941567-71-1Relevant articles and documents
Synthesis and characterization of substituted polynorbornene derivatives
Mulpuri, Syamkumar V.,Shin, Jinbok,Shin, Boo-Gyo,Yoon, Do Y.,Greiner, Andreas
, p. 4377 - 4386,10 (2011)
This paper describes palladium (II) catalyst based synthesis and detailed characterization of vinyl-type polynorbornenes (PNBs) with bulky phenyl, adamantane, or norbornane substituents linked by ester, ether, or alkyl bridges. The structure-property relationships of the substituted PNBs were investigated concerning the thermal stability, glass transition temperature, wide-angle X-ray scattering (WAXS) patterns, mechanical properties, and dielectric characteristics. PNBs with phenyl substituted pendant groups improved the solubility and film forming properties due to aromatic-aromatic interactions. The substituted PNBs exhibited good thermal and thermo-mechanical properties with thermal decomposition temperature (Td,5%) above 300 °C and glass transition temperature in the range of 134-325 °C.WAXS studies revealed the presence of local nano-scale order in the noncrystalline state, especially in ester bridged adamantane and norbornane substituted polymers, probably due to the steric packing requirements of bulky side groups coupled with dipolar interactions. Nanoindentation results showed high modulus (6.5-7.9 GPa) and hardness (0.11-0.38 GPa) for PNBs with diester adamantane and norbornane substituted polymers. Excellent dielectric properties with a dielectric constant (ε) of 2.5 and a dielectric loss tangent (tan δ) of 0.0005 were measured for poly [2-(4-phenylbutyl)-5-norbornene] at 1 GHz, rendering it very attractive for interconnect dielectric films in high-frequency electronic devices.
Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer
Knowles, Robert R.,Metrano, Anthony J.,Tsuchiya, Yuto,Tsui, Elaine
supporting information, p. 11845 - 11849 (2020/05/22)
We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII-based photoredox catalyst, a Br?nsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
Catalytic Living Ring Opening Metathesis Polymerisation: The Importance of Ring Strain in Chain Transfer Agents
Liu, Peng,Yasir, Mohammad,Kilbinger, Andreas F. M.
supporting information, p. 15278 - 15282 (2019/09/17)
A recently developed catalytic living ring opening metathesis polymerisation (ROMP) was investigated using a series of reversible chain transfer agents (CTA) carrying either cyclopentene or cyclohexene rings, differing only in ring strain. All cyclopentene derivatives examined showed significantly faster reaction rates than the corresponding cyclohexene derivatives. This resulted in lower molecular weight dispersities and better control of the molecular weight for the cyclopentene compared to the cyclohexene CTAs. Both Grubbs’ second and third generation catalysts could be employed in catalytic living ROMP using cyclopentene CTA derivatives. The kinetics of different CTAs were studied, block copolymers were synthesised and residual ruthenium quantified by ICP-OES. All polymers were fully characterised by NMR, GPC and MALDI-ToF mass spectrometry. The new cyclopentene CTAs are readily synthesised in a few straightforward steps and provide faster reaction kinetics than all previously reported reversible CTAs.
Mechanistic and Kinetic Studies of the Ring Opening Metathesis Polymerization of Norbornenyl Monomers by a Grubbs Third Generation Catalyst
Hyatt, Michael G.,Walsh, Dylan J.,Lord, Richard L.,Andino Martinez, José G.,Guironnet, Damien
supporting information, p. 17918 - 17925 (2019/11/11)
The mechanism of ring-opening metathesis polymerization (ROMP) for a set of functionalized norbornenyl monomers initiated by a Grubbs third generation precatalyst [(H2IMes)(pyr)2(Cl)2Ru═CHPh] was investigated. Through a series of 12C/13C and 1H/2H kinetic isotope effect studies, the rate-determining step for the polymerization was determined to be the formation of the metallacyclobutane ring. This experimental result was further validated through DFT calculations showing that the highest energy transition state is metallacyclobutane formation. The effect of monomer stereochemistry (exo vs endo) of two types of ester substituted monomers was also investigated. Kinetic and spectroscopic evidence supporting the formation of a six-membered chelate through coordination of the proximal polymer ester to the Ru center is presented. This chelation and its impact on the rate of polymerization are shown to vary based on the monomer employed and its stereochemistry. The combination of this knowledge led to the derivation of a generic rate law describing the rate of polymerization of norbornene monomers initiated by a Grubbs third generation catalyst.
Synthesis of an energetic polynorbornene with pendant bis-azidoacetyloxymethyl groups (PNBAA)
Jiang, Kun,Deng, Han-Lin,Zhang, Qi,Wang, Shuifeng,Wu, Hao,Liu, Yan,Chai, Chunpeng,Huang, Mu-Hua
, p. 2813 - 2820 (2018/06/29)
A novel energetic polynorbornene with pendant bisazidoacetyloxymethyl (named PNBAA) was designed, by combining its intrinsic energetic properties, potential good mechanical properties, its compatibility with a plasticizer and odourless polynorbornene in one polymer. A green synthesis of PNBAA was achieved starting from easily available materials, by using the solvent-free Diels-Alder reaction, chloroacetylation of norbornene dimethanol in water, solvent-free ring opening metathesis polymerization (ROMP), azidation in aqueous 3-pentanone and tandem ROMP and azidation in one pot. In addition, the Nuclear Magnetic Resonance (NMR) technique was utilized to investigate the key ROMP and azidation steps in situ. PNBAA as an energetic polymer was demonstrated by measuring its TG-IR, DSC and mechanical sensitivity. The strategy reported in this paper will lead to the general green synthesis of diverse energetic polymers in the future.
Selective Polymerization Catalysis from Monomer Mixtures: Using a Commercial Cr-Salen Catalyst To Access ABA Block Polyesters
St??er, Tim,Williams, Charlotte K.
supporting information, p. 6337 - 6341 (2018/05/03)
ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring-opening copolymerization and subsequently by lactone ring-opening polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post-functionalization and chain-extension reactions. The ability to use a commercial catalyst and switchable catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers.
Epimerization of Tertiary Carbon Centers via Reversible Radical Cleavage of Unactivated C(sp3)-H Bonds
Wang, Yaxin,Hu, Xiafei,Morales-Rivera, Cristian A.,Li, Guo-Xing,Huang, Xin,He, Gang,Liu, Peng,Chen, Gong
, p. 9678 - 9684 (2018/07/21)
Reversible cleavage of C(sp3)-H bonds can enable racemization or epimerization, offering a valuable tool to edit the stereochemistry of organic compounds. While epimerization reactions operating via cleavage of acidic C(sp3)-H bonds, such as the Cα-H of carbonyl compounds, have been widely used in organic synthesis and enzyme-catalyzed biosynthesis, epimerization of tertiary carbons bearing a nonacidic C(sp3)-H bond is much more challenging with few practical methods available. Herein, we report the first synthetically useful protocol for the epimerization of tertiary carbons via reversible radical cleavage of unactivated C(sp3)-H bonds with hypervalent iodine reagent benziodoxole azide and H2O under mild conditions. These reactions exhibit excellent reactivity and selectivity for unactivated 3° C-H bonds of various cycloalkanes and offer a powerful strategy for editing the stereochemical configurations of carbon scaffolds intractable to conventional methods. Mechanistic study suggests that the unique ability of N3? to serve as a catalytic H atom shuttle is critical to reversibly break and reform 3° C-H bonds with high efficiency and selectivity.
Removal of Nerve Agent Simulants from Water Using Light-Responsive Molecular Baskets
Border, Sarah E.,Pavlovi?, Radoslav Z.,Zhiquan, Lei,Badji?, Jovica D.
supporting information, p. 18496 - 18499 (2018/01/11)
We found that molecular baskets 1-3, with amino acids at their rim, undergo photoinduced decarboxylations to give baskets 4-6 forming a solid precipitate in water. Furthermore, organophosphonates 7-9 (OP), akin in size and shape to G-type nerve agents, form inclusion complexes with baskets 1-3 (K = 6-2243 M-1). Light irradiation (300 nm) of an aqueous solution of 1-3?OP led to the formation of precipitate containing an OP compound thereby amounting to a novel strategy for light-induced sequestration of nerve agents or, perhaps, other targeted compounds. Importantly, the stability of basket OP complexes in addition to functional groups at the basket's rim play a role in the efficiency (up to 98%) by which OPs are removed from water.
Simple Preparation of Rhodococcus erythropolis DSM 44534 as Biocatalyst to Oxidize Diols into the Optically Active Lactones
Martinez-Rojas, Enriqueta,Olejniczak, Teresa,Neumann, Konrad,Garbe, Leif-Alexander,Boraty?ski, Filip
, p. 623 - 627 (2016/10/11)
In the current study, we present a green toolbox to produce ecological compounds like lactone moiety. Rhodococcus erythropolis DSM 44534 cells have been used to oxidize both decane-1,4-diol (2a) and decane-1,5-diol (3a) into the corresponding γ- (2b) and δ-decalactones (3b) with yield of 80% and enantiomeric excess (ee)?=?75% and ee?=?90%, respectively. Among oxidation of meso diols, (?)-(1S,5R)-cis-3-oxabicyclo[4.3.0]non-7-en-2-one (5a) with 56% yield and ee?=?76% as well as (?)-(2R,3S)-cis-endo-3-oxabicyclo[2.2.1]dec-7-en-2-one (6a) with 100% yield and ee?=?90% were formed. It is worth mentioning that R. erythropolis DSM 44534 grew in a mineral medium containing ethanol as the sole source of energy and carbon Chirality 28:623–627, 2016.
Stereo- and regioselective halogenation of norbornenes directed by neighboring group participation
Pavlovi?, Radoslav Z.,Border, Sarah E.,Gallucci, Judith,Badji?, Jovica D.
supporting information, p. 5584 - 5587 (2016/11/23)
Directing the outcome of electrophilic addition reactions of norbornenes could be a challenging task. We have found that the ionic addition of bromine to dichloro-norbornene 2 is accompanied with the formation of a bromonium cation followed by anchimeric assistance of juxtaposed chlorine to give five-membered chloronium cation, which upon reacting with bromide gives norbornane 4 in >90% yield. At higher temperatures, however, the radical addition of Br2dominates so that dibromo compound 3 appears as the principal reaction product (72%). Stereo- and regioselective rearrangements of norbornenes, reported herein, could be of interest for the syntheses of complex haloalkanes.
