Ring-closing metathesis in aqueous micellar medium

Underwater exploration: The ring-closing metathesis of N,N-diallyltosylamine (DATs) and diallyldiethyl malonate has been studied in aqueous micellar medium, at room temperature, in the presence of four different gemini cationic surfactants and various ruthenium catalysts. For the first time, the adsorption mechanisms and the reaction steps involved in this heterogeneous catalytic process were elucidated.     

Probing lipids in biological membranes using SERS

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Automatic peak assignment and visualisation of copolymer mass spectrometry data using the ‘genetic algorithm’

Copolymer analysis is vitally important as the materials have a wide variety of applications due to their tunable properties. Processing mass spectrometry data for copolymer samples can be very complex due to the increase in the number of species when the polymer chains are formed by two or more monomeric units. In this paper, we describe the use of the genetic algorithm for automated peak assignment of copolymers synthesised by a variety of polymerisation methods. We find that in using this method we are able to easily assign copolymer spectra in a few minutes and visualise them into heat maps. These heat maps allow us to look qualitatively at the distribution of the chains, by showing how they alter with different polymerisation techniques, and by changing the initial copolymer composition. This methodology is simple to use and requires little user input, which makes it well suited for use by less expert users. The data outputted by the automatic assignment may also allow for more complex data processing in the future.     

Copper‐Mediated Polymerization without External Deoxygenation or Oxygen Scavengers

As a method for overcoming the challenge of rigorous deoxygenation in copper‐mediated controlled radical polymerization processes [e.g., atom‐transfer radical polymerization (ATRP)], reported here is a simple Cu⁰‐RDRP (RDRP=reversible deactivation radical polymerization) system in the absence of external additives (e.g., reducing agents, enzymes etc.). By simply adjusting the headspace of the reaction vessel, a wide range of monomers, namely acrylates, methacrylates, acrylamides, and styrene, can be polymerized in a controlled manner to yield polymers with low dispersities, near‐quantitative conversions, and high end‐group fidelity. Significantly, this approach is scalable (ca. 125 g), tolerant to elevated temperatures, compatible with both organic and aqueous media, and does not rely on external stimuli which may limit the monomer pool. The robustness and versatility of this methodology is further demonstrated by the applicability to other copper‐mediated techniques, including conventional ATRP and light‐mediated approaches.     

Transition Metal Promoted Addition of Methanol to Cyanoguanidine. Molecular Structure and Properties of the Generated Copper(II) and Nickel(II) Complexes

The reaction of the Cu^II and Ni^II complexes of saccharin with dicyandiamide (cyanoguanidine, cnge) in methanol produces the addition of methanol to the nitrile moiety of this molecule. Furthermore, the product of the reaction coordinates the metal centers generating two new complexes containing saccharinate as the counter anion. The crystal structures of [Cu(cnge‐OCH₃)₂](sac)₂ and of [Ni(cnge‐OCH₃)₂](sac)₂·2H₂O (cnge‐OCH₃ = 1‐amidino‐O‐methylurea) were solved by single crystal X‐ray diffractometry. Both complexes crystallize in the triclinic space group and the metallic cations present a quite similar centrosymmetric planar conformation. The complexes were characterized by means of electronic and infrared spectroscopy and also their magnetic and thermal behavior was investigated.     

Uniform approximation of the heat kernel on a manifold

We approximate the heat kernel h(x, y, t) on a compact connected Riemannian manifold M without boundary uniformly in \((x,y,t)\in M\times M\times [a,b]\), \(a>0\), by n-fold integrals over \(M^n\) of the densities of Brownian bridges. Moreover, we provide an estimate for the uniform convergence rate. As an immediate corollary, we get a uniform approximation of solutions of the Cauchy problem for the heat equation on M.     

Mechanistic Insights on the Mechanosynthesis of Phenytoin,a WHO Essential Medicine**

In recent years, mechanochemistry has enriched the toolbox of synthetic chemists, enabling faster and more sustainable access to new materials and existing products, including active pharmaceutical ingredients (APIs). However, molecular-level understanding of most mechanochemical reactions remains limited, delaying the implementation of mechanochemistry in industrial applications. Herein, we have applied in situ monitoring by Raman spectroscopy to the mechanosynthesis of phenytoin, a World Health Organization (WHO) Essential Medicine, enabling the observation, isolation, and characterization of key molecular-migration intermediates involved in the single-step transformation of benzil, urea, and KOH into phenytoin. This work contributes to the elucidation of a reaction mechanism that has been subjected to a number of interpretations over time and paints a clear picture of how mechanosynthesis can be applied and optimized for the preparation of added-value molecules.     

Activated sulfahydantoin as Boc-glycine enolate equivalent: highly diastereoselective α-hydroxyalkylation and application to the synthesis of aldopentonate analogues

N-Boc-activated sulfahydantoin can be seen as glycine enolate equivalent. It appeared as a convenient starting material for the stereocontrolled preparation of threonine homologues through an alkaline syn aldolization involving a Boc migration. The methodology allowed the one-pot preparation of constrained analogues of polyoxamic acid.     

Microwave-assisted multi-step synthesis of novel pyrrolo-[3,2-c]quinoline derivatives

A new approach for the synthesis of original substituted pyrrolo-[3,2-c]quinoline derivatives using microwave-assisted chemistry is described. The use of microwave activation in this synthesis resulted in high yielding and clean steps. The key step for introducing diversity is the amination or the Pd-catalyzed cross-coupling of an imidoyl chloride derivative, obtained in a straightforward manner and in good yield.