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CN-122010775-A - Method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis

CN122010775ACN 122010775 ACN122010775 ACN 122010775ACN-122010775-A

Abstract

The invention discloses a method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis, belonging to the field of organic synthesis. The invention takes p-tolunitrile as raw material, the p-tolunitrile is dissolved in organic solvent, then brominating reagent is added, 4-cyano benzyl bromide is obtained through photocatalysis bromination reaction. The method has the advantages of mild catalytic reaction process conditions, simple operation, few byproducts, high purity of the obtained product and stable performance. Aiming at the defects of the traditional synthesis process, the method does not need complex operation steps, is not only suitable for small-scale synthesis in a laboratory, but also can meet the requirement of industrialized mass production, and has wide application prospect.

Inventors

  • MENG XIANGMING
  • HU CHI
  • GUO YUXUAN

Assignees

  • 安徽大学

Dates

Publication Date
20260512
Application Date
20260202

Claims (7)

  1. 1. A method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis, which is characterized by comprising the following steps: Step 1, raw material preparation, namely adding p-tolunitrile and an organic solvent into a reaction kettle, uniformly stirring to obtain a solution a for standby, placing hydrogen peroxide into a container to obtain a solution b for standby, and placing hydrobromic acid into the container to obtain a solution c for standby; Step 2, bromination reaction, namely pumping the solution a, the solution b and the solution C into a continuous flow photocatalytic reactor by using water cooling and opening the photocatalytic reactor, controlling the temperature to be 10-40 ℃ and reacting to 1-20 min to obtain a reaction solution; step 3, quenching, namely adding a quenching agent into the reaction liquid obtained in the step 2, extracting by using an organic solvent to obtain an extract, and washing by using brine; step 4, refining, namely performing reduced pressure distillation on the extract obtained in the step 3 to obtain 4-cyano benzyl bromide; The reaction scheme is as follows: 。
  2. 2. The method according to claim 1, characterized in that: in the step 1, the organic solvent is one or a combination of more of dimethyl sulfoxide, methanol and cyclohexane.
  3. 3. The method according to claim 1, characterized in that: in the step 1, the concentration of the p-tolunitrile in the solution a is 1.7-17 mol/L, the mass concentration of the H 2 O 2 in the solution b is 10-50%, and the mass concentration of the HBr in the solution c is 10-50%.
  4. 4. A method according to claim 3, characterized in that: In step 1, the molar ratio of H 2 O 2 to p-tolunitrile is 1.2-2:1, and the molar ratio of HBr to p-tolunitrile is 1.0-1.5:1.
  5. 5. The method according to claim 1, characterized in that: In the step 2, the wavelength of light of the continuous flow photocatalytic reactor is 365 nm-480 nm, the reaction time is 1-20 min, and the reaction temperature is 10-50 ℃.
  6. 6. The method according to claim 5, wherein: in the step 2, the light wavelength of the continuous flow photocatalytic reactor is 365-395 nm, the reaction time is 5-15 min, and the reaction temperature is 20-40 ℃.
  7. 7. The method according to claim 1, characterized in that: In the step 3, the quenching agent is one or a combination of a plurality of water, saturated sodium bicarbonate solution and saturated sodium hydroxide solution.

Description

Method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis Technical Field The invention belongs to the field of organic synthesis, and particularly relates to a method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis. Background 4-Cyanobenzyl bromide is an important organic synthesis intermediate, and the molecular structure of the intermediate consists of benzene ring, cyano and bromomethyl. The compounds have wide application in the fields of organic chemistry and material science. In organic synthesis, 4-cyanobenzyl bromide is often used as an alkylating agent due to high reactivity, a bromine atom is used as a good leaving group to perform substitution reaction with a nucleophile, and a cyanobenzyl structure is introduced into a target molecule to construct a complex compound containing cyano. Furthermore, cyano groups can be converted to amino groups by reduction reactions or hydrolyzed to carboxylic acids, further expanding their potential for use in drug synthesis, for example as precursors for antitumor or antibacterial drugs. The traditional kettle type reaction is complex in operation, and operators are high in labor intensity and easy to contact dangerous medicine reagents. Disclosure of Invention The invention provides a safer method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis, which is used for synthesizing a target compound by continuous photocatalysis reaction, so as to remarkably improve the yield of the target compound and reduce the incidence rate of side reaction. The invention adopts the following technical scheme for realizing the purpose: the invention relates to a method for preparing 4-cyano benzyl bromide by continuous flow photocatalysis, which comprises the following steps: Step 1, raw material preparation, namely adding p-tolunitrile and an organic solvent into a reaction kettle, uniformly stirring to obtain a solution a for standby, placing hydrogen peroxide into a container to obtain a solution b for standby, and placing hydrobromic acid into the container to obtain a solution c for standby; Step 2, bromination reaction, namely pumping the solution a, the solution b and the solution C into a continuous flow photocatalytic reactor by using water cooling and opening the photocatalytic reactor, controlling the temperature to be 10-40 ℃ and reacting to 1-20 min to obtain a reaction solution; step 3, quenching, namely adding a quenching agent into the reaction liquid obtained in the step 2, extracting by using an organic solvent to obtain an extract, and washing by using brine; step 4, refining, namely performing reduced pressure distillation on the extract obtained in the step 3 to obtain 4-cyano benzyl bromide; The reaction scheme is as follows: 。 in the step 1, the organic solvent is one or a combination of more of dimethyl sulfoxide, n-heptane, methanol and cyclohexane. In the step 1, the concentration of the p-tolunitrile in the solution a is 1.7-17 mol/L, the mass concentration of the H 2O2 in the solution b is 10-50%, and the mass concentration of the HBr in the solution c is 10-50%. Further, the molar ratio of H 2O2 to p-tolunitrile is 1.2-2:1, and the molar ratio of HBr to p-tolunitrile is 1.0-1.5:1. In the step 2, the wavelength of light of the continuous flow photocatalytic reactor is 365 nm-480 nm, the reaction time is 1-20 min, and the reaction temperature is 10-50 ℃. Further, the wavelength of light of the continuous flow photocatalytic reactor is 365-395 nm, the reaction time is 5-15 min, and the reaction temperature is 20-40 ℃. In the step 3, the quenching agent is one or a combination of a plurality of water, saturated sodium bicarbonate solution and saturated sodium hydroxide solution. Compared with the prior art, the invention has the beneficial effects that: The core technical route innovation is that continuous flow photocatalysis replaces the traditional kettle type reaction, which is the most core innovation of the patent and changes the synthesis mode of the substance. The reaction system is upgraded, the traditional open/semi-open kettle type reaction is abandoned, and the problems of uneven material mixing and difficult control of reaction conditions in the traditional process are solved by adopting a continuous flow photocatalytic reactor and adopting closed continuous feeding, reacting and discharging processes. The invention has mild reaction conditions, excellent mass transfer of continuous flow, and heat transfer capability, which is helpful for inhibiting side reaction, and ensures the stability and controllability of reaction. The invention has short reaction time, and the generation of byproduct of polybrominated is reduced due to the high irradiation intensity of the photocatalysis light source and shorter reaction time. The method is not only suitable for small-scale synthesis in a laboratory, but also can meet the requirement of industrialized mass production. Has important sign