The Nitration of Some 4,6-Dimethoxyindoles

A range of 3-substituted-4,6-dimethoxyindoles bearing electron-withdrawing groups in either the 2- or 7-position, can be nitrated using nitric acid adsorbed on silica, to give 7-nitro and 2-nitro-indoles, respectively. A 1-cyano-indole gives regioselectively the 2-nitro-indole with loss of the cyano group.