The possibility of synthesizing a nitrogen heterocycle by acting on a nitro compound in such a manner as to effect direct ring closure first suggested itself as a result of our experience with the Fischer and Heiler (1) method for the preparation of phenazine. Their reaction involves oxidation of 2-aminodiphenylamine by dry distillation with litharge:

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The present paper continues the illustration of the applicability to a wide variety of phenazines of the general method of ring closure through the nitro group (1). There are here described, in addition to the syntheses of various substituted phenazines, those of three compounds embodying another heterocyclic ring in addition to the pyrazine system. These compounds are shown in the following representation, in which the structures of two of these three compounds (II and VI) have been written as the angular isomers, on the reasonable assumption that ring closure of the corresponding intermediates (I and V) occurred across the double bond of the heterocyclic moiety. In the instance of IV, it is obvious that only one structure is possible. Cl 4n xaxzz/xz VZxn^xZ II 6-(4-ChIoro-2-mtroanilmo)quinoline 10-Chloropyrido

In continuation of the project of demonstrating the general applicability of ring closure through the nitro group to the synthesis of a wide variety of phenazines, the formation of phenazinecarbonitriles was studied. The present paper describes the findings in this investigation.The reactions all take the usual course (1), with the exception of the ring closure as applied to 2'-amino-4-cyano-2-nitrodiphenylamine (4-o-aminoanilino-3-nitrobenzonitrile). In this reaction the amino group is eliminated (at least in part as ammonia) and unsubstituted 2-phenazinecarbonitrile results:H No trace of any aminophenazine could be found in the reaction products. This behavior of the amino group ortho to the imino linkage of the unnitrated benzene ring parallels that of alkoxy groups in the same position, whose elimination occurs in the "Type B" reaction previously reported (1). While no generalization can be drawn from the single example given herein, it seems likely, in view of the general behavior of the 2'-alkoxy compounds, that all 2,-amino groups will likewise be eliminated whenever 2-nitrodiphenylamines containing them are subjected to ring closure.Because it was desirable to have an intermediate bearing the nitrile group in the same ring as the nitro group, the following method of synthesis of 1-phenazinecarbonitrile was devised:

The preparation of the simpler phenazines, as distinguished from the numerous more complex phenazines developed by the dye industry, has hitherto been hampered by cumbersome methods of synthesis and relatively poor yields. The general synthesis of Waterman and Vivian (1) has now, however, made more accessible a wide variety of phenazines (2), as well as a number of other nitrogen heterocycles. The nitro-group ring-closure of "Type A" (1), used in the synthesis of all the phenazine derivatives dealt with in this paper, is most simply represented3 by: i\r '' v +2 Fe 0 0 (220e-300°) (FeO from: Fe C204 • 2 H20-»~FeO + C02+C0 + 2H20)The present series of papers details the preparation of representative examples of these newly available compounds, so that with respect to the phenazine syntheses, the scope, flexibility, and limitations of the reaction may be more clearly delineated. SUMMARY 1. A number of new 2-nitrodiphenylamines and phenazines derived therefrom have been synthesized.