Acetic Acid → Indole

Participants

Reaction Steps

Ketone 2 (1.84 gr, 8.75 mmol) and 4-trifluoromethoxy phenylhydrazine hydrochloride (2.00 gr, 4.76 mmol) were stirred at 100° C. in acetic acid (40 ml, 0.22M) for 1 hour under nitrogen atmosphere to give a 1:2 mixture of 4- and 6-trifluoromethoxy indoles (desired 6-substituted indole is slightly less polar by TLC). The reaction was cooled to room temperature, the acetic acid was removed under reduced pressure and the residue was diluted with ethyl acetate and washed with water (1×) and brine (1×). The organic layer was dried with sodium sulfate, filtered and evaporated to afford 3 as a yellow oil after column chromatography (hexanes/ethyl acetate/1% acetic acid, 6:1); 1H-NMR (CDCl3, 500 MHz) δ 8.43 (br s, 1H), 8.16 (dd, 1H), 7.46 (d, 1H), 7.23 (t, 1H), 7.14 (t, 1H), 7.03 (d, 1H), 6.74 (d, 1H), 2.54 (s, 3H).

Provenance & Evidence