Phenanthridines 1,10-Phenanthroline

Azonia substitution at a naphthalene bridgehead position gives the quinolizinium ion (16). Oxonia substitution, elsewhere, forms the 1- and 2-benzopyrylium ions (17) and (18). The two most well-known monoaza systems with three aromatie fused rings are aeridine (19), derived structurally from anthraeene, and phenanthridine (20), an azaphenanthrene. The better-known diaza systems inelude phenazine (21) and 1,10-phenanthroline (22), while systems with three linearly fused pyridine rings are ealled anthyridines, e.g. the 1,9,10-isomer (23). 

Mesitonitrile oxide, but not benzonitrile oxide, adds to aza-analogs of phenan-threne, viz., benzo[/z]quinoline, 1,10-, 1,7-, and 4,7-phenanthrolines to give low yields of mono-cycloadducts at the C(5)=C(6> bond. Only 4,7-phenanthroline gave minor products, of which one the bisadduct 167 was isolated in approximately 7% yield. Phenanthridine reacts with two nitrile oxides but affords phenanthridin-6-one rather than a cyclo-adduct (336). 

Phenanthridine chemistry, recent developments in, 13, 315 Phenanthrolines, 22, I Phenolhiazines, chemistry of, 9, 321 Phenoxazines, 8, 83 Photochemistry of helerocycles, 11, 1... 

The most well-known monoaza aromatic systems with three six-membered rings are acridine 25 and phenanthridine 26 (Figure 3). Acridine derivatives were among the earliest antibacterial agents. The better known diaza systems include phenazine 27 and 1,10-phenanthroline 28. Systems with three linearly fused pyridine rings are called anthyr-idines, e.g., 29. A derivative of the tetraza ring system 30 is found in vitamin B2. 

ET-initiated alkylation of azines in the presence of alkyl halides has been found to occur under electrochemical conditions according to Scheme 43. Either alkylated dihydroheterocycles or the rearomatized products are obtained. As an example, electroreduction of quinoline in the presence of 1-bromoadamantane gives alkylated quinolines (10 % in position 2, 5 % in position 7) and 2-methyl- and 2-methoxyquinoline give the 7-adamantyl derivative in 20 and 23 % yield, respectively. 1,10-Phenanthroline gives bis(adamantyl) derivatives, whereas isoquinoline and phenanthridine give the 6-adamantyl-5,6-dihydro and the 9-adamantyl-9,10-dihydro derivatives, respectively [132]. Reaction with terr-butyl chloride also gives alkylated dihydroheterocycles [133]. Arylation has also been performed, e.g. in the synthesis of pyrazolophenanthridines (62, Scheme 44) [134]. 

Phenanthridine Amaryllidaceae alkaloids, total synthesis of 81YZ295. 1,10-Phenanthroline and its complexes 79H(12)1207. 

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