Heterogenisation of a Carbonylation Catalyst on Dispersible Microporous Polymer Nanoparticles

The methanol carbonylation catalyst, cis-[Rh(CO)2I2]–, has been heterogenised within a dispersible microporous polymer support bearing cationic functionality. The microporous polymer has a core-shell structure in which the porous and insoluble...

Optimal Method for Disulfide Bond Closure in the Synthesis of Atosiban—Antagonist of Oxytocin Receptors

This work is devoted to the large-scale solid-phase synthesis (SPS) of Atosiban, Mpa1-D-Tyr(OEt)-Ile-Thr-Asn-Cys6-Pro-Orn-Gly-NH2 cyclic 1,6 disulfide, the only clinically used oxytocin receptor antagonist. The conditions have been selected for the closure of the disulfide bond (S–S) in the Atosiban molecule both in the solution and solid phase with the minimal formation of by-products. A comparative assessment of the formation of the S–S bond was carried out under various conditions. The formation of by-products during the closure of the disulfide bond has been studied both in solution and on the polymer support. The developed technique allows for the synthesis of Atosiban on an enlarged scale (10–20 mmol) involving the cyclization of a protected intermediate with the formation of the S–S bond during solid-phase synthesis with the minimal formation of by-products.

PEG-Supported Hypervalent Iodine Reagent for Sulfonamide Synthesis

A reusable and recoverable PEG-supported hypervalent iodine reagent is reported. This hypervalent iodine reagent, immobilized in a soluble polymer support, was easily prepared in six steps from PEG-OH 2000. This reagent was successfully applied in a mild sulfonamide synthesis using a sulfinate salt and an amine in up to 95% yield. The use of the soluble polymer allowed a facile workup procedure and reaction monitoring, by simple precipitation and filtration of the reagent, with an easy recovery and subsequent re-oxidation and reuse. This approach greatly improves the sustainability of this sulfonamide synthesis method, avoiding frequent preparation of reagents and generation of waste during the purification steps.

Review: Mixed-Matrix Membranes with CNT for CO2 Separation Processes

The membranes’ role is of supreme importance in the separation of compounds under different phases of matter. The topic addressed here is based on the use of membranes on the gases separation, specifically the advantages of mixed-matrix membranes (MMMs) when using carbon nanotubes as fillers to separate carbon dioxide (CO2) from other carrier gas. MMMs consist of a polymer support with additive fillers to improve their efficiency by increasing both selectivity and permeability. The most promising fillers in the MMM development are nanostructured molecules. Due to the good prospects of carbon nanotubes (CNTs) as MMM fillers, this article aims to concentrate the advances and developments of CNT–MMM to separate gases, such as CO2. The influence of functionalized CNT or mixtures of CNT with additional materials such as zeolites, hydrogel and, graphene sheets on membranes performance is highlighted in the present work.

Heterogenisation of a Carbonylation Catalyst on Dispersible Microporous Polymer Nanoparticles

<div>The methanol carbonylation catalyst, <i>cis</i>-[Rh(CO)₂I₂]^–, has been heterogenised within a dispersible microporous polymer support bearing cationic functionality. The microporous polymer has a core-shell structure in which the porous and insoluble core (a co-polymer of divinylbenzene and 4-vinylpyridine) is suspended in solution by long hydrophilic poly(ethylene glycol) chains, allowing a stable suspension of the nanoparticles to form. Incorporation of 4-vinylpyridine as a co-monomer allows post-synthetic modification to generate <i>N</i>-methylpyridinium sites for electrostatic attachment of the anionic rhodium(I) complex. The dispersibility of the polymer-supported catalyst material facilitates the use of <i>in</i> <i>situ</i> transmission IR spectroscopy to obtain kinetic data for the oxidative addition of iodomethane to immobilised <i>cis</i>-[Rh(CO)₂I₂]^– (the rate-limiting step of the carbonylation cycle). Remarkably, the oxidative addition proceeds faster than for the homogeneous system (Bu₄N⁺ counter-ion, CH₂Cl₂, 25 °C). The polymer-supported catalyst was found to be active for methanol carbonylation, with a turnover frequency similar to that of the homogeneous analogue under the same conditions (10 bar CO, MeI/MeOH/CHCl₃, 120 °C). The supported catalyst is easily recovered and is shown to maintain comparable activity upon recycling.</div>

Heterogenisation of a Carbonylation Catalyst on Dispersible Microporous Polymer Nanoparticles

<div>The methanol carbonylation catalyst, <i>cis</i>-[Rh(CO)₂I₂]^–, has been heterogenised within a dispersible microporous polymer support bearing cationic functionality. The microporous polymer has a core-shell structure in which the porous and insoluble core (a co-polymer of divinylbenzene and 4-vinylpyridine) is suspended in solution by long hydrophilic poly(ethylene glycol) chains, allowing a stable suspension of the nanoparticles to form. Incorporation of 4-vinylpyridine as a co-monomer allows post-synthetic modification to generate <i>N</i>-methylpyridinium sites for electrostatic attachment of the anionic rhodium(I) complex. The dispersibility of the polymer-supported catalyst material facilitates the use of <i>in</i> <i>situ</i> transmission IR spectroscopy to obtain kinetic data for the oxidative addition of iodomethane to immobilised <i>cis</i>-[Rh(CO)₂I₂]^– (the rate-limiting step of the carbonylation cycle). Remarkably, the oxidative addition proceeds faster than for the homogeneous system (Bu₄N⁺ counter-ion, CH₂Cl₂, 25 °C). The polymer-supported catalyst was found to be active for methanol carbonylation, with a turnover frequency similar to that of the homogeneous analogue under the same conditions (10 bar CO, MeI/MeOH/CHCl₃, 120 °C). The supported catalyst is easily recovered and is shown to maintain comparable activity upon recycling.</div>