Regioselective 6-iodination of 5,7-dioxygenated flavones by benzyltrimethylammonium dichloroiodate

The iodination of 5,7-dioxygenated flavones with 1 equiv of benzyltrimethylammonium dichloroiodate (BTMA·ICl2) in the system CH2Cl2–MeOH–CaCO3 at room temperature is presented in this note. Flavones with a free phenol group at C5 and an alkoxy or a peracylglycosyloxy at C7 lead to the 6-iodoflavones with a good regioselectivity (ratio 6-iodination/8-iodination about 9).