Olefin insertion in a metal alkyl in a Ziegler polymerization system

Clawson, Leigh; Soto, Jorge; Buchwald, Stephen L.; Steigerwald, Michael L.; Grubbs, Robert H.

doi:10.1021/ja00297a070

Cited by 119 publications

(51 citation statements)

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“…The most frequently used method for detecting ␣-agostic interactions in the transition states for olefin insertions has been isotopic perturbation of stereochemistry as first proposed by Grubbs and coworkers (58). The use of this probe is best illustrated by the work of Bercaw and coworkers (59, 60) who showed that [Me 2 Si(C 5 Me 4 ) 2 ]Sc(PMe 3 )H catalyzes the hydrocyclization 1,6-dideuterio-1,5-hexadiene to produce a 1.23:1.00 ratio of the trans:cis products (Scheme 3).…”

Section: Role Of Agostic Interactions In Reaction Intermediates and Tmentioning

confidence: 99%

Agostic interactions in transition metal compounds

Brookhart

Green

Parkin

2007

Proc. Natl. Acad. Sci. U.S.A.

1,025

831

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Section: Role Of Agostic Interactions In Reaction Intermediates and Tmentioning

confidence: 99%

Agostic interactions in transition metal compounds

Brookhart

Green

Parkin

2007

Proc. Natl. Acad. Sci. U.S.A.

1,025

831

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“…146 An alternative mechanism that does not involve β-Me elimination is a reverse Green−Rooney mechanism 147 where C−H bond activation generates the metallacyclobutane 79, followed by retrocyclization affording 80 (Scheme 25). This latter mechanism is unlikely, considering that the Green−Rooney mechanism has been sufficiently disproven, 148 and furthermore no H/D exchange was observed during the transformation.…”

Section: Substrate Effect On β-Alkyl Eliminationmentioning

confidence: 99%

β-Alkyl Elimination: Fundamental Principles and Some Applications

2016

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This review describes organometallic compounds and materials that are capable of mediating a rarely encountered but fundamentally important reaction: β-alkyl elimination at the metal-Cα-Cβ-R moiety, in which an alkyl group attached to the Cβ atom is transferred to the metal or to a coordinated substrate. The objectives of this review are to provide a cohesive fundamental understanding of β-alkyl-elimination reactions and to highlight its applications in olefin polymerization, alkane hydrogenolysis, depolymerization of branched polymers, ring-opening polymerization of cycloalkanes, and other useful organic reactions. To provide a coherent understanding of the β-alkyl elimination reaction, special attention is given to conditions and strategies used to facilitate β-alkyl-elimination/transfer events in metal-catalyzed olefin polymerization, which provide the well-studied examples.

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“…A cisitruns ratio of 1 .O has also been reported for the AI(C,H,)CI,-induced, stoichiometric cyclization of Cp,TiCI-CHD-(CH,), -CH = CH, [14] Asahi Research Center: Hundhook af Pralon NMR-Speclru and Dulu r--- ~7 to Cp,TiCI-CH,-CH-(CH2),-CHD [9]. Vol.…”

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confidence: 95%

2‐Pentylcyclopent‐2‐en‐1‐one by Catalytic Pauson‐Khand Reaction

Rautenstrauch

Mégard

Conesa

et al. 1990

Angew. Chem. Int. Ed. Engl.

122

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Scheme 1. Reaction paths with alternative a-agostic transition states leading to threo-2 (left) and erylhro-2 (right) via two consecutive olefin insertions with opposite and identical olefin orientations, respectively. of the migrating alkyl unit, has been proposed by Brookhart and Green." 21 The observations reported here constitute the first experimental evidence for such an a-agostic transition state in zirconocene-catalyzed olefin polymerizations.['31 Experimental (E-I-deuterio-1-hexene: Reaction of 1-hexyne with 1 equiv. diisobutylaluminum hydride in toluene at 0 "C; cleavage with D,O and fractional distillation [G. Wjlke, H. Miiller, Justus Liehigs Ann. Chem. 629 (1960) 222, G . Zweifel, R L. Miller, J. Am. Chem. Sac. 92 (1970) 66781; the 'H-NMR spectrum (doublet of triplets, b = 4.98, ' J = 17.1, "J = 1.5 Hz, 1 H; symmetric multiplet, b = 5.82, 1 H [14]) indicates that (Q-1-deuterio-1-hexene is the only olefin present. (Z)-1 -deuterio-1-hexene-Cleavage with H,O of the hydroalumination product of I-deuterio-1-hexyne [G. W. Kabalka, R. J. Newton, J. Jacobus, J. Org. Chem. 43 (1978) 15671. 'H NMR: 6 = 4.91 (d, ' J = 10.4 Hz), 5 80(m). The presence of ca. 15% [D,]hexane, 10% toluene and 5 % [D,lbutane, indicated by gas chromatography does not interfere with the catalysis or with the isolation of the hydrodimer 2; traces of I-hexyne have to be removed by prolonged stirring with and distilling from solvent-free n-butyllithium.Hydrodimerizations: 3.5 mL (33 mmo!) of (Q-or (a-1-deuterio-1-hexene, 430 mg MA0 (6.6 mmol CH'AIO, Schering AG, M , =z 1300, in 4.5 mL toluene) and 33 pmol of either rac-1 or (C,H,),ZrCI, in 0.5 mL toluene (all under N,)were exposed in a 50 mL autoclave at -5°C to initial H, pressures of 20 and 15 atm. respectively. for 16-20 h; during this time H, pressures fell by ca. 5 atm After quenching with 10 mL 1.5 M aq. HCI and separation ofthe organic layer, 2 was isolated by fractional distillation. Admixtures of ca. 5 % 6,7-[D,]n-dodecane (the tail-to-tail rnis-insertion product) gave weak D-NMR signals just separable from the adjacent signal of eryrhro-2.

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Olefin insertion in a metal alkyl in a Ziegler polymerization system

Cited by 119 publications

References 1 publication

Agostic interactions in transition metal compounds

Agostic interactions in transition metal compounds

β-Alkyl Elimination: Fundamental Principles and Some Applications

2‐Pentylcyclopent‐2‐en‐1‐one by Catalytic Pauson‐Khand Reaction

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