231963-91-0Relevant articles and documents
Highly selective olefin trimerization catalysis by a borane-activated titanium trimethyl complex
Sattler, Aaron,Labinger, Jay A.,Bercaw, John E.
supporting information, p. 6899 - 6902 (2014/01/06)
Reaction of a trimethyl titanium complex, (FI)TiMe3 (FI = phenoxy-imine), with 1 equiv of B(C6F5)3 gives [(FI)TiMe2][MeB(C6F5)3], an effective precatalyst for the selective trimerization of ethylene. Mechanistic studies indicate that catalyst initiation involves generation of an active TiII species by olefin insertion into a Ti-Me bond, followed by β-H elimination and reductive elimination of methane, and that initiation is slow relative to trimerization. (FI)TiMe3/B(C6F 5)3 also leads to a competent catalyst for the oligomerization of α-olefins, displaying high selectivity for trimers (>95%), approximately 85% of which are one regioisomer. This catalyst system thus shows promise for selectively converting light α-olefins into transportation fuels and lubricants.
Enantioselective aerobic oxidation of α-hydroxy-ketones catalyzed by oxidovanadium(V) methoxides bearing chiral, N-salicylidene- tert -butylglycinates
Chen, Chien-Tien,Kao, Jun-Qi,Salunke, Santosh B.,Lin, Ya-Hui
supporting information; experimental part, p. 26 - 29 (2011/03/22)
Chiral oxidovanadium(V) methoxides prepared from 3,5-disubstituted-N- salicylidene-l-tert-butylglycines and vanadyl sulfate in air-saturated MeOH serve as highly enantioselective catalysts for asymmetric aerobic oxidations and kinetic resolution of alkyl, aryl, and heteroaryl α-hydroxy-ketones with differed α-substituents at ambient temperature in toluene or TBME (tert-butyl methyl ether). The best scenarios involve the use of complexes which bear the tridendate templates derived from 3,5-diphenyl- or 3-o-biphenyl-5-nitro-salicyaldehyde. The kinetic resolution selectivities of the aerobic oxidation process are in the range of 12 to >1000 based on the selectivity factors (krel).
Titanium-salan-catalyzed asymmetric oxidation of sulfides and kinetic resolution of sulfoxides with H2O2 as the oxidant
Bryliakov, Konstantin P.,Talsi, Evgenii P.
experimental part, p. 3369 - 3376 (2009/04/07)
Asymmetric oxidation of sufides to sulfoxides by aqueous hydrogen peroxide with catalysis by titanium-salan complexes is presented. Optically active sulfoxides have been obtained with good to high enantioselectivities (up to 97% ee) by a tandem enantioselective oxidation and kinetic resolution procedure, the catalyst performing over 500 turnovers with no loss of enantioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
(+)-Sorangicin A synthetic studies. Construction of the C(1-15) and C(16-29) subtargets
Smith III, Amos B.,Fox, Richard J.,Vanecko, John A.
, p. 3099 - 3102 (2007/10/03)
(Chemical Equation Presented) Effective stereocontrolled syntheses of subtargets (-)-2 and (-)-4, comprising respectively the C(16-29) and C(1-15) tetrahydropyran and dihydropyran moieties of the potent antibiotic (+)-sorangicin A (1), have been achieved. The cornerstone for the synthesis of (-)-2 involved an aldol tactic exploiting 1,4-induction, followed in turn by an acid-mediated cyclization/ketalization and hydrosilane reduction promoted by TMSOTf, while construction of (-)-4 entailed a stereoselective conjugate addition/α-oxygenation sequence.
Asymmetric cycloaddition reactions
-
Page column 48, (2010/01/31)
The present invention relates to a process for stereoselective cycloaddition reactions which generally comprises a cycloaddition reaction between a pair of substrates, each either chiral or prochiral, that contain reactive π-systems, in the presence of a non-racemic chiral catalyst, to produce a stereoisomerically enriched product. The present invention also relates to novel asymmetric catalyst complexes comprising a metal and an asymmetric tridentate ligand.
A family of zirconium complexes having two phenoxy - imine chelate ligands for olefin polymerization
Matsui,Mitani,Saito,Tohi,Makio,Matsukawa,Takagi,Tsuru,Nitabaru,Nakano,Tanaka,Kashiwa,Fujita
, p. 6847 - 6856 (2007/10/03)
A zirconium complex having two phenoxy - imine chelate ligands, bis[N-(3-tert-butylsalicylidene)-anilinato]zirconium(IV)dichloride (1), was found to display a very high ethylene polymerization activity of 550 kg of polymer/mmol of cat·h with a viscosity average molecular weight, (Mv) value of 0.9 × 104 at 25 °C at atmospheric pressure using methylalumoxane (MAO) as a cocatalyst. This activity is 1 order of magnitude larger than that exhibited by Cp2ZrCl2 under the same polymerization conditions. The use of Ph3CB(C6F5)4/i-Bu3Al in place of MAO as a cocatalyst resulted in extremely high molecular weight polyethylene, Mv 505 × 104, with an activity of 11 kg of polymer/mmol of cat·h at 50 °C. This Mv value is one of the highest values displayed by homogeneous olefin polymerization catalysts. Complex 1, using Ph3CB(C6F5)4/i-BU3Al as a cocatalyst, provided a high molecular weight ethylene-propylene copolymer, Mv 109 × 104, with 8 kg of polymer/mmol of cat·h activity at a propylene content of 20.7 mol %. X-ray analysis revealed that complex 1 adopts a distorted octahedral coordination structure around the zirconium metal and that two oxygen atoms are situated in trans position while two nitrogen atoms and two chlorine atoms are situated in cis position. DFT calculations suggest that the active species derived from complex 1 possesses two available cis-located sites for efficient ethylene polymerization. Changing the tert-butyl group in the phenoxy benzene ring enhanced the polymerization activity. Bis[N-(3-cumyl-5-methylsalicylidene)cyclohexylaminato]zirconium(IV)dichloride (7) with MAO displayed an ethylene polymerization activity of 4315 kg of polymer/mmol of cat·h at 25 °C at atmospheric pressure. This activity corresponds to a catalyst turnover frequency (TOF) value of 42 900/s· atm. This TOF value is one of the largest not only for olefin polymerization but also for any known catalytic reaction. Ligands with additional steric congestion near the polymerization reaction center gave increased Mv values. The maximum Mv value, 220 × 104 using MAO, was obtained with bis[N-(3,5-dicumylsalicylidene)-2′-isopropylanilinato]zirconium (IV)dichloride (15). Thus, polyethylenes ranging from low to exceptionally high molecular weights can be obtained from these zirconium complexes by changing the ligand structure and the choice of cocatalyst.
Highly enantio- and diastereoselective hetero-Diels-Alder reactions catalyzed by new chiral tridentate chromium(III) catalysts
Dossetter, Alexander G.,Jamison, Timothy F.,Jacobsen, Eric N.
, p. 2398 - 2400 (2007/10/03)
Even moderately nucleophilic dienes react with simple aldehydes in the presence of a new Cr(III) catalyst in a hetero-Diels-Alder reaction [Eq. (1)]. Tetrahydropyranyl products with up to three stereogenic centers are generated in near-perfect diastereose
