Simple and efficient syntheses of 2-hydroxy-3H-phenoxazin-3-ones by aerobic oxidative cross-cyclocondensation in water

A novel, simple and versatile synthetic approach that utilized natural renewable low-toxic gallic acid as an organocatalyst was developed for efficient aerobic oxidative cross-cyclocondensations of equimolar 2-aminophenols and 2-hydroxylphenols to afford various 2-hydroxy-phenoxazin-3-ones with moderate to high isolated yields at room temperature in water.