Transition-Metal-Free Tandem Oxidative Removal of Benzylic Methylene Group by C-C and C-N Bond Cleavage Followed by Intramolecular New Aryl C-N Bond Formation under Radical Conditions

A novel tandem oxidative conversion of 10,11-dihydro-5H-dibenzo[b,e][1,4]diazepines to phenazines has been achieved under transition-metal-free, mild conditions using K2S2O8 or DDQ as the oxidizing agent. The transformation proceeds through oxidative removal of a benzylic methylene group by C-C and C-N bond cleavage followed by a new aryl C-N bond formation under radical conditions.