阅读说明：本技术 一种高选择性合成9-芴甲醇的方法 (Method for synthesizing 9-fluorenemethanol with high selectivity ) 是由 叶翠平 郭美鑫 李文英 梁美生 于 2021-02-26 设计创作，主要内容包括：本发明公开了一种高选择性合成9-芴甲醇的方法,是先将芴在乙醇钠乙醇溶液碱催化剂存在下的DMSO溶剂体系中50～55℃加热溶解后,加入酰基化试剂甲酸乙酯,同样温度下酰基化反应制备9-芴甲醛,再加入可溶性金属无机盐助剂,然后利用NaBH-4进行还原反应,调节反应液pH值至中性析出9-芴甲醇固体沉淀。本发明方法利用一段温度使芴完全转化,并通过加入可溶性金属无机盐助剂,不经溶剂转换就可以高选择性地还原得到9-芴甲醇,并在缩短反应时间的前提下提高了9-芴甲醇的收率。(The invention discloses a method for synthesizing 9-fluorene methanol with high selectivity, which comprises the steps of heating and dissolving fluorene in a DMSO solvent system at 50-55 ℃ in the presence of a sodium ethoxide ethanol solution alkali catalyst, adding an acylation reagent ethyl formate, carrying out an acylation reaction at the same temperature to prepare 9-fluorene formaldehyde, adding a soluble metal inorganic salt auxiliary agent, and then utilizing NaBH 4 And (3) carrying out reduction reaction, and adjusting the pH value of the reaction solution to be neutral to precipitate 9-fluorenylmethanol solid precipitate. The method of the invention utilizes a certain temperature to completely convert fluorene, and can highly selectively reduce and obtain 9-fluorenylmethanol by adding soluble metal inorganic salt auxiliary agent without solvent conversion, and improve the yield of 9-fluorenylmethanol on the premise of shortening the reaction time.)

1. A method for synthesizing 9-fluorenylmethanol with high selectivity is characterized by comprising the following steps:

1) according to the mass ratio of fluorene to sodium ethoxide to ethyl formate of 1: 1.6-2.1: 1.4-2.3, firstly, taking fluorene as a raw material, heating and dissolving the fluorene in a DMSO solvent system in the presence of a sodium ethoxide ethanol solution alkali catalyst at 50-55 ℃, then adding an acylation reagent ethyl formate, carrying out an acylation reaction at the same temperature to prepare 9-fluorene formaldehyde, and adding water for quenching reaction after the fluorene is completely converted to obtain a DMSO-alkali water solution of the 9-fluorene formaldehyde;

2) adding soluble metal inorganic salt auxiliary agent into the DMSO-alkaline aqueous solution of the 9-fluorenylformaldehyde according to the mass ratio of the fluorene, the sodium borohydride and the soluble metal inorganic salt auxiliary agent of 1 to (1.0-1.5) to (1.5-2.0) to obtain suspension, and then adding NaBH₄And (3) carrying out reduction reaction, and adjusting the pH value of the reaction solution to be neutral after the reaction is finished so as to separate out 9-fluorenylmethanol solid precipitate.

2. The method for synthesizing 9-fluorenemethanol with high selectivity according to claim 1, wherein the soluble inorganic metal salt is CaCl₂、BaCl₂、ZnCl₂Or Ca (NO)₃)₂。

3. The method for synthesizing 9-fluorenemethanol with high selectivity according to claim 1, wherein the mass fraction of the sodium ethoxide ethanol solution is 20%.

4. The method for synthesizing 9-fluorenemethanol with high selectivity according to claim 1, wherein the acylation reaction is carried out for 65-80 min under the protection of nitrogen.

5. The method for synthesizing 9-fluorenemethanol with high selectivity as claimed in claim 1, wherein water with the same volume as that of DMSO is added for quenching reaction after the acylation reaction is finished.

6. The method for highly selectively synthesizing 9-fluorenemethanol according to claim 1, wherein the reduction reaction time is 90 to 120 min.

7. The method for highly selectively synthesizing 9-fluorenylmethanol according to claim 1, wherein the pH of the reaction solution is adjusted to 7.0 to 7.5 with 1 to 2mol/L of a dilute hydrochloric acid solution.

8. The method for synthesizing 9-fluorenemethanol with high selectivity according to claim 1, wherein the 9-fluorenemethanol is prepared by recrystallization and purification.

Technical Field

The invention relates to a method for preparing 9-fluorenemethanol, in particular to a method for preparing 9-fluorenemethanol by using fluorene as a raw material.

Background

The 9-fluorenylmethanol is a raw material for preparing a polypeptide Fmoc protective agent, and is used as a carboxyl protective agent, an internal electron donor of a Ziegler-Natta catalyst and the like. Meanwhile, 9-fluorenylmethanol is used as a very important chemical intermediate, and is widely applied in the fields of biomedicine, functional pigments, high polymers and the like, and the demand is increasing continuously. And the fluorene is the main component of the coal tar, and the content of the fluorene in the coal tar is 1-2%. China has abundant fluorene resources, and the production of 9-fluorene methanol with high added value by using cheap fluorene as a raw material has important significance.

The existing method for synthesizing 9-fluorene methanol by using fluorene as a raw material mainly comprises a one-step synthesis method and a two-step synthesis method.

In the one-step synthesis method, fluorene is reacted with formaldehyde or paraformaldehyde in the presence of a strong base catalyst such as n-butyllithium, sodium methoxide and the like to directly synthesize 9-fluorenylmethanol, wherein the synthesis yield is 72-74%.

The one-step method for synthesizing 9-fluorenylmethanol does not need to separate out the generated 9-fluorenylformaldehyde, and has the advantages of few reaction steps and simple process. But the defect is that the catalyst n-butyllithium is a high-price strong basic catalyst, the property of the catalyst is extremely active, combustible gas can be released when the catalyst meets water and in the synthetic process, the potential safety hazard in the storage, transportation and production processes is large, the requirements on equipment and operation technology are high, and therefore, the cost for synthesizing the 9-fluorene methanol by the one-step synthesis method is very high.

In addition, theoretically, the method can adopt a one-step method to control the reaction by controlling the dosage of the hydroxymethylation reagent formaldehyde so as to directly generate the 9-fluorene methanol from fluorene. However, in the process of performing fluorene hydroxymethylation by a one-step method by using formaldehyde/paraformaldehyde as a hydroxymethylation reagent, two products, namely 9-fluorenylmethanol and 9, 9-bis-hydroxymethyl fluorene, are simultaneously generated, and insoluble and infusible resinous viscous byproducts are easily generated in the product under an alkaline condition, so that the target product, namely 9-fluorenylmethanol, is difficult to separate and purify.

The two-step synthesis method is a main method for synthesizing 9-fluorenylmethanol and is also a method for realizing industrialization at present. Firstly, under the action of strong base catalysts such as sodium methoxide, sodium ethoxide or sodium ethoxide ethanol solution and the like, removing one hydrogen on 9-position of fluorene in a proton form to generate fluorene negative ions, then performing formylation reaction with an acylation reagent ethyl formate, adding water for quenching reaction, and preparing 9-fluorene formaldehyde; and secondly, reducing 9-fluorenylformaldehyde into 9-fluorenylmethanol by using reducing agents such as metal borohydride, formaldehyde or paraformaldehyde, wherein the yield is from 36.7 to 75.36%.

The first step described above uses ethyl formate as the acylating agent, which has a low boiling point and therefore needs to be carried out at a low temperature in order to reduce solvent loss. The common method is that firstly fluorene is converted into fluorene negative ions at a higher temperature, and then ethyl formate is added to react at a lower temperature to generate 9-fluorene formaldehyde. The reaction needs to be carried out at two different temperatures, so the operation process has certain difficulty.

In the second step of reduction reaction, more byproducts are generated when formaldehyde is used as a reducing agent, the selectivity is low, and the reaction conditions are not easy to control; while metal borohydride is used as a reducing agent, although selectivity is high and byproducts are few, sodium borohydride is easy to hydrolyze in water, and 9-fluorene-formaldehyde needs to be separated from a water-quenched acylation reaction system and then dissolved in solvents such as methanol and ethanol for reduction, so that a solvent conversion process needs to be involved, and operation complexity is increased.

Therefore, the currently reported method for synthesizing 9-fluorenylmethanol by a two-step method has long period and complex process.

Disclosure of Invention

The invention aims to provide a method for synthesizing 9-fluorenylmethanol with high selectivity, which shortens the reaction time and simplifies the synthesis process while improving the selectivity of 9-fluorenylmethanol.

The method for synthesizing 9-fluorenylmethanol with high selectivity comprises the following steps:

1) according to the mass ratio of fluorene to sodium ethoxide to ethyl formate of 1: 1.6-2.1: 1.4-2.3, firstly, taking fluorene as a raw material, heating and dissolving the fluorene in a DMSO solvent system in the presence of a sodium ethoxide ethanol solution alkali catalyst at 50-55 ℃, then adding an acylation reagent ethyl formate, carrying out an acylation reaction at the same temperature to prepare 9-fluorene formaldehyde, and adding water for quenching reaction after the fluorene is completely converted to obtain a DMSO-alkali water solution of the 9-fluorene formaldehyde;

2) adding soluble metal inorganic salt auxiliary agent into the DMSO-alkaline aqueous solution of the 9-fluorenylformaldehyde according to the mass ratio of the fluorene, the sodium borohydride and the soluble metal inorganic salt auxiliary agent of 1 to (1.0-1.5) to (1.5-2.0) to obtain suspension, and then adding NaBH₄And (3) carrying out reduction reaction, and adjusting the pH value of the reaction solution to be neutral after the reaction is finished so as to separate out 9-fluorenylmethanol solid precipitate.

Wherein the soluble metal inorganic saltIncluding but not limited to CaCl₂、BaCl₂、ZnCl₂Or Ca (NO)₃)₂。

Further, the invention preferably adopts 20 percent of sodium ethoxide ethanol solution by mass fraction as the base catalyst.

In the method, the acylation reaction is carried out under the protection of nitrogen, and the preferable reaction time is 65-80 min.

In the method of the present invention, after the acylation reaction is completed, water equal in volume to the solvent DMSO is preferably added to quench the reaction.

In the method, the time of the reduction reaction is preferably 90-120 min.

In the method, preferably, after the reduction reaction is finished, 1-2 mol/L of dilute hydrochloric acid solution is added to adjust the pH value of the reaction solution to 7.0-7.5.

Further, a small amount of 9-fluorenylmethanol product still exists in the reaction liquid after the 9-fluorenylmethanol solid precipitate is separated out, ice blocks can be added into the filtrate after the 9-fluorenylmethanol solid precipitate is filtered out and kept stand overnight to separate out a part of 9-fluorenylmethanol, the rest filtrate is extracted by ethyl acetate, and the solvent ethyl acetate is removed by rotary evaporation after the extract liquid is washed by water and dried by anhydrous magnesium sulfate to obtain the rest 9-fluorenylmethanol.

The method also comprises refining the prepared 9-fluorenylmethanol. Various conventional purification methods may be employed, including but not limited to recrystallization, column chromatography, distillation, and the like.

Preferably, the present invention is a recrystallization method. The solvent used for recrystallization is a solvent having a small solubility for 9-fluorenemethanol, and may be, for example, cyclohexane, n-heptane, toluene, petroleum ether, or the like, with cyclohexane being preferably used in the present invention.

The method for synthesizing 9-fluorene methanol comprises the steps of firstly using ethyl formate at the stage of generating 9-fluorene formaldehyde through fluorene formylation, and completely converting fluorene at a certain temperature, so that the temperature conversion in the prior art for shortening the reaction time is avoided, namely, the fluorene anion preparation stage is reacted at a higher temperature of 75 ℃ for 30-60 min, the fluorene anion acylation reaction is reacted at a lower temperature of 53 ℃ for 100-120 min, DMSO with a high dielectric constant is used as a solvent, a sodium ethylate ethanol solution is used as an alkali catalyst, and the fluorene, the alkali catalyst and an acylation reagent are reacted at a section of temperature of 50-55 ℃ for 65-80 min by adjusting and optimizing the material ratio of fluorene, the alkali catalyst and an acylation reagent, so that the fluorene can be completely converted.

Furthermore, in the reaction stage of adding water to quench the reaction, and reducing the 9-fluorenylformaldehyde into 9-fluorenylmethanol, the invention uses sodium borohydride as a reducing agent, and can reduce the 9-fluorenylformaldehyde into the 9-fluorenylmethanol in a high selectivity manner without solvent conversion by adding a soluble metal inorganic salt auxiliary agent, thereby simplifying the operation steps, improving the reduction efficiency and reducing the influence of the sodium borohydride dosage on the reduction product, under the condition of the same sodium borohydride dosage, the selectivity of the 9-fluorenylmethanol is improved from about 90 percent to about 100 percent, the yield is improved from about 90 percent to about 98 percent, and the reaction time is shortened from more than 180min to within 120 min.

Detailed Description

The following examples further describe embodiments of the present invention. The following examples are only for illustrating the technical solutions of the present invention more clearly, and do not limit the scope of the present invention. Various changes, modifications, substitutions and alterations to these embodiments will be apparent to those skilled in the art without departing from the principles and spirit of this invention.

Example 1.

Adding 1.66g of fluorene and 20mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 55 ℃ at a stirring speed of 300r/min, adding 7mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 1.2mL of ethyl formate, reacting for 70min under the protection of nitrogen, adding 20mL of water, quenching, and stopping the reaction to prepare 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed and 1.65g of CaCl was added to the resulting DMSO solution of 9-fluorenecldehyde₂After stirring to form a uniform suspension, 0.46g of sodium borohydride was added. Reacting for 90min at normal temperature, and then taking out the reactionThe content of 9-fluorenylmethanol is nearly 100 percent by GC detection.

And adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out a white 9-fluorenylmethanol solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three fractions were combined and recrystallized from cyclohexane to give 9-fluorenylmethanol as a white needle-like solid with a purity of greater than 99% in a calculated yield of 98.14%.

Example 2.

Adding 1.66g of fluorene and 20mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 8mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 2mL of ethyl formate, reacting for 65min under the protection of nitrogen, adding 20mL of water, quenching, and stopping the reaction to obtain 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed and 2.22g CaCl was added to the resulting 9-fluorenecldehyde DMSO solution₂After stirring to form a uniform suspension, 0.57g of sodium borohydride was added. After reacting for 90min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is nearly 100%.

And (3) adjusting the pH value of the reaction solution to 7.0-7.5 by using 1mol/L HCl solution, and separating out 9-fluorenylmethanol white solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three products were combined and recrystallized from cyclohexane to give 9-fluorenylmethanol as a white needle-like solid with a purity of greater than 99% in a calculated yield of 98.06%.

Example 3.

Adding 1.66g of fluorene and 25mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 8mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 2mL of ethyl formate, reacting for 65min under the protection of nitrogen, adding 25mL of water, quenching, and stopping the reaction to obtain 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed, and 2.46g of Ca (NO) was added to the resulting DMSO solution of 9-fluorenecldehyde₃)₂After stirring to form a uniform suspension, 0.38g of sodium borohydride was added. After reacting for 120min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is nearly 100%.

And adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out a white 9-fluorenylmethanol solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three fractions were combined and recrystallized from cyclohexane to give 9-fluorenylmethanol as a white needle-like solid with a purity of greater than 99% in a calculated yield of 97.83%.

Example 4.

Adding 1.66g of fluorene and 25mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 7mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 1.2mL of ethyl formate, reacting for 70min under the protection of nitrogen, adding 25mL of water, quenching, and stopping the reaction to prepare 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed, and 3.66g of BaCl was added to the resulting DMSO solution of 9-fluorenecldehyde₂·2H₂O, stirring to form a uniform suspension, and then adding 0.49g of sodium borohydride. After reacting for 90min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is approximate to that of100%。

And adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out a white 9-fluorenylmethanol solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three products were combined and recrystallized from cyclohexane to give 9-fluorenylmethanol as a white needle solid with a purity of greater than 99% in a calculated yield of 97.96%.

Example 5.

Adding 1.66g of fluorene and 25mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 7mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 1.2mL of ethyl formate, reacting for 80min under the protection of nitrogen, adding 25mL of water, quenching, and stopping the reaction to prepare the 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed, and 2.04g of ZnCl was added to the resulting DMSO solution of 9-fluorenecarboxylic acid₂After stirring to form a uniform suspension, 0.46g of sodium borohydride was added. After reacting for 120min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is nearly 100%.

And adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out a white 9-fluorenylmethanol solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three products were combined and recrystallized from cyclohexane to give 9-fluorenylmethanol as a white needle solid with a purity of greater than 99% in a calculated yield of 97.62%.

From the above examples 1 to 5, it can be seen that the generation of by-products can be effectively inhibited by adding the soluble metal inorganic salt assistant before using sodium borohydride in the reduction stage without solvent conversion, so that the selectivity and yield of 9-fluorenylmethanol are increased, the selectivity of 9-fluorenylmethanol is close to 100%, and the yield can reach 98.14% at most.

Comparative example 1.

Adding 1.66g of fluorene and 20mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 7mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 1.2mL of ethyl formate, reacting for 80min under the protection of nitrogen, adding 20mL of water, quenching, and stopping the reaction to prepare the 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed and 0.46g of sodium borohydride was added to the resulting DMSO solution of 9-fluorenecldehyde. After reacting for 180min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is 92.26%.

Adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out 9-fluorenylmethanol white solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

Adding ice blocks into the filtered filtrate, standing overnight, and performing suction filtration to obtain a part of 9-fluorenylmethanol.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The three fractions were combined and recrystallized from cyclohexane, and the yield of 9-fluorenylmethanol was calculated to be 90.38%.

Comparative example 2.

Adding 1.66g of fluorene and 20mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 7mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 2mL of ethyl formate, reacting for 70min under the protection of nitrogen, adding 20mL of water, quenching, and stopping the reaction to obtain 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed and 0.38g of sodium borohydride was added to the resulting DMSO solution of 9-fluorenecldehyde. After reacting for 240min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is 90.08%.

Adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out 9-fluorenylmethanol white solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The two fractions were combined and recrystallized from cyclohexane, and the yield of 9-fluorenylmethanol was calculated to be 88.29%.

Comparative example 3.

Adding 1.66g of fluorene and 25mL of DMSO into a jacketed reactor provided with a magnetic stirrer and a condenser tube, heating to 50 ℃ at a stirring speed of 300r/min, adding 8mL of 20% sodium ethoxide-ethanol solution after the solid is dissolved, slowly adding 2mL of ethyl formate, reacting for 65min under the protection of nitrogen, adding 25mL of water, quenching, and stopping the reaction to obtain 9-fluorenylformaldehyde.

The condenser tube and nitrogen were removed and 0.57g of sodium borohydride was added to the resulting DMSO solution of 9-fluorenecldehyde. After reacting for 180min at normal temperature, taking reaction liquid and detecting by GC, wherein the content of 9-fluorenylmethanol is 89.23%.

Adjusting the pH value of the reaction solution to 7.0-7.5 by using 2mol/L HCl solution to separate out 9-fluorenylmethanol white solid precipitate. After solid 9-fluorenylmethanol was filtered out, 9-fluorenylmethanol was obtained by drying.

And extracting the residual filtrate by using ethyl acetate, washing the obtained extract liquor by using water, drying the extract liquor by using anhydrous magnesium sulfate, and performing rotary evaporation to remove the ethyl acetate to obtain the 9-fluorenylmethanol.

The two fractions were combined and recrystallized from cyclohexane, and the yield of 9-fluorenylmethanol was calculated to be 87.24%.

As can be seen from comparative examples 1 to 3, in the reduction stage, no soluble metal inorganic salt auxiliary agent is added, and sodium borohydride is directly used for reduction reaction without solvent conversion, so that the selectivity and yield of the 9-fluorenylmethanol preparation are only about 90%, which are obviously lower than those of the above examples.