5-Methylisatoic anhydride

5-Methylisatoic anhydride is prepared from 5-methyl indole (9e) by stirring in a 4:1 mixture of DMF/H2O for 16 h at room temperature.
¹ H NMR (DMSO-d6): δ11.61 (s, br., 1H), 7.69 (s Hz, 1H), 7.55 (d, J = 7.8 Hz, 1H), 7.05 (d, J = 8.7 Hz, 1H).