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

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.