Cascade Processes with Micellar Reaction Media: Recent Advances and Future Directions

Reducing the use of solvents is an important aim of green chemistry. Using micelles self-assembled from amphiphilic molecules dispersed in water (considered a green solvent) has facilitated reactions of organic compounds. When performing reactions in micelles, the hydrophobic effect can considerably accelerate apparent reaction rates, as well as enhance selectivity. Here, we review micellar reaction media and their potential role in sustainable chemical production. The focus of this review is applications of engineered amphiphilic systems for reactions (surface-active ionic liquids, designer surfactants, and block copolymers) as reaction media. Micelles are a versatile platform for performing a large array of organic chemistries using water as the bulk solvent. Building on this foundation, synthetic sequences combining several reaction steps in one pot have been developed. Telescoping multiple reactions can reduce solvent waste by limiting the volume of solvents, as well as eliminating purification processes. Thus, in particular, we review recent advances in “one-pot” multistep reactions achieved using micellar reaction media with potential applications in medicinal chemistry and agrochemistry. Photocatalyzed reactions in micellar reaction media are also discussed. In addition to the use of micelles, we emphasize the process (steps to isolate the product and reuse the catalyst).     

Optically active core/shell nanoparticles prepared using self‐assembled polymer micelle as reactive nanoreactor

This article reports on optically active core/shell nanoparticles constituted by chiral helical polymers and prepared by a novel approach: using self‐assembled polymer micelles as reactive nanoreactors. Such core/shell nanoparticles were composed of optically active helical‐substituted polyacetylene as the core and thermosensitive poly(N‐isopropylacrylamide) as the shell. The synthetic procedure is divided into three major steps: (1) synthesis of amphiphilic diblock copolymer bearing polymerizable C[tbond]C bonds via atom transfer radical polymerization, followed by (2) self‐assembly of the diblock copolymer to form polymer micelles; and (3) catalytic emulsion polymerization of substituted acetylene monomer conducted using the polymer micelles as reactive nanoreactors leading to the core/shell nanoparticles. The core/shell nanoparticles simultaneously exhibited remarkable optical activity and thermosensitivity. The facile, versatile synthesis methodology opens new approach toward preparing novel multifunctional core/shell nanoparticles.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and Catalytic Applications of Dendrimer-Templated Bimetallic Nanoparticles

Dendrimers, well-defined hyper-branched macromolecules with characteristic globular structure, have emerged as an attractive material in the field of catalysis and have been considered as a new type of host for the accommodation of guest molecules by virtue of their three-dimensional structure having interior void space. In line with the prospect of dendrimer as a nanoreactor, various metal nanoparticles have been successfully prepared via encapsulation in or formation of particles surrounded by dendrimer branches. However, it is worth noting that most of the previous studies have been confined to the monometallic nanoparticles, and bimetallic nanoparticles have been scarcely exploited yet. In this article, we present the synthesis and characterization of dendrimer-templated bimetallic nanoparticles and their application to catalysis.     

Distribution of magnetic nanoparticles in spherical polyelectrolyte brushes as observed by small-angle X-ray scattering

Magnetic nanoparticles (MNPs) with a size of about 2 nm are prepared in nanoreactors of spherical polyelectrolyte brushes (SPBs) consisting of a solid polystyrene (PS) core and a shell of linear poly(acrylic acid) (PAA) chains densely grafted onto the core by one end. The synthesized MNP are strongly adhered to PAA chains due to the intense interaction of chemical coordination with the carboxyl groups. The generation of MNP in SPB layer is legibly revealed by small-angle X-ray scattering (SAXS) due to the significant increase in electron density. The radial distribution of MNP in SPB is built by fitting SAXS data. Most of MNP are found to locate nearby the surface of PS core. Compared to dynamic light scattering and transmission electron microscopy, SAXS can observe the generation and distribution of MNP in SPB as well as the changes upon changing pH and salt concentration in real time. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1681–1688     

Transient Metallo-Lipidoid Assemblies Amplify Covalent Catalysis of Aqueous and Non-Aqueous Reactions

Dissipative supramolecular assemblies are hallmarks of living systems, contributing to their complex, dynamic structures and emerging functions. Living cells can spatiotemporally control diverse biochemical reactions in membrane compartments and condensates, regulating metabolite levels, signal transduction or remodeling of the cytoskeleton. Herein, we constructed membranous compartments using self-assembly of lipid-like amphiphiles (lipidoid) in aqueous medium. The new double-tailed lipidoid features Cu(II) coordinated with a tetravalent chelator that dictates the binding of two amphiphilic ligands in cis-orientation. Hydrophobic interactions between the lipidoids coupled with intermolecular hydrogen bonding led to a well-defined bilayer vesicle structure. Oil-soluble S_NAr reaction is efficiently upregulated in the hydrophobic cavity, acting as a catalytic crucible. The modular system allows easy incorporation of exposed primary amine groups, which augments the catalysis of retro aldol and C−N bond formation reactions. Moreover, a higher-affinity chelator enables consumption of the Cu(II) template leveraging the differential thermodynamic stability, which allows a controllable lifetime of the vesicular assemblies. Concomitant temporal upregulation of the catalytic reactions could be tuned by the metal ion concentration. This work offers new possibilities for metal ion-mediated dynamic supramolecular systems, opening up a massive repertoire of functionally active dynamic “life-like” materials.     

A Chaperonin as Protein Nanoreactor for Atom‐Transfer Radical Polymerization

The group II chaperonin thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom‐transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N‐isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein–catalyst conjugate only yielded polymers with PDIs above 1.84.     

Optimization of a nano‐enzymatic reactor for on‐line tryptic digestion of polypeptide conjugates by capillary electrophoresis

This work aims at studying the optimization of an on‐line capillary electrophoresis (CE)‐based tryptic digestion methodology for the analysis of therapeutic polypeptides (PP). With this methodology, a mixture of surrogate peptide fragments and amino acid were produced on‐line by trypsin cleavage (enzymatic digestion) and subsequently analyzed using the same capillary. The resulting automation of all steps such as injection, mixing, incubation, separation and detection minimizes the possible errors and saves experimental time. In this paper, we first study the differents parameters influencing PP cleavage inside the capillary (plug length, reactant concentration, incubation time, diffusion and electrophoretic plugs mixing). In a second part, the optimization of the electrophoretic separation conditions of generated hydrolysis products (nature, pH and ionic strength (I) of the background electrolyte (BGE)) is described. Using the optimized conditions, excellent repeatability was obtained in terms of separation (migration times) and proteolysis (number of products from enzymatic hydrolysis and corresponding amounts) demonstrating the robustness of the proposed methodology.     

环糊精作为纳米反应器催化的有机反应

环糊精是由六、七或八个D-吡喃葡萄糖单元通过a-1,4糖苷键连接成的环状低聚糖, 由于其特殊的结构使其在水溶液中可以复合包结系列底物. 这个特殊的性能使其在模拟酶及催化等许多领域有着广阔的应用, 特别适合作为一种纳米级的反应器来使用. 概述了近几年环糊精及其衍生物作为有机反应纳米反应器的功能特点.