170355-38-1

20 g (147 mmol) of aluminum chloride are added portion-wise to a solution of 10 g (67 mmol) of ethyl thiophene-3-carboxylate in 160 ml of dichloro-methane, cooled to 0oC. The reaction medium is warmed to room temperature, and a solution of 4 ml (73 mmol) of bromine in 10 ml of dichloromethane is added. After reaction for 50 minutes at room temperature, the reaction medium is poured into a water + ice mixture and extracted with dichloromethane. The organic phase is dried over magnesium sulfate, filtered, and evaporated under vacuum. The residue obtained is purified by chromatography on a column of silica eluted with a 9/1 HEPTANE/ETHYL acetate mixture. 9 g (57percent) of ethyl 5-bromothiophene-3-carboxylate are obtained.

Ethyl 5-bromothiophene-3-carboxylate is an important organic reagent that can be used as a building block for the synthesis of many organic compounds. After hydrolysis, it can synthesize 5-Bromothiophene-3-carboxylic acid.

[1] Patent: WO2004/113331, 2004, A1. Location in patent: Page 39
[2] Patent: WO2007/145921, 2007, A1. Location in patent: Page/Page column 83-84