BuLi (1.6 M)
Indole (10.8 mmol)
THF
t-BuLi (1.7 M)
Toluenesulfonyl fluoride

BuLi (11.2 mmol) was added dropwise to a stirred solution of indole in THF (40 ml) at -78 ^o C. After about 30 minutes CO₂ (gas - dried through CaCl₂ tube) was passed through the solution which was then allowed to stand for 10 minutes and the solvent was evaporated at 0 ^oC (1 mm Hg- using a pump attached directly to the reaction vessel). This takes about an hour. The resulting material (white solid) was then dissolved in THF (40 ml) and cooled to -78 ^oC. t-BuLi (18.7 mmol) was then added dropwise and the solution stirred for about 20 minutes. TsF (1.91 11 mmol) in THF (8 ml) was then added at -78 ^oC and the mixture stirred at this temperature for one hour and then allowed to warm to r.t. The reaction was then stirred at room temperature for a couple of hours and the solkution then poured onto ice-brine solution and then extracted with ether. Purification was by chromatography using silica-gel, and petrol:ether as eluent (20:1, - 3:1, gradient) to give the product (1.04 g, 35%)

Although the yield of this product is only moderate, its not a bad way of making this compound. The key point is to ensure that the temperature is maintained around 0^oC when removing the solvent after the first lithiation. We have used this to prepare 2-tosyl-pyrrole - but that is not quite as reproducible.

¹ H NMR 8.82, 1H, br s; 7.89, 2H, d, J = 8.4 Hz; 7.67, 1H, d, J = 8.2 Hz; 7.42, 2H, d, J = 8.2 Hz; 7.34, 1H, d, 6.8 Hz; 7.2-7.14, 3H, m; 2.4, 3H, s

S. Caddick, K. Aboutayab, K. Jenkins, R. I. West, J. Chem. Soc. Perkin Trans. 1, 1996, 675

A. R. Katritzky, K. Akutagava, tetrahedron Lett. 1985, 24, 5935