Triisopropyl borate → (1-Ethyl-1H-indazol-5-yl)boronic acid
Reaction equation
Br[C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[N:7]([CH2:11][CH3:12])[N:6]=[CH:5]2.C([Li])CCC.[B:18](OC(C)C)([O:23]C(C)C)[O:19]C(C)C>O1CCCC1.CCCCCC>[CH2:11]([N:7]1[C:8]2[C:4](=[CH:3][C:2]([B:18]([OH:23])[OH:19])=[CH:10][CH:9]=2)[CH:5]=[N:6]1)[CH3:12]Participants
Conditions
- Temperature
- -10 °C
Procedure
A solution of 5-bromo-1-ethyl-1H-indazole (598 mg, 2.67 mmol) in dry tetrahydrofuran (30 mL) was cooled below −60° C. Then a solution of butyllithium in hexane (2.5 ml, 2.5M) 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 (1.5 g, 7.98 mmol). After warming to room temperature the mixture was quenched with hydrochloric acid (3N) 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 vacuum to give 1-ethyl-1H-indazol-5-ylboronic acid (450 mg, 89%) which was used for the next step without further purification.
Workup
- temperatureThe mixture was cooled again below −60° C.
- temperatureAfter warming to room temperature the mixture
- customwas quenched with hydrochloric acid (3N)
- stirringstirred for 1 h
- extractionextracted with ethyl acetate (3×80 ml)
- dry with materialdried over sodium sulfate
- concentrationconcentrated in vacuum
Sources & evidence
- ORD record
- ord-69a1f5424e9346dcbde6991080d0b7fa
- Source dataset
- uspto-grants-2014_12
- Patent number
- US08912188B2
Reaction notes
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