反应详情

To a dry flask under N2 with a stirbar was added 6 g (29.1 mmol) of 4-bromothiophene-2-carboxylic acid (as prepared in the previous step) and dry methanol (100 mL). The solution was cooled in an ice-salt bath for 15 min and 2.55 mL (34.9 mmol) of thionyl chloride was added over 15 min, keeping the temperature <−5° C. The reaction mixture was stirred on the ice-salt bath for an additional 15 min, then for 1 h at rt, and finally refluxed for 8 h under N2. The resulting solution was cooled and concentrated to 6.7 g of pale amber oil. This oil was passed through 150 g of silica with ˜600 mL CH2Cl2 (discarded the first 120 mL which contained minor impurities and no ester). The solvent was removed in vacuo to afford 6.11 g (95% yield) of the title compound as a colorless solid, which was used in the next step without further purification.

1. temperatureThe solution was cooled in an ice-salt bath for 15 min
2. customthe temperature <−5° C
3. temperaturefinally refluxed for 8 h under N2
4. temperatureThe resulting solution was cooled
5. concentrationconcentrated to 6.7 g of pale amber oil
6. customThe solvent was removed in vacuo