Sulfuric Acid → 1-(1,1-Dimethylethyl) 2-borono-6-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-1H-indole-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a solution of 1 g 1-(tert-butoxycarbonyl)-6-(tert-butyldimethylsiloxy)indole in 15 mL anhydrous tetrahydrofuran at −78° C. under nitrogen is added tert-butyllithium (2.30 mL of a 1.5 M solution in pentane) over 3 min, and the reaction is stirred at ˜78° C. After 32 min, 0.66 mL trimethylborate are added in one portion, and the reaction is stirred at 0° C. After 2 h, 9 mL saturated aqueous ammonium chloride are added, the mixture diluted with 25 mL ether, and stirred at ambient temperature. The reaction is acidified with 4 mL of a solution made from 10% aqueous KHSO4 (60 mL) and concentrated H2SO4 (2 mL). After stirring for 15 min, the layers are separated and the organics are washed with water (15 mL) and brine (15 mL) successively, dried (Na2SO4), and the solvent is removed under reduced pressure to yield a partially solidified material. The material is washed with hot hexanes (5 mL) and filtered. The collected solid is washed with hexanes (2×5 mL) to give 635 mg (56%) of 1-(tert-butoxycarbonyl)-6-(tert-butyldimethylsiloxy)indole-2-boronic acid as a white powder.

Provenance & Evidence