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 stirred at −78° C. After 32 min, 0.66 mL trimethylborate are added in one portion and the reaction 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 ished with water (15 mL) and brine (15 mL) successively, dried (Na2SO4), and the solvent removed under reduced pressure to yield a partially solidified material. The material is ished with hot hexanes (5 mL) and filtered. The collected solid is ished 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