Search for antihistamine drugs among imidazobenzimidazoles and triazolobenzimidazoles

One-pot Regioselective Synthesis of 2,9-Disubstituted Imidazo[1,2-a] Benzimidazoles from 2-Aminobenzimidazole and α-Tosyloxy Ketones

“…Imidazo [1,2-a]benzimidazoles are versatile compounds useful as analgesics, 1 anxiolytics and anticonvulsants, 2 and as corticotropin-releasing factor 1 receptor angonists 3 . The dihydro and tetrahydro imidazo [1,2-a]benzimidazoles derivatives have been shown to exhibit antihypertensive, 4 antihistamine 5 and antiproliferative activity 6 . The synthesis of imidazo [1,2-a]benz imidazoles has been reported utilising thermal rearrangement of 3-(o-aminophenyl)-2-imino-4-phenyl-4-thiazoline, 7 gas phase pyrolysis of 1-(2-azidophenyl)imidazole 8 and condensation of 2-amino-benzimidazole and α-bromoketones 1 or hydrazonoyl bromides 9 involving a number of steps.…”

Syntheses of [1,2,4]triazolo[1,5-a]benzazoles enabled by the transition-metal-free oxidative N–N bond formation

“…[1,2,4]Triazolo [1,5-a]benzimidazole is an interesting type of N-N bond containing heterocycle which shows promising biological activities, such as antifungal, anti-inflammatory and analgesic, 4 as well as anti-histamine effects. 5 Although three methods have been reported for the synthesis of this type of structure, they all suffered either long synthetic routes or harsh reaction conditions and only a handful of substrates were prepared (Scheme 1). 6 The lack of efficient synthetic methodology hindered the application of this type of heterocycles in chemical biology and drug discovery.…”

Hypervalent Iodine Mediated Oxidation of 1,2-Diaminobenzimidazole and Its Schiff Bases: Efficient Synthesis of 3-Amino-1,2,4-benzotriazine and 2-Aryl-1,2,4-triazolo[1,5-a]benzimidazoles

“…7 Similarly, triazolo[1,5-a]benzimidazoles, derived from 1,2-diaminobenzimidazole, have been found to possess antifungal, anti-inflammatory and analgesic 8 as well as anti-histamine effects. 9 Bearing in mind the biological importance of 1,2,4-benzotriazines and 2-aryl-1,2,4-triazolo[1,5-a]benzimidazoles, it was thought to be of interest to provide an efficient synthesis of these molecules by the oxidation of 1,2-diaminobenzimidazole and its Schiff bases utilizing hypervalent iodine reagents.…”