BENZOTHIOPHENE-4-CARBOXYLIC ACID Chemical Properties

Melting point:

188-189℃

Boiling point:

376.2±15.0 °C(Predicted)

Density 

1.419±0.06 g/cm3 (20 ºC 760 Torr)

storage temp. 

Sealed in dry,Store in freezer, under -20°C

pka

3.34±0.10(Predicted)

Appearance

Off-white to light brown Solid

Safety Information

Hazard Codes 

Xn

Risk Statements 

22

HS Code 

2934999090

BENZOTHIOPHENE-4-CARBOXYLIC ACID Usage And Synthesis

Synthesis

Benzo[b]thiophene-4-carboxylic acid was prepared as follows: a small amount of iodine crystals was added as initiator to a stirring suspension of magnesium (Mg, 4.79 g, 197 mmol) in anhydrous tetrahydrofuran (THF, 100 mL) under nitrogen protection. Subsequently, a solution of 4-bromobenzo[b]thiophene (40.0 g, 188 mmol) in anhydrous THF (150 mL) was added slowly and dropwise. Initially, only 5% of the total amount (~1 mL) was added to initiate the reaction, after which the remaining solution was added at a rate that maintained the reaction temperature at 50-55 °C, a process that took about 30 min. After addition, the reaction mixture was continued to be stirred at 50°C for 1 hour. After most of the magnesium has been consumed, the reaction is cooled to 23°C and carbon dioxide (CO2) gas produced from dry ice is passed into the solution. The reaction is exothermic and the solution temperature needs to be maintained at about 23°C by an ice bath. The gas is continuously vented for 15-20 minutes until a large amount of precipitate generation is observed. Upon completion of the reaction, the reaction is carefully quenched with 10% aqueous hydrochloric acid (HCl) solution at 0°C. Saturated aqueous sodium chloride solution was added and the mixture was extracted with ethyl acetate (EtOAc). The organic phase was extracted with 2 M aqueous sodium hydroxide (NaOH) and subsequently the aqueous phase was acidified to pH 1 with 37% aqueous HCl to form a suspension. After filtration and drying, benzo[b]thiophene-4-carboxylic acid was obtained as a white solid (24.9 g, 74% yield).

References

[1] Patent: US2008/306082, 2008, A1. Location in patent: Page/Page column 18

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