Camphorsulfonic Acid-Catalyzed Synthesis of a Series of 2-Aryl/heteroaryl/alkyl-1H-anthra[ 1,2-d]imidazole-6,11-dione Derivatives

Anthraquinone moiety is very common among naturally occurring bioactive compounds. Many commercially available drug molecules also possess anthraquinone moiety. In recent times, among many other anthraquinone derivatives, specifically, 2- substituted-1H-anthra[1,2-d]imidazole-6,11-diones are gaining extra attention due to their significant anti-cancer, anti-HIV, anti-inflammatory activities, etc. This study aimed to report a simple, straightforward, organocatalyzed method for the efficient synthesis of a series of 2-aryl/heteroaryl/alkyl-1H-anthra[1,2-d]imidazole-6,11-diones from the reactions of 1,2-diaminoanthraquinone and various aldehydes using a catalytic amount of camphorsulfonic acid as an efficient organocatalyst in aqueous ethanol under refluxed conditions. Under the same optimized reaction conditions, along with aryl or heteroaryl aldehydes, aliphatic aldehydes also underwent a smooth reaction and afforded the desired products in excellent yields. All the synthesized compounds were obtained pure in excellent yields by simple filtration and washing subsequently with ethanol. The use of less toxic solvent, low-cost, commercially available metal-free organocatalyst, no column chromatographic separation, good yields, and easy isolation procedure are some of the major advantages of this newly developed protocol.