Method for producing 5-(bromomethyl)-1-benzothiophene

1. A method for producing 5-bromomethyl-1-benzothiophene, comprising:

(1) introducing 5-methyl-1-benzothiophene, a brominating agent and a solvent into a reactor to obtain a reaction mixture;

(2) irradiating the interior of the reactor with light having a wavelength range of 200 to 780 nm; and

(3) recovering the reaction mixture comprising 5-bromomethyl-1-benzothiophene from the reactor, wherein the 5-bromomethyl-1-benzothiophene is directly used without isolation in a next cyanation step,

wherein

the reactor is a flow-type photochemical reactor,

the solvent is at least one selected from the group consisting of methyl acetate and ethyl acetate,

a peak area ratio of 5-bromomethyl-1-benzothiophene in the reaction mixture is 79% or more,

a peak area ratio of 5-dibromomethyl-1-benzothiophene in the reaction mixture is 3% or less, and

a peak area ratio of 3-bromo-5-methyl-1-benzothiophene in the reaction mixture is 3% or less.

2. The method according to claim 1 , wherein the brominating agent is at least one selected from the group consisting of bromine, N-bromocaprolactam, N-bromosuccinimide, 1,3-dibromo-5,5-dimethylhydantoin, a bromine-pyridine complex and copper(II) bromide.

3. The method according to claim 1 , wherein the brominating agent is at least one selected from the group consisting of N-bromosuccinimide and 1,3-dibromo-5,5-dimethylhydantoin.

4. The method according to claim 1 , wherein the brominating agent is 1,3-dibromo-5,5-dimethylhydantoin.

5. The method according to claim 1 , wherein a reaction temperature is from 5 to 70° C.