A sequential acidic ionic liquid catalyzed one pot approach was conducted for preparation of 3‐substituted indoles starting from in situ generated chalcones involving Claisen‐Schmidt condensation of substituted aromatic aldehydes with acetophenone followed by Michael‐like addition of indoles to these chalcones under solvent‐free thermal reactions. For this purpose, some new and some reported Brönsted acidic ionic liquids, 2‐alkyl‐1, 3‐disulfoimidazolium carboxylate [RDSIM][X] (where R=Me & Et and X=CH3COO−, CCl3COO−, CF3COO−), were analyzed to compare their Brönsted acidic strength and thermal stabilities. From this investigation, 2‐methyl‐1, 3‐disulfoimidazolium trifluoroacetate [MDSIM][CF3COO] and 2‐ethyl‐1,3‐disulfoimidazolium trifluoroacetate [EDSIM][CF3COO] were determined as efficient ionic liquid catalysts for study of the two‐step one pot synthesis of 3‐substituted indoles.

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Ion Exchange Resins (IER) are insoluble polymers having styrene divinylbenzene copolymer backbone that contain acidic or basic functional groups and have the ability to exchange counter ions with the surrounding aqueous solutions. From the past many years they have been widely used for purification and softening of water and in chromatographic columns, however recently their use in pharmaceutical industry has gained considerable importance. Due to the physical stability and inert nature of the resins, they can be used as a versatile vehicle to design several modified release dosage forms The ionizable drug is complexed with the resin owing to the property of ion exchange. This resin complex dissociatesin vivo to release the drug. Based on the dissociation strength of the drug from the drug resin complex, various release patterns can be achieved. Many formulation glitches can be circumvented using ion exchange resins such as bitter taste and deliquescence. These resins also aid in enhancing disintegrationand stability of formulation. This review focuses on different types of ion exchange resins, their preparation methods, chemistry, properties, incompatibilities and their application in various oral drug delivery systems as well as highlighting their use as therapeutic agents.