Showing papers on "Norbornene published in 2020"
TL;DR: A distal-selective alkenyl C-H arylation method is reported through a directed palladium/norbornene (Pd/NBE) cooperative catalysis, with initial success on distal alkylation using MeI and methyl bromoacetate as electrophiles.
Abstract: A distal-selective alkenyl C-H arylation method is reported through a directed palladium/norbornene (Pd/NBE) cooperative catalysis. The key is to use an appropriate combination of the directing group and the NBE cocatalyst. A range of acyclic and cyclic cis-olefins are suitable substrates, and the reaction is operated under air with excellent site-selectivity. Preliminary mechanistic studies are consistent with the proposed Pd/NBE-catalyzed C-H activation instead of the Heck pathway. Initial success on distal alkylation has also been achieved using MeI and methyl bromoacetate as electrophiles.
52 citations
TL;DR: This Perspective highlights the development of three types of smNBEs: C1-substituted, C2-subStituted and C5-subSTituted or C5,C6-disubstituting NBEs, as well as their synthetic applications toward site-selective C-H functionalization.
Abstract: Palladium/norbornene (Pd/NBE) cooperative catalysis has received enormous attention and found numerous synthetic applications in the past two decades. Considering the critical roles that NBE plays ...
51 citations
TL;DR: In this article, the authors report the synthesis and study of two soluble microporous ladder polymers, CANAL-TBs, by combining catalytic arene-norbornene annulation (CANAL) and Troger's base (TB) formation.
Abstract: We report the facile synthesis and study of two soluble microporous ladder polymers, CANAL–TBs, by combining catalytic arene-norbornene annulation (CANAL) and Troger’s base (TB) formation. The poly...
50 citations
TL;DR: A pyrene functionalized norbornene (1) and its homopolymer (P1), which was obtained by the ring opening metathesis polymerization (ROMP) method, have been designed and synthesized as discussed by the authors.
42 citations
TL;DR: This work employed an activated norbornene to trap the ortho-palladation intermediate and relay to the meta-position, leading to a meta-selective C-H arylation of fluoroarenes, and suggests that this meta-arylation is initiated by ortho C- H activation and the catalytic cycle is terminated by the C-2 protonation.
Abstract: Fluorine is known to promote ortho-C-H metalation. Based upon this reactivity, we employed an activated norbornene that traps the ortho-palladation intermediate and is then relayed to the meta position, leading to meta-selective C-H arylation of fluoroarenes. Deuterium experiment suggests that this meta-arylation is initiated by ortho C-H activation and the catalytic cycle is terminated by C-2 protonation. A dual-ligand system is crucial for the observed high reactivity and site selectivity. Applying this approach to simple benzene or other arenes also affords arylation products with good yield and site selectivity.
40 citations
TL;DR: Three types of poly(norbornene)s were investigated, functionalized with phenothiazine units through either a direct connection or ester linkages, as well as their crosslinked derivatives, and demonstrated excellent rate capability and cycling stability.
Abstract: Organic cathode materials are handled as promising candidates for new energy-storage solutions based on their transition-metal-free composition. Phenothiazine-based polymers are attractive owing to their redox potential of 3.5 V vs. Li/Li+ and high cycling stabilities. Herein, three types of poly(norbornene)s were investigated, functionalized with phenothiazine units through either a direct connection or ester linkages, as well as their crosslinked derivatives. The directly linked poly(3-norbornylphenothiazine)s demonstrated excellent rate capability and cycling stability with a capacity retention of 73 % after 10 000 cycles at a C-rate of 100 C for the crosslinked polymer. The polymer network structure of the crosslinked poly(3-norbornylphenothiazine) was beneficial for its rate performance.
37 citations
TL;DR: This work embarked on exploring the para -selective C-H arylation which is contemplated by a unique combination of a meta -directing group and norbornene as transient mediator and subsequently para -C-HArylation is achieved for diverse scaffolds with aryl iodides.
Abstract: Biaryl compounds are extremely important structural motifs in natural products, biologically active components and pharmaceuticals. Selective synthesis of biaryls by distinguishing the subtle reactivity difference of distal arene C-H bonds are significantly challenging. Herein, we describe para-selective C-H arylation, which is acheived by a unique combination of a meta-directing group and norbornene as a transient mediator. Upon direct meta-C-H palladation, one-bond relay palladation occurs in presence of norbornene and subsequently para-C-H arylation is achieved for sulfonates, phosphonates and phenols bearing 2,6-disubstitution patterns. The protocol is amenable to electron-deficient aryl iodides. Multisubstituted arenes and phenols are obtained by postsynthetic modification of the products. The protocol allows the synthesis of hexa-substituted benzene by sequential selective distal C-H functionalization.
33 citations
TL;DR: In this paper, the addition polymerization of readily available bifunctional norbornene derivatives, 5-alkylidene-2-norbornenes, in the presence of modified Pd complexes with N-heterocyclic carbene lig...
Abstract: We studied the addition polymerization of readily available bifunctional norbornene derivatives, 5-alkylidene-2-norbornenes, in the presence of modified Pd complexes with N-heterocyclic carbene lig...
32 citations
TL;DR: In this article, the authors incorporate epoxy group functionalized side chain and imidazolium-terminated flexible side chain to norbornene copolymer backbone to form a space cross-linked topological structure for alkaline anion exchange membrane.
28 citations
TL;DR: The versatile cis-selective controlled living ROMP of various endo-tricyclo[4.2.02,5]deca-3,9-diene and various norbornene derivatives using a fast-initiating dithiolate-chelated Ru catalyst could compare cis- and trans-rich polynorbornene and found the former to have enhanced resistance to shear degradation.
Abstract: An unsaturated polymer's cis/trans-olefin content has a significant influence on its properties. For polymers obtained by ring-opening metathesis polymerization (ROMP), the cis/trans-olefin content can be tuned by using specific catalysts. However, cis-selective ROMP has suffered from narrow monomer scope and lack of control over the polymerization (giving polymers with broad molecular weight distributions and prohibiting the synthesis of block copolymers). Herein, we report the versatile cis-selective controlled living ROMP of various endo-tricyclo[4.2.2.02,5]deca-3,9-diene and various norbornene derivatives using a fast-initiating dithiolate-chelated Ru catalyst. Polymers with cis-olefin content as high as 99% could be obtained with high molecular weight (up to Mn of 105.1 kDa) and narrow dispersity (<1.4). The living nature of the polymerization was also exploited to prepare block copolymers with high cis-olefin content for the first time. Furthermore, owing to the successful control over the stereochemistry and narrow dispersity, we could compare cis- and trans-rich polynorbornene and found the former to have enhanced resistance to shear degradation.
25 citations
TL;DR: In this paper, the synthesis of benzoquinone and naphthoquinone-bearing polymers by ring-opening metathesis polymerization of monomers with an exo-type four-membered ring between polymerizable norbornene and redoxactive quinone units is reported.
Abstract: Organic electrode materials have attracted great interest for next-generation lithium-ion batteries owing to their merits of low cost, resource sustainability, and environmental friendliness. Dissolution in organic electrolyte is one of critical factors that limit their development, and constructing corresponding polymers is an effective way to prevent it. Herein, the synthesis of benzoquinone- and naphthoquinone-bearing polymers by ring-opening metathesis polymerization of monomers with an exo-type four-membered ring between polymerizable norbornene and redox-active quinone units is reported. They exhibit significantly reduced solubility and clearly enhanced electrochemical performance. In particular, a high capacity (189.7 mAh g-1 at 0.1 C, 1 C=216.1 mA g-1 ), stable cycling (75.6 % capacity retention after 500 cycles at 2 C), and good rate capability (retaining 80.4 % from 0.1 to 2 C) were obtained for the naphthoquinone-bearing polymer, which stand out among naphthoquinone-bearing polymer electrode materials. This work offers rational molecular design and a new polymerization strategy to construct high-performance polymer electrode materials.
TL;DR: A simple, inexpensive means of controlling molecular weight, using alpha olefins as chain transfer agents, and was used to synthesize a functionalized norbornene copolymer in a range of molecular weights for specific materials applications.
Abstract: Photo-redox mediated ring-opening metathesis polymerization (photo-ROMP) is an emerging ROMP technique that uses an organic redox mediator and a vinyl ether initiator, in contrast to metal-based initiators traditionally used in ROMP. The reversibility of the redox-mediated initiation and propagation steps enable spatiotemporal control over the polymerization. Herein, we explore a simple, inexpensive means of controlling molecular weight, using alpha olefins as chain transfer agents. This method enables access to low molecular weight oligomers, and molecular weights between 1 and 30 kDa can be targeted simply by altering the stoichiometry of the reaction. This method of molecular weight control was then used to synthesize a functionalized norbornene copolymer in a range of molecular weights for specific materials applications.
TL;DR: This work proposes a strategy to prepare C-C main-chain sequence-regulated polymers with controlled molecular weights from vinyl monomers via a combination of iterative atom transfer radical additions and olefin metathesis reactions, and demonstrates the utility of this strategy by formation of block copolymers consisting of sequence- regulated vinyl polymer segments by combining living ROMP of norbornene derivatives.
Abstract: Monomer sequence control in terms of a single monomer unit, particularly in vinyl polymers, is one of the largest challenges in polymer chemistry. Furthermore, multifactor control of monomer sequence, molecular weight, and stereoregularity is an ultimate goal. In this work, we propose a strategy to prepare C-C main-chain sequence-regulated polymers with controlled molecular weights from vinyl monomers via a combination of iterative atom transfer radical additions and olefin metathesis reactions. This strategy enabled the synthesis of sequence-regulated polymers with exact styrene-acrylate-styrene sequences in the C-C main chains, controlled molecular weights of up to 104, and stereoregularities varying with syndiotacticity, isotacticity, and heterotacticity. The utility of this strategy is further demonstrated by formation of block copolymers consisting of sequence-regulated vinyl polymer segments by combining living ROMP of norbornene derivatives.
TL;DR: In this article, a novel benzonorbornadiene derivative (BenzoNBD-Bis(Im+Br−-Im+I−)) grafted by multi-imidazolium cations side-chains combined the rigid alkyl spacer and flexible alkoxy spacer is designed and synthesized.
TL;DR: First Ln(ii) ring-expanded NHC complexes (er-NHC)Ln[N(SiMe3)2]2 (Ln = Sm, Yb) are synthesized and proved to be highly efficient pre-catalysts for the intermolecular hydrophosphination of such indolent substrates as 1-alkenes, cyclohexene and norbornene.
TL;DR: The incorporation of secondary co-units may not only change the kinetics and polymorphism of crystallization but also affect the melting behavior of polymers, leading to the memory effect as mentioned in this paper.
Abstract: The incorporation of the secondary co-units may not only change the kinetics and polymorphism of crystallization but also affect the melting behavior of polymers, leading to the memory effect even ...
TL;DR: In this paper, a simple synthetic method to functionalize norbornene at the 5-position with a base-stable tetraaminophosphonium cation was developed, and upon confirmation that the cationic monomer could be p...
Abstract: Herein, a simple synthetic method to functionalize norbornene at the 5-position with a base-stable tetraaminophosphonium cation was developed. Upon confirmation that the cationic monomer could be p...
TL;DR: In this paper, norbornene imidazolium hexafluorophosphate (NM-MIm-PF6) was modified on the surface of aminopropyl silica by ring-opening metathesis polymerization (ROMP).
TL;DR: The cyclic five-membered frustrated phosphane/ borane Lewis pairs 11a, b featuring the bulky octaethylhydrindacenyl- (Eind-) substituent or its mono-bromo derivative at phosphorus are monomeric at r.t..
Abstract: The cyclic five-membered frustrated phosphane/borane Lewis pairs 11 a, b featuring the bulky octaethylhydrindacenyl- (Eind) substituent or its mono-bromo derivative (Br Eind) at phosphorus are monomeric at room temperature. The reactive frustrated Lewis pairs (FLPs) cleave dihydrogen. The cyclic FLP 11 b (Br Eind) undergoes 1,2-P/B addition to ethylene to give the zwitterionic heteronorbornane derivative 14 b. It reacts similarly with the carbon-carbon double bond of norbornene. With a variety of organic π-reagents, the cyclic FLP 11 b often undergoes reaction sequences reminiscent of the Alder-Rickert reaction: the cycloaddition reaction is followed by rapid cycloreversion to form new five-membered heterocyclic FLP products with extrusion of ethene. Reactions of 11 b with benzaldehyde or with acetylenes follow this reaction pattern.
TL;DR: The use of ball mills enabled the efficient mechanosynthesis of a variety of N-aryl, N-alkyl imidazolium salts and corresponding NHC silver(I) complexes as discussed by the authors.
TL;DR: An ortho-amination, ipso-C-H arylation mediated by palladium/norbornene cooperative catalysis is reported, applicable to the formation of dibenzazepinones.
TL;DR: A highly enantioselective Pd/Xiang-Phos-catalyzed carbohetero-functionalization of norbornene is described, giving a direct access to various chiral norbornane-fused dihydrofurans and diHydro-pyrroles.
TL;DR: In this paper, the norbornene moiety was selectively polymerized via ring-opening metathesis polymerization (ROMP) under ambient conditions where Cyrene™ was explored for the first time as a green bio-alternative organic solvent for ROMP reactions.
TL;DR: The kinetic curve proves that pivalic acid accelerates the reaction rate of unactivated C(sp2)-H activation, and thus this rate can keep up with the five membered aryl-norbornene-palladacycle (ANP) intermediate.
TL;DR: The copolymerization of norbornene and α-olefins was achieved with high activity using (tBuNSiMe2Flu)TiMe2 (1)-[Ph3C][B(C6F5)4] and 2...
Abstract: The copolymerization of norbornene (NB) and various α-olefins [1-octene (O), 1-decene (De), and 1-dodecene (Do)] was achieved with high activity using (tBuNSiMe2Flu)TiMe2 (1)-[Ph3C][B(C6F5)4] and 2...
TL;DR: In this article, Pd-catalyzed 1:2 coupling of five-membered haloheteroarenes with NBEs was shown to yield a 1:1 coupling of halo(hetero)arenes and norbornene derivatives.
Abstract: Complementary to Catellani-type reactions and 1:1 coupling of six-membered halo(hetero)arenes and norbornene (NBE) derivatives, Pd-catalyzed 1:2 coupling of five-membered haloheteroarenes with NBEs...
TL;DR: In this article, the reaction of triflamide with norbornene and norbornadiene in nitriles RCN (R = Me, i-Bu, Ph) or THF in the presence of t-BuOI, NBS or NIS as oxidants was studied.
TL;DR: The reaction mechanism, ligand and norbornene effects, and origins of meta-selectivity in Pd/norbornene-catalyzed alkylation and arylation via C–H activation are theoretically elucidated by DFT computation.
Abstract: The reaction mechanism, ligand and norbornene effects, and origins of meta-selectivity in Pd/norbornene-catalyzed alkylation and arylation via C–H activation are theoretically elucidated by DFT computation. The reaction proceeds through six major steps: ortho-C–H activation, norbornene insertion into Pd–C bonds, meta-C–H activation, meta-C–C bond formation, β-carbon elimination, and protodemetallation. Both ortho-C–H and meta-C–H activations undergo a concerted metalation–deprotonation pathway. The meta-C–C bond formation, which is the selectivity-determining step, follows a Pd(IV) pathway via oxidative addition on a Pd(II) five-membered-ring intermediate. The oxidative addition of alkyl iodide adopts an SN2 pathway, whereas aryl iodide prefers concerted oxidative addition rather than the SN2 pathway. The Pd(II) pathway via meta-C–C reductive coupling on dinuclear palladium species is not the dominant pathway because of the low concentration of Pd(0)L2. For methylation, with norbornene and pyridine (or its derivative) as ligands, the C–C reductive coupling and C–C reductive elimination from the Pd(IV) intermediate are found to be the selectivity-determining steps for meta-functionalization and benzocyclobutene formation, respectively, whereas the use of large ligands such as acridine and quinoline-type ligands (L1 and L2) moves the selectivity-determining step back to the oxidative addition and the C–C reductive elimination steps on the Pd(II) intermediate. The geometric and electronic properties of L1 and L2 further suppress the benzocyclobutene formation by increasing the energy difference between meta-functionalization and benzocyclobutene formation. The combination of 2-carbomethoxynorbornene and L2 promotes meta-ethylation and -arylation by disfavoring the C–C reductive elimination steps from the Pd(II) and Pd(IV) intermediates as well as slightly favoring the oxidative addition step.
TL;DR: In this article, a cobaltocenium-containing norbornene derivative has been synthesized and homopolymerized with ring-opening metathesis polymerization (ROMP) with quantitative yields.