Current Organic Chemistry - Volume 21, Issue 24, 2017

In this review modification of cellulose and alumina membranes are studied. Cellulose membranes are classified by the derivatives used for its modification. General biomedical applications of modified cellulose membranes with organic substrates are studied and their specific applications with organic substrates are also analysed. Review includes preparation of zwitterionic polymers on cellulose membranes and its biocompatibility, antioxidant activity and the fabrication of biosensors and biochips by immobilising biomolecules; the study of drug delivery systems; membranes for anti-contaminant activity, wastewater filtration and finally the modification of regenerated cellulose membranes with lipid nanoparticles and layers. Regarding the alumina membranes modified with organic compounds, specific applications in biomedical field are studied.

The functionalization of mesoporous silica nanoparticles (MSNs) is a very important step in the preparation of these systems for a variety of applications. The surface of MSNs can be widely functionalized with different organic groups. There are essentially two ways to covalently modify the surface of nanoparticles: co-condensation and post-grafting. Generally, for both of these methods, the precursors are: [(R'O)3SiR] and [Cl3SiR]. The paper summarizes the main experimental contributions and the recent advances in the study of interactions among organosilanes and the MSNs surface. In particular, it provides relevant and innovative examples of Solid State and Solution NMR (SSNMR and SolNMR) and Fourier Transform InfraRed (FTIR) spectroscopy that highlight different possible approaches to understand the MSNs-pendants interaction.

Metal nanoparticles (MNPs) have attracted widespread interest as catalytic materials due to their small size and high surface to volume ratio, which lead to a greater catalytic activity. To preserve such features however, agglomeration of MPNs must be prevented by the use of stabilizing agents of which ionic liquids (ILs) are probably the best ever reported compounds. ILs offer unique environments suitable for both the synthesis, the stabilization, and the segregration of highly dispersed MNPs. Such dispersions have been successfully tested for catalysis in a number of different processes mostly including hydrogenations, hydroformylations, and C-C bond forming reactions (Heck, Suzuki, Sonogashira, and Ullman couplings). In this review, an introductory section is focused on major aspects accounting for the stabilizing effects of ILs on MNPs. Then, model examples of catalytic applications are given for Pd-, Rh-, and Ru- NPs in multiphase systems composed of binary and ternary immiscible liquid phases which are able not only to improve the catalytic performance of NPs, but to allow also the recycling of nanocatalysts and the easy separation of reaction products.

This chapter will give a brief outline on recent advances in grafting techniques for the surface modification of membranes made from synthetic materials or biopolymers, specifically cellulose. In addition, it highlights how these techniques may lead to polymeric surfaces with increased functionality by providing examples where various grafting techniques are used to change the nature of surfaces.

Background: Supramolecular interactions within polylactides chains allows for the creation of highly ordered structures with unique features that could enlarge the applications of polylactide-based materials. Method: Stereocomplexation is a supramolecular interaction which leads to the formation of complex structures from enantiomeric polylactides and interactions of L- and D-lactide unit sequences is a driving force of this process. Result: This provides a tool for the creation of the smart materials that undergo structural rearrangement under the external stimulus, self-heal after applying the external stress or release their payloads in a desired part of human body. Conclusion: This review outlines the applied supramolecular approaches that lead to the control over the properties and morphology of polylactides at interfaces. The relevance of different combinations of supramolecular interactions and their influences on the properties of the obtained materials is discussed.

This review presents recent achievements in manufacturing of supports with controlled hydrophilicity/ hydrophobicity. The broad spectrum of reactions and polymerization processes leading to polymers tethered to surfaces is described. Commonly, brush-like polymers or copolymer layers attached to solid supports constitute the interface between the support and the surroundings. Modification of solid supports by polymer brushes is required to improve or change the attributes of the solid materials and introduce functionalities to modify their properties. For instance, designed polymer supports with appropriate hydrophilicity/ hydrophobicity assure controlled adsorption or covalent immobilization of biomolecules and cells as well as the growth process of cell colonies. Similarly, charge carrier transport occurs across properly developed polymer layers fixed to the metal surfaces of organic electronic devices (sensors, organic light-emitting diodes, and organic photovoltaics). In turn, the development of modern materials requires the application of various controlled polymerization methods and techniques to achieve polymer/copolymer layers with the desired properties and thickness, appropriate hydrophilicity/hydrophobicity balance, and stable attachment to supports. In this paper, attention is focused on the requirements that must be fulfilled to prepare supports and achieve controlled polymerization processes suitable for fabrication of novel materials of various sizes for various applications. Methods tailored for preparing inorganic and organic materials for binding polymer chains are described, as well as procedures for realizing grafting of polymers/copolymers in a variety of arrangements of desired thickness and hydrophilic/hydrophobic balance.

Background: In recent years, the preparation, characterization, and surface modification of nanostructured materials have become topics of great interest because of their unique properties and possible uses in technological applications. One powerful example is the embracement of “interfacial organic chemistry” by the materials science community. Objective: This study was mainly directed towards incorporating solution phase reaction systems into the structure of self-assembled monolayers on gold nanoparticles to develop strategies to exploit the interfacial reactions of these systems to serve as probes to aid in our basic understanding of the mechanistic factors that control molecular interactions and organic reactions at organized monolayer interfaces. Method: A series of aldehyde- and azide-terminated alkanethiols with varied alkyl chain lengths were synthesized and successfully incorporated onto the surface of small gold nanoparticles through the place-exchange reaction. Results: Employing NMR technique, the physical organic chemistry aspects of these tailored gold nanoparticles, especially the interfacial reactivity of them for the imine formation and 1,3-dipolar cycloaddition reactions were evaluated in some detail. Furthermore, the effect of electronic parameter on these interfacial reactions was probed, and it was found that this parameter plays a key role and controls the progress of reaction. Synthesis and characterization of modified nanoparticles were studied by 1HNMR, TEM, FTIR, and UV/Vis technique. Conclusion: In summary, this study has tried to extend the simple organic synthetic pathways into the surface chemistry of nanoparticles and also two well-known organic reactions; namely click reaction and imine formation on the surface of nanoparticles could be carried out under ambient conditions.

Background: While C-S bonds coupling is playing a crucial role in the syntheses of many biologically active substances, the well concerned C-H functionalization reactions have been barely employed yet in construction of such sulfur compounds. Objective: The primary objective of this study was to expand the application of copper, a cheap metal, to catalyze C-S bond construction reactions of indoles. Methods: We chose copper compounds of various oxidant states as catalysts. Substituted indoles were picked as substrates, and disulfides as sulfur source. The variants of catalyst, solvent and reaction temperature were screened to optimize the reaction condition. After that, we explored the scope of diversely substituted indoles and disulfides substrates of the reaction. Results: The reactions were all smoothly performed to provide corresponding products in good yields. The main product is tunable between C3-sulfenylindoles and C2,3-sulfenylindoles according to the amount of disulfides. C3-sulfenylindoles were synthesized in 85 to 99% yields. C2,3-sulfenylindoles were also fruitfully obtained in from 66 to 98% yields. Conclusion: A facile and efficient method for sulfenylation of indole, which employed CuI as catalyst, to give C3- and C2,3- sulfenylindoles, was presented. Our methodology features easy operation, excellent yields and cheapness of catalyst.