A 1.6 M solution of BuLi in pentane (6.57 ml, 10.5 mmol) was added to a solution of 6-(tert-butyl-dimethyl-silanyloxy)-1H-indole (2 g, 8.1 mmol) in THF (40 ml) at −78° C. within 20 min under an argon atmosphere. The reaction mixture was stirred for 20 min at −78° C. tert-Butyldimethylsilyl chloride (1.6 g, 10.5 mmol) was added and the reaction mixture was stirred for 10 min at −78° C. and for 1 h at RT. The mixture was chilled to −78° C., N-bromosuccinimide (1.6 g, 8.9 mmol) was added and stirring was continued for 1 h at −78° C. and for 1 h at RT. The solution was diluted with diethyl ether and washed with saturated aqueous NaHCO3 solution and water. The ether phase was dried over sodium sulfate, concentrated under reduced pressure and the residue was purified by column chromatography (silica gel, n-heptane/ethyl acetate 1:19) to give 2.64 g (6 mmol, 74%) 3-bromo-1-(tert-butyl-dimethyl-silanyl)-6-(tert-butyl-dimethyl-silanyloxy)-1H-indole as brown solid.
