676-22-2Relevant academic research and scientific papers
(Z)-(E) Interconversion of Olefins by the Addition-Elimination Sequence of the (TMS)3Si(.) Radical
Chatgilialoglu, C.,Ballestri, M.,Ferreri, C.,Vecchi, D.
, p. 3826 - 3831 (1995)
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.
The crystal structure of (η6-C6Me6)Ti2 and the catalytic activity of the (C6Me6)TiAl2Cl8-xEtx (x = 0-4) complexes towards butadiene
Troyanov, Sergei I.,Polacek, Jindrich,Antropiusova, Helena,Mach, Karel
, p. 317 - 325 (1992)
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.
16-Electron Nickel(0)-Olefin Complexes in Low-Temperature C(sp2)-C(sp3) Kumada Cross-Couplings
Lutz, Sigrid,Nattmann, Lukas,N?thling, Nils,Cornella, Josep
supporting information, p. 2220 - 2230 (2021/05/07)
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.
Studies on partial hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene
Gaube,David,Sanchayan,Wuchter,Klein
experimental part, p. 21 - 27 (2012/02/15)
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.
Indenylidene complexes of ruthenium bearing NHC ligands - structure elucidation and performance as catalysts for olefin metathesis
Monsaert, Stijn,De Canck, Els,Drozdzak, Renata,Van Voort, Pascal Der,Verpoort, Francis,Martins, Jose C.,Hendrickx, Pieter M. S.
scheme or table, p. 655 - 665 (2009/07/17)
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
Synthesis of (14C6-3,4,7,8,11,12)-(1E,5E,9E)- cyclododeca-1,5,9-triene
Diel, Bruce N.,Han, Mingcheng,White, Jonathan M.
, p. 407 - 409 (2008/02/08)
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
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
Cermak, Jan,Kvicalova, Magdalena,Blechta, Vratislav
, p. 355 - 363 (2007/10/03)
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
Titanium-catalyzed [4+2] and [6+2] cycloadditions of 1,4-bis(trimethylsilyl)buta-1,3-diyne
Kaagman, Jan-Willem F.,Rep, Marco,Horacek, Michal,Sedmera, Petr,Cejka, Jiri,Varga, Vojtech,Mach, Karel
, p. 1722 - 1728 (2007/10/03)
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.
Interaction of vinylpyridines with 1,3-dienes catalyzed by transition metal complexes
Selimov, F. A.,Ptashko, O. A.,Fatykhov, A. A.,Khalikova, N. R.,Dzhemilev, U. M.
, p. 872 - 878 (2007/10/02)
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.
EFFECT OF TRIPHENYLPHOSPHINE ON THE CYCLOTRIMERIZATION OF BUTADIENE CATALYZED BY THE TiCl4-EtAlCl2 SYSTEM
Polacek, Jindrich,Antropiusova, Helena,Petrusova, Lidmila,Mach, Karel
, p. 1756 - 1762 (2007/10/02)
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.
