Hydrochloric Acid → 1-(phenylsulfonyl)-1H-indol-3-ylboronic acid

Participants

Reaction Conditions

Reaction Steps

A 1.7 M solution of tert-butyl lithium (t-BuLi) in pentane (3.8 ml; 6.45 mmol) was added over ~5 minutes, to a solution of the title product of Step (B) (1 g; 3 mmol) in THF at -100° C. The temperature was kept below -84° C. during the addition. After stirring 5 minutes at -100° C., trimethylborate was added in one portion and the reaction mixture was allowed to warm to room temperature over 4 hours. At this time, 10 ml of 10% HCl was added and the mixture was extracted with methylene chloride (3×30 ml). The combined organic layers were washed with water (3×30 ml) and brine (30 ml). Drying (MgSO4), decolorizing (Darco) and concentration afforded a tan foam. Due to apparent decomposition at room temperature, the foam was stored at -80° C. overnight. The residue was then partitioned between ether (20 ml) and 0.5 N NaOH (20 ml). The purple ether layer was extracted with 10 ml of 0.5N NaOH. The combined green basic layer was washed with ether (20 ml), acidified to pH 2 with saturated KHSO4 solution to afford a purple mixture, which was extracted with methylene chloride (2×30 ml). Drying (MgSO4) and concentration afforded 623 mg (69%) of the title product of this step as a purple foam.

Provenance & Evidence