反应详情

温度

-10 °C

To a solution of 5-chlorobenzofuran (14 g, crude) in dry tetrahydrofuran (250 mL) were added tetramethylethylenediamine (12.82 g, 110 mmol). The solution was kept below −60° C. under argon, while the solution of butyllithium in hexane (44 ml, 2.5 M) was added dropwise. It was warmed to −10° C. during 45 min and stirred at this temperature for another 30 min. The mixture was cooled again below −60° C. followed by dropwise addition of triisopropyl borate (51.88 g, 276 mmol). After warming to room temperature the mixture was quenched with hydrochloric acid (70 ml, 2N) and stirred for 1 h. The alkaline aqueous layer was brought to pH 5 and extracted with ethyl acetate (3×80 ml). All organic layers were combined, dried over sodium sulfate, and concentrated in vacuo to give 5-chlorobenzofuran-2-ylboronic acid (7.5 g) which was used for the next step without further purification.

1. additionwas added dropwise
2. temperatureThe mixture was cooled again below −60° C.
3. temperatureAfter warming to room temperature the mixture
4. customwas quenched with hydrochloric acid (70 ml, 2N)
5. stirringstirred for 1 h
6. extractionextracted with ethyl acetate (3×80 ml)
7. dry with materialdried over sodium sulfate
8. concentrationconcentrated in vacuo