Synthesis and utilization of alternative chain transfer agent in cobalt catalyzed 1,3-butadiene polymerization reaction to produce cis-polybutadiene rubber

The cyclodimerization of 1,3-butadiene was performed to synthesize 1,5-cyclooctadiene by using nickel-phosphite based catalyst system. The optimization of cyclodimerization reaction was done to achieve up to 80% selectivity towards 1,5-cyclooctadiene. 1,5-Cyclooctadiene, thus synthesized, was subsequently employed as a chain transfer agent (CTA) for controlling the molecular weight (M.W.) of cis-polybutadiene rubber (BR) in cobalt-complex catalyzed 1,3-butadiene polymerization reaction. The M.W. of BR was reduced from 6.7 to 1.88 × 10⁵ g/mol by escalating the concentration of 1,5-cyclooctadiene from 0% to 0.5% with respect to 1,3-butadiene (monomer) concentration. Similar reducing trend was observed for the Mooney viscosity and gel content of BR with increasing 1,5-cyclooctadiene concentration. The efficacy of 1,5-cyclooctadiene as a CTA for 1,3-butadiene polymerization reaction was further explored by conducting polymerization reaction in various solvents and at higher monomer conversion (∼70%). The effect of 4-vinyl cyclohexene, which was a dominant byproduct during cyclodimerization of 1,3-butadiene, was also investigated. The presence of 4-vinyl cyclohexene has shown adverse effect in the polymerization reaction and was not functioning as a chain transfer agent. Finally, a feasibility of replacement of commercially used gaseous CTA, 1,2-butadiene, by in-house synthesized liquid CTA, 1,5-cyclooctadiene, was also investigated.     

Planar-to-planar chirality transfer in the excited state. Enantiodifferentiating photoisomerization of cyclooctenes sensitized by planar-chiral paracyclophane

Photochemical planar-to-planar chirality transfer was effected by using (R)-[10]paracyclophane-12-carboxylates as a planar-chiral sensitizer and (Z)-cyclooctene and (Z,Z)-1,5-cyclooctadiene as prochiral substrates to give a planar-chiral (E)- and (E,Z)-isomer in up to 44% and 87% enantiomeric excess, respectively, the latter of which being the highest ever reported for a sensitized photochirogenic reaction.     

Synthesis of 2,3-disubstituted benzofurans by platinum-olefin-catalyzed carboalkoxylation of o-alkynylphenyl acetals

The PtCl2-catalyzed cyclization reaction of o-alkynylphenyl acetals 1 in the presence of 1,5-cyclooctadiene produces 3-(alpha-alkoxyalkyl)benzofurans 2 in good to high yields. For example, the reaction of acetaldehyde ethyl 2-(1-octynyl)phenyl acetal (1a), acetaldehyde ethyl 2-(cyclohexylethynyl)phenyl acetal (1c), and acetaldehyde ethyl 2-(phenylethynyl)phenyl acetal (1f) in the presence of 2 mol % of platinum(II) chloride and 8 mol % of 1,5-cyclooctadiene in toluene at 30 degrees C gave the corresponding 2,3-disubstituted benzofurans 2a, 2c, and 2f in 91, 94, and 88% yields, respectively.     

Synthesis of 1,2,3-tripnictolide anions by reaction of group 15 Zintl ions with acetylene. Isolation of [E3C2H2](-) (E = P, As) and preliminary reactivity studies

Dimethylformamide solutions of K(3)E(7) (E = P, As) react with acetylene yielding the 1,2,3-tripnictolide anions [E(3)C(2)H(2)](-) (R = P (1), As (2)). Preliminary studies have shown that 1 and 2 displace labile ligands in [Ru(COD){η(3)-CH(3)C(CH(2))(2)}(2)] (COD = 1,5-cyclooctadiene) to yield the novel complexes [Ru(η(5)-E(3)C(2)H(2)){CH(3)C(CH(2))(2)}(2)}](-) (E = P (3), As (4)).     

A bifunctional monomer derived from lactide for toughening polylactide

(6S)-3-Methylene-6-methyl-1,4-dioxane-2,5-dione was synthesized from L-lactide and used as the dienophile to prepare spiro[6-methyl-1,4-dioxane-2,5-dione-3,2'-bicyclo[2.2.1]hept[5]ene] via an exoselective and diastereofacial-selective Diels-Alder reaction. Polymerizations of this bifunctional lactide derivative were successfully carried out under ring-opening and ring-opening metathesis polymerization conditions to yield high molecular weight and high Tg polymers. We further demonstrated that by incorporating a small percentage of spiro[6-methyl-1,4-dioxane-2,5-dione-3,2'-bicyclo[2.2.1]hept[5]ene] into poly(1,5-cyclooctadiene) and copolymerizing it with DL-lactide, novel polymeric alloys of PLA can be created that have tremendous improvements in toughness over PLA and the corresponding binary blend of PLA and poly(1,5-cyclooctadiene).     

Intermolecular hydroaminations via strained (E)-cycloalkenes

A photoinduced procedure for the intermolecular hydroamination of alkenes using azoles is described. This reaction occurs in modest to good yield for 6- and 7-membered cyclic alkenes. Upon irradiation at 254 nm in the presence of methyl benzoate and a small amount of triflic acid as an additive (20 mol %), imidazoles, pyrazoles, triazoles, and tetrazole can react with the alkene to afford complex Markovnikov adducts. The proposed mechanism involves photoisomerization to generate highly strained (E)-cycloalkene intermediates and (E)-cycloalkene protonation followed by reaction with the azole nucleophile. Alkene isomerization was found to be a competing side reaction under these conditions.     

Evidence for a reactive (alkene)peroxoiridium(III) intermediate in the oxidation of an alkene complex with O2

An (alkene)peroxoiridium(III) complex, [Ir(L)(cod)(O(2))] [where LH = PhN=C(NMe(2))NHPh and cod = 1,5-cyclooctadiene], was identified as an intermediate in the reaction of the Ir(I) precursor [Ir(L)(cod)] with O(2) and characterized by spectroscopic methods. Decay of the intermediate and further reaction with 1,5-cyclooctadiene produced 4-cycloocten-1-one.     

Enantioselective carbonyl propargylation by iridium-catalyzed transfer hydrogenative coupling of alcohols and propargyl chlorides

It takes alkynes! Exposure of propargyl chlorides to primary benzylic alcohols in the presence of [Ir(cod){(R)-segphos}]OTf (cod = 1,5-cyclooctadiene, segphos = 5,5'-bis(diphenylphosphino)-4,4'-bi-1,3-benzodioxole, Tf = trifluoromethanesulfonyl) results in hydrogen exchange to give allenyliridium-aldehyde pairs that combine to form products of propargylation with high ee?value (see scheme). The reaction can also be conducted using aldehydes.     

PEG-stabilized palladium nanoparticles： An efficient and recyclable catalyst for the selective hydrogenation of 1,5-cyclooctadiene in thermoregulated PEG biphase system

Polyethylene glycol （PEG）-stabilized palladium nanoparticles were prepared and applied to the selective hydrogenation of 1,5- cyclooctadiene （1,5-COD） in thermoregulated PEG biphase system, which allows a reaction in a single-phase at a higher temperature followed by a phase split at a lower temperature. Under the optimized reaction conditions, the conversion of 1,5-COD and the selectivity of cyclooctene （COE） were 100 and 98%, respectively. The catalyst could be easily separated from the product by phase separation and reused for 6 times without evident loss in activity and selectivity. 2007 Yan Hua Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Reactions of Trifluoromethylsulfenyl Chloride with 1,5-Cyclooctadiene

The reaction of 1,5-cyclooctadiene with F 3 CSCl at m 80;C has been examined and found to furnish both di- and tetrasubstituted adducts. Their mass spectra show the presence of the intact cyclooctyl ring. However, photolyis of a solution of 1,5-cyclooctadiene and F 3 CSCl in dry pentane yields addition, isomerization and dimerization as well as free radical products. The rationalization of the formation of the above products along with their mass spectral characterization is described in this communication.     

Synthesis and Characterization of a Bis(&mgr;-beta-diketonato)bis((1,2,5,6-eta)-1,5-dimethyl-1,5- cyclooctadiene)disilver Complex. An Intermediate in the Synthesis of an Isomerically Pure (beta-Diketonato)((1,2,5,6-eta)-1,5-dimethyl-1,5-cyclooctadiene)copper(I) Complex

Dimethyl-1,5-cyclooctadiene (DMCOD) is synthesized by the Ni-catalyzed dimerization of isoprene and consists of 80% 1,5-dimethyl-1,5-cyclooctadiene (1,5-DMCOD) and 20% 1,6-dimethyl-1,5-cyclooctadiene (1,6-DMCOD). Reaction of Hhfac (1,1,1,5,5,5-hexafluoro-2,4-pentanedione) with Ag(2)O in the presence of DMCOD results in the formation of isomeric Ag(I) species. Repeated recrystallizations yield an isomerically pure compound ((1,5-DMCOD)Ag(hfac))(2) that was characterized by X-ray crystallography and (1)H and (13)C NMR and IR spectroscopy. X-ray crystallography revealed a dinuclear complex with a short Ag-Ag spacing (3.0134(3) ? at -150 degrees C and 3.0278(5) ? at -20 degrees C) and bridging hfac ligands (&mgr;(2) bonding). The overall geometry around the Ag atoms is a deformed tetrahedron with two short Ag-O bonds (2.375 ? average) and two Ag-diene bonds. The methyl groups of the 1,5-DMCOD ligand are pointed toward the center of the molecule. Decomposition of the silver complex in a biphasic HCl (1 M)/CH(2)Cl(2) mixture liberates isomerially pure 1,5-DMCOD; this diene is subsequently used to synthesize isomerically pure (1,5-DMCOD)Cu(hfac). The latter compound was characterized by (1)H and (13)C NMR and IR spectroscopy and is a useful liquid precursor for Cu CVD. Crystallographic data: C(30)H(34)Ag(2)F(12)O(4), monoclinic, P2(1)/c (No. 14), Z = 4; at -150 degrees C, a = 12.428(1) ?, b = 11.071(1) ?, c = 24.520(2) ?, beta = 101.98(1) degrees; at -20 degrees C, a = 12.597(1) ?, b = 11.191(1) ?, c = 24.641(2) ?, beta = 102.08(1) degrees.     

Elektrochemische synthesen metallorganischer verbindungen III. Darstellung und umwandlung von π-cyclooctenyl-1,5-cyclooctadiencobalt

By electrolysis of cobalt(II)-acetylacetonate in the presence of 1,5-cyclooctadiene there is obtained π-cyclooctenyl-1,5-cyclooctadienecobalt (I). By heating of I to 60° in 1,5-cyclooctadiene, π-bicyclo[3.3.0]octadienyl-(1,5-cyclooctadiene)cobalt (II) and cyclooctene are formed.     

磷化氢与环烯烃反应的原位^3^1P NMR研究

本文应用加压原位核磁共振波谱技术, 在反应温度50-70℃、反应压力1.0-2.0MPa, 氘代苯为溶剂, 偶氮二异丁腈为引发剂的条件下, 考察了磷化氢与环烯烃1, 5-环辛二烯、双环戊二烯、1, 3-环己二烯、1, 4-环己二烯及1, 5, 9-环十二三烯的反应。实验结果表明, 磷化氢与1, 5-环辛二烯反应主要生成双环膦杂环壬烷; 与其它环烯烃均不生成膦杂环化合物, 仅为一取代伯膦或二取代仲膦产物。磷化氢与环烯烃反应仍为串行机理。     

When is a nanoparticle a cluster? An operando EXAFS study of amine borane dehydrocoupling by Rh(4-6) clusters

X-ray absorption fine structure (XAFS) is used to determine the structure of the rhodium cluster present during the catalyzed dehydrocoupling of amine boranes under operando conditions. We show how a variety of XAFS strategies can be used in combination with other analytical methods to differentiate homogeneous from heterogeneous systems. Analysis of the in situ XAFS spectra using a series of amine boranes (NH3BH3, R2NHBH3, and RNH2BH3 where R = methyl, isopropyl, tert-butyl, and cyclohexyl) and rhodium catalyst precursor compounds (including chloro-(1,5-cyclooctadiene)rhodium (I) dimer, bis(1,5-cyclooctadiene)rhodium (I) trifluoromethanesulfonate, chlorodicarbonylrhodium (I) dimer, dichloro(pentamethylcylcopentadienyl)rhodium (III) dimer, hexarhodium hexadecacarbonyl, and tetrarhodium dodecacarbonyl) strongly suggest that the active catalyst species for this reaction is a homogeneous rhodium complex. Rhodium clusters containing four or six rhodium atoms (Rh(4-6)) bound to amine boranes are observed as the major (>99%) rhodium containing species during and after the catalyzed anaerobic dehydrocoupling. During the later stages of the reaction a nonmetallic rhodium complex precipitates in which individual Rh(4-6) clusters likely form polymer chains ligated by the reaction products that have two or more ligating sites. The best fits of the XAFS data, using ab initio calculations of FEFF theory, show that the major rhodium species (80%) has each rhodium atom directly bound to three rhodium atoms with an observed bond distance of 2.73 A and to two boron atoms at 2.10 A. A minor (20%) rhodium species has each rhodium atom bound to four rhodium atoms with a bond distance of about 2.73 A and a single rhodium atom at a nonbonding distance of 3.88 A. No metallic rhodium was observed at any time during the anaerobic reaction.     

Enantiomerically pure rhodium complexes bearing 1,5-diphenyl-1,5-cyclooctadiene as a chiral diene ligand. Their use as catalysts for asymmetric 1,4-addition of phenylzinc chloride

[reaction and structures: see text] A rhodium complex coordinated with 1,5-diphenyl-1,5-cyclooctadiene (Ph-cod), [RhCl((R)-Ph-cod)]2, was obtained enantiomerically pure through optical resolution of diastereomeric isomers [Rh(Ph-cod)((R)-1,1'-binaphthyl-2,2'-diamine)]BF4. The enantiomerically pure rhodium complexes showed high catalytic activity and enantioselectivity (up to 98% ee) in the asymmetric 1,4-addition of phenylzinc chloride to alpha,beta-unsaturated ketones and esters in the presence of chlorotrimethylsilane.     

Pt(0) and Pd(0) olefin complexes of the metalloid N-heterocyclic carbene analogues [E(I)(ddp)] (ddp=2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino}-2-pentene; E=Al, Ga): ligand substitution, H--H and Si--H bond activation, and cluster formation

Various products of the reaction of [E(ddp)] (ddp=2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino}-2-pentene; E=Al, Ga) with Pt(0) and Pd(0) olefin complexes are reported. Thus, the reaction of [Pt(cod)(2)] (cod=1,5-cyclooctadiene) with two equivalents of [Ga(ddp)] yields [Pt(1,3-cod){Ga(ddp)}(2)] (1), whereas treatment of [Pd(2)(dvds)(3)] (dvds=1,1,3,3-tetramethyl1,3-divinyldisiloxane) with [E(ddp)] leads to the monomeric compounds [(dvds)Pd{E(ddp)}] (E=Ga (2 a), Al (2 b)) by substitution of the bridging dvds ligand. Both 1 and 2 a readily react with strong pi-acceptor ligands such as CO or tBuNC to give the dimeric compounds [M{mu(2)-Ga(ddp)}(L)] (L=CO, tBuNC; M=Pt (3 a, 5 a), Pd (3 b, 5 b)), respectively. Based on (1)H NMR spectroscopic data, [Pt{Ga(ddp)}(2)(CO)] is likely to be an intermediate in the formation of 3 a. Furthermore, reactions of 1 with H(2) and HSiEt(3) yield the monomeric compounds [Pt{Ga(ddp)}(2)(H)(2)] (7) and [Pt{Ga(ddp)}(2)(H)(SiEt(3))] (8). Finally, the reaction of [Pt(cod)(2)] with one equivalent of [Ga(ddp)] in the presence of H(2) in hexane gives the new dimeric cluster [Pt{mu(2)-Ga(ddp)}(H)(2)](2) (9).     

Cyclic homo- and cooligomerization of 2-cyclopropylbutadiene with 1,3-dienes

Conclusions We were the first to study the cyclic homo- and cooligomerization of 2-cyclopropyl-1,3-butadiene with butadiene and isoprene in the presence of catalysts based on nickel. The conditions were found for obtaining 1,5-dicyclopropyl-1,5-cyclooctadiene, 1-cyclopropyl-1,5-cyclooctadiene, 1-cyclopropyl-5-methyl-1,5-cyclooctadiene, and 1-cyclopropyl-5,9 (8)-dimethyl-1,5,9-cyclododecatriene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2634–2636, November, 1979.     

Carbon-13 nuclear magnetic resonance spectra and conformations of cis,cis-1,5-cyclooctadiene monoepoxide and cis,syn,cis-1,5-cyclooctadiene diepoxide

The natural-abundance ¹³C NMR spectra of cis,cis-1,5-cyclooctadiene monoepoxide and cis,syn,cis-1,5-cyclooctadiene diepoxide have been investigated over the temperature range of – 10 to – 180°C. Whereas the spectra of the former showed no dynamic NMR effect, two different conformations in the ratio of 3:1 were observed at low temperatures for the latter. The free-energy barrier (ΔG^≠) for conversion of the major conformation to the minor conformation is calculated to be 5.9°0.2 kcal mol^?1 from a line-shape analysis of spectra obtained at intermediate temperatures. It is shown that cis,syn,cis-1,5-cyclooctadiene diepoxide exists in solution in chair (major) and in twist-boat (minor) conformations of slightly different energies. Interconversion paths between these conformations are discussed. The monoepoxide is suggested to have a twist-boat conformation that is rapidly pseudorotating via a boat conformation even at – 180°C.     

Chimie organométallique: IV. Réversibilité de l'amination des complexes diènes-palladium (II)

An elimination reaction takes place with palladium compounds arising from the reaction of benzylamine with 1,5-cyclooctadiene—PdCl₂ (IV) and 1,5-hexadiene—PdCl₂ (VI) complexes. Evidence for this retroamination reaction is given by the reaction of hydrogen chloride on the cyclooctadiene derivative (V) and by a study of the products resulting from the amination of the hexadiene complex (VI) under various conditions.     

Direct in situ synthesis of cationic N-heterocyclic carbene iridium and rhodium complexes from neat ionic liquid: Application in catalytic dehydrogenation of cyclooctadiene

A direct synthetic route to cationic N-heterocyclic carbene (NHC) complexes of rhodium and iridium from neat dialkyl-imidazolium ionic liquids (ILs) has been found. The method uses complexes bearing basic anionic ligands, [M(COD)(PPh₃)X], X = OEt, MeCO₂, which react with the inactivated imidazolium cation in the absence of external bases yielding one M-NHC moiety and the free protonated base. This new one-pot synthesis leaving pure, catalytically active IL solutions is faster, cleaner and more efficient than traditional syntheses of such NHC complexes. The observed reactivity also gives insight into NHC incorporation of rhodium and iridium catalyzed reactions performed in common dialkyl-imidazolium ILs.The complexes synthesised in this manner are compared with their bis-phosphine analogues in terms of activity for catalytic dehydrogenation of 1,5-cyclooctadiene and 1,3-cyclooctadiene in neat [BMIM][NTf₂] as solvent. Even at high temperature, no ligand exchange reaction is observed with [(COD)M(PPh₃)₂] [NTf₂] catalysts. As expected, the yields of all the reactions were low, iridium was much more active in C-H activation than rhodium and the NHC ligands were more stable than triphenylphosphine. For all catalysts, the isomerisation of 1,5-cyclooctadiene is the major reaction. However, the phosphine-NHC complex of iridium seems to be more selective for dehydrogenation than its bis-phosphine counterpart, which is more active in transfer-hydrogenation and less stable under the applied conditions. Different reaction conditions were tried in order to optimise selectivity for dehydrogenation over isomerisation and transfer-hydrogenation. Surprisingly, with 1,3-cyclooctadiene as substrate selectivity for dehydrogenation is much higher than with 1,5-cyclooctadiene for all catalysts.