To 4.2 g (10 mmol) Trifluoro-methanesulfonic acid 1-(4-bromo-phenyl)-1H-indol-5-yl ester in 30 ml piperidine, 580 mg (0.5 mmol) tetrakis-(triphenylphosphine)-palladium and 100 mg (0.625 mmol) CuI were added. The solution was evaporated and purged with argon three times, before 1.4 ml (10 mmol) ethynyltrimethylsilane were added. The solution was stirred at RT for 48 h. Additional 0.38 ml (3.3 mmol) ethynyltrimethylsilane were added and the mixture was stirred at 50° C. for 1 h. The solution was concentrated and the residue redissolved in 0.5M HCl and ether. The inorganic phase was extracted with ether, the organic phases were washed with water and dried over Na2SO4. Purification on silica gel with hexane/EtOAc 19:1 yielded 1.7 g (38%) Trifluoro-methanesulfonic acid 1-(4-trimethylsilanylethynyl-phenyl)-1H-indol-5-yl ester as orange oil, MS: 437 (M).
