Interaction of 2,2-di(3,5-dimethylphenyl)-1,1,3,3-tetraoxo-2,2,3,3-tetrahy- dro-1h,1h-6,6-di(benzo[de]isoquinoline)-7,7-dicarboxylic acid with thiourea dioxide in water-alkaline solution

Reducing cyclization of 2,2' -di(3,5-dimethylphenyl) -1,1',3,3' -tetraoxo -2,2',3,3' - tetra- hydro - 1H,1'H - 6,6' -bi(benzo[de]isoquinoline) -7,7'-dicarboxylic acid under the action of thio-urea dioxide in an aqueous-alkaline solution under aerobic and anaerobic conditions has been studied. It was found that the formation of cyclization product in the form of 2,9 -bis(3,5-dime- thylphenyl)antra[2,1,9-def:6,5,10-d'e'f']diisoquinoline - 1,3,8,10(2H,9H) -tetraone containing two or four oxogroups occurs through an intermediate (anion-radical). It was found that the amount of the intermediate product, as well as the composition and quantity of the final products of cycliza-tion depend on the concentration of the reducing agent and the presence of air oxygen in the solu-tion, which is related to the nature and quantity of reducing intermediates: sulfoxylic acid anions, dithionite and sulfur dioxide anion-radical. It should also be noted that in the studied reaction of cycling 2,2' -di(3,5-dimethylphenyl) -1,1',3,3' -tetraoxo -2,2',3,3' - tetrahydro - 1H,1'H -6,6' -bi(benzo[de]isoquinoline) -7,7'-dicarboxylic acid was not found to form a by-product with two non-cleaved carboxyl groups, in contrast to the reduction of 2,2'-di(4-chlorophenyl)-1,1',3,3'-tetraoxo-2,2',3,3'-tetrahydro-1H,1'H-6,6' bi(benzo[de]isoquinoline)-7,7'-dicarboxylic acid by thio-urea dioxide. This fact is probably related to the inductive effect of substituents at nitrogen atoms in the molecules of these compounds. The final product of the reductive cyclization of 2,9-bis(3,5- dimethylphenyl)anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline - 1,3,8,10(2H,9H)??? tetraone was iso-lated in the solid state. Its elemental composition is established, IR and electronic absorption spec-tra were obtained. Based on experimental and published data in the literature, a step-by-step stoi-chiometric mechanism of reductive cyclization of 2,2'-di(3,5-dimethylphenyl) -1,1',3,3'-tetraoxo -2,2',3,3' - tetrahydro - 1H,1'H - 6,6'-bi(benzo[de]isoquinoline) -7,7'-dicarboxylic acid in an aque-ous-alkaline solution under the action of thiourea dioxide was proposed.