DBSA mediated chemoselective synthesis of 2-substituted benzimidazoles in aqueous media

Brønsted acid-catalyzed metal-free one-pot synthesis of benzimidazoles via [4+1] heteroannulation of ortho-phenylenediamines with β-oxodithioesters

“…The spectral data of all the products are in accordance with the literature [16][17][18][19][20][21][22] values. A plausible reaction mechanism for the domino annulation of ortho-phenylenediamine with β-oxodithioester is shown in Scheme 2.…”

“…13 Owing to the vast importance of benzimidazoles in drug discovery and other fields, enormous efforts have been made to develop the operationally simple and efficient synthetic methods for their construction. [14][15][16][17][18][19][20][21][22] Classical approaches to benzimidazoles derivatives involve coupling of 1,2-phenylenediamines with aldehydes/carboxylic acids/nitriles/ortho-esters and their derivatives under varying conditions. 23 …”

Remarkable Acceleration of Benzimidazole Synthesis and Cyanosilylation Reactions in a Supramolecular Solid Catalyst

“…It was found that 4‐heptylbenzoic acid also promotes the transformation, a fact that was expected as we can find several reports in the literature that claim that acidic catalysts favor the formation of 2‐substituted benzimidazoles . However, we observed that 4‐heptylbenzoic acid was not selective in the transformation, resulting in mixtures of products, imine 3 a and benzimidazole 4 a , in varied proportions depending on the amount of acid catalyst employed (Table , entries 5–7).…”

“…This mildly basic surface‐active compound affords predominantly 1,2‐disubstituted benzimidazoles of type 5 a . Nonetheless, acidic surfactant, dodecylbenzenesulfonic acid (DBSA) with the aid of the additional presence of I 2 , is reported to yield preferably 2‐substituted benzimidazoles of type 4 a .…”

p‐Dodecylbenzenesulfonic Acid: An Efficient Brønsted Acid‐Surfactant‐Combined Catalyst to Carry out Diverse Organic Transformations in Aqueous Medium

“…A number of metal catalysts such as In(OTf) 3 , tungstate promoted zirconia, Sm(OTf) 3 , nano‐MnFe 2 O 4 , etc were employed for the synthesis of 2‐substituted benzimidazoles ( 34 ) starting from aromatic aldehydes ( 8 ) and o‐phenylenediamines ( 33 ) in absence or presence of various organic solvents such as methanol, acetonitrile, 1,4‐dioxane etc . In 2013, Kumar et al . developed an aqueous mediated eco‐friendly protocol for the chemoselective synthesis of 2‐substituted benzimidazoles ( 34 ) using p ‐dodecylbenzenesulfonic acid (DBSA) as catalyst and molecular iodine as co‐catalyst at room temperature (Scheme ).…”