Ultraviolet spectra acridines

In a study of the lithium aluminum hydride reduction of a series of nitrogen aromatic heterocyclics, Bohlmann97 found that this metal hydride effected a conversion of acridine to 9,1O-dihydroacridine (91) in high yield and purity. The ultraviolet spectrum of the isolated dihydroacridine (Amax 288 mp, loge = 4.18) was confirmed by Braude et al.92 as a part of a study of the hydride donor properties of a series of aromatic nitrogen-heterocycles. These workers found that the dihydroacridine underwent a slow oxidation to acridine in air and a rapid hydrogen transfer in the presence of chloranil to form the quinol and acridine. The dihydroacridine was, however, quite stable under dry nitrogen. 

Like acridine, phenanthridine and dimethyl acetylenedicarboxylate in methanol give a high yield of 1 1 1 molar adduct. Ultraviolet absorption spectrum comparisons show that this is best formulated as 9,10-dihydro-9-methoxy-10- (tran.s-l,2-dimethoxycarbonylvinyl) phenanthridine (142) rather than the corresponding phenanthridinium methoxide (143) under neutral conditions acidification changes the spectrum to that characteristic of the phenanthridinium cation. Crystallization of the adduct (142) from methanol containing 5-15% of water gave the betaine [(144) the positions of the ester and carboxylate groups have not been established], while in the presence... 

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