“All-water” one-pot diverse synthesis of 1,2-disubstituted benzimidazoles: hydrogen bond driven ‘synergistic electrophile–nucleophile dual activation’ by water

Synthesis and Characterization of Imidazo[1,2-a]pyridines and Zolimidine

“…The reaction gave similar high yield as in water (91 % vs. 88 %). This result is in contrast to the results obtained in literature [18]. The NMR data of the product 3b obtained in heavy water was same as the one obtained in water.…”

H2O‐Mediated Epoxide Ring‐Opening with Concomitant C–S Bond Formation: A One‐Pot Method to 3‐Hydroxy‐oxindolino‐dithiocarbamates as Cytotoxic Agents

“…Initially, an in situ formation of reactive dithiocarbamate intermediate takes place by inserting CS 2 into the N−H bond with saturated heterocyclic secondary amine 2 . Further, the reaction is proceeding in water, which act as hydrogen‐bond donor and acceptor to activate both dithiocarbamate intermediate and the epoxide thereby enhances the electrophilicity of spiro ‐epoxide ring ,. Finally, the nucleophilic attack of the sulphur (activated dithiocarbamate) on the electrophilic carbon centre of Isatin spiro ‐epoxide from the less hindered side leads to the formation of a new C–S bond in the desired product 3 ,…”

Tandem Photocatalysis: An Efficient Synthesis of Multisubstituted Benzimidazoles by Visible‐Light‐Induced Intramolecular Cyclization and Deprotection

“…[2] The classic method is the condensation of anilines with aldehydes under relatively harsh conditions. [3] Compared to the classic condensation reactions, the transition metal-catalyzed intramolecular couplingr eaction [4] and the directo xidative coupling of aminest oi mines withoutu sing any carbonyl compounds have also been frequently reported, [5] which provide alternative methods to prepare benzimidazoles. Althoughs ome considerable progress has been made, these transformationss till suffered the common drawbacks of harsh reactionc onditions including high temperature, using equivalent oxidants, and so forth.…”

“…Herein, we report an efficient syn- thesis of multisubstituted benzimidazoles by visible-light-induced intramolecular cyclization/deprotection sequence from diaminesu nder very mild conditions. Our initial study began with the reaction of diamine 1a using Ru(bpy) 3 Cl 2 (5 mol %) as photocatalyst and MeOH as solvent under the irradiation of a4 5W household fluorescent lamp. After 24 h, the conversion of the starting material is 24 %; After 108 h, the starting material wasc ompletely consumed to give 2a in 71 %y ield, along with an oxidation byproduct 2a'' (N-methyl-N-(2-(4-methylphenylsulfonamido)phenyl)benzamide) [7n] (Table 1, entry 1).…”