The present review summarizes various organic transformations carried out by using sulfonated β-cyclodextrins such as β-cyclodextrin sulfonic acid, β-cyclodextrin propyl sulfonic acid, and β-cyclodextrin butyl sulfonic acid as an efficient, supramolecular reusable catalyst under diverse reaction conditions.

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Synthesis of biologically promising heterocyclic scaffolds under greener conditions is one of the most promising areas of research today in organic chemistry. Heterogeneous catalysis has received greater attention versus homogeneous catalysis as it is much more beneficial in terms of reusability of the catalysts. Among many others, various heteropoly acids have been used as efficient heterogeneous catalysts for diverse organic transformations. In the present review, we have summarized the literature related to the synthesis of various biologically promising heterocyclic scaffolds utilizing a catalytic amount of one such efficient and reusable heteropoly acid, the Preyssler catalyst.

Melting points were recorded on a Digital Melting Point Apparatus (Model No. MT-934) and are uncorrected. TLC was performed on silica gel 60 F254 (Merck) plates. 1 H and 13 C NMR spectra were obtained at 500 MHz Jeol (JNM ECX-500) NMR machines with DMSO-d 6 as the solvent. Mass spectra (TOF-MS ES + ) were measured on a Bruker Impact HD QTOF Micro mass spectrometer.General procedure for the synthesis of 2-amino-4-aryl-6-(arylthio)pyridine-3,5dicarbonitrile (4a-4i)