Norbornene Derivatives Research Articles

Preparation and Applications of the Chiral Norbornene Derivatives

Preparation and Applications of the Chiral Norbornene Derivatives

Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol

From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2-a]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA) protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.

A Ring-Opening Metathesis Polymerization Catalyst That Exhibits Redox-Switchable Monomer Selectivities.

A ring-opening metathesis polymerization catalyst supported by a redox-active N-heterocyclic carbene was synthesized and found to undergo reversible reduction. In its neutral form, the catalyst polymerized 1,5-cis,cis-cyclooctadiene at a higher rate than that of a norbornene derivative; however, upon reduction, the selectivity was found to reverse. Utilizing this oxidation state dependent selectivity, a series of copolymers with controlled compositions, microstructures, and physical properties were prepared by redox-switching the catalyst over the course of a series of polymerization reactions.

Multifunctional macromolecular design as a self-standing electrolyte for high-temperature single-ion lithium batteries

A macromolecular electrolyte is designed with different chemical moieties to perform different functions, and it is extremely suitable to be applied in solid high-temperature lithium ion batteries. The preparation of the electrolyte involves synthesis of a comb-like macromolecule and immobilization of lithium ions. The comb-like macromolecule is synthesized via a ring-opening metathesis copolymerization of norbornene derivatives anchored with phosphate and polyethylene glycol monomethyl ether (–O(CH2CH2O) n CH3) and is partially cross-linked through polyethylene glycol (–(CH2CH2O) n –) bridge. The immobilization of lithium ions is carried out by lithium bis(trifluoromethyl-sulfonyl)imide. The as-prepared electrolyte membrane has a bicontinuous morphology consisting of a cross-linked mechanical scaffold intertwined with continuous Li+ ions conducting channels. Apart from lithium ion transference number close to unity and remarkable ionic conductivity, the electrolyte also displays strong strength, high flexibility, good thermal stability and outstanding flame retardancy. At 80 °C, LiFePO4/macromolecular electrolyte/Li coin cells, with the discharge capacity of 134.1 mAh g−1 at a current density of 0.2 C, are able to maintain a value of 120.7 mAh g−1 after 100 cycles of charge and discharge. Monodisperse and multifunctional copolymer is prepared via ring-opening metathesis copolymerization and modified to be used as a single-ion electrolyte for lithium ion batteries. The as-synthesized electrolyte involves a bicontinuous morphology consisting of a cross-linked mechanical scaffold intertwined with continuous Li+ ions conducting channels, resulting in outstanding high-temperature electrochemical performance.

Synthesis of Novel Cyclic Olefin Polymer with High Glass Transition Temperature via Ring‐Opening Metathesis Polymerization

Three norbornene derivatives containing bulky hydrocarbon groups (M1–M3) have been prepared and polymerized efficiently via ring‐opening metathesis polymerization (ROMP) using different Grubbs catalysts (G1–G3) to afford polymers in high yield. Gel permeation chromatography curves show that all the obtained polymers exhibit unimodal distribution. Unsaturated moieties in the main chain of the obtained polymers are hydrogenated based on the chemistry of the reactive intermediate diimide (HNNH) in quantitative conversion, confirmed by 1H NMR measurement. All the polymers display relatively high thermal stability according to thermogravimetric analyses test. The results of differential scanning calorimetry measurement show that the cardo‐like structure such as M2 and M3 is contributed to improve the Tg of cyclicolefin polymer materials. The highest Tg (up to 277 °C) of hydrogenated polymer H‐PM3 is achieved, which is so far the highest value obtained by the ROMP approach, to the best of our knowledge. Furthermore, all the hydrogenated polymers show excellent transparency because of their amorphous structure. image

ChemInform Abstract: Chiral N‐Heterocyclic Carbene Ligand Enabled Nickel(0)‐Catalyzed Enantioselective Three‐Component Couplings as Direct Access to Silylated Indanols.

AbstractThe title reaction between norbornene derivatives, aromatic aldehydes, and silanes provides silyl protected indanol scaffolds as single diastereomers with high enantiomeric excess.

Ring-Opening Metathesis Polymerization of Cyclic Olefins by (Arylimido)vanadium(V)-Alkylidenes: Highly Active, Thermally Robust Cis Specific Polymerization.

Ring-opening metathesis polymerization (ROMP) of various cyclic olefins especially using three (arylimido)vanadium(V)-alkylidene catalysts, V(CHSiMe3)(N-2,6-Cl2C6H3) (OC6F5) (PMe3)2 (3), V(CHSiMe3) (NR)[OC(CF3)3](PMe3)2 [R = Ph (6), 2,6-Cl2C6H3 (7)] have been explored. Complex 3 exhibited the highest catalytic activity (ex. TOF = 603 000 h(-1), 168 s(-1)) for ROMP of norbornene (NBE) among a series of (imido)vanadium(V)-alkylidenes, and the cis-specific living ROMPs of NBE proceeded with remarkable activities (TOF = 125 000-157 000 h(-1) at 25 °C) by the fluorinated alkoxo analogues (6, 7). The activities by 6, 7 increased at high temperature (50 and 80 °C) and/or upon addition of PMe3 without decrease in the cis selectivity (98%). The ROMPs in the presence of 1-hexene by 3, 7 proceeded without significant decrease in the activities, and the Mn values could be controlled by degree of chain transfer (cross metathesis). These dichlorophenylimido analogues (3, 7) were effective for ROMPs of various norbornene derivatives; ROMP of cyclooctene took place by 3, and the activity increased at high temperature (50, 80 °C).

Design and synthesis of oxacycles from norbornene derivatives via ring-opening metathesis and ring-rearrangement metathesis

Norbornene derivatives containing oxygen atom(s) are found to undergo ring-rearrangement metathesis sequence to deliver cyclic ethers. Here, we have established a simple, efficient and an atom-economic process for the synthesis of fused and spiro-oxacyclic compounds starting with cyclopentadiene. Compounds prepared in this study are difficult to assemble by conventional retrosynthetic routes.

Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis.

Here, we report a simple synthetic strategy to the bridgehead vicinal diallylation of norbornene derivatives. These substrates are useful to generate propellanes via ring-closing metathesis. Single-crystal X-ray diffraction analysis of four compounds led to the realization of configurational correction of earlier reported molecules.

Structure of fenchone by broadband rotational spectroscopy.

The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction.

Tuning the molecular weight of ROMP polymers by using Grubbs type catalysts and terminal alkynes

In this study, ruthenium vinyl carbene derivatives were obtained in situ by reacting Grubbs 1st and 2nd generation catalysts with terminal alkynes in toluene at 85 °C. These active species were used in ROMP of norbornene derivatives. The effect of alkyne/Ru (mol/mol) ratio and alkyne substituent on number average molecular weights (Mn) of ROMP polymers were investigated in detail. ROMP polymers with Mn values between 75 and 680 kDa were synthesized by varying alkyne/Ru (mol/mol) ratio in the presence of Grubbs type catalysts. The mechanism of the reaction and the role of alkyne in ROMP reactions were investigated in detail by 1H NMR.

Ring‐Rearrangement‐Metathesis Approach to Polycycles: Substrate‐Controlled Stereochemical Outcome During Grignard Addition

A variety of structurally intricate polycycles have been assembled through ruthenium‐catalysed ring‐rearrangement metathesis of norbornene derivatives. The various substrates required for this work were prepared using Diels–Alder reactions and Grignard additions as key steps. Enyne ring‐rearrangement metathesis of a norbornene system containing a propargyl moiety produced a 1,3‐diene; this was then treated with an appropriate dienophile to deliver the corresponding cycloaddition product.

ChemInform Abstract: Target Specific Tactics in Olefin Metathesis: Synthetic Approach to cis‐syn‐cis‐Triquinanes and ‐Propellanes.

A concise and simple synthetic approach to cis-syn-cis-triquinanes and -propellanes has been demonstrated via olefin metathesis starting with exo-nadic anhydride. This approach involves a ring-opening and ring-closing metathesis sequence of norbornene derivatives using Grubb’s catalyst. Early-stage diallylation of norbornene derivatives is demonstrated followed by ring-closing metathesis that delivers propellanes exclusively. Surprisingly, ring-opening metathesis, late-stage diallylation, followed by ring-closing metathesis delivers triquinane as well as propellane derivatives.

A Domino Ring‐Closure Followed by Retro‐Diels–Alder Reaction for the Preparation of Pyrimido[2,1‐a]isoindole Enantiomers

A simple method was developed to prepare pyrimido[2,1‐a]isoindole derivatives by using di‐endo‐ and di‐exo‐ethyl 3‐aminobicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate enantiomers as chiral sources. The method is based on a domino ring‐closure reaction of norbornene 2‐aminohydroxamic acid followed by microwave‐induced retro‐Diels–Alder reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1‐a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross‐peaks and 3JH,H coupling constants] and X‐ray crystallography.

Experimental and Theoretical Electron Density Determination for Two Norbornene Derivatives: Topological Analysis Provides Insights on Reactivity.

The electron density distribution of two substituted norbornene derivatives (cis-5-norbornene-endo-2,3-dicarboxylic anhydride (1) and 7-oxabicylo[2.2.1]hept-5-ene-exo-2,3-dicarboxylic anhydride (2) has been determined from low-temperature (20 K) X-ray diffraction data and from DFT calculations with periodic boundary conditions. Topological analysis of the electron density is discussed with respect to exo-selective additions, the partial retro-Diels-Alder (rDA) character of the ground state, and intermolecular interaction energies.

Spontaneously Healable Thermoplastic Elastomers Achieved through One-Pot Living Ring-Opening Metathesis Copolymerization of Well-Designed Bulky Monomers.

We report here a series of novel spontaneously healable thermoplastic elastomers (TPEs) with a combination of improved mechanical and good autonomic self-healing performances. Hard-soft diblock and hard-soft-hard triblock copolymers with poly[exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-benzeno-l,4-methanoanthracene] (PHBM) as the hard block and secondary amide group containing norbornene derivative polymer as the soft block were synthesized via living ring-opening metathesis copolymerization by use of Grubbs third-generation catalyst through sequential monomer addition. The microstructure, mechanical, self-healing, and surface morphologies of the block copolymers were thoroughly studied. Both excellent mechanical performance and self-healing capability were achieved for the block copolymers because of the interplayed physical cross-link of hard block and dynamic interaction formed by soft block in the self-assembled network. Under an optimized hard block (PHBM) weight ratio of 5%, a significant recovery of tensile strength (up to 100%) and strain at break (ca. 85%) was achieved at ambient temperature without any treatment even after complete rupture. Moreover, the simple reaction operations and well-designed monomers offer versatility in tuning the architectures and properties of the resulting block copolymers.

Target Specific Tactics in Olefin Metathesis: Synthetic Approach to cis-syn-cis-Triquinanes and -Propellanes.

A concise and simple synthetic approach to cis-syn-cis-triquinanes and -propellanes has been demonstrated via olefin metathesis starting with exo-nadic anhydride. This approach involves a ring-opening and ring-closing metathesis sequence of norbornene derivatives using Grubb's catalyst. Early-stage diallylation of norbornene derivatives is demonstrated followed by ring-closing metathesis that delivers propellanes exclusively. Surprisingly, ring-opening metathesis, late-stage diallylation, followed by ring-closing metathesis delivers triquinane as well as propellane derivatives.

Low-temperature plasma polymerization of dicyclopentadiene for anti-corrosion properties

We successfully synthesized plasma-polymerized films from a highly crosslinkable monomer, dicyclopentadiene (a norbornene derivative), using a low-temperature plasma process as an anti-corrosion coating for Cu metal plates. Plasma-enhanced deposition of polymer films from a dicyclopentadiene precursor was carried out using radio frequency (13.6 MHz) plasma generation with argon or nitrogen carrier gas and varying the input power (50–200 W). The surfaces of plasma-polymers synthesized using an argon carrier gas were more hydrophobic than those prepared with a nitrogen carrier gas, which can be attributed to the formation of CNCHx bonds due to nitrogen dissociation. The inhibition efficiency (IE) for Cu corrosion was estimated from potentiodynamic polarization curves to be enhanced up to ∼93%, which was proportional to the input power in the polymer synthesis. Interestingly, when using a nitrogen carrier gas, the plasma-polymerized films showed shifts of the corrosion potential to negative values. We suspect that nitrogen insertion into the films may result in polarization between nitrogen and copper atoms.

Hydrogenation of alkenes over nickel nanoparticles under atmospheric pressure of hydrogen

Nickel nanoparticles have been shown to be an accessible catalyst which allows hydrogenation of unsaturated compounds to be accomplished under atmospheric pressure of hydrogen at relatively low temperatures. Linear and cyclic alkenes, styrene and norbornene derivatives, as well as pinenes and camphene have been smoothly hydrogenated under these conditions. In some cases, selective hydrogenation of unsaturated carbon–carbon bond is possible with the other functional group remaining intact.

Synthesis of Functional Block Copolymers Carrying One Poly(p-phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure

Block copolymers composed of a MEH–PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60–95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optical properties depending on the polymer composition and the micellization procedure. Furthermore, the reactive ester carrying block copolymers enabled the introduction of anchor groups which facilitated the preparation of nanocomposites with CdSe/CdZnS core–shell QDs. The obtained composites were studied using time-resolved photoluminescence measurements. The results revealed an increased interaction based on an accelerated decay of the QD emission for composites as compared to the mixture of the QDs with unfunctionalized polymers.