Efficient one-step synthesis of 3-nitroflavones via cascade nitration-cyclization.

A mild and regioselective nitration-cyclization of alkynyl aryl ketones has been developed to access 3-nitroflavones promoted by Zn(OTf)2. Tandem nitration and intramolecular cyclization is achieved using 68% HNO3 under room-temperature conditions, delivering substituted 3-nitroflavones in generally good to excellent yields.