4-Toluenesulfonyl chloride → 5-Bromo-1-(4-methylbenzene-1-sulfonyl)-1H-indole

Participants

Reaction Steps

A 100 mL round bottom flask was sequentially charged with 5-bromoindole (1.96 g, 10 mmol), p-toluenesulfonyl chloride (2.30 g, 12 mmol), tetrabutylammonium hydrogen sulfate (240 mg, 0.70 mmol) and toluene (40 mL). An aqueous solution of potassium hydroxide (13 mL, 50%) was added dropwise and the mixture was stirred at room temperature overnight. At this point the organic layer was separated, diluted with ethyl ether (40 mL), washed with two portions of dilute potassium hydroxide solution (2×20 mL, 2M) and dried over MgSO4. The solvent was removed at reduced pressure and the product was purified by flash chromatography on silica gel (hexane/ethyl acetate 1:1) to provide the desired product as a light yellow solid (3.50 g,99% yield). Mp 135° C. (lit. 139-140° C., See Fresneda, M. P.; Molina, P.; Bleda, A. J. Tetrahedron 2001, 57, 2355). 1H NMR (400 MHz, CDCl3, J values are reported in Hz, lit. See Fresneda, M. P.; Molina, P.; Bleda, A. J. Tetrahedron 2001, 57, 2355): δ 7.88 (d, J=8.8, 1H), 7.76 (d, J=8.6, 2H), 7.68 (d, J=1.8, 1H), 7.59 (d, J=3.5, 1H), 7.42 (dd, J=8.8, J=2.0, 1H), 7.25 (d, J=8.6, 2H), 2.37 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 145.7, 135.3, 133.9, 132.9, 130.4, 128.0, 127.9, 127.2, 124.5, 117.2, 115.4, 108.7, 22.0.

Provenance & Evidence