Phenazines, synthesis

The more traditional methods of phenazine synthesis falling into the type A synthesis are altogether less satisfactory than the application of the Beirut reaction. Traditionally, Ris prepared phenazine in low yield by heating o-phenylenediamine and catechol in a sealed tube at 200 °C (1886CB2206) however, the method appears to be unsatisfactory at best and gives, in addition to phenazine, 5,10-dihydrophenazine in varying amounts (Scheme 53). Several variants of this procedure exist o-benzoquinone has been used in condensation with 0-phenylenediamine and yields as high as 35% have been reported, and 1,2,3,4-tetrahydrophenazine has been prepared by condensation of o-phenylenediamine with cyclohexane- 1,2-dione. 

W 0 H L - A U E Phenazine synthesis Synthesis of phenazine N-oxide from anilines and nitrobenzene... 

Here, we will present a selection of the most attractive naturally occurring phenazines that have been newly discovered. Also, we will deal with the general methods of phenazine synthesis and its most recent applications in natural product chemistry. Until now, the relevance of Pd-catalyzed N-arylations to this... 

The parent heterocycle and methyl- and methoxy-substituted derivatives have been obtained in low yields by reactions of anilinonitro-pyridines with ferrous oxalate at 260-280°. This extension of a conventional phenazine synthesis is the only reported approach to simple examples of this ring system. ... 

The amino group from glutamine is enzymatically transferred by PhzE, the phenazine synthesis-specific... 

The most cited strategy for phenazine synthesis goes via 2-nitrodiphenylamine which, upon reductive ring closure, affords the desired phenazine. 

Scheme 8. General Scheme for Phenazine Synthesis by Condensation of Catechol or 1,2-Cyclohexyldione with Benzene-1,2-diamine...

Scheme 10. Phenazine Synthesis by Sequential Palladium(II)-Catalyzed Aryl Amination" ...

---