2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 4-methyl-5-nitro-1H-indole

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Reaction Steps

To a suspension of 4-methyl-5-nitroindoline (4.767 g, 0.0268 mol) in 100 mL of methanol was added 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (6.697 g, 0.0295 mol) all at once and the resulting mixture was stirred at room temperature for 1 h. The reaction mixture was then evaporated and the residue was taken up in dichloromethane. This solution was then washed with saturated aqueous NaHCO3 (×4), dried (Na2SO4) and evaporated to give a solid. Crystallization of this material from ethyl acetate-hexane (-20° C.) afforded 4.161 g of the title compound as greenish-gold needles, mp 179°-180° C. Chromatography of the mother liquor (SiO2 /ethyl acetate-hexane, 1:1 ) gave an additional 0.417 g of the pure product. Total yield=4.578 g (97%): IR (KBr) 3318, 1604, 1585 cm-1 ; 1H NMR (DMSO-d6, 200 MHz) δ11.72 (br s, 1H), 7.81 (d, J=9.0 Hz, 1H), 7.56 (t, J=2.8 Hz, 1H), 7.39 (d, J=8.9 Hz, 1H), 6.79 (m, 1H), 2.75 (s, 3H). Anal. Calcd for C9H8N2O2 : C, 61.35; H, 4.58; N, 15.90. Found: C, 61.32; H, 4.40; N, 15.96.

Provenance & Evidence