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3109148 
Journal Article 
The use of diethylene glycol in the synthesis of 2,2 '-bibenzimidazole from o-phenylenediamine and oxalic acid 
Madrzak-Litwa, I; Borowiak-Resterna, A 
2014 
Yes 
Heterocyclic Communications
ISSN: 0793-0283 
20 
3 
177-180 
WOS:000337175400007 
One- and two-step syntheses of 2,2'-bibenzimidazole were compared. Diethylene glycol was used as solvent that provides good solubility of the substrates. The limitation of the one-step preparation is the formation of the by-product, fluoflavine. The two-step synthesis proceeds with the separation of the intermediate product, 1,4-dihydroquinoxaline-2,3-dione, and the final product is only 2,2'-bibenzimidazole. The total yield of the two-step synthesis is above 85%. 
2,2 '-bibenzimidazole; diethylene glycol; 1,4-dihydroquinoxaline-2,3-dione; o-phenylenediamine; oxalic acid