Trimethyl borate → [3-(Methylamino)phenyl]boronic acid

Participants

Reaction Conditions

Reaction Steps

161 mL (242 mmol) of 1.5M methyllithium in diethyl ether are added dropwise to a solution precooled to −78° C. of 37.6 g (202 mmol) of (3-bromophenyl)methylamine (prepared according to Example 24f) in 300 mL of tetrahydrofuran. After stirring for 1 hour at −78° C., 261 mL (444 mmol) of a 1.7M solution of tert-butyllithium in pentane are added dropwise and the medium is again stirred at −78° C. for 1 hour. At −65° C., 103.5 mL (808 mmol) of trimethyl borate are added dropwise and the reaction medium is then stirred, while allowing the temperature to rise to room temperature over 1 hour. After addition of ice, the reaction medium is extracted with a 1/1 heptane/ethyl acetate mixture and then with 1-butanol. The organic phases are combined, washed with water, dried over magnesium sulfate, filtered and evaporated; 11 g (40%) of 3-methylaminophenylboronic acid are obtained.

Provenance & Evidence