Triisopropyl borate → Isoquinoline-4-boronic acid

Participants

Reaction Steps

A solution of 2.0 gm (9.6 mMol) 4-bromoisoquinoline in 30 mL tetrahydrofuran was cooled to −100° C. To this solution were added dropwise 6.3 mL (10.1 mMol) n-butyl-lithium (1.6 M in hexane) dropwise, and the resultant solution was stirred for 30 minutes. To this solution was then added dropwise a solution of 4.4 mL (19.2 mMol) triisopropylborate and the reaction mixture was then stirred for 18 hours at room temperature. The reaction mixture was then partitioned between ethyl acetate and saturated aqueous sodium chloride. The phases were separated and the aqueous phase extracted well with ethyl acetate. The combined organic phases were washed with saturated aqueous sodium chloride, dried over sodium sulfate and concentrated under reduced pressure. The residue was sonicated in a mixture of hexane:ethyl acetate. The resulting suspension was filtered to provide 0.57 gm (34%) isoquinolin-4-ylboronic acid as a light orange solid.

Provenance & Evidence