Synthesis Of Dihydro - 5,7,12,14 - Tetraazobenzene And Its Derivatives

Dihydro-5,7,12,14-azapentacene is the important intermediate of phacolysin, an anti-cataract drug. Phacolysin can infiltrate into the crystal lens, then protect soluble protein from being oxidated, denaturalization. It can activate enzymes of protein decomposing, and promote the degradation and absorption of turbid protein. So it can maintain the lens transparent. At the same time as nitrogen-containing heteroacene compounds dihydro-5,7,12,14-tetraazapentacene in the field of optoelectronic materials also has important applications.We identify two synthetic routes on the basis of the relevant literatures, study the two routes and do a certain amount of optimization on the experimental condition. The intermediates in the two routes are all characterized, and the two routes are also summarized and compared.In the first route, o-phenylenediamine is oxidized to 2,3-diaminophenazine and 2-amino-3-hydroxyphenazine using ferric chloride as oxidant. Dihydro-5,7,12,14-azapentacene can be generated from the two derivatives of phenazine with phenylcarbinol as solvent under refluxing condition. We also study the relationship of the ratio of the two phenazine derivatives and the strength of acid. In the second route, 2,5-dihydroxyquinone is obtained after a oxidizing reaction of hydroquinone with H2O2 as oxidant.2,5-dihydroxyquinone can directly react with o-phenylenediamine to generate the product through one-step. Dihydro-5,7,12,14-azapentacene can also be obtained via the intermediate of 2,3-dihydroxyphenazine. The yield of the dihydro-5,7,12,14-tetraazapentacene in the second route is lower than the first route, but some derivatives of dihydro-5,7,12,14-tetraazapentacene can be obtained through the second route. We also synthesise some derivatives using second route. Some reaction condition of the route is also optimized.About the controversies on the structure of dihydro-5,7,12,14-azapentacene, we try to get some information from the computational view. After optimizing, the energy of the benzenoid structure is lower than the quinonoid structure. Meantime we also compare theoretical and experimental absorption spectra. We believe the two structures are tautomers, and the benzenoid structure is privileged structure.