Showing papers on "Norbornadiene published in 2018"

Simple Alkaline-Earth Metal Catalysts for Effective Alkene Hydrogenation.

Abstract: Alkaline earth metal amides (AeN''2 : Ae=Ca, Sr, Ba, N''=N(SiMe3 )2 ) catalyze alkene hydrogenation (80-120 °C, 1-6 bar H2 , 1-10 mol % cat), with the activity increasing with metal size Various activated C=C bonds (styrene, p-MeO-styrene, α-Me-styrene, Ph2 C=CH2 , trans-stilbene, cyclohexadiene, 1-Ph-cyclohexene), semi-activated C=C bonds (Me3 SiCH=CH2 , norbornadiene), or non-activated (isolated) C=C bonds (norbornene, 4-vinylcyclohexene, 1-hexene) could be reduced The results show that neutral Ca or Ba catalysts are active in the challenging hydrogenation of isolated double bonds For activated alkenes (eg styrene), polymerization is fully suppressed due to fast protonation of the highly reactive benzyl intermediate by N''H (formed in the catalyst initiation) Using cyclohexadiene as the H source, the first Ae metal catalyzed H-transfer hydrogenation is reported DFT calculations on styrene hydrogenation using CaN''2 show that styrene oligomerization competes with styrene hydrogenation Calculations also show that protonation of the benzylcalcium intermediate with N''H is a low-energy escape route, thus avoiding oligomerization

A Versatile and Highly Z-Selective Olefin Metathesis Ruthenium Catalyst Based on a Readily Accessible N-Heterocyclic Carbene

Abstract: A ruthenium catalyst for Z-selective olefin metathesis has been synthesized from a readily accessible N-heterocyclic carbene (NHC) ligand that is prepared using an efficient, practical, and scalable multicomponent synthesis. The desired ruthenium complex with cyclometalated NHC ligand is obtained by means of selective C(sp3)-H activation at the adamantyl fragment and X-ray diffraction analysis unambiguously confirmed the structure of the precatalyst. The catalyst demonstrated attractive catalytic performance in self- and cross-metathesis at low catalyst loading to afford the desired internal olefins with high conversion and very high Z-selectivity (up to >99%). The versatility of the chelated catalyst is illustrated by the high cis-selectivity (up to >98%) and high tacticity control (up to >98% syndiotactic) achieved in ring-opening polymerization, allowing for the production of highly microstructurally controlled norbornene-, norbornadiene-, and cyclopropene-derived polymers.

Cis-Cisoid Helical Structures of Poly(3,5-disubstituted phenylacetylene)s Stabilized by Intramolecular n → π* Interactions

Abstract: A pair of enantiomeric cis-poly(phenylacetylene)s (PPAs) substituted at the meta-positions of pendant phenyl rings by an achiral methoxycarbonyl group and a chiral 1-methylpropyloxycarbonyl group (i.e., sP-Me-C4/rP-Me-C4) as well as two cis-PPAs bearing either just a methoxycarbonyl (i.e., m-aP-Me) or a 1-methylpropyloxycarbonyl (i.e., m-sP-C4) meta substituent were synthesized under the catalysis of [Rh(nbd)Cl]2 (nbd = norbornadiene). Various techniques including 1H NMR, FTIR, Raman, UV–vis, CD, DSC, STM, DLS/SLS, and computer calculation were applied to characterize the helical structures of these polymers in both solution and solid states. sP-Me-C4/rP-Me-C4 adopted contracted cis-cisoid helical conformations in THF, toluene, CH2Cl2, and ClCH2CH2Cl but cis-transoid ones in CHCl3 and Cl2CHCHCl2. The cis-cisoid helices were considered to be stabilized by the existence of six n → π* interaction bands along the polyene backbones between vicinal carbonyl groups. Such interactions were insensitive to the diel...

Three-Input Molecular Keypad Lock Based on a Norbornadiene–Quadricyclane Photoswitch

Abstract: The photo- and acidochromic properties of a new generation norbornadiene derivative have been harnessed for the realization of a three-input keypad lock, where a specific sequence of inputs induces a unique output. Reversible quadricyclane/norbornadiene photoisomerization is reported, and this rare feature allows the first example of a norbornadiene-based molecular logic system. The function of this system is clearly rationalized in terms of the interconversion scheme and the absorption spectra of the involved species.

Thermally Stable Gold(III) Alkene and Alkyne Complexes: Synthesis, Structures, and Assessment of the trans-Influence on Gold-Ligand Bond Enthalpies

Abstract: The reaction of [C^C)Au(OEt2 )2 ]+ with 1,5-cyclooctadiene or norbornadiene affords the corresponding olefin complexes [(C^C)Au(COD)]SbF6 and [(C^C)Au(NBD)]SbF6 , which are thermally stable in solution and the solid state (C^C=4,4'-di-tert-butylbiphenyl-2,2'-diyl). The crystal structures of these complexes have been determined. By contrast, dienones such as dibenzylideneacetone are O- rather than C=C-bonded. The reactions of (C^C)Au(OAcF )(L) (L=PMe3 or CNxyl) with B(C6 F5 )3 in the presence of bis(1-adamantyl)acetylene give the mixed-ligand alkyne complexes [(C^C)Au(AdC≡CAd)(L)]+ , the first complexes of their type in gold chemistry. In the presence of an excess of acetylene these compounds are thermally stable in solution and as solids. The bonding of n- and π-donor ligands to AuIII fragments and the effect of the trans influence exerted by N- and C-donors was explored with the aid of DFT calculations. Results show that the Au-L bond enthalpies trans to anionic C are 35-60 % of the enthalpies trans to N, with strong π-acceptors being particularly affected. In comparison with [Me2 Au]+ , the [(C^C)Au]+ fragment is more polar and in bond enthalpy terms resembles Me2 Pt.

Heteroaryl-linked norbornadiene dimers with redshifted absorptions.

Abstract: Development of Molecular Solar Thermal (MOST) systems for harvesting and storing solar energy is based on molecular photoswitches that undergo photoisomerizations to metastable isomers. One challenge is to achieve low-molecular weight molecules that absorb at sufficiently long wavelengths to match the solar spectrum. Here we show that this can be achieved by linking two norbornadiene (NBD) photoswitches to a central heterocycle, thiophene or carbazole, via alkyne appendages. In this approach, the same heteroaryl is used to tune the properties of two photoswitches at the same time, thereby keeping the molecular weight as low as possible. A series of NBD dimers was prepared by Sonogashira coupling reactions, and these compounds showed remarkable redshifted absorptions, with onsets of absorption as high as 468 nm, and thermal half-lives ranging from 44 seconds to 16 hours.

Formation and reactions of active five-membered phosphane/borane frustrated Lewis pair ring systems

Abstract: The reactive five-membered frustrated P/B Lewis pair 6a was generated from Tipp-P(vinyl)2 (Tipp: 2,4,6-triisopropylphenyl) by a series of anti-Markovnikov and Markovnikov hydroboration reactions. The in situ generated compound dimerized to give 7a under kinetic control and the dimer pair 8a/9a under thermodynamic control. The Mes*-P(vinyl)2 analogue (Mes*: 2,4,6-tri-tert-butylphenyl) reacts in a similar way, but in this case the thermodynamic dimers are observed at r.t. whereas the monomer 6b is the dominant species at 80 °C in solution. It is an active dihydrogen splitting reagent. The in situ generated monomeric five-membered P/B FLPs undergo addition reactions to various organic π-reagents. With benzaldehyde or phenylacetylene this gave the respective zwitterionic heteronorbornene or -norbornadiene type products, the latter with liberation of ethylene.

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

Abstract: A series of water-soluble zwitterionic complexes featuring a carboxylate bridge-functionalized bis-N-heterocyclic carbene ligand of formula [Cp*MIIICl{(MeIm)2CHCOO}] and [MI(diene){(MeIm)2CHCOO}] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; M = Rh, Ir; MeIm = 3-methylimidazol-2-yliden-1-yl; diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd)) were prepared from the salt [(MeImH)2CHCOO]Br and suitable metal precursor. The solid-state structure of both types of complexes shows a boat-shaped six-membered metallacycle derived of the κ2C,C′ coordination mode of the bis-NHC ligand. The uncoordinated carboxylate fragment is found at the bowsprit position in the Cp*MIII complexes, whereas in the MI(diene) complexes it is at the flagpole position of the metallacycle. The complexes [RhI(diene){(MeIm)2CHCOO}] (diene = cod, nbd) exist as two conformational isomers in dichloromethane, bowsprit and flagpole, that interconvert through the boat-to-boat inversion of the metallacycle. An inversion barrier of ∼17 kcal·mo...

Microporous Materials Based on Norbornadiene-Based Cross-Linked Polymers

Abstract: New microporous homopolymers were readily prepared from norbornadiene-2,5, its dimer and trimer by addition (vinyl) polymerization of the corresponding monomers with 60⁻98% yields. As a catalyst Pd-N-heterocyclic carbene complex or Ni(II) 2-ethylhexanoate activated with Na⁺[B(3,5-(CF₃)₂C₆H₃)₄]- or methylaluminoxane was used. The synthesized polynorbornenes are cross-linked and insoluble. They are glassy and amorphous polymers. Depending on the nature of the catalyst applied, BET surface areas were in the range of 420⁻970 m²/g. The polymers with the highest surface area were obtained in the presence of Pd-catalysts from the trimer of norbornadiene-2,5. The total pore volume of the polymers varies from 0.39 to 0.79 cm³/g, while the true volume of micropores was 0.14⁻0.16 cm³/g according to t-plot. These polymers gave CO₂ uptake from 1.2 to 1.9 mmol/g at 273 K and 1 atm. The porous structure of new polymers was also studied by means of wide-angle X-ray diffraction and positron annihilation lifetime spectroscopy.

Sequential double C–H functionalization of 2,5-norbornadiene in flow

Abstract: An anionic species of 2,5-norbornadiene was generated and brominated using a flow reactor. In the second step, 2-bromo-2,5-norbornadiene was lithiated with LTMP and reacted with tributyltin chloride. Finally, an integrated one-flow synthesis using various electrophiles was achieved within 3 min to prepare 2-bromo-2,5-norbornadienes bearing a functional group at the 3-position.

Hydride transfer mechanism in the catalytic allylation of norbornadiene with allyl formate

Abstract: Allylation of norbornadiene with allyl formate in the presence of the palladium catalytic systems is characterized by several peculiarities associated with the new reaction route: hydroallylation (reductive allylation) occurs along with the traditional allylation (oxidative allylation). Both processes are considered from the single point of view, and the mechanism assuming different routes of the hydride transfer in the key intermediates was proposed. It was proved by using deuterated reactants that the hydride transfer can involve the allyl, norbornenyl, or formyl moieties. In all cases, the hydrogen atom bound to the carbon atom in the β-position relative to palladium is eliminated in this step.

Synthesis of perinaphthenones through rhodium-catalyzed dehydrative annulation of 1-naphthoic acids with alkynes.

Abstract: An efficient approach to the synthesis of perinaphthenones via the rhodium-catalyzed dehydrative annulation of 1-naphthoic acids with internal alkynes was developed. Norbornadiene can act as an acetylene equivalent to give unsubstituted perinaphthenones at the 2- and 3-positions via dehydrative annulation followed by a retro Diels–Alder reaction.

Synthesis and Properties of Energy-Rich Methanofullerenes Containing Norbornadiene and Quadricyclane Moieties.

Abstract: The energy-rich methanofullerenes were synthesized for the first time by the reaction of fullerene C60 with mono- and bisquadricyclane esters of malonic acid. The C–C bond cleavage in the quadricyclane moieties of new hybrid molecules takes place in the presence of catalytic amounts of Cu, Pd, and Pt salts or complexes or SiO2 and is accompanied by heat evolution.

Cross-link in norbornadiene-based polymers from ring-opening metathesis polymerization with pyrrolidine-based Ru complex

Abstract: Ring-opening metathesis polymerization (ROMP) of norbornadiene (NBD) with [RuCl2(PPh3)2(pyrrolidine)] as the starting complex was evaluated as a function of reaction time, solvent volume, and atmosphere type at 25 °C. Quantitative yields of polyNBD were obtained either under inert argon atmosphere or in air, with 2 mL of CHCl3, for 30 min. Copolymerization of NBD with norbornene (NBE) resulted in 100–70% yield under argon, depending on the NBE/NBD molar ratio, and in 70% yield in air, with 2 mL, for 120 min. TGA, DSC, and DMA measurements and swelling tests supported the occurrence of cross-linking in homopolyNBD and in the copolymers isolated from polymers. SEM micrographs showed porous polymeric NBD materials with pores that decreased in size when increasing the amount of NBD in the starting reaction composition. Results from amine parent complexes when the amine was piperidine or perhydroazepine are also discussed, with high cross-linking degree from reaction with the pyrrolidine complex.

Alkene-alkyl interconversion: an experimental and computational study of the olefin insertion and β-hydride elimination processes.

Abstract: The preparation and characterization of various alkyl, allyl or alkene Rh(iii) and Ir(iii) complexes as well as studies on the intramolecular reactions leading to transformation of one into another are reported. The silyl-hydrido-Rh(iii) complex {Rh(H)[SiMe(o-C6H4SMe)2](PPh3)}[BArF4], with a vacant coordination site, reacts with 1,5-cyclooctadiene (cod) leading to olefin insertion into the Rh-H bond and rearrangement to yield the 16e cyclooctenyl-Rh(iii) complex {Rh(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]}[BArF4] (1). This compound can be also synthesized by reaction of the 18e chloride precursor {Rh(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]Cl} with NaBArF4. The reaction of the thioether-silane SiMeH(o-C6H4SMe)2 with [Rh(nbd)Cl]2 (nbd = norbornadiene) leads to {Rh(σ-ntyl)[SiMe(o-C6H4SMe)2]Cl} (ntyl = nortricyclyl) (2). The abstraction of chloride from this neutral 16e ntyl-Rh(iii) complex with NaBArF4 results in the unusual isomerization of σ-nortricyclyl into σ,π-norbornenyl forming the 16e and cationic {Rh(σ,π-nbyl)[SiMe(o-C6H4SMe)2][BArF4] (nbyl = norbornenyl)} compound 3. Coordinatively saturated {Ir(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]Cl} (4) has been synthesized by the reaction of [Ir(cod)Cl]2 with SiMeH(o-C6H4SMe)2. The reaction of 4 with NaBArF4 led to the formation of the unsaturated and cationic Ir(iii) compound {Ir(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]}[BArF4] (5). Compound 5 shows low stability in solution and undergoes successive β-hydride elimination and olefin insertion steps, which were elucidated by DFT calculations, to form 18e {Ir(H)[SiMe(o-C6H4SMe)2](η4-cod)}[BArF4] (6).

Versatile Coordination Modes of Triphospha-1,4-pentadiene-2,4-diamine.

Abstract: 1,3,5-Triphospha-1,4-pentadiene-2,4-diamine reacts with [M(CO)4L] (M = Mo, L = nbd (norbornadiene); M = W, L = 2 CH3CN) to give the chelate complexes [M(CO)4(PMes{C(NHCy)PMes}2-κ P1 ,P3)]. In contrast, an unusual intramolecular rearrangement occurred with [Cu(CH3CN)4]PF6 leading to the dimeric copper(I) complex [Cu(CNCy){PHMesPMesC(NHCy)PMes-κ P1 ,P3}]2(PF6)2. The mechanism of the rearrangement was supported by quantum-mechanical calculations. The transition-metal complexes were characterized by multinuclear NMR spectroscopy, mass spectrometry, infrared spectroscopy, and X-ray crystallography.

New heterogenized catalytic systems in norbornadiene allylation

Abstract: New heterogenizated catalysts for the allylation of norbornadiene (NBD) were prepared by the adsorption immobilization and surface assembly methods. The obtained catalysts were screened in the allylation of NBD, and the main technological parameters of the process were determined.

The theoretical investigation of global reactivity descriptors, NLO behaviours and bioactivity scores of some norbornadiene derivatives

Abstract: In this study, global reactivity descriptors such as ionization potential, electron affinity, electronegativity, chemical hardness, softness and electrophilicity index of norbornadiene derivatives which include some halogen atoms and atom groups, have been investigated with DFT/BPV86/B3LYP/B3PW91 methods with 6-31G(d,p) basis set. To determine the non-linear optical behaviours of the structures, the total dipole moment, polarizability, and first-order hyperpolarizability values have been examined at the same theoretical level. It has been determined that thiol-bonded groups on comparison with others have a much better NLO material property. In addition, the potentials of the structures as drug-active compounds have been inspected with Lipinski’s rule of 5 and bioactivity scores. T hiol and hydroxyl-bonded groups have a good drug-likeness and bioactivity score relative to the others.

Activating Ru nanoparticles on oxide supports for ring-opening metathesis polymerization

Abstract: Nano-sized particles mounted on heterogeneous oxide supports such as silica have altered reactivity when compared to their homogeneous analogs. In particular, catalyzed olefin metathesis using supported Ru nanoparticles has shown great promise and various methods have been employed to develop functional heterogeneous Ru catalysts. This article reports a method for synthesizing Ru nanoparticles supported on silica and titania. The nanoparticles were characterized using XPS showing Ru(0) dominates when not exposed to air. TEM showed Ru nanoparticle sizes of 3.1 ± 0.8 nm for Ru supported on SiO2 and 5.6 ± 1.3 nm for Ru supported on TiO2. The materials demonstrated modest activity in ring-opening metathesis reactions via diazo activation and nanoparticle-embedded polymers of norbornene and norbornadiene were synthesized using dry box and Schlenk line techniques. The Ru/support/polymer composite materials were characterized using proton NMR, XPS, and SEM/EDS.

Synthesis of Hybrid Pharmacophores Based on Adducts of N -Sulfinylaniline and Norbornadiene

Abstract: Acylation of benzothiazinesulfonamides obtained by the oxidation of N-sulfinylaniline and norbornadiene adducts with acid chlorides and carboxylic anhydrides led to the formation of N-acylated sulfonamide hybrid pharmacophores. Molecular and crystal structure of the acylated products was established by X-ray diffraction method.

Energy storage material based on 2,5-norbornadiene derivative and preparation method thereof

Abstract: The invention discloses an energy storage material based on a 2,5-norbornadiene derivative and a preparation method thereof. An esterification method is used for preparing an ortho grafted bisazo benzene 2,5-norbornadiene derivative; two azobenzene groups are introduced at 2,5-norbornadiene in an ortho manner, so that norbornadiene is obviously subjected to Einstein shift; the photon yield is effectively improved. 2,5-norbornadiene and the azobenzene groups are combined, so that the heat storage energy density can be effectively improved; the storage energy is increased. The material has excellent optical performance and is hopeful to be applied in the fields of light and heat conversion and energy storage.

Novel method for ruthenium-catalyzed selective boronation reaction of amides

Abstract: The present invention relates to a novel method for ruthenium-catalyzed selective boronation reaction of amides. According to the method, a hexacoordinated metal ruthenium complex containing a norbornadiene (NBD) ligand is taken as a catalyst, an N,N-disubstituted amide and bis(pinacolato)diboron are taken as reaction substrates, and in the absence of reaction solvents and under mild reaction conditions, a carbon-hydrogen bond of methylene at the ortho position of a nitrogen atom in the N,N-disubstituted amide is selectively subjected to a boronation reaction under efficient catalysis, so thata corresponding amide borate product is obtained. Compared with currently reported methods, the novel method generally has the advantages of wide substrate applicability, low catalyst usage amount, simple operation and the like. The method of the present invention realizes for the first time a selective C(sp3)-H boronation reaction of N,N-dimethyl substituted aromatic amide derivatives. In addition, the method realizes for the first time a metal-ruthenium-catalyzed selective dehydro-boronation reaction of N,N-disubstituted amides, and provides a completely new reaction strategy for organic synthetic intermediates of amide borates.

New method for selective dehydrogenation boronation reaction by catalyzing methyl ester through ruthenium

Abstract: The invention relates to a new method for a selective dehydrogenation boronation reaction by catalyzing a methyl ester derivative through ruthenium. The method comprises the following steps: by usinga hexa-coordinated metal ruthenium complex, containing a norbornadiene (NBD) ligand, as a catalyst and using the methyl ester derivative and bis(pinacolato)diboron as reaction substrates, in a mild reaction condition, efficiently catalyzing a carbon-hydrogen bond of ortho-position methyl of an oxygen atom in the methyl ester derivative to selectively generate a boronation reaction, so as to obtaina corresponding methyl ester borate product. At present, selective dehydrogenation boronation reaction of the carbon-hydrogen bond of the ortho-position methyl of the oxygen atom in an ester derivative is not reported yet. The new method is used for realizing that the methyl ester derivative is enabled to selectively generate the dehydrogenation boronation reaction of the ortho-position methyl ofthe oxygen atom for the first time, and a brand-new reaction strategy is provided for the preparation of a novel organic synthetic intermediate of organic ester borate.