A convenient laboratory preparation of 2,2'-diaminobenzophenone is described. Benzo[u][3,6]phenanthroline, its dimethyl, methylphenyl, and tetra-, penta-, and hexa-cyclic derivatives have been prepared from it for biological investigation.HYPOTHESES relating structure to *activity in polycyclic carcinogenic compounds 1 appear to be inapplicable to tricycloquinazoline.2 In azapolycyclic carcinogens, there are indications that activity is influenced by the number of heterocyclic nitrogen atoms and, within a given series, by their relative position^.^ These considerations have led to an investigation of possible connexions between steric factors and activity in tricycloquinazoline. We now describe certain 3,6-phenanthrolines, which have been prepared from 2,Z'-diaminobenzophenone, and which have structural features in common with tricycloquinazoline and with carbocyclic carcinogens.Syntheses of 2,2'-diaminobenzophenone starting with the nitration of benzophenone or of its o-nitro-derivative involve inconvenient separations of mixed isomers.4 2,2'-Dinitrodiphenylmethane would be a useful intermediate, but was produced in only 15% yield by the deamination of 4,4'-diamino-Z,2'-dinitrodiphenylmethane as described by Schnitz~pahn.~ Efficient deamination was achieved when the product of diazotisation with nitrosylsulphuric acid was heated in ethanol with cuprous oxide,6 whereas other standard methods were much less effective. Chromic acid oxidation of the crude deamination product furnished 2,Z'-dinitrobenzophenone, which, on reduction, gave 2,2'-diaminobenzophenone in 44% overall yield. 2,Z'-Dinitrodiphenylmethane, isolated from the deamination, and the corresponding diamine, formed by its reduction, differed from the materials hitherto reported 6*7 as these compounds.2,Z'-Dinitrobenzophenone depressed the melting point of the ketone resulting from the oxidation of the 2,2'-dinitrobenzilic acid previously described. Orientation of the latter ketone was effected by a Beckmann transformation of its oxime to 4,4'-dinitrobenzanilide and by its reduction to 4,4'-diaminobenzophenone. In contrast, 2,2'-dinitrobenzophenone failed to yield an oxime and to undergo a Beckmann transformation under the conditions of Anet, Bavin, and D e~a r .~ Condensation of 2,Z'-diaminobenzophenone with 1,1,3,3-tetraethoxypropane afforded the 3,6-phenanthroline (I; R = R' = H), isosteric with the skin carcinogen, benzo[c]phenanthrene,lO but having the position corresponding to the K-region blocked by azasubstitution. The phenanthrolines (I; R = R' = Me, and R = Me, R' = Ph) were prepared similarly from acetylacetone and benzoylacetone respectively. A non-planar homologue (11) was likewise obtained from dimedone. With indane-1,3-dione an analogous condensation gave the uniplanar hexacyclic compound (111) , substantially isosteric with tricycloquinazoline; further a similar hexacyclic analogue (IV), in which
