-10 hours to obtain the supported noble metal catalyst; the reducing gas is hydrogen or a mixture of hydrogen and nitrogen.

(ii) When the supported noble metal catalyst is composed of a carrier, an active component loaded on the carrier and a co-catalyst, the preparation method is: according to the loading of the co-catalyst, the weight of the support is 0-20%, and the calculation and co-catalyst The theoretical amount of the soluble metal salt of the metal element and other substances, weigh the theoretical amount of the soluble metal salt and dissolve it in water to make the auxiliary agent impregnating solution, completely immerse the carrier in the auxiliary agent impregnating liquid, at 15 ~ 350 ° C ( (preferably 20-30°C) for 2-8 hours, then dry all the additive impregnating liquid and the carrier at 80-150°C for 2-12 hours, and then bake at 400-800°C for 2-8 hours to get the support. Catalyst intermediates for catalysts;

According to the loading amount of the noble metal is 0.5-10.0% by weight of the carrier, calculate the theoretical amount of the soluble noble metal salt with the amount of loaded noble metal elements and other substances, weigh the theoretical amount of the soluble noble metal salt and dissolve it in water to make a noble metal impregnation solution, The soluble noble metal salt is usually noble metal nitrate, noble metal chloride, noble metal acetate or noble metal sulfate, and the catalyst intermediate loaded with co-catalyst is completely immersed in the noble metal impregnation solution, at 15 ~ 35 ° C (preferably 20 ~ 30°C) for 2-8 hours, dried at 80-150°C for 2-12 hours, then roasted at 400-800°C for 2-8 hours, and finally reduced by passing a reducing gas at 300-700°C for 1-10 hours. The supported noble metal catalyst is prepared; the reducing gas is hydrogen or a mixed gas of hydrogen and nitrogen.

The present invention compares with prior art, and its beneficial effect is reflected in:

1. The prepared noble metal catalyst has high activity and stability and good selectivity; the conversion rate of nitrobenzene compounds is 100%, and the selectivity of N-benzylidene aniline compounds can be greater than 95%; the preparation of the catalyst does not pollute environment, and the catalyst can be recycled.

2. The reaction uses nitrobenzene compounds and benzyl alcohol as starting materials, and the reaction does not need to provide an additional hydrogen source. The process is simple, low in cost, safe and environmentally friendly.

(4) Specific implementation methods:

The technical scheme of the present invention is described below with specific examples, but protection scope of the present invention is not limited thereto:

Example 1:

1) Preparation of porous carbon carrier, 9.4g of phenol at 50°C, add 10mL of 0.5mol/L sodium hydroxide solution, stir for 10-15 minutes, add dropwise 4.1g of 37% formaldehyde solution, phenol, formaldehyde and sodium hydroxide The molar ratio is 2:1:0.1, the temperature rises to 85-95°C, reacts for 1 hour under stirring, the temperature drops to room temperature, adjusts the pH value to neutrality with 0.5mol/L hydrochloric acid solution, and then removes the water by vacuum distillation to obtain Brown liquid 11g, add absolute ethanol to prepare 20% phenolic resin absolute ethanol solution. Dissolve 8g of F127 in 32g of absolute ethanol, the mass ratio to absolute ethanol is 1:4, mix well with the above-mentioned 20% phenolic resin absolute ethanol solution, let stand at room temperature for 4-6 hours, distill under reduced pressure to remove ethanol, and then Thermally polymerized at 100-120°C for 24 hours to obtain a polymer. Finally, in a tubular resistance furnace under nitrogen protection, keep at 400°C for 1 hour and at 800°C for 0.5 hour to calcinate to obtain 3 g of porous carbon materials.

2) load the active component, set the palladium load to 2.0%, add 1 g of the porous carbon carrier obtained in step 1) to 2 mL of H ₂ PdCl ₆ solution with a mass concentration of Pd of 0.010 g/mL, and magnetically stir at room temperature for 2 hour, then add reducing agent sodium borohydride 0.029g, then stir at room temperature for 3 hours and suction filter, the filter cake is washed with distilled water until there is no acid anion in the filtrate, and finally vacuum-dried at 80°C for 3 hours to obtain a palladium loading of 2.0% 1 g of supported palladium catalyst.

3) Add 0.24 g of the above catalyst into a 100 ml reactor, then add 1.20 g of nitrobenzene, 8.5 g of benzyl alcohol, 0.25 g of potassium hydroxide solid, and 30 ml of toluene into the reactor, and replace the air in the reactor with nitrogen and keep Nitrogen atmosphere, reaction temperature 160°C, reaction time 18 hours, the conversion rate of nitrobenzene was 100% and the selectivity of N-benzylidene aniline was 96.7% as detected by gas chromatography. The reaction solution was filtered, and the filtrate was rotary evaporated to remove the solvent, and then recrystallized with 70% ethanol aqueous solution to obtain 1.64 g of N-benzylidene aniline.

Example 2:

The catalyst preparation process is the same as in Example 1, except that the palladium loading of the catalyst is 5.0%, that is, 1 g of the porous carbon carrier is added to 5 mL of Pd with a mass concentration of 0.010 g/mL in the H ₂ PdCl ₆ solution, and magnetically stirred at room temperature for 2 Hour, then add reductive agent sodium borohydride 0.073g, follow-up steps are identical, make palladium loading and be the supported palladium catalyst of 5%. 0.36 gram of catalyst was added into 100 milliliters of reactor, other reaction conditions were the same as in Example 1, and the reaction time was 16 hours. Gas chromatography detected that the conversion rate of nitrobenzene was 100%, and the selectivity of N-benzylidene aniline was 85.0%.

Example 3:

The catalyst preparation process is the same as in Example 1, except that the palladium content of the catalyst is 3.0%, that is, adding 1 g of the porous carbon carrier to 3 mL of Pd with a mass concentration of 0.010 g/mL in the H ₂ PdCl ₆ solution, and stirring magnetically for 2 hours at room temperature , and then add reducing agent sodium borohydride 0.044g, follow-up steps are the same, the prepared palladium loading is 3% supported palladium catalyst. 0.36 gram of catalyzer was added into 100 milliliters of reactors, other reaction conditions were the same as in Example 1, and the reaction time was 18 hours. Gas chromatography detected that the conversion rate of nitrobenzene was 100%, and the selectivity of N-benzylidene aniline was 97.8%.

Example 4:

Catalyst preparation process is the same as embodiment 1, and difference is that 0.36 gram of catalyzers are added into 100 milliliters of autoclaves, and other reaction conditions are with embodiment 1, and reaction time is 18 hours, and gas chromatography detects that the transformation efficiency of nitrobenzene is 100%, N - The selectivity of benzylidene aniline is 98.0%.

Example 5:

The catalyst preparation process is the same as in Example 1, except that the reaction temperature is 180°C, and other reaction conditions are the same as in Example 1, and the reaction time is 18 hours. Gas chromatography detects that the conversion rate of nitrobenzene is 100%, and N-benzylidene The selectivity of aniline is 88.9%.

Embodiment 6:

The catalyst preparation process is the same as in Example 1, except that 0.125 grams of potassium hydroxide solids are added to a 100 milliliter reactor, and other reaction conditions are the same as in Example 1, and the reaction time is 18 hours. The conversion rate of nitrobenzene detected by gas chromatography is 100 %, the selectivity of N-benzylidene aniline is 94.1%.

Embodiment 7:

The catalyst preparation process is the same as in Example 1, except that the metal Ru is supported on the porous carbon material, and the ruthenium content is 5.0%, that is, the mass concentration of 1g of the porous carbon carrier is added to 5mL Ru in the _RuCl solution of 0.010g/mL, Stir magnetically at room temperature for 2 hours, then add 0.075 g of sodium borohydride as a reducing agent, and follow the same steps to prepare a supported ruthenium catalyst Ru/C with a ruthenium loading of 5%. 0.36 gram of Ru/C catalyzer is added 100 milliliters of reactors, and other reaction conditions are with embodiment 1, and reaction time is 22 hours, and gas chromatography detects that the transformation rate of nitrobenzene is 100%, and the selectivity of N-benzylidene aniline is 94.1%.

Embodiment 8:

The catalyst preparation process is the same as in Example 1. Add 0.24g of palladium catalyst to a 100ml reactor, then add 1.89g of 3,5-dichloronitrobenzene, 8.5g of benzyl alcohol, 0.25g of potassium hydroxide solid, and 30ml of toluene into the reactor, the reaction temperature is 160°C, nitrogen atmosphere, the reaction time was 18 hours, the conversion rate of 3,5-dichloronitrobenzene was 100% as detected by gas chromatography, and the selectivity of N-benzylidene 3,5-dichloroaniline was 96.0%.

Embodiment 9:

The catalyst preparation process is the same as in Example 1. Add 0.24 grams of palladium catalyst into a 100 ml reaction kettle, then add 1.35 grams of o-nitrotoluene, 8.5 grams of benzyl alcohol, 0.25 grams of potassium hydroxide solid, and 30 milliliters of toluene into the reaction kettle, the reaction temperature is 160°C, the reaction time is 18 Hour, gas chromatography detects that the conversion rate of o-nitrotoluene is 100%, and the selectivity of N-benzylidene o-toluidine is 86.8%.

Example 10:

Preparation of Pd/SiO ₂ catalyst: add 1g of SiO ₂ carrier to 6mL of H ₂ PdCl ₆ solution with a mass concentration of Pd of 0.005g/mL, soak at room temperature for 6 hours, dry at 110°C for 12 hours, and then bake at 500°C 4 hours, and finally 300 ° C by passing hydrogen for 4 hours to prepare a Pd/SiO ₂ catalyst with a Pd loading of 3%.

0.36 gram of above-mentioned palladium catalysts were added into 100 milliliters of reactors, other reaction conditions were the same as in Example 1, and the reaction time was 18 hours. Gas chromatography detected that the conversion rate of nitrobenzene was 100%, and the selectivity of N-benzylidene aniline was 93.6 %.

Example 11:

The preparation process of the catalyst is the same as in Example 10, except that the noble metal palladium is supported on the _SiO2 modified by the auxiliary agent lanthanum oxide. The preparation process of the catalyst is as follows: according to the loading amount of the auxiliary agent lanthanum oxide as 5.0% based on the mass of the carrier, 0.133g of La(NO ₃ ) ₃ 6H ₂ O was weighed and dissolved in 5mL of water to obtain an aqueous solution of lanthanum nitrate. Completely immerse 1g _of SiO2 support in lanthanum nitrate aqueous solution, immerse at 20°C for 5 hours, then dry at 110°C for 12 hours, and then calcinate at 500°C for 4 hours to obtain the catalyst intermediate _La2O3 loaded with lanthanum _oxide -SiO ₂ ; set the palladium load to 3.0%, add 1g La ₂ O ₃ -SiO ₂ to 6mL H ₂ PdCl ₆ solution with a mass concentration of Pd of 0.005g/mL, soak at room temperature for 6 hours, 110℃ Dry for 12 hours, then calcined at 500°C for 4 hours, and finally reduce with hydrogen at 300°C for 4 hours to prepare a Pd/La ₂ O ₃ -SiO ₂ catalyst with a Pd loading of 3%.

0.36 gram of above-mentioned palladium catalysts are added into 100 milliliters of reaction kettles, other reaction conditions are the same as embodiment 1, 16 hours of reaction time, gas chromatography detects that the transformation rate of nitrobenzene is 100%, and the selectivity of N-benzylidene aniline is 95.8 %.

Claims (10)

1. the synthetic method of the N-benzylidene aniline compound shown in a kind of formula II is characterized in that described method is: with the nitrobenzene compound shown in formula I and benzyl alcohol under solvent-free condition or reaction In a solvent, under the action of a supported noble metal catalyst, add an inorganic base, and stir the reaction at a temperature of 50-240°C under a nitrogen atmosphere. After reacting for 1-30 hours, the reaction solution is post-treated to prepare the N-substance represented by formula II. Benzylaniline compounds; the ratio of the amount of nitrobenzene compounds shown in the formula I to benzyl alcohol is 1:2～30; the reaction solvent is toluene, methanol, ethanol, acetonitrile, acetone or water;

In the formula I or II, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each independently hydrogen, halogen, methyl, ethyl, methoxy, ethoxy, formyl or vinyl, The halogen is fluorine, chlorine, bromine or iodine; The supported noble metal catalyst includes a carrier and an active component loaded on the carrier, the carrier is SiO ₂ , Al ₂ O ₃ , activated carbon, porous carbon material, TiO ₂ , ZrO ₂ or molecular sieve; the active component It is a noble metal, and the noble metal is palladium, ruthenium, gold, silver, iridium, platinum or rhodium; the loading amount of the noble metal is 0.5-10.0% based on the mass of the carrier. 2. method as claimed in claim 1, is characterized in that described supported noble metal catalyst comprises carrier and the active component and promotor that are loaded on carrier, and described promotor is alkali metal oxide, alkaline earth metal oxide, A combination of one or more of rare earth element oxides and non-noble metals; the loading amount of the co-catalyst is 0-20% based on the mass of the carrier, where 0 means that it is infinitely close to 0 but not 0. 3. the method for claim 2 is characterized in that described non-precious metal is nickel, copper, cobalt or molybdenum, and described alkali metal oxidation is sodium oxide, potassium oxide, and described alkaline earth metal oxide is calcium oxide, Barium oxide or magnesium oxide; the rare earth element oxide is cerium oxide, lanthanum oxide or samarium oxide. 4. The method according to claim 1 or 2, characterized in that the noble metal is palladium or ruthenium. 5. The method according to claim 1 or 2, characterized in that said inorganic base is sodium bicarbonate, sodium carbonate, salt of wormwood, potassium hydroxide, sodium hydroxide or ammoniacal liquor. 6. The method according to claim 1 or 2, characterized in that the mass ratio of the inorganic base to the nitrobenzene compound represented by formula I is 0.05-2:1. 7. The method according to claim 1 or 2, characterized in that the mass ratio of the supported noble metal catalyst to the nitrobenzene compound represented by formula I is 0.01-0.3:1. 8. The method according to claim 1 or 2, characterized in that the mass ratio of the nitrobenzene compound represented by the formula I to the reaction solvent is 1:5-35. 9. The method according to claim 1, wherein the post-treatment method of the reaction solution is: after the reaction, the reaction solution is filtered, and the filtrate is evaporated to remove the solvent and then recrystallized with an ethanol aqueous solution with a volume concentration of 20% to 70%. The N-benzylidene aniline compound represented by formula II is obtained. 10. The method according to claim 1 or 2, characterized in that the method is: according to the ratio of the amount of nitrobenzene compounds and benzyl alcohol substances is 1:5 ~ 30, the nitrobenzene compounds and the reaction solvent The mass ratio of the inorganic base is 1:5-35, the mass of the inorganic base is 0.05-2.0 times the mass of the nitrobenzene compound, the amount of the supported noble metal catalyst is 0.01-0.3 times the mass of the nitrobenzene compound, and the nitrobenzene Add the quasi-compound, benzyl alcohol, reaction solvent, and inorganic base into the reactor, replace the air in the reactor with nitrogen and maintain the nitrogen atmosphere, keep the temperature rising at 50-240°C, stir and react for 1-30 hours, and filter the reaction solution after the reaction is completed. After the filtrate was evaporated to remove the solvent, it was recrystallized with an aqueous ethanol solution with a volume concentration of 70% to obtain N-benzylidene aniline compounds represented by formula II.