Iodoethane → N-(Benzensulfonyl)-5-chloro-2-ethylindole

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Reaction Steps

t-BuLi (3.7 mL of 1.7 M solution in pentane) was added dropwise to a solution of N-(benzensulfonyl)-5-chloroindole (1) (J. Org. Chem. 1981, 46, 3859) (1.5 g, 5.14 mmol) in THF (35 mL) at −70° C., under a nitrogen atmosphere. The mixture was stirred for 15 min, allowed to warm to room temperature over 20 min, cooled to −70° C., and treated with a solution of ethyl iodide (0.84 mL, 10.5 mmol) in dry THF (5 mL). The mixture was stirred at −78° C. for 1 h, allowed to warm to room temperature, stirred for 2 h, poured into ice (15 g), and a saturated aqueous NH4Cl solution and then extracted with ether (3×20 mL). The combined organic extracts were washed with brine, dried (Na2SO4) and evaporated in vacuo to give a residue which was purified by flash chromatography (silica gel, cyclohexane/ethyl acetate, 8:2) and crystallization from ethylacetate/cyclohexane.

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