Rapid One‐Pot Preparation of 2‐Substituted Benzimidazoles from Esters using Microwave Conditions

Synthesis and biological activity of novel inhibitors of topoisomerase I: 2-Aryl-substituted 2-bis-1H-benzimidazoles

“…Traditionally, benzimidazoles have most commonly been prepared from the reaction of 1,2-diaminobenzenes with carboxylic acids under harsh dehydrating reaction conditions, utilizing the strong acid such as polyphosphoric acid, hydrochloric acid, boric acid or p-toluenesulfonic acid [29]. However, the use of milder reagents, particularly Lewis acids, [30] inorganic clays [31] or mineral acids [32] has improved both the yield and purity of the reaction [33].…”

Wells–Dawson Heteropolyacid: An Efficient Recyclable Catalyst for the Synthesis of Benzimidazoles Under Microwave Condition

“…A number of methods have been developed for the synthesis of benzimidazole derivatives. Traditionally, benzimidazoles have most commonly been prepared from the reaction of 1,2-diaminobenzenes with carboxylic acids under harsh dehydrating reaction conditions, utilizing strong acids such as polyphosphoric acid, hydrochloric acid, boric acid, or p-toluenesulfonic acid [21]. However, the use of milder reagents, particularly Lewis acids [22], inorganic clays [23], or mineral acids [24], has improved both the yield and purity of this reaction [25].…”

KF/Al2O3: an efficient solid heterogeneous base catalyst in one-pot synthesis of benzimidazoles and bis-benzimidazoles at room temperature

“…The synthesis of benzimidazoles has been achieved by two different strategies. In the first popular known strategy, o-PDA reacts in two steps with aldehydes in the presence of an oxidizing agent [14][15][16][17][18][19], and in the second strategy, o-PDA reacts with carboxylic acids or their derivatives such as nitriles [20], amides [21], orthoesters [22,23], carboxylic acids [24,25], esters [26,27], and acyl chlorides [28][29][30][31]. However, as far as we know, there are only a few reports on the synthesis of bis-benzimidazoles in which 3,3 0 -diaminobenzidine reacts with aldehydes in the presence of an oxidizing agent or with a,a,a-trifluoromethyl aryl ketones in the presence of strong acid catalysts [11][12][13].…”