Metathesis Reaction Products Research Articles

Separation of Fatty Acid Dimethyl Esters on an Ionic Liquid Gas Chromatographic Column.

An ionic liquid (IL) 111 column was compared with other commonly employed stationary phases including polydimethyl siloxane and polyethylene glycol for the separation of fatty acid monomethyl and dimethyl esters. The fatty acid esters employed in this study were derived from metathesis reactions of vegetable oils both with and without olefins. The IL 111 column demonstrated enhanced performance compared with conventional columns for the separation of these esters. These advantages included significantly enhanced retention of dimethyl esters relative to monomethyl esters, excellent cis/trans isomer separation and the ability to analyze higher carbon number dimethyl esters. As a result, these columns are highly suited for the analysis of mixtures of mono- and dimethyl fatty acid esters found in lipid metathesis reaction products or to determine monofunctional impurities in samples of commercial dimethyl esters.

Semiheterogeneous Purification Protocol for the Removal of Ruthenium Impurities from Olefin Metathesis Reaction Products Using an Isocyanide Scavenger

A low-waste, time-economical, and scalable semiheterogeneous purification protocol for the removal of ruthenium residues from olefin metathesis (OM) reactions has been developed. It is based on the non-covalent immobilization of the commercially available isocyanide 1,4-bis(3-isocyanopropyl)piperazine (QA) on unmodified silica gel. The use of the heterogeneous scavenger QA@SiO2 synthesized in situ during the purification process was shown to yield OM products with metal contamination usually below 5 ppm. Furthermore, the new purification protocol was effective on a gram scale in the ring-closing OM of an intermediate in the synthesis of cathepsin K inhibitors, leading to a product containing only 0.29 ppm Ru. Finally, QA was used in an aqueous medium and reduced the metal contamination from 9977 to 21 ppm.

A Strategy for Hydroxide Exclusion in Nanocrystalline Solid-State Metathesis Products

We demonstrate a simple strategy to either prevent or enhance hydroxide incorporation in nanocrystalline solid-state metathesis reaction products prepared in ambient environments. As an example, we show that ZnCO3 (smithsonite) or Zn5(CO3)2(OH)6 (hydrozincite) forms extremely rapidly, in less than two minutes, to form crystalline domains of 11 ± 2 nm and 6 ± 2 nm, respectively. The phase selectivity between these nanocrystalline products is dominated by the alkalinity of the hydrated precursor salts, which may in turn affect the availability of carbon dioxide during the reaction. Thus, unlike traditional aqueous precipitation reactions, our solid-state method offers a way to produce hydroxide-free, nanocrystalline products without active pH control.

Multinuclear Magnetic Resonance Spectroscopy and Density Function Theory Calculations for the Identification of the Equilibrium Species in THF Solutions of Organometallic Complexes Suitable As Electrolyte Solutions for Rechargeable Mg Batteries

We present a multinuclear nuclear magnetic resonance (NMR) and density functional theory (DFT) study of electrolyte solutions based on organometallic complexes with aromatic ligands. These solutions constitute a unique electrolyte family possessing a wide electrochemical window, making them suitable for rechargeable magnesium batteries. In our previous study we identified equilibrium species in the solutions based on a combination of Raman spectroscopy and single-crystal XRD analyses,(1) and herein we extend our studies to include multinuclear NMR analyses. These solutions are comprised of the metathesis reaction products of MgCl2–xPhx and AlCl3–yPhy in various proportions, in THF. In principle, these reactions involve the exchange of ligands between the magnesium and the aluminum based compounds, forming ionic species and neutral molecules, such as Mg2Cl3+·6THF, MgCl2·4THF and AlCl4–yPhy– (y = 0–4). The identification of the solution phase species from the spectroscopic results is supported by spectral a...

Separation of metathesis catalysts and reaction products in flow reactors using organic solvent nanofiltration

Organic solvent nanofiltration (OSN), a relatively new low energy separation technology, has been used to reduce metal contamination of ring closing metathesis reaction products. The catalysts used were readily available commercial Hoveyda–Grubbs and Umicore M series catalysts. These reactions were performed in a flow reactor with in-line membrane separation, and high catalyst retention can be achieved. In the flow reactor set up a beneficial effect on catalyst life-time on changing from solvents such as dichloromethane to environmentally more benign acetone, which reduces initiation rates, was demonstrated.

Purification of Olefin Metathesis Reaction Products via Straightforward and Low-Cost Protocols

From the point of view of an organic chemist, the discovery of novel and efficient carbon-carbon bond forming reactions is a continuous scientific quest. Olefin metathesis, a metal-catalyzed reaction, can be considered as one of the most robust tools in this respect. As a result, metathesis has been widely used over various chemistry and materials science fields. The increased popularity of this powerful transformation is mostly due to the development of highly efficient, functional group tolerant, and air- and moisture-stable ruthenium catalysts. However, the complete removal of ruthenium from the reaction products, in order to avoid undesired side-reactions, isomerization, or even the decomposition of products, is very often a highly challenging task. The present article focuses on the most straightforward and efficient methodologies for the removal of ruthenium residues from olefin metathesis post reaction mixtures. These purification protocols can be easily carried out in any common organic synthesis laboratory, needless of specialized reagents and experimental setup.

Removing Ruthenium Residues from Olefin Metathesis Reaction Products

Olefin metathesis has revolutionized the way chemists design and synthesize molecules, mostly due to the development of well-defined ruthenium catalysts with high oxygen-, moisture-, and functional-group tolerance. However, the complete removal of residual ruthenium after the end of a metathesis reaction often imposes significant challenges. This Minireview summarizes the strategies for the sequestration of ruthenium impurities from olefin metathesis post-reaction mixtures, thus comprising a practical guide for synthetic chemists employing ruthenium-catalyzed metathesis reactions in the synthesis of organic or polymeric materials.

Synthesis and reactivity of platinacycloalkanes

Novel large platinacycloalkane compounds containing 19- and 21- membered rings of the type L 2Pt(CH 2) n (L 2 = dppp and n = 18, 20) are synthesized through the ring closing metathesis (RCM) reaction of bis(1-alkenyl)platinum(II) complexes using Grubbs’ catalysts. These compounds are characterized by various spectroscopic and analytical techniques. The cross metathesis reactions with different dienes and substituted alkynes yielded interesting inter- and intra- molecular metathesis reaction products. Various factors such as concentration, solvent, phosphine ligand and length of the alkenyl chains affect the RCM reaction significantly to yield different products such as monomeric, dimeric and polymeric species. The novel chemical reactivity aspects of these title compounds with elemental sulfur, carbon monoxide and methyl iodide are discussed.

A simple oxidative procedure for the removal of ruthenium residues from metathesis reaction products

Ruthenium residues can be easily and rapidly removed from Grubbs metathesis products by washing with 15% aqueous hydrogen peroxide, which converts any ruthenium complexes into highly insoluble ruthenium dioxide, which then catalyzes the conversion of excess peroxide into water and oxygen. Ruthenium levels lower than 2 ppm can be routinely obtained; an additional advantage is that any phosphines are also rapidly oxidized to the corresponding, more polar phosphine oxides thereby facilitating their removal as well in many cases.

An efficient method for removal of ruthenium byproducts from olefin metathesis reactions.

[reaction: see text] Sequential treatment of the ring-closing metathesis reaction products with silica gel, activated carbon (50 equiv wt relative to the crude products), and column chromatography on silica gel efficiently removed dark brown ruthenium byproducts from the reaction mixture. After this treatment, colorless compounds could be obtained with a ruthenium level of 0.06-0.53 microg per 5 mg of product.

Purification technique for the removal of ruthenium from olefin metathesis reaction products

Ring-closing metathesis (RCM) products of reactions utilizing RuCl 2(CHPh)(PCy 3) 2 ( 1) as a catalyst were successfully purified of unwanted ruthenium using a water-soluble coordinating phosphine, tris(hydroxymethyl)phosphine, P(CH 2OH) 3. Several simple and efficient purification procedures were compared for the isolation of the product of the RCM of diethyl diallylmalonate. The efficiency of this procedure was demonstrated for the isolation of crown-ether 3.

Studies on the Reactivity of Dicyanodihydroborate with Some Lewis Base Hydrochlorides

Abstract The reactions of sodium dicyanodihydroborate with various Lewis base hydrochlorides produce mainly the metathesis reaction products in contrast to those of sodium cyanotrihydroborate, which produces cyanoborane adducts. This has been established with the help of IR, 1H and 11B NMR data.