- (Z)-(E) Interconversion of Olefins by the Addition-Elimination Sequence of the (TMS)3Si(.) Radical
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Tris(trimethylsilyl) radical is effective inisomerizing either acyclic or cyclic olefins by an addition-elimination sequence.The E/Z ratio after equilibration generally reflects the thermodynamic stability of (Z)- and (E)-alkenes.It has been shown for (E)- and (Z)-hexen-1-ol that equilibration (Z/E = 18/82) is reached with the (TMS)3Si(.) radical in 10 h at 80 deg C, whereas with PhS(.) and Bu3Sn(.) radicals the same isomeric composition is reached in 1 and 4 h, respectively.In cyclic systems like (Z)-cyclododecene the ratio of Z/E = 46/54 is reached in 8 h, while with PhS(.) and Bu3Sn(.) it is much slower.An explanation of this phenomenon has been advanced.Additional information on the impact of this addition-elimination methodology in organic synthesis is given.
- Chatgilialoglu, C.,Ballestri, M.,Ferreri, C.,Vecchi, D.
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- The crystal structure of (η6-C6Me6)Ti2 and the catalytic activity of the (C6Me6)TiAl2Cl8-xEtx (x = 0-4) complexes towards butadiene
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The composition of (C6Me6)TiAl2Cl8-xEtx complexes in (C6Me6)TiAl2Cl8 + n Et3Al (n = 0.5-6) systems was studied by UV-Vis spectroscopy and the X-ray crystal structure of one of them, (η6-C6Me6)Ti2 (IIa-2), has been determined.The complex crystallizes in the orthorhombic space group Pna21 with Z = 4 and lattice parameters a 15.634(3), b 11.355(2), c 14.417(a) Angstroem.The ethyl groups of IIa-2 reside in outer positions of aluminate ligands farther away from the C6Me6 ligand.The other part of the complex does not differ remarkably from structures of other (arene)TiII complexes.Negligible activity of (C6Me6)TiAl2Cl8 towards the butadiene cyclotrimerization is considerably increased by addition of 2.5-3.0 equivalents of Et3Al.As follows from UV-Vis spectra, such systems contain mainly the (C6Me6)TiAl2Cl5Et3 complex.It is suggested that the introduction of three Et substituents destabilizes the Ti-(η6-C6Me6) bond so that the replacement of hexamethylbenzene by butadiene in the first step of a catalytic cycle becomes more feasible.
- Troyanov, Sergei I.,Polacek, Jindrich,Antropiusova, Helena,Mach, Karel
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- 16-Electron Nickel(0)-Olefin Complexes in Low-Temperature C(sp2)-C(sp3) Kumada Cross-Couplings
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Investigations into the mechanism of the low-temperature C(sp2)-C(sp3) Kumada cross-coupling catalyzed by highly reduced nickel-olefin-lithium complexes revealed that 16-electron tris(olefin)nickel(0) complexes are competent catalysts for this transformation. A survey of various nickel(0)-olefin complexes identified Ni(nor)3as an active catalyst, with performance comparable to that of the previously described Ni-olefin-lithium precatalyst. We demonstrate that Ni(nor)3, however, is unable to undergo oxidative addition to the corresponding C(sp2)-Br bond at low temperatures (a nickel(0)-alkylmagnesium complex. We demonstrate that this unique heterobimetallic complex is now primed for reactivity, thus cleaving the C(sp2)-Br bond and ultimately delivering the C(sp2)-C(sp3) bond in high yields.
- Lutz, Sigrid,Nattmann, Lukas,N?thling, Nils,Cornella, Josep
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supporting information
p. 2220 - 2230
(2021/05/07)
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- Studies on partial hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene
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The selective hydrogenation of 1,5,9-cis,trans,trans-cyclo-dodecatriene (1,5,9-ctt-CDT) towards cyclo-dodecene (CDE) depends strongly on the pressure of hydrogen, respectively the hydrogenation rate. High yields of CDE (>90%) can only be reached at extremely low hydrogen pressure. In order to elucidate this exceptional reaction performance the course of reaction has been studied for a wide range of hydrogen pressure, 0.01>pH2>2.5MPa, taking into consideration data of other research groups. The CDT hydrogenations were discontinuously carried out in liquid phase on Pd/Al2O3 at T = 353 K. The resulting hypothesis of this study is that the very low reaction rate at low pH2 is necessary in order to realize a dense surface coverage of 1,5,9-CDT and 1,5-cyclo-dodecadiene (CDD) isomers where these molecules show adsorption on Pd via two double bonds so that readsorption of formed CDE and subsequent hydrogenation to cyclo-dodecane (CDA) is hardly possible. On the whole this new hypothesis on the reaction course of CDT hydrogenation gives a sound and fully consistent view on this rather complicated reaction.
- Gaube,David,Sanchayan,Wuchter,Klein
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experimental part
p. 21 - 27
(2012/02/15)
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- Indenylidene complexes of ruthenium bearing NHC ligands - structure elucidation and performance as catalysts for olefin metathesis
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Second-generation catalysts of the general formula Cl2Ru-(SIMes) (L)(3-phenylinden-1-ylidene), 3a (L = PCy3), 3b (L =PPh3), 3c (L = py), and Cl2Ru(SIMe)(L)(3-phenylinden-1-yl-idene), 4a (L = PCy 3), 4b (L = PPh
- Monsaert, Stijn,De Canck, Els,Drozdzak, Renata,Van Voort, Pascal Der,Verpoort, Francis,Martins, Jose C.,Hendrickx, Pieter M. S.
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scheme or table
p. 655 - 665
(2009/07/17)
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- Synthesis of (14C6-3,4,7,8,11,12)-(1E,5E,9E)- cyclododeca-1,5,9-triene
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Trimerization of butadiene in the presence of Ni(0) affords (1E,5E,9E)-cyclododeca-1,5,9-triene 1 (ttt-CDT), (1E,5E,9Z)-cyclododeca-1,5,9- triene 2 (ttc-CDT), and other isomers/oligomers. After optimization of reaction conditions, [14C6-3,4,7,8,11,12]-ttt-CDT 1 was synthesized efficiently either by homogenous or heterogeneous Ni(0) catalytic trimerization of [1,4-14C2]butadiene 10, in 60-82% yield. Depending on the exact reaction conditions employed, the yields and ratio of 1/2 ranged from (59-90%) / (41-10%). The all-trans isomer was conveniently isolated via Ag +-mediated reversed-phase HPLC. The important intermediate [1,4- 14C2]-1,3-butadiene 10 was prepared from potassium [ 14C]cyanide and 1,2-dibromoethane 3 as starting materials, in seven steps with a 57% yield. The total radioactive yield of [14C 6-3,4,7,8,11,12]-ttt-CDT 1 is 30% from [14C]KCN. Copyright
- Diel, Bruce N.,Han, Mingcheng,White, Jonathan M.
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p. 407 - 409
(2008/02/08)
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- Nickel(0) and palladium(0) complexes with 1,3,5-triaza-7-phosphaadamantane. Catalysis of buta-1,3-diene oligomerization or telomerization in an aqueous biphasic system
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New homoleptic nickel(0) and palladium(0) complexes with a water-soluble ligand, 1,3,5-triaza-7-phosphaadamantane, were prepared and characterized by 1H, 13C, and 31P NMR spectra. The complexes, together with the known ana
- Cermak, Jan,Kvicalova, Magdalena,Blechta, Vratislav
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p. 355 - 363
(2007/10/03)
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- Titanium-catalyzed [4+2] and [6+2] cycloadditions of 1,4-bis(trimethylsilyl)buta-1,3-diyne
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The (C2H5)2AlCl/TiCl4 catalyst induces the [4+2] cycloaddition of butadiene or the [6+2] cycloaddition of 1,3,5-cycloheptatriene (CHT) to individual acetylenic moieties of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD). Heating of the 2:1 butadiene adduct, bis(2-trimethylsilylcyclohexa-1,4-dien-1-yl), to 250°C yields 2,2′-bis(trimethylsilyl)biphenyl. The 1:1 adduct of BSD with CHT, 7-trimethylsilyl-8-trimethylsilylethynylbicyclo[4.2.1]nona-2,4-diene, is obtained as virtually the only product if the initial molar ratio CHT:BD equal to 1.86 is used.
- Kaagman, Jan-Willem F.,Rep, Marco,Horacek, Michal,Sedmera, Petr,Cejka, Jiri,Varga, Vojtech,Mach, Karel
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p. 1722 - 1728
(2007/10/03)
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- Interaction of vinylpyridines with 1,3-dienes catalyzed by transition metal complexes
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The linear and cyclic cooligomerization of 2-vinyl-, 2-methyl-5-vinyl-, and 4-vinylpyridines with 1,3-dienes and trienes catalyzed by complexes of transition metals (Fe, Co, Ni, Mn, Cr, Pd, Ru, Rh, and Zr) was carried out to give unsaturated pyridines containing alkenyl and cycloalkenyl substituents.
- Selimov, F. A.,Ptashko, O. A.,Fatykhov, A. A.,Khalikova, N. R.,Dzhemilev, U. M.
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p. 872 - 878
(2007/10/02)
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- EFFECT OF TRIPHENYLPHOSPHINE ON THE CYCLOTRIMERIZATION OF BUTADIENE CATALYZED BY THE TiCl4-EtAlCl2 SYSTEM
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Addition of PPh3 to the TiCl4 + n EtAlCl2 (n = 4-10) systems, which normally exhibit mostly Friedel-Crafts and polymerization activity towards butadiene, turns these systems into highly specific catalysts for the cyclotrimerization of butadiene to (Z, E, E)-1,5,9-cyclododecatriene.The effect of PPh3 lies in removal of AlCl3, which is formed in the reduction of TiCl4 with EtAlCl2 and in the disproportionation of EtAlCl2, for the AlCl3.PPh3 complex displays higher stability in comparison with the analogous complexes with ethylaluminium chlorides.The composition of the (η6-benzene)Ti(II) complexes, which are the catalytically active species, was determined by electronic absorption spectroscopy in the post-reaction mixtures.
- Polacek, Jindrich,Antropiusova, Helena,Petrusova, Lidmila,Mach, Karel
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p. 1756 - 1762
(2007/10/02)
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- THE INFLUENCE OF ALKALI METAL HALIDES ON THE BUTADIENE CYCLOTRIMERIZATION CATALYZED BY (BENZENE)TITANIUM(II) COMPLEXES
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Addition of alkali chlorides (MCl) to (η6-C6H6)Ti(AlCl4)2 (Ia) decreases the catalytic activity of Ia while the selectivity of the (Z,E,E)-1,5,9-cyclododecatriene formation is improved only when NaCl is used at the optimum molar ratio NaCl/Ia ca 5.The alkali chlorides remove free AlCl3, which is present in the system as an admixture, probably in the form of MAlCl4 complexes; however, an excess of MCl brings about decomposition of catalytic trinuclear Ti(II) complexes during the butadiene cyclotrimerization.In addition to inactive TiCl2, this decomposition yields some AlCl3 which induces the formation of cationic byproducts, 1-phenylbut-2-ene and (E)-1,4-poly(butadiene), before it is deactivated or quenched with MCl.
- Polacek, Jindrich,Petrusova, Lidmila,Antropiusova, Helena,Mach, Karel
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p. 1839 - 1845
(2007/10/02)
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- Polymer supported 2,2'-dipyridylmethane: catalytic activity of transition metal complexes in hydrogenations and oligomerizations
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The palladium(II) acetate complex of the chelating ligand 2,2'-dipyridylmethane supported on polystyrene-2percent divinylbenzene is an efficient catalyst for hydrogenation of alkenes and alkynes.Cyclopentadiene can be reduced with high selectivity to cyclopentene, but no selectivity is observed for the non-conjugated diene 1,5-cyclooctadiene.In the hydrogenation of 3-methylcyclohex-2-en-1-ol only small amounts of ketone are formed as a by-product, in contrast to the reaction catalysed by palladium on charcoal.Nickel(II) complexes of the same ligand catalyze the trimerization of butadiene to 1,5,9-cyclododecatrienes.
- Moberg, Christina,Rakos, Laszlo
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p. 125 - 132
(2007/10/02)
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- THERMAL CONVERSION OF 1,5,9-TRIYNES. CYCLOADDITIONS OR SIGMATROPIC SHIFTS?
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The gas phase pyrolyses of variously labeled 1,5,9-decatriynes (1) and 1,5,9-cyclododecatriynes (2) were investigated to determine possible modes of thermal isomerizations.Conditions included temperatures in the range 400-600 deg C, pressures of 40 -10E-4 Torr, and contact times of ca 1 ms to 15 s.The labeling patterns in 1 and 2 were chosen such as to be able to distinguish direct intramolecular cycloadditions of the alkyne units to form an aromatic ring (perhaps with subsequent rearrangements), and sigmatropic shifts of the 1,5-diyne moieties.Methods for synthesizing the isotopically (particularly (13)C) labeled triynes were devised and implemented.The route to 5,6-(13)C2-1,5,9-decatriyne (1c) made use of a new procedure for the synthesis of symmetrically disubstituted alkynes involving coupling between two equivalents of an alkyl copper reagent and diiodoacetylene-(13)C2.The synthesis of 1,10-(13)C2-1,5,9-cyclododecatriyne (2b) was accomplished starting with K(13)CN, elaboration to labeled diethyl succinate, a crucial bis-Wittig condensation to labeled 1,5,9-cyclododecatriene 10, and bromination-dehydrobromination of the latter (NaOH-ethylene glycol).Products from the pyrolysis of unlabeled 1a included dicyclobutabenzene, naphtalene and 3,4-dimethylidene-1-(but-3-ynyl)cyclobutene.Pyrolysis of 1b gave 3,6-dideuteriodicyclobutabenzene and partially deuterated naphthalene, that of 1c produced 1,2-(13)C2-dicyclobutabenzene and 9,10-(13)C2-naphthalene.While the pyrolysis of 2a resulted in hexamethylidenecyclohexane (hexaradialene), 2b furnished 1,4-(13)C2-hexaradialene.The results rule out the occurence of cycloadditions of the alkyne units, but are consistent with the intervention of a series sigmatropic shifts which connect starting materials with products.
- Dower, William V.,Vollhardt, K. Peter C.
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p. 1873 - 1882
(2007/10/02)
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- Use of Functionalized Ethylene Oligomers To Prepare Recoverable, Recyclable Nickel(0) Diene Cyclooligomerization Catalysts
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Polyethylene-bound alkyl diaryl and triaryl phosphites that act as ligands for homogeneous nickel (0) butadiene cyclooligomerization catalysts are described.The homogeneous nickel (0) catalysts prepared in the presence of these ligands are shown to have the same product selectivity and reactivity as similar nickel catalysts prepared from low molecular weight phosphite ligands in reactions carried out at 100 deg C.By varying the ligand/nickel ratio, it is possible to vary the product selectivity of these polyethylene-bound nickel(0) catalysts.High product selectivities (>90percent) for 1,5-cyclooctadiene are attainable.These ethylene oligomer ligated nickel(0) catalysts take advantage of the temperature-dependent solubility properties of polyethylene in order to maintain catalyst homogeneity at 100 deg C during the oligomerization.Recovery and recycling of the catalyst is possible because the catalyst and polyethylene quantitatively coprecipitate on cooling the reaction mixture to 25 deg C.
- Bergbreiter, David E.,Chandran, Rama
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p. 4754 - 4760
(2007/10/02)
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- STRAINED CYCLOALKENYNES
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Presently known strained cycloalkynes with one, two or three additional cis- or trans-configurated double bonds are summarized in Table 3.The main topics of the article are the geometrical ring strain, the preparation or in situ generation of these compounds by fragmentation of the corresponding 1,2,3-selendiazoles, and the thermal isomerisation processes performed at room temperature or in flash pyrolysis experiments at 440-640 deg C.
- Meier, Herbert,Hanold, Norbert,Molz, Thomas,Bissinger, Hans Joachim,Kolshorn, Heinz,Zountsas, Johannes
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p. 1711 - 1720
(2007/10/02)
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- TITANIUM-CATALYZED DIELS-ALDER CYCLOADDITION OF CONJUGATED DIENES TO BIS(TRIMETHYLSILYL)ACETYLENE. 1,2-BIS(TRIMETHYLSILYL)CYCLOHEXA-1,4-DIENE, 1,2-BIS(TRIMETHYLSILYL)BENZENE, AND THEIR METHYL DERIVATIVES
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The catalytic system Et2AlCl/TiCl4 induces Diels-Alder cycloaddition of bis(trimethylsilyl)acetylene to 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and (E)-1,3-pentadiene affording 1,2-bis(trimethylsilyl)cyclohexa-1,4-dienes in high yields.The cyclohexadienes are readily converted to the corresponding 1,2-bis(trimethylsilyl)benzenes upon heating to 240 deg C.Mass, infrared, 1H, 13C and 29Si NMR spectra of all the products obtained are reported and briefly discussed.The crowded character of aromatic compounds is reflected in their mass, 13C and 29Si NMR spectra.
- Mach, K.,Antropiusova, H.,Petrusova, L.,Turecek, F.,Hanus, V.,et al.
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p. 331 - 340
(2007/10/02)
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- Polyethylene-entrapped Nickel(0) Diene Cyclo-oligomerization Catalysts
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The use of precipitates of polyethylene as a matrix quantitatively to entrap and recover selective homogeneous Ni(0) diene cyclo-oligomerization catalysts complexed by ligands composed of ethylene oligomers containing dialkylphosphito and diarylphosphito
- Bergbreiter, David E.,Chandran, Rama
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p. 1396 - 1397
(2007/10/02)
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- Multi Electron Ligands, VIII. Connection of the all-trans-1,5,9-Cyclododecatriene System with Additional Donor Groups
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Nine potential ligands (2 - 10) for transition metals were obtained from the well accessible all-trans-1,5,9-cyclododecatriene (ttt-CDT) by introduction of donor groups.The synthesis was achieved via ttt-3-bromo-CDT (1) and the hitherto unknown ttt-3-iodo-CDT (2).To the contrary, introduction of donor groups via nucleophilic ttt-CDT derivatives was successful in one case only (15). ttt-3-Lithio-CDT (13), obtained by organoelement-Li exchange, revealed to be extremely basic (quick deprotonation of diethyl ether at low temperature).In situ made Ni0 complexes of someof the new ligands failed to oligomerize or polymerize butadiene.
- Kauffmann, Thomas,Fauss, Waltraud
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p. 2330 - 2342
(2007/10/02)
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- CYCLOADDITIONS CATALYZED BY TITANIUM COMPLEXES
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The Ziegler catalyst TiCl4-Et2AlCl and the arenetitanium(II) complex (η6-C6H6)Ti(II)(AlCl4)2 induce cycloaddition reactions of cycloheptatriene with dienes and acetylenes.Addition to 1,3-butadiene affords 7-endo-vinyl-bicyclonona-2,4-diene (main product) and bicyclo-undeca-2,4,8-triene, a product of cycloaddition.Isoprene reacts similarly, yielding mainly 7-endo-isopropenyl-bicylonona-2,4-diene. 2,3-Dimethyl-1,3-butadiene gives 8,9-dimethylbicycloundeca-2,4,8-triene, a product of cycloaddition, while cross-adducts are minor products.The reaction of cycloheptatriene with norbornadiene gives mainly hexacyclo2.7.03.12.06.10.09.13>tetradec-4-ene via cycloaddition followed by intramolecular Diels-Alder reaction.As a by-product, pentacyclo2.7.03.5.04.8>tetradeca-10,12-diene is formed by a mechanism.Addition of cycloheptatriene to phenylacetylene and bis-(trimethylsilyl)acetylene furnishes substituted bicyclonona-2,4,7-trienes.Alkenes, E,E-2,4-hexadiene and 1,3-cyclooctadiene are unreactive.The cycloaddition is made possible by coordination of cycloheptatriene to titanium, which changes the symmetry of the frontier orbitals in the triene.The reactivity of the trienophile is also enhanced by coordination to the catalyst.
- Mach, Karel,Antropiusova, Helena,Petrusova, Lidmila,Hanus, Vladimir,Turecek, Frantisek,Sedmera, Petr
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p. 3295 - 3302
(2007/10/02)
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- ?6s + ?2s> Cyloadditions Catalysed by the TiCl4-Et2AlCl System
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The catalyst system TiCl4-Et2AlCl induces ?6s + ?2s> cycloadditions of cycloheptatriene to buta-1,3-diene, norbornadiene, and acetylenes.
- Mach, Karel,Antropiusova, Helena,Sedmera, Petr,Hanus, Vladimir,Turecek, Frantisek
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p. 805 - 806
(2007/10/02)
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- CIS-TRIS--?-HOMOBENZENE - SYNTHESIS AND THERMOLYSIS
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The cis-tris--?-homobenzene 7 has been synthesised.From vapour phase thermolyses (400-500 deg C) it is concluded, that the ?2s+?2s+?2s>-cycloreversion reaction is - at most - only a minor pathway in the thermal stabilisation of 7.
- Maas, M.,Lutterbeck, M.,Hunkler, D.,Prinzbach, H.
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p. 2143 - 2146
(2007/10/02)
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