Mechanochemical Synthesis of Benzo[a]phenazin-5-ol and Its 9,10-Dihalo-Substituted Derivatives under Ball-Milling Conditions

Phenazines are known to possess a wide range of biological activities and new methods for their synthesis are of high demand. Herein, a mechanochemical approach was proposed for the synthesis of benzo[a]phenazin-5-ols by the SNH/SNipso tandem reaction between 1,4-naphthoquinone and o-phenylenediamines and their halo-disubstituted derivatives under ball-milling conditions. The advantages of the method are high atom economy, short reaction time, room temperature and solvent-free conditions, low E-factor and high yields of the target phenazines.