20063-97-2Relevant articles and documents
Synthesis and catalytic activity of η1-allyl and η3-allyl, ethyl, and hydrido complexes of ruthenium- pentamethyl[60]fullerene
Matsuo, Yutaka,Uematsu, Takashi,Nakamura, Eiichi
, p. 2729 - 2733 (2007)
η1-Allyl and η3-allyl, ethyl, and hydrido ruthenium complexes of pentamethyl[60]fullerene, Ru(η5-C 60Me5)R(CO)2 (R = η1-allyl, Et, H) and Ru(η5-C60Me5)(η3- allyl)(CO) were synthesized by the reaction of a chlorido complex Ru(η5-C60Me5)Cl(CO)2 with an allyl and an ethyl Grignard reagent or lithium aluminum hydride. Conversion of the η1-allyl complex to the corresponding η3-allyl complex and the catalytic performance of the hydrido and the chlorido complexes in the isomerization reaction of 1-decene to internal decenes are described. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Isomerization of terminal alkenes by the Cp2TiCl2/Mg/BrCH2CH2Br system
Rao, S. Achyutha,Periasamy, M.
, p. 15 - 20 (1988)
The reagents prepared in situ in tetrahydrofuran (THF) by reaction of Cp2TiCl2 with isobutyl or t-butylmagnesium halides or with Grignard grade magnesium and 1,2-dibromomethane bring about isomerization of some 1-alkenes into trans-2-alkenes under mild conditions.
Kinetics of the Isomerization of 1-Decene to cis- and trans-2-Decene
Aimar, Mario L.,Rossi, Rita H. de
, p. 4255 - 4257 (1995)
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Modular Ni(0)/Silane Catalytic System for the Isomerization of Alkenes
Chang, Alison Sy-Min,Cook, Amanda K.,Kawamura, Kiana E.,Martin, Daryl J.,Morris, Parker T.,Smith, Haley M.
supporting information, p. 486 - 496 (2022/03/02)
Alkenes are used ubiquitously as starting materials and synthetic targets in all areas of chemistry. Controlling their geometry and position along a chain is vital to their reactivity and properties yet remains challenging. Alkene isomerization is an atom-economical process to synthesize targeted alkenes, and selectivity can be controlled using transition metal catalysts. The development of mild, selective isomerization reactivity has enabled efficient tandem catalytic systems for the remote functionalization of alkenes, a process in which a starting alkene is isomerized to a new position prior to the functionalization step. The key challenges in developing isomerization catalysts for remote functionalization applications are (i) a lack of modularity in the catalyst structure and (ii) the requirement of nonmodular and/or harsh additives during catalyst activation. We address both challenges with a modular (NHC)Ni(0)/silane catalytic system (NHC, N-heterocyclic carbene), demonstrating the use of triaryl silanes and readily accessible (NHC)Ni(0) complexes to form the proposed active (NHC)(silyl)Ni-H species in situ. We show that modification of the steric and electronic nature of the catalyst via modification of the ancillary ligand and silane partner, respectively, is easily achieved, creating a uniquely versatile catalytic system that is effective for the formation of internal alkenes with high yield and selectivity for the E-alkene. The use of silanes as mild activators enables isomerization of substrates with a variety of functional groups, including acid-labile groups. The broad substrate scope, enabled by catalyst design, makes this catalytic system a strong candidate for use in tandem catalytic applications. Preliminary mechanistic studies support a Ni-H insertion/elimination pathway.
Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism
Kim, Daniel,Pillon, Guy,Diprimio, Daniel J.,Holland, Patrick L.
supporting information, p. 3070 - 3074 (2021/03/08)
Double-bond transposition in alkenes (isomerization) offers opportunities for the synthesis of bioactive molecules, but requires high selectivity to avoid mixtures of products. Generation of Z-alkenes, which are present in many natural products and pharmaceuticals, is particularly challenging because it is usually less thermodynamically favorable than generation of the E isomers. We report a β-dialdiminate-supported, high-spin cobalt(I) complex that can convert terminal alkenes, including previously recalcitrant allylbenzenes, to Z-2-alkenes with unprecedentedly high regioselectivity and stereoselectivity. Deuterium labeling studies indicate that the catalyst operates through a π-allyl mechanism, which is different from the alkyl mechanism that is followed by other Z-selective catalysts. Computations indicate that the triplet cobalt(I) alkene complex undergoes a spin state change from the resting-state triplet to a singlet in the lowest-energy C-H activation transition state, which leads to the Z product. This suggests that this change in spin state enables the catalyst to differentiate the stereodefining barriers in this system, and more generally that spin-state changes may offer a route toward novel stereocontrol methods for first-row transition metals.
Careful investigation of the hydrosilylation of olefins at poly(ethylene glycol) chain ends and development of a new silyl hydride to avoid side reactions
Shin, Hyunseo,Moon, Bongjin
, p. 527 - 536 (2018/01/27)
Hydrosilylation of olefin groups at poly(ethylene glycol) chain ends catalyzed by Karstedt catalyst often results in undesired side reactions such as olefin isomerization, hydrogenation, and dehydrosilylation. Since unwanted polymers obtained by side reactions deteriorate the quality of end-functional polymers, maximizing the hydrosilylation efficiency at polymer chain ends becomes crucial. After careful investigation of the factors that govern side reactions under various conditions, it was related that the short lifetime of the unstable Pt catalyst intermediate led to the formation of more side products under the inherently dilute conditions for polymers. Based on these results, two new chelating hydrosilylation reagents, tris(2-methoxyethoxy)silane (5) and 2,10-dimethyl-3,6,9-trioxa-2,10-disilaundecane (6), have been developed. It was demonstrated that the hydrosilylation efficiency at polymer chain ends was significantly increased by employing the internally coordinating hydrosilane 5. In addition, employment of the internally coordinating disilane species 6 in an addition polymerization with 1,5-hexadiene by hydrosilylation reaction yielded a polymer with high molecular weight (Mn = 9300 g/mol), which was significantly higher than that (Mn = 2600 g/mol) of the corresponding polymer obtained with non-chelating dihydrosilane, 1,1,3,3-tetramethyldisiloxane.
