Norbornene Derivatives Research Articles

Synthesis, Characterization and Radical Scavenging Ability of 3,5-di-tert-Butyl-4-hydroxyphenoxy-Functionalized Polynorbornenes Synthesized Using Ring-Opening Metathesis Polymerization

Novel norbornene derivatives bearing a 3,5-di-tert-butyl-4-hydroxyphenoxy (DBHO) group were synthesized and used as sterically hindered phenol functionalized norbornene monomers (1–4). The ring-opening metathesis polymerization (ROMP) of these functional monomers was carried out with a typical ruthenium catalyst (bis(tricyclohexylphosphine)benzylidene ruthenium (IV) dichloride, a Grubbs first-generation catalyst) to prepare sterically-hindered phenol-functionalized polymers possessing radical scavenging function. The resulting polymers bearing a DBHO side-chain were characterized by means of gel-permeation chromatography, 1H-NMR and 13C-NMR. The radical scavenging ability of polymers was determined using the α,α-diphenyl-β-picrylhydrazyl (DPPH⋅) free radical. Due to the electron-donating effect of the oxygen atom located in the para-position of phenol, the resulting polymers showed high efficiency to scavenge DPPH⋅free radical. The molecular weight of polymers was dependent on the molar ratio of monomer to catalyst ([M]/[C]), and the ROMP activity was dependent on the stereostructure of monomers themselves.

Synthesis of novel polymeric HALS stabilizers and chain transfer effect of hindered amine norbornene derivatives on ring-opening metathesis polymerization

Cyclooctadiene (COD) was polymerized via ring-opening metathesis polymerization (ROMP) in the presence of 5-norbornene-exo, endo-2-carboxylic acid 2,2,6,6-tetramethyl-4-piperidinyl ester (PN) or 5-norbornene-2-exo-3-endo-dicarboxylic acid bis(2,2,6,6-tetramethyl-4-piperidinyl) ester (2,3-PN) to prepare a new kind of polymeric hindered amine (HALS) stabilizers. Unexpectedly, hindered amine norbornene derivatives PN and 2,3-PN did not act as comonomer but acted as chain transfer agent (CTA). The resulting polymers were characterized by gel permeation chromatography (GPC) and 1H-NMR. Investigation of polymerization behavior showed that hindered amine groups were introduced into polymer chain by virtue of chain degradation resulted from chain transfer. The molecular weight (Mn) and HALS content of the resulting polymeric HALS stabilizer could be regulated by varying molar ratio of initial monomer to catalyst.

Large Amplitude, Proton- and Cation-Activated Latch-Type Mechanical Switches: O-Protonated Amides Stabilized by Intramolecular, Low-Barrier Hydrogen Bonds within Macrocycles

Large amplitude molecular switches have been developed using oxonium ions as the novel switching mechanism. Macrocycles that contain a polyether ring that are preorganized and of optimum geometry such that strong, linear Low-Barrier Hydrogen Bonds (LBHB, 2.4 to 2.6 A in length) are formed between a protonated amide oxygen and a cyclic ether, that lend significant iminol character to the amide. Deprotonation yields a large conformational change between closed and open forms, mindful of a new hinged, latch-type mechanical proton switch. Numerous open and closed forms have been characterized by X-ray crystallography, and the intramolecular hydrogen bond that forms between the protonated amide oxygen and the cyclic polyether oxygen accounts for the stability of these new acids. The open form of the deprotonated adducts persist in solution as indicated by the magnitude of coupling constants and other Nuclear Overhauser Effect experiments. Different saturated and unsaturated solid acids have been characterized including products derived from acetonitrile, propionitrile, caprylonitrile, acrylonitrile and adiponitrile, and also by reaction with primary amides in the case of phenyl and norbornene derivatives. We have also demonstrated that metal cations can replace the proton in the switching mechanism, characteristic of nascent synthetic pores.

Nanoporous Thin Films Based on Polylactide-Grafted Norbornene Copolymers

Thermally stable vinyl polymerized polynorbornene (PNB) is one of the challenging materials in porous low dielectric films for packaging applications. Nanoporous PNB thin films were obtained with poly(d,l-lactide) (PLA)-grafted norbornene copolymers. Thermally labile PLA chains act as pore generators in PNB films. Thermally stable PNB main chains were synthesized by Pd-catalyzed vinyl polymerization and PLA side chains were grafted onto the PNB main chains by ring opening polymerization. The brittle and poor processible properties of PNB could easily be controlled by the copolymerization with norbornene derivatives. In thin films, the PLA chains were found to thermally decompose at about 250 °C while the PNB matrix was stable during this pore generating process. The porosity of the porous PNB thin films could be controlled up to 18% with pore sizes below 5 nm range by varying the chain length of grafted PLA. Introduction of cross-linking epoxy groups onto the PNB main chains resulted in the formation of w...

Syntheses of Ester-Substituted Norbornyl Palladium Complexes Ligated with tBu3P: Studies on the Insertion of exo- and endo-Monomers in the Ester-Substituted Norbornene Polymerization

Exo- and endo-isomers of an ester-substituted norbornene derivative [5-norbornene carboxylic acid methyl ester (NBE)] are compared in the addition polymerization using tBu3P-ligated palladium compl...

Amphiphilic ABA triblock copolymers via combination of ROMP and ATRP in ionic liquid: Synthesis, characterization, and self-assembly

A new amphiphilic ABA triblock copolymer was synthesized by ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) in ionic liquid (IL). The bromo-terminated macroinitiator was prepared via ROMP of norbornene derivative, which is compatible with ionic liquid [bmim][BF 4], in conjunction with a chain transfer agent (CTA) in [bmim][BF 4]. ROMP with CTA in [bmim][BF 4] exhibited a different performance by changing the reaction conditions, and importantly there has been a good control over polymerization process and relatively low polydispersity index of polymer in [bmim][BF 4]. Based on the telechelic macroinitiator, the amphiphilic ABA triblock copolymer was synthesized by ATRP in [bmim][BF 4]. The prepared PDMAEMA–PNBEDE–PDMAEMA triblock copolymer can self-assemble spontaneously in H 2O to form polymeric micelles, which was characterized by DLS, AFM, and TEM.

Asymmetric Diels-Alder reactions of cyclopentadiene in the synthesis of chiral norbornene derivatives

The review discusses available data on asymmetric Diels-Alder reactions of cyclopentadiene, which were published in the past decade. Both noncatalytic and catalytic (in the presence of achiral and chiral catalysts) versions of these reactions are considered. Effects of various factors on the chemical and optical yields, stereoselectivity, and optical purity of the Diels-Alder adducts are analyzed. Prospects in the development of this field of organic chemistry are examined.

A novel asymmetric approach to a densely functionalized lactarane ring system through a domino ring opening–ring closing metathesis of a norbornene derivative

A novel route for the synthesis of a highly functionalized lactarane skeleton in enantiomerically pure form is described via ROM–RCM of an appropriately constructed norbornene derivative as the key step.

The Joy and Challenge of Small Rings Metathesis

Recent decades have seen a burgeoning of interest in olefin metathesis, as witnessed by a rapidly growing number of elegant applications. Using this tool, chemists can now efficiently synthesize an impressive range of molecules that only a decade ago required significantly longer and tedious routes.[1] Several types of olefin metathesis have been identified so far, among them ring-closing metathesis (RCM) and cross-metathesis (CM) being widely and successfully applied in the synthesis of biologically active complex compounds (Scheme 1). Ring closing metathesis occurs when a diene undergoes intramolecular metathesis affording a cyclic olefin. Analogous intramolecular reaction of an enyne is sometimes called enyne cycloisomerisation or enyne RCM.[2] Ring-closing metathesis reactions of dienes and enynes represent an attractive and powerful tool for formation of medium and large cycles (≥5 members). However, it is generally acknowledged that small rings (threeand four-membered) and strained cannot be formed by RCM.[3] In such cases, the ring opening process can be far more thermodynamically favourable than ring closing. Indeed, various strained molecules, such as norbornene derivatives, are well known substrates for ring-opening metathesis polymerization (ROMP) reactions (Scheme 1).[4]

Conductive Block Copolymers Integrated into Polynorbornene-Derived Scaffolds

The synthesis and electrochemical properties of novel block copolymers are reported. Three different norbornene derivatives having phenylene−thiophene, phenylene−bithiophene, and phenylene−furan structures were copolymerized with either norbornene or 7-oxanorbornene derivatives via ring-opening metathesis polymerization (ROMP). Block copolymers’ stabilities and solubilities could be improved by hydrogenation of double bonds in the polymer backbone. The block copolymers were subsequently cross-linked by anodic electropolymerization of phenylene−heterocycle moieties, affording conducting polymers. All of these three block copolymers were readily deposited on the electrode substrates, and their cyclic voltammograms (CVs) revealed an excellent reversibility in the redox cycles.

Synthesis of Chiral Porphyrins through Pd‐Catalyzed [3+2] Annulation and Heterochiral Self‐Assembly

Positive discrimination: Palladium-catalyzed [3+2] annulation of meso-bromoporphyrin with norbornene derivatives efficiently provides novel chiral meso,β-fused porphyrins with a rigid structure (as shown). A chiral benzoazanorbornene-fused zinc porphyrin assembles selectively to form the slipped cofacial dimer in a heterochiral association, which allows construction of a heterodimer from two porphyrin components through chiral discrimination. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z801269_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Polymers for nanolithography: A new strategy for design and synthesis of copolymers of maleimide, norbornene, and styrene derivatives with hexafluoroisopropanol and tert-butyl carbonate side groups

Polymers for nanolithography: A new strategy for design and synthesis of copolymers of maleimide, norbornene, and styrene derivatives with hexafluoroisopropanol and tert-butyl carbonate side groups

Nonconventional allylation of norbornene and norbornadiene derivatives: stoichiometry and catalysis

The key trends for the development of catalytic reactions of allyllic esters of carboxylic acids with norbornene, norbornadiene, and their heterocyclic analogs in the presence of the nickel and palladium complexes are discussed. The main approaches to investigation of the mechanism using model stoichiometric reactions and quantum chemical calculations are described.

Characterization of the micellar ring opening metathesis polymerization in water of a norbornene derivative initiated by Hoveyda‐Grubbs' catalyst

AbstractSolubilization of the hydrophobic Hoveyda‐Grubbs' catalyst in micellar aqueous phase has been achieved using dodecyl and cetyl ammonium chloride as surfactants. The domain of solubilization has been estimated before carrying out ring‐opening metathesis polymerization in these micellar solutions with a hydrophilic monomer. Kinetics orders have been determined relative to monomer, initiator, and surfactant. A good control of the molecular weight has been obtained for ratios [micelles]/[initiator] over 1. The better control of the polymerization obtained in micellar solution has been explained by a difference of reactivity leading to a more efficient initiation step in the presence of the micelles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2833–2844, 2008

Tandem [2+1] Cycloaddition-Ring Expansion of Bicyclic Alkenes with Tertiary Propargylic Acetates Catalyzed by Palladium(II)-Coordinated Phosphinous Acid

Palladium-SPO complex catalyzed the tandem [2+1] cycloaddition-ring expansion of norbornene derivatives with tertiary propargylic acetates to afford bicyclo[3.2.1]octadienes.

Bromination of norbornene derivatives: synthesis of brominated norbornanes and norbornenes

The low and high temperature bromination of 7-bromobicyclo[2.2.1]hept-2-ene and 2,7-dibromobicyclo[2.2.1]hept-2-ene were studied and the possible role of a neighboring group participation in rearrangements was investigated. The formation mechanism of the isomers as well as the role of the substituent on the rearrangement were discussed. The structure elucidation of the formed compounds was achieved by NMR spectral data; particularly, the γ- gauche effect was discussed in connection with the configuration of the bromine atoms.

SYNTHESIS OF NOVEL BI-FUNCTIONAL COPOLYMER BEARING STERICALLY HINDERED PHENOL AND HINDERED AMINE GROUPS VIA RING-OPENING METATHESIS POLYMERIZATION

Norbornene derivatives exo,endo-2-[2-(3,5-di-tert-butyl-4-hydroxyphenoxy)-acetoxy]methyl-5-norbornene (M1) and 3,3,5,5- etramethyl-4-piperidinyl 5-norbornene-exo,endo-2-carboxylate (M2) were synthesized and polymerized by RuCl2 (=CHPh)(PCy3)2 to prepare a novel kind of bi-functional polymer bearing sterically hindered phenol (SHP) and hindered amine (HLAS) groups via ring-opening metathesis polymerization (ROMP). The resulting copolymers were characterized by gel permeation chromatography (GPC), 1H-NMR and differential scanning calorimetry (DSC). The number average molecular weight (Mn) and functional unit content of the resulting copolymer could be regulated by varying the concentration of catalyst and monomer feed.

Controlled living ring-opening metathesis polymerization with a ruthenium indenylidene initiator

The novel initiator for living ring- opening metathesis polymerization (ROMP) [(H2IMes)(py)Cl2Ru(3-phenyl-indenylid-1-ene)] (H2IMes = N,N-bis(mesityl) 4,5-dihydroimidazol-2-yl, py = pyridine) was obtained by the reaction of [(H2IMes)(PCy3)Cl2Ru(3-phenyl-indenylid-1-ene)] with excess pyridine in excellent yield. The complex was fully characterized and the test polymerizations of several norbornene derivatives revealed the capability of the initiator to promote controlled living polymerization. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Penultimate effect in radical copolymerization of 2-trifluoromethylacrylates

Electron-deficient 2-trifluoromethylacrylates (TFMA) undergo radical copolymerization with electron-rich norbornene derivatives, vinyl ethers, and styrene derivatives, which can be described by the penultimate model much better than by the commonly employed terminal model. In an attempt to directly observe the effect of the CF3 group in the penultimate unit on the radical reactivity, we employed the Giese's mercury method. 4,4,4-Trifluorobutyl and n-butyl radicals produced from respective alkylmercuric chlorides were competitively reacted with t-butyl 2-trifluoromethylacrylate (TBTFMA) and t-butyl methacrylate (TBMA) and the products analyzed with gas chromatography. While TBTFMA has been found to be about 24times more reactive than TBMA toward the n-butyl radical, the former is about 12 times more reactive than the latter toward the 4,4,4-trifluorobutyl radical. Thus, the reactivity of the propagating radical toward TBTFMA in comparison with TBMA is suppressed by a factor of two when the penultimate unit has the CF3 group. We observed a sextet electron spin resonance of the TFMA propagating radical with a coupling constant of ca. 25 gauss between the β-proton and β-fluorine. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1559–1565, 2008

Rapid assembly of the functionalized tricyclic core of umbellactal through domino metathesis involving ROM-RCM of a norbornene derivative

A novel approach to the construction of the functionalized core structure of the anticancer diterpene umbellactal is described using a domino metathesis protocol involving ROM-RCM of an appropriately constructed norbornene derivative.