The preparation of substituted dibenz[b.flazepin required several substituted diphenylamines, especially 2,2'-dichloro-diphenylamine (I) and its derivatives. The observations made in this investigation are believed to be of some general interest.
BROMINATION of diphenylamine-4,4'-dicarboxylic acid (II, R = H)' and its methyl ester (II, R = CH,)' in glacial acetic acid at low temperature gave 2,2'-dibromodiphenylamine-4,4'-dicarboxylic acid (III, R = H) and its dimethyl ester as the most probable structures in analogy with the following chlorination experiments. As it proved impossible to decarboxylate the acid III, which tended to carbonize, the chlorination in glacial acetic acid at 10" was undertaken. The product containedfive chlorine atoms, one of which was bound to the nitrogen and could be eliminated by treatment with sodium iodide. The chlorination products, according to the rules of substitution, would, therefore, be IV and V, respectively. Both were decarboxylated by copper bronze in boiling quinoline to the same 2,2',6,6'-tetrachlorodiphenylamine (VI).
In order to limit the extent of chlorination of II (R = H), we employed t-butyl ROOC~~~OOR ROOC~3rB@OOl