35648-55-6Relevant academic research and scientific papers
Lewis acid promoted titanium alkylidene formation: Off-cycle intermediates relevant to olefin trimerization catalysis
Sattler, Aaron,Vandervelde, David G.,Labinger, Jay A.,Bercaw, John E.
, p. 10790 - 10800 (2014/08/18)
Two new precatalysts for ethylene and α-olefin trimerization, (FI)Ti(CH2SiMe3)2Me and (FI)Ti(CH2CMe3)2Me (FI = phenoxy-imine), have been synthesized and structurally characterized by X-ray diffraction. (FI)Ti(CH2SiMe3)2Me can be activated with 1 equiv of B(C6F5)3 at room temperature to give the solvent-separated ion pair [(FI)Ti(CH2SiMe3)2][MeB(C6F5)3], which catalytically trimerizes ethylene or 1-pentene to produce 1-hexene or C15 olefins, respectively. The neopentyl analogue (FI)Ti(CH2CMe3)2Me is unstable toward activation with B(C6F5)3 at room temperature, giving no discernible diamagnetic titanium complexes, but at -30 °C the following can be observed by NMR spectroscopy: (i) formation of the bis-neopentyl cation [(FI)Ti(CH2CMe3)2]+, (ii) α-elimination of neopentane to give the neopentylidene complex [(FI)Ti(=CHCMe3)]+, and (iii) subsequent conversion to the imido-olefin complex [(MeOAr2N=)Ti(OArHC=CHCMe3)]+ via an intramolecular metathesis reaction with the imine fragment of the (FI) ligand. If the reaction is carried out at low temperature in the presence of ethylene, catalytic production of 1-hexene is observed, in addition to the titanacyclobutane complex [(FI)Ti(CH(CMe3)CH2CH2)]+, resulting from addition of ethylene to the neopentylidene [(FI)Ti(=CHCMe3)]+. None of the complexes observed spectroscopically subsequent to [(FI)Ti(CH2CMe3)2]+ is an intermediate or precursor for ethylene trimerization, but notwithstanding these off-cycle pathways, [(FI)Ti(CH2CMe3)2]+ is a precatalyst that undergoes rapid initiation to generate a catalyst for trimerizing ethylene or 1-pentene.
Decene formation in ethylene trimerization reaction catalyzed by Cr-pyrrole system
Zilbershtein, Timur M.,Kardash, Vladislav A.,Suvorova, Vladlena V.,Golovko, Anatoly K.
, p. 371 - 378 (2014/03/21)
Decene formation in the ethylene trimerization reaction was studied using a chromium(III) 2-ethylhexanoate/2,5-dimethylpyrrole/triethylaluminum/ diethylaluminum chloride catalyst system. Kinetic investigations revealed that some decene formation reactions did not depend on 1-hexene concentration, because 1-hexene and catalyst may react with ethylene before dissociation of 1-hexene-catalyst complex after 1-hexene formation. The results demonstrated that decene formation is an intrinsic part of the trimerization reaction mechanism. It was also shown that a stepwise elimination mechanism for the decomposition of the chromacycloheptane intermediate cannot explain the observed product distribution. The dependencies found allow selection of appropriate conditions for low or high decene formation in the ethylene trimerization reaction.
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.
Synthesis of Farnesol Analogues through Cu(I)-Mediated Displacements of Allylic THP Ethers by Grignard Reagents
Mechelke, Mark F.,Wiemer, David F.
, p. 4821 - 4829 (2007/10/03)
The synthesis of a family of farnesol analogues, incorporating aromatic rings, has been achieved in high yields through the development of a regioselective coupling of allylic tetrahydropyranyl ethers with organometallic reagents. The allylic THP group is displaced readily by Grignard reagents in the presence of Cu(I) halides but is stable in the absence of added copper. Thus, an allylic THP group can fulfill its traditional role as a protecting group or serve as a leaving group depending on reaction conditions. An improved synthesis of (2E,6E)-10,11-dihydrofarnesol also has been accomplished using this methodology, and some preliminary studies on the reactivity and regioselectivity of THP ether displacements were conducted. The farnesol analogues reported herein may be useful probes of the importance of nonbonding interactions in enzymatic recognition of the farnesyl chain and allow development of more potent competitive inhibitors of enzymes such as farnesyl protein transferase.
