137 results about "Ester hydrolysis" patented technology

Disclosed herein are a catalyst for polyester depolymerization or cyclic ester synthesis, a preparation method therefor and a use thereof. The catalyst is a long-chain catalyst having a main chain carbon atom number greater than or equal to 8, and containing a terminal ion group and a terminal hydroxyl structure; the catalyst may be used to catalyze polyester hydrolysis, alcoholysis or cyclic depolymerization, so as to recover corresponding monomers or monomers and oligomers, or used to catalyze hydroxy acid or hydroxy acid esters to synthesize cyclic ester monomers or cyclic ester monomers and cyclic oligomers by means of polycondensation and cyclization reactions. The catalyst may reduce the viscosity of a reaction system, and may greatly improve the utilization rate of a catalytic active center, reduce the consumption of the catalyst and improve overall catalytic efficiency, achieving high-efficiency, high-yield and selective depolymerization of polyester homopolymers, copolymers, blends or compounds.

The present disclosure provides PEG lipids and transfer vehicle compositions including the same. Incorporation of the PEG lipids of this disclosure into a transfer vehicle can provide for one or more desirable properties, including low immune response and / or immunogenicity, fast-shedding of the PEG lipid from the transfer vehicle, and / or degradability of the PEG lipid, e.g., via ester hydrolysis or cleavage.

The invention relates to the field of molecular sieves, in particular to a titanium silicalite molecular sieve TS-1 nanosheet and a preparation method and application thereof.The titanium silicalite molecular sieve TS-1 nanosheet is prepared by using tetrapropylammonium hydroxide, tetraethyl orthosilicate, tetrabutyl titanate and urea as raw materials through crystallization and calcination. A urea-assisted synthesis method is adopted, urea can be spontaneously dispersed on the surface, perpendicular to the b axis, of a crystal, growth of the crystal in the direction of the b axis is inhibited, and then the sheet-shaped titanium silicalite molecular sieve TS-1 is formed after calcination. According to the invention, isopropanol is not required to be used as a solvent and a regulator for hydrolysis of tetraethyl orthosilicate and tetrabutyl titanate, so that the purpose of synthesizing the titanium silicalite molecular sieve TS-1 nanosheet at low cost is achieved, and the technical defect of structural collapse caused by calcination in the prior art is overcome.

The invention relates to the technical field of nanofiber membrane materials, in particular to a heat-insulation and warm-keeping nanofiber membrane material and a preparation method thereof.A mixed solution of tetraethoxysilane hydrolysate and a polyvinyl alcohol aqueous solution serves as a precursor of electrostatic spinning, modified titanium dioxide hollow microspheres are added in the preparation process, and the nanofiber membrane material is prepared; a near-vacuum environment is formed in the titanium dioxide hollow microspheres, heat is conducted by inhibiting collision of gas molecules, so that radiation heat transfer is blocked, the prepared nanofiber membrane material has a good heat preservation and heat insulation effect, a silane coupling agent forms hybrid bonds on the surfaces of the microspheres and is combined with polyvinyl alcohol molecular chains through chemical bonds, and the heat preservation and heat insulation effects are improved. The interface adhesion force is obviously improved, so that the hollow microspheres are prevented from collapsing during mechanical friction or bending; secondly, different types of quaternary ammonium salt antibacterial agents are compounded, the synergistic sterilization effect can be achieved, four quaternary ammonium salts are synergistic through different action targets, and the problem that a single antibacterial agent is prone to generating drug resistance can be solved.

The invention discloses a synthesis process of trans-p-aminocyclohexanol, and belongs to the technical field of chemical synthesis. The synthesis process of the trans-p-acetamido cyclohexanol comprises the following steps: performing catalytic hydrogenation on p-acetamido phenol, a catalyst A, an additive and a solvent A at a certain pressure and temperature to obtain p-acetamido cyclohexanol, and performing esterification, recrystallization and separation on acetic anhydride and p-acetamido cyclohexanol to obtain trans-p-acetamido cyclohexanol acetate; then, the trans-p-acetamido cyclohexanol acetate is hydrolyzed, and trans-p-aminocyclohexanol is obtained; the trans-p-aminocyclohexanol prepared by the method disclosed by the invention is high in yield and high in purity.

The invention discloses a FeNi soft magnetic composite material based on tetrabutyl orthosilicate hydrolysis coating and a preparation method of the FeNi soft magnetic composite material. According to the method, through a controllable sol-gel process, tetrabutyl orthosilicate is hydrolyzed to generate SiO2 gel, then a uniform and ultrathin SiO2 gel layer is generated on the surface of FeNi powder in situ, and then heat treatment densification is performed to obtain the FeNi soft magnetic composite material coated with SiO2 in an insulation mode. The SiO2 insulating layer is firmly combined with the matrix metal powder, the thermal stability is good, high frequency and high resistivity are achieved, and meanwhile dilution of non-magnetic relative magnetic performance is reduced to a great extent. The final magnetic core is obtained through compression molding and annealing heat treatment, has the excellent characteristics of high effective magnetic conductivity and low high-frequency magnetic core loss, and is particularly suitable for various efficient and miniaturized power electronic devices in the MHz frequency band.

The invention relates to the technical field of medicines, in particular to a method for synthesizing an Itrimod intermediate through asymmetric ester hydrolysis. According to the method, the key chiral intermediate (R)-formula I-a or (R)-formula I-b of the itramod is prepared through biological enzyme resolution, the chiral intermediate with the ee value larger than 98% and high optical purity is obtained through stereoselective hydrolysis of hydrolase, the product yield is increased to 40-45%, and a green synthesis route suitable for large-scale production is developed. # imgabs0 #

The invention discloses a preparation method of an arfamarana key intermediate, which comprises the following steps: carrying out nucleophilic addition reaction on a compound I and 1-[3-chloro-5-(trifluoromethyl) phenyl]-2, 2, 2-trifluoroethanone under the action of an organic solvent A and alkali to obtain a compound II; dissolving the compound II in an organic solvent B, adding concentrated sulfuric acid, carrying out intramolecular dehydration and cyanogen hydrolysis, and after the reaction is finished, cooling to room temperature for crystal growing to obtain a compound III; dissolving the compound III in an organic solvent C, carrying out intramolecular cyclization and ester hydrolysis reaction on the compound III and hydroxylamine hydrochloride under the action of a certain amount of sodium hydroxide aqueous solution, and after the reaction is finished, collecting a water phase and adjusting the pH value of the water phase, so as to obtain the key intermediate of arfampanaga. The reaction in each step has a high conversion rate, the purity of the prepared arfamarin intermediate is high, and powerful support and guarantee are provided for preparation of high-purity arfamarin.

The invention relates to a preparation method of a Pd-based catalyst and application of the Pd-based catalyst in catalytic synthesis of biphenyltetracarboxylic dianhydride. According to the method, an alkaline substance is added, and nickel oxide is modified and regulated through hydroxyl, so that the specific surface area of the Pd / NiO catalyst is increased, and the effect between Pd and NiO is enhanced; the obtained catalyst can promote coupling of halogenated phthalic anhydride, and the synthesis efficiency of biphenyl tetracarboxylic dianhydride is improved. The catalyst is simple in preparation process and excellent in performance and is applied to synthesis of biphenyltetracarboxylic dianhydride, and esterification and ester hydrolysis steps do not need to be added.

The utility model relates to the technical field of chemical production equipment, and discloses an ester hydrolysis reactor, which is characterized in that a gas channel and a liquid channel are arranged in a spray head, gas is conveyed into a tank body through the gas channel, and liquid is injected into the tank body through the liquid channel. In the process, the gas and the liquid can be injected into the tank body through the spray head at the same time. Meanwhile, the gas and the liquid are immediately mixed after being sprayed out from the spray head, and hydrolysis is carried out to generate corresponding acid and alcohol. And secondly, in the downward scattering process of the gas and the liquid sprayed by the spray head, the gas and the liquid are further mixed. In addition, the liquid is sputtered when being scattered to the bottom of the tank body, and the sputtered liquid is mixed with surrounding gas again. Therefore, the mixing efficiency can be improved, and the hydrolysis reaction of gas and liquid is more sufficient.

The present invention provides a monodisperse colloidal silica with controllable particle size and a preparation method and application thereof, belonging to the technical field of polishing liquid. The present invention first prepares a mother liquor, then heats it to a reflux state, and uniformly drips an alkyl silicate hydrolyzate to control the growth rate of silica particles. The pre-preparation of the alkyl silicate hydrolyzate allows the alkyl silicate to grow particles at a higher temperature, thereby obtaining silica particles with better monodispersity. An alkaline catalyst is added to maintain the pH value of the reaction liquid, promote further hydrolysis of the alkyl silicate, and prevent the reaction liquid from gelling, thereby ensuring the normal progress of the hydrolysis reaction. The alcohol is removed by heating and concentration to obtain monodisperse colloidal silica with controllable particle size. The colloidal silica prepared by the present invention has uniform particle size, regular morphology, moderate hardness, good stability and good dispersibility, and can be used as CMP polishing liquid grinding particles. The method of the present invention is simple to operate, low in cost, and suitable for large-scale production.

The application discloses a preparation method of a titanium dioxide coated MIL-53(Fe) electrocatalyst. First, a catalyst MIL-53(Fe) is obtained through a hydrothermal method, then the catalyst is heated, stirred and dried under mild conditions, and titanium dioxide obtained by hydrolysis of tetra-n-butyl titanate is uniformly coated on the MIL-53(Fe) under the action of dodecyl sulfate, finally, the catalyst is improved in contact with nitrogen through heat treatment, so that the titanium dioxide coated MIL-53(Fe) with good stability is prepared.

The application discloses a Pseudomonas atacamensis STR8 and an application thereof, and belongs to the technical field of microorganisms. The strain is classified and named as Pseudomonas atacamensis STR8, and the preservation number is CCTCC NO: M 2025609. The hydrolysis circle HC value of the strain on a tributyrin plate is 2.78, and the lipase activity reaches 139.86 U / mL. The application also provides an application of the strain and a lipase produced by the strain in catalyzing hydrolysis of tocopherol succinate to prepare tocopherol. The strain STR8 is fermented to obtain a crude enzyme liquid, and the crude enzyme liquid is added into a reaction system containing the tocopherol succinate to perform a hydrolysis reaction. After 9 hours of reaction, the content of the tocopherol is increased by 750% compared with a control group. The strain and the method provided by the application have high catalytic efficiency, mild reaction conditions and environmental friendliness, and are suitable for green industrialized production of the tocopherol.

The invention belongs to the technical field of electrolysis, and discloses a method for preparing p-hydroxyanisole through electrolytic oxidation of anisole. The method comprises the following steps: S1, adding anisole, an acylation reagent, an organic alkali proton trapping agent and an alkaline amine group-containing solvent into a single-chamber electrolytic bath together, starting electrification, carrying out electrolysis, and obtaining a product liquid containing p-methoxytrifluoroacetic acid phenyl ester in the single-chamber electrolytic bath after electrolysis is finished; the organic base proton trapping agent is at least one of N, N-diisopropylethylamine, tributylamine and tripropylamine; and S2, adding a saturated sodium bicarbonate aqueous solution into the product liquid containing p-methoxytrifluoroacetic acid phenyl ester in the step S1 to hydrolyze p-methoxytrifluoroacetic acid phenyl ester, and extracting to obtain p-hydroxyanisole. The selectivity of para-position and ortho-position products of methoxyl on anisole is regulated and controlled, so that the selectivity of p-hydroxyanisole prepared by the method is higher.

This invention belongs to the field of chemical pharmaceutical technology, and particularly relates to a method for preparing an anti-puncture flash evaporation material. Addressing the issue that the hydrophilicity of the molecular structure in existing technologies needs improvement, this invention provides a maleic methylamine polyethylene glycol activated ester and its preparation method, comprising a reaction condensation of 3-maleimide propionic acid and tert-butyl methylamine polyethylene glycol propionate, followed by acid hydrolysis of the ester, and then adding the activated ester for a catalytic reaction to obtain the final product Mal-CH2CH2COO-N(CH3)-(PEG). n -CH2CH2COONHS. This invention creatively designs a maleic methylamine polyethylene glycol activated lipid structure. The methylamine structure can increase solubility in aqueous media, making it more hydrophilic than the existing Mal-CH2CH2COO-PEG-COONHS molecular structure, which is more conducive to the binding of drugs to the human body environment.

The invention provides a preparation method of polypeptide, which comprises the following steps: dissolving a compound as shown in a formula I, a compound as shown in a formula II, pivaloic anhydride, an alkaline substance and N-methylimidazole in an organic solvent to obtain a reaction mixed solution, reacting at 15-80 DEG C for 3-10 hours, performing post-treatment on the obtained reaction solution to obtain a dipeptide compound as shown in a formula III, and performing ester hydrolysis on the dipeptide compound as shown in the formula III to obtain the polypeptide. The preparation method comprises the following steps: dissolving a compound as shown in a formula I in an organic solvent to obtain a dipeptide compound only containing an Fmoc protecting group, dissolving the dipeptide compound only containing the Fmoc protecting group, a compound as shown in a formula II, pivaloic anhydride, an alkaline substance and N-methylimidazole in the organic solvent, reacting at 15-80 DEG C for 4-10 hours, and post-treating the obtained mixed solution to obtain the polypeptide. According to the invention, pivaloic anhydride is used as a condensing agent, the structure is simple, the reaction is safe, cheap and non-toxic, only a catalytic amount of N-methylimidazole is needed in the reaction, a large amount of nitrogen-containing by-products are not generated, and purification is easy; various amino acid side chains can be tolerated, and racemization isomerization cannot occur in the reaction; environment-friendly solvents such as ethyl acetate are used, and the reaction conditions are mild.

The present invention generally pertains to methods of quantifying free fatty acids in a pharmaceutical formulation. In particular, the present invention pertains to a method of quantifying free fatty acids released from polysorbate hydrolysis in a pharmaceutical formulation comprising a pharmaceutical product, polysorbate and free fatty acids, using liquid chromatography-mass spectrometry, without the use of an extraction step.

The invention discloses a preparation method and application of a catalyst for synthesizing cyclohexanone oxime through ammoxidation of cyclohexanone, and belongs to the technical field of molecular sieve synthesis and catalysis. The preparation method comprises the following steps: uniformly mixing a silicon source, a tetrapropylammonium hydroxide aqueous solution and deionized water to obtain estersil hydrolysate A; adding a titanium source into the low-carbon alcohol to obtain a titanium ester hydrolysate B, and then adding a crystallization auxiliary agent; uniformly mixing the obtained estersil hydrolysate A with the titanium ester hydrolysate B, heating to remove alcohol, and crystallizing for 24-96 hours at the temperature of 150-180 DEG C under self-generated pressure to obtain titanium silicalite molecular sieve mother liquor; the method comprises the following steps: adding a ferric salt aqueous solution and aluminum sol or silica sol or silicon-aluminum sol into a titanium silicalite molecular sieve mother solution, aging for 10-72 hours at 60-80 DEG C under a stirring condition, carrying out spray molding, drying the obtained titanium silicalite molecular sieve, and roasting for 8-24 hours at 500-650 DEG C to obtain the TS-1 molecular sieve. The TS-1 molecular sieve prepared by the method can be used for preparing cyclohexanone-oxime under relatively mild reaction conditions, and the conversion rate of raw materials and the selectivity of products are effectively improved.

The invention provides a purification method of empagliflozin. The method comprises the following steps: (1) extracting raw material liquid containing empagliflozin and impurities by using an extracting agent to obtain extract liquid containing empagliflozin; the impurities comprise one or more of an isomer, an ester and a hydrolysate of empagliflozin, the solvent in the raw material liquid is selected from a non-polar solvent and / or a weakly polar solvent, and the extraction agent comprises an ionic liquid or a mixture of the ionic liquid and a polar solvent; and (2) carrying out back extraction and concentration on the extract liquor containing empagliflozin to obtain empagliflozin. The method has the advantages of high separation efficiency, low solvent consumption, low production cost, safety, environment friendliness, easiness in industrial production and the like.

Methods for preparing an L-6-hydroxytryptophan (HTP) derivative and intermediates thereof are provided. The methods for preparing the various intermediates of the L-6-HTP derivative are provided, on the basis of which the L-6-HTP derivative could be obtained. Specifically, the L-6-HTP derivative is obtained by using a compound A6-0 with a structure shown in Formula 1 as a starting reaction raw material, and subjecting the compound A6-0 to triisopropylsilyl (TIPS) protection, coupling, carbon-boron bond oxidation, hydroxyl-targeted benzyl protection, TIPS protective group removal, tert-butoxycarbonyl (Boc) protective group removal, methyl ester hydrolysis, and amino-targeted 9-fluorenylmethoxycarbonyl (Fmoc) protection in sequence.

The application relates to a preparation method and application of an azobenzene-based pH / UV intelligent response information reversible load hydrogel robot, and belongs to the technical field of hydrogels. The application aims to solve the problem that a light response information load material cannot be rewritable, high-strength, fast in response speed and multifunctional. The azobenzene-based pH / UV intelligent response information reversible load hydrogel robot is prepared by the following steps: synthesizing 4-hydroxy azobenzene by a diazo method; taking 4-hydroxy azobenzene, potassium carbonate, 6-bromohexyl acetate and acrylamide as raw materials; adopting Williamson ether reaction, nucleophilic substitution reaction, ester hydrolysis and amide reaction to prepare azobenzene-based gel monomers; taking acrylamide and the azobenzene-based gel monomers as a gel matrix; taking N,N'-methylene bisacrylamide as a crosslinking agent; and adopting free radical polymerization, hydrogen bond crosslinking and hydrophobic crystallization crosslinking strategies to prepare the azobenzene-based pH / UV intelligent response information reversible load hydrogel robot, which is applied to intelligent information load and rewritable code transmission.

The present invention proposes a polyester fiber super-hydrophilic fabric and a preparation method thereof, which belongs to the technical field of super-hydrophilic textiles, and is used to solve the technical problems of poor rapid tiling and rapid transmission effect of liquid water in polyester fabrics. Specifically, it includes five steps: blending, weaving, finishing, washing and baking. Polyester fiber and wool fiber are blended to prepare polyester / wool blended yarn with a certain mixing ratio, and polyester / wool blended fabric is prepared by weaving. The yarn is placed in a finishing liquid containing a certain amount of reducing agent with a pH value between 12-14 for treatment. The wool is hydrolyzed to form free amino acids and react with the products of polyester ester hydrolysis, thereby constructing a rough hydrophilic interface on the surface of the polyester fiber. After washing and baking, the polyester fiber super-hydrophilic fabric is obtained. The present invention provides a method for preparing a polyester fiber super-hydrophilic fabric. The prepared polyester fiber super-hydrophilic fabric has super-hydrophilicity, simple process, strong operability, and high market application value.

The invention discloses a preparation method of lithium difluoro (oxalato) borate. Lithium hydroxide, trimethyl borate, dimethyl oxalate and anhydrous ammonium bifluoride steam are used as raw materials to react in an ionic liquid medium. The method adopts a plasma activation technology, can be efficiently carried out in a low-temperature environment without traditional heating, not only shortens the reaction period, but also can inhibit fluorine source decomposition, oxalate hydrolysis and other side reactions, improves the selectivity of a target product, and uses the ionic liquid as a reaction medium, and the high polarity and low volatility of the ionic liquid can ensure the uniform dispersion of raw materials. Meanwhile, supercritical carbon dioxide extraction replaces traditional recrystallization, one-step purification is achieved by means of the selective dissolution characteristic of supercritical carbon dioxide extraction, the process steps are simplified, and solvent residues are reduced.

This invention relates to a method for preparing trinitromethyl tricyclic compounds containing nitrogen-rich groups, belonging to the field of energetic materials technology. The specific preparation steps are as follows: Scheme 1 uses 2,3-diaminomaleonitrile to obtain the corresponding methyl ester-substituted intermediate through multiple steps of cyclization, acidification, and esterification. Then, through multiple steps of hydrazine substitution, cyclization with ethyl 3-ethoxy-3-iminopropionate hydrochloride, ester hydrolysis, and nitration, the target compound trinitromethyl tricyclic compound 2 is successfully synthesized. Scheme 2 uses ethyl diazonium acetate to obtain the corresponding methyl ester-substituted intermediate through multiple steps of cyclization, acidification, and esterification. Then, through multiple steps of hydrazine substitution, cyclization with ethyl 3-ethoxy-3-iminopropionate hydrochloride, nitration, salt formation, and renitration, the target compounds trinitromethyl tricyclic compounds 1, 3, and 4 are synthesized. The target compound has advantages such as high nitrogen content, high density, good thermal stability and excellent detonation performance, and can be used as a component of energetic materials, showing potential application value.

This invention relates to the field of molecular sieves, specifically to titanium-silicon molecular sieve TS-1 nanosheets, their preparation method, and applications. The invention uses tetrapropylammonium hydroxide, tetraethyl orthosilicate, tetrabutyl titanate, and urea as raw materials. The process involves crystallization followed by calcination to prepare titanium-silicon molecular sieve TS-1 nanosheets. This invention employs a urea-assisted synthesis method, where urea spontaneously disperses on the surface of the crystals perpendicular to the b-axis, inhibiting crystal growth along the b-axis direction. This results in the formation of sheet-like titanium-silicon molecular sieve TS-1 after calcination. This invention eliminates the need for isopropanol as a solvent and the regulation of hydrolysis of tetraethyl orthosilicate and tetrabutyl titanate, achieving low-cost synthesis of titanium-silicon molecular sieve TS-1 nanosheets and overcoming the technical defects of existing technologies where calcination leads to structural collapse.

The present invention relates to a method for synthesizing high-purity magnesium isoglycyrrhizinate, and belongs to the field of drug synthesis. It uses diammonium glycyrrhizinate as a starting material, and obtains magnesium isoglycyrrhizinate through esterification, hydrolysis and salt formation. The preparation process of magnesium isoglycyrrhizinate of the present invention has achieved a major technical breakthrough, and its impurity control level is significantly better than the current pharmacopoeia standard. Compared with commercially available products (single impurity <1.0%, total impurities <3.0%), the present invention achieves single impurity content control below 0.1% and total impurity content below 1.0% through process optimization, and the reduction rate reaches 90% and 83% or more respectively. This breakthrough effectively solves the safety hazards such as allergic reactions and phlebitis that may be caused by impurities in intravenous drugs, so that the purity of the product reaches the international advanced level, meets the strict requirements of EMA and FDA on impurities in injections, and provides reliable guarantee for clinical safe drug use.

The present invention relates to a process for the preparation of a thermoplastic composition comprising an aromatic polycarbonate, a polyester, a hydrolysis stabilizer composition, optionally an impact modifier and optionally further components, comprising the steps of: a) combining the polyester with the hydrolysis stabilizer composition in a first melt mixing device to form a stabilized polyester, b) combining the stabilized polyester with an aromatic polycarbonate and optionally an impact modifier in a second melt mixing device, wherein the hydrolytic stabilizer composition comprises at least one compound containing diimide and / or epoxy functional groups.

The invention relates to a synthesis method of an etogliflozin impurity (a compound as shown in a formula I). The method comprises the following steps: by taking a compound in a formula II as a starting raw material, firstly carrying out oxidation reaction to prepare carboxylic acid, and then carrying out hydrogenation debenzylation and ester hydrolysis to obtain a compound in a formula I, according to the present invention, with the method, the etogliflozin impurity can be efficiently and simply synthesized, and the etogliflozin bulk drug and the etogliflozin preparation can be conveniently subjected to quality research and analysis so as to ensure the safety of etogliflozin production and medication.

The application provides a kind of imaging photothermal gold shell coated long afterglow nanomaterial and its preparation and application.The nanomaterial includes Cr doped zinc-gallium-germanium oxide long afterglow nanometer core, mesoporous silica shell layer coated on the surface of the nanometer core and gold shell layer coated on the outer surface of the mesoporous silica shell layer.The preparation method includes: hydrothermal reaction and calcination to prepare long afterglow nanometer core;Under the condition of alkali, make tetraethyl orthosilicate (TEOS) hydrolysis and condensation to form mesoporous silica shell layer, remove template and carry out amination under cetyltrimethylammonium bromide (CTAB) template;Gold ions are adsorbed on the aminated surface and reduced to form gold seeds using borohydride, and gold shell layer is formed by promoting growth using hydroxylamine salt in a gold precursor solution containing carbonate.The obtained nanomaterial has near-infrared long afterglow luminescence capability, and generates photothermal heating under 808 nm laser irradiation, which can be used for bacterial imaging and photothermal treatment of bacterial samples.

This invention provides a method for preparing pyrrolidine derivatives, belonging to the field of organic synthesis. The method comprises the following steps: Step 1, reacting compound 1 in the presence of an alkaline ester hydrolysis reagent to obtain compound 2; Step 2, adding compound 2 to an aqueous solution of hydrogen bromide, followed by the addition of sodium nitrite to react and obtain compound 3; Step 3, reacting compound 3 in the presence of a dehalogenating reducing agent to obtain compound 4; Step 4, reacting compound 4 in the presence of a carbonyl reducing agent to obtain compound 5. The preparation method provided by this invention enables the industrial production of compound 5 and its derivatives.