Boron trifluoride etherate → 1H-Indole-1-carboxylic acid, 2-borono-5-[[4-[(1,1-dimethylethoxy)carbonyl]-1-piperazinyl]sulfonyl]-, 1-(1,1-dimethylethyl) ester (9CI)

Participants

Reaction Conditions

Reaction Steps

A solution of tert-butyllithium (1.7 M, 4.55 mL, 7.73 mmol, 2.00 equiv) in pentane was added to a solution of tert-butyl 5-{[4-(tert-butoxycarbonyl) piperazin-1-yl]sulfonyl}-1H-indole-1-carboxylate (2-2, 1.80 g, 3.87 mmol, 1 equiv) in THF (100 mL) at −78° C. The resulting orange-colored reaction mixture was stirred at −78° C. for 1.5 hour before trimethyl borate (1.10 mL, 9.66 mmol, 2.50 equiv) was added. The mixture was warmed to 0° C. and stirred for 20 minutes. Boron trifluoride diethyl etherate (1.20 mL, 9.66 mmol, 2.50 equiv) was then added, and the resulting mixture was partitioned between aqueous half-saturated ammonium chloride solution (200 mL) and EtOAc (2×200 mL). The organic layer was dried over sodium sulfate and concentrated to give 1-(tert-butoxycarbonyl)-5-{[4-(tert-butoxycarbonyl) piperazin-1-yl]sulfonyl}-1H-indol-2-ylboronic acid (2-3) as a tan solid. LCMS [M+H]+ observed=510.3; calculated=510.4.

Provenance & Evidence