In this review, a comprehensive summary of supramolecular transformations within discrete coordination-driven supramolecular architectures, including helices, metallacycles, metallacages, etc., is presented. Recent investigations have demonstrated that coordination-driven self-assembled architectures provide an ideal platform to study supramolecular transformations mainly due to the relatively rigid yet dynamic nature of the coordination bonds. Various stimuli have been extensively employed to trigger the transformation processes of metallosupramolecular architectures, such as solvents, concentration, anions, guests, change in component fractions or chemical compositions, light, and post-modification reactions, which allowed for the formation of new structures with specific properties and functions. Thus, it is believed that supramolecular transformations could serve as another highly efficient approach for generating diverse metallosupramolecular architectures. Classified by the aforementioned various stimuli used to induce the interconversion processes, the emphasis in this review will be on the transformation conditions, structural changes, mechanisms, and the output of specific properties and functions upon induction of structural transformations.

Supramolecular transformations within discrete coordination-driven supramolecular architectures

Selective oxidation has an important role in environmental and green chemistry (e.g., oxidative desulfurization of fuels and oxidative removal of mercury) as well as chemicals and intermediates chemistry to obtain high-value-added special products (e.g., organic sulfoxides and sulfones, aldehydes, ketones, carboxylic acids, epoxides, esters, and lactones). Due to their unique physical properties such as the nonvolatility, thermal stability, nonexplosion, high polarity, and temperature-dependent miscibility with water, ionic liquids (ILs) have attracted considerable attention as reaction solvents and media for selective oxidations and are considered as green alternatives to volatile organic solvents. Moreover, for easy separation and recyclable utilization, IL catalysts have attracted unprecedented attention as “biphasic catalyst” or “immobilized catalyst” by immobilizing metal- or nonmetal-containing ILs onto mineral or polymer supports to combine the unique properties of ILs (chemical and thermal stabili...

Ionic Liquids in Selective Oxidation: Catalysts and Solvents

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Recent developments in penta-, hexa- and heptadentate Schiff base ligands and their metal complexes

The selective oxidation of thiols to disulfides and sulfides to sulfoxides using graphite oxide (GO), a heterogeneous carbocatalyst obtained from low cost, commercial starting materials is described. The aforementioned oxidation reactions were found to proceed rapidly (as short as 10 min in some cases) and in good yield (51–100%) (19 examples). No over-oxidation of the substrates was observed, and GO's heterogeneous nature facilitated isolation and purification of the target products.

Graphite oxide: a selective and highly efficient oxidant of thiols and sulfides

Selective oxidation of sulfides to sulfoxides and sulfones at room temperature using H2O2 and a Mo(VI) salt as catalyst

The role of MoO2Cl2 and some complexes containing MoO2Cl2 as catalysts for various Lewis acid catalysed organic transformations, oxidation and reduction reactions is reviewed.

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Application of molybdenum(VI) dichloride dioxide (MoO2Cl2) in organic transformations

Acetylation of alcohols, phenols, amines, thiols and aldehydes is performed using acetic anhydride as acylating agent and M(ClO 4 ) 2 ·6H 2 O as catalyst where M is Mn, Co, Ni, Cu and Zn at room temperature under solvent free conditions. Transition metal perchlorates used here are found to be more efficient than the already reported metal triflates and s, p-block perchlorates. Substrates containing acid sensitive protecting groups are acylated successfully without any cleavage of the protection. Remarkably, less nucleophlic thiols (e.g. 2-mercaptobenzothiazole) are acylated with reasonable yields using transition metal perchlorates as catalyst whereas otherwise active acylation catalyst Mg(ClO 4 ) 2 was found to be inefficient.

Copper perchlorate: Efficient acetylation catalyst under solvent free conditions

Simple and efficient method for the oxidation of sulfides to sulfones using hydrogen peroxide and a Mo(VI) based catalyst

An interesting phenomenon of ligand exchange is observed in the DMSO solution of certain self-assembled molecules generated from cis-protected PdII and organic ligands. Upon heating, assemblies such as [{Pd(en)}x(ligand)y](NO3)2x change to [Pdm(ligand)n](NO3)2m and [Pd(en)2](NO3)2. The change is also possible at room temperature when 0.5 equiv. Pd(en)(NO3)2 is added in excess to the system. The transformation is incomplete when the ligand moiety is monodentate in nature, for example in the case of 4-phenylpyridine. However, multinuclear assemblies containing nonchelating, polydentate ligands used in this study entirely favor the transformation. This process is not possible with some related PtII compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Kandasamy Jeyakumar

Papers

Selective oxidation of sulfides to sulfoxides and sulfones at room temperature using H2O2 and a Mo(VI) salt as catalyst

Application of molybdenum(VI) dichloride dioxide (MoO2Cl2) in organic transformations

Copper perchlorate: Efficient acetylation catalyst under solvent free conditions

Simple and efficient method for the oxidation of sulfides to sulfones using hydrogen peroxide and a Mo(VI) based catalyst

Self-Assembly by Ligand-Exchange Reactions