The stoichiometry for the initial part of the reaction, Mn II catalysed periodate oxidation of p-anisidine (PMA), has been found to be 1 mol of PMA consuming 2 mol of periodate ion. The kinetic-mechanistic study of reaction in acetone-water medium was made spectrophotometrically by noting the increase in the absorbance of reaction intermediate. Reaction is first order in reactants and catalyst each. A decrease in dielectric constant of the medium results in decrease in the rate of reaction suggesting an iondipole type interaction. Free radical scavengers do not affect the reaction rate. A special type of rate-pH profile shows a maximum at pH = 7.0. This pH effect also suggests the involvement of at least three differently reactive reactant species in the reaction and this fact has been considered by us while deriving the rate law. Under pseudo first order conditions [IO4 -] >> [PMA] and in agreement with the derived rate law, the 1/kcat versus [H + ] plot passes through the minimum and the results can be fitted to the equation:where kK3K4 is the empirical composite rate constant, Kw is ionic product of water, K2 is acid dissociation constant of H4IO6 -and Kb is base dissociation constant of PMA. The experimental value of [H + ]min is in good agreement with the value calculated by using the derived rate law equation and is characteristic of the substrate involved relating to the base dissociation constant of PMA. The value of thermodynamic parameters have been evaluated.

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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INTRODUCTION: A facile, convenient and general method has been developed for the one-pot three-component synthesis of structurally diverse 2-amino pyran annulated heterocycles from the reactions of aromatic aldehydes, malononitrile and various C-H activated acids in the presence of a catalytic amount of glycine as an efficient metal-free organocatalyst in aqueous ethanol under refluxed conditions. METHOD: Using this developed protocol, we were able to synthesize a series of structurally diverse 2-amino pyran derivatives viz., 2-amino-4,5-dihydropyrano[3,2-c]chromenes, 2-amino-4,5-dihydropyrano[4,3-b]pyrans, 2-amino-5,6,7,8-tetrahydro-4H-chromenes, 2'-amino-2,5'-dioxo-5'H-spiro[indoline-3,4'-pyrano[3,2-c]chromene]-3'-carbonitrile and 2'-amino-1,3,5'-trioxo-1,3-dihydro-5'H-spiro[indene-2,4'-pyrano[3,2-c]chromene]-3'-carbonitrile in excellent yields. RESULT: Synthesis of biologically promising pyrans and spiropyrans, high atom economy, excellent yields, use of metal-free catalyst, less toxic solvents, no chromatographic column purifications, multiple carbon-carbon and carbon-heteroatom bond formations are some of the major advantages of this newly developed protocol.