5.32 Hydrovinylation Reactions in Organic Synthesis
01 Jan 2014-pp 1582-1620
TL;DR: In the presence of nickel, ruthenium, or cobalt complexes, the most active catalysts have been shown to provide high yields and exceptional stereoselectivities.
Abstract: Codimerization of ethylene and various functionalized vinylarenes, 1,3-dienes, or strained alkenes can be carried out in the presence of nickel, ruthenium, or cobalt complexes in very high yields and exceptional regio- and stereoselectivities Nickel appears to provide the most active catalyst, even though more recent work indicates that the other metals may have unique advantages of their own Many of these reactions proceed under exceedingly mild conditions (−50 °C to 25 °C, 1 atm of ethylene) to produce valuable intermediates including 3-arylbutenes and skipped 1,4-dienes with a chiral carbon at the benzylic or bis-allylic center The 3-arylbutenes can be transformed into nonsteroidal antiinflammatory drugs such as ibuprofen, naproxen, and fenoprofen in two steps Cyclic and acyclic 1,3-dienes also undergo efficient addition of ethylene and terminal alkenes catalyzed by either Ni(II), Ru(II), or Co(II) complexes The regio- and stereoselectivities of many of these reactions can be controlled by judicious choice of metals and ligands In addition, the hydrovinylation reaction can be used to generate molecules with an all-carbon quaternary center These discoveries open expeditious routes to several biologically relevant classes of compounds including bisabolanes, herbindoles, trikentrins, steroid- D -ring 20( S ) or 20( R )-derivatives, pyrrolidinoindolines, pseudopterosins, and various members of the serrulatane and amphilectane classes of compounds
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01 Mar 2011
TL;DR: In this paper, a nickel-catalyzed allylic substitution process of simple alkenes was described, whereby an important structural motif, a 1,4-diene, was prepared.
Abstract: This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. The key to success is the use of an appropriate nickel-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented.
94 citations
TL;DR: The novel results including ligand, counterion, and solvent effects uncovered during the course of these investigations show a unique role of a possible cationic Co(I) intermediate in these reactions, which have further implications for the expanding use of low-valent group 9 metal complexes in organic synthesis.
Abstract: 1,3-Dienes are ubiquitous and easily synthesized starting materials for organic synthesis, and alkyl acrylates are among the most abundant and cheapest feedstock carbon sources. A practical, highly enantioselective union of these two readily available precursors giving valuable, enantio-pure skipped 1,4-diene esters (with two configurationally defined double bonds) is reported. The process uses commercially available cobalt salts and chiral ligands. As illustrated by the use of 20 different substrates, including 17 prochiral 1,3-dienes and 3 acrylates, this hetero-dimerization reaction is tolerant of a number of common organic functional groups (e.g., aromatic substituents, halides, isolated mono- and di-substituted double bonds, esters, silyl ethers, and silyl enol ethers). The novel results including ligand, counterion, and solvent effects uncovered during the course of these investigations show a unique role of a possible cationic Co(I) intermediate in these reactions. The rational evolution of a mecha...
76 citations
TL;DR: In this article, a vinyl thianthrenium salt was introduced as an effective vinylating reagent, which can be readily prepared from ethylene gas at atmospheric pressure in one step and is broadly useful in the annulation chemistry of (hetero)cycles, N-vinylation of heterocyclic compounds, and palladium-catalyzed crosscoupling reactions.
Abstract: The use of vinyl electrophiles in synthesis has been hampered by the lack of access to a suitable reagent that is practical and of appropriate reactivity. In this work we introduce a vinyl thianthrenium salt as an effective vinylating reagent. The bench-stable, crystalline reagent can be readily prepared from ethylene gas at atmospheric pressure in one step and is broadly useful in the annulation chemistry of (hetero)cycles, N-vinylation of heterocyclic compounds, and palladium-catalyzed cross-coupling reactions. The structural features of the thianthrene core enable a distinct synthesis and reactivity profile, unprecedented for other vinyl sulfonium derivatives.
39 citations
TL;DR: In this paper, an enantioselective cross-electrophile divinylation reaction of nonaromatic substrates, 2-bromo-1,6-dienes, was reported.
Abstract: Catalytic asymmetric dicarbofunctionalization of tethered alkenes has emerged as a promising tool for producing chiral cyclic molecules; however, it typically relies on aryl-tethered alkenes to form benzene-fused compounds. Herein, we report an enantioselective cross-electrophile divinylation reaction of nonaromatic substrates, 2-bromo-1,6-dienes. The approach thus offers a route to new chiral cyclic architectures, which are key structural motifs found in various biologically active compounds. The reaction proceeds under mild conditions, and the use of chiral t-Bu-pmrox and 3,5-difluoro-pyrox ligands resulted in the formation of divinylated products with high chemo-, regio-, and enantioselectivity. The method is applicable for the incorporation of chiral hetero- and carbocycles into complex molecules.
34 citations
TL;DR: An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed and a modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates.
Abstract: An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2 CoCl2 ] complexes are employed that are activated in situ with Et2 AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99 % ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2 , CN, and CO2 R, are tolerated.
25 citations
References
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1,378 citations
TL;DR: In this article, the synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMXn, bearing chelating 2,6-bis(imino)pyridyl ligands L [L = 2.6-(ArNCR1)2C5H3N] is reported.
Abstract: The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMXn (M = Fe, X = Cl, n = 2, 3, X = Br, n = 2; M = Co, X = Cl, n = 2), bearing chelating 2,6-bis(imino)pyridyl ligands L [L = 2,6-(ArNCR1)2C5H3N] is reported. X-ray diffraction studies show the geometry at the metal centers to be either distorted square pyramidal or distorted trigonal bipyramidal. Treatment of the complexes LMXn with methylaluminoxane (MAO) leads to highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE). LFeX2 precatalysts with ketimine ligands (R1 = Me) are approximately an order of magnitude more active than precatalysts with aldimine ligands (R1 = H). Catalyst productivities in the range 3750−20600 g/mmol·h·bar are observed for Fe-based ketimine catalysts, while Co ketimine systems display activities of 450−1740 g/mmol·h·bar. Molecular weights (Mw) of the polymers produced are in the range 14000−611000. Changing reaction ...
970 citations
TL;DR: A long-standing challenge to synthesis can now be met through the use of new and powerful catalytic asymmetric reactions for the assembly of complex chiral molecules with quaternary stereocenters from achiral building blocks.
Abstract: A long-standing challenge to synthesis can now be met through the use of new and powerful catalytic asymmetric reactions for the assembly of complex chiral molecules with quaternary stereocenters from achiral building blocks. The reaction sequence shown below is just one example discussed in this review.
941 citations
TL;DR: In this article, a taxonomy of one-pot, coupled catalytic transformations is presented, which distinguishes between onepot, domino/cascade, and tandem catalysis, and the proposed taxonomy is illustrated with examples drawn from olefin metathesis and hydroformylation chemistry.
Abstract: A scheme is advanced for the classification of one-pot, coupled catalytic transformations, which distinguishes between one-pot, domino/cascade, and tandem catalysis. The last of these is divided into three subclasses: orthogonal, auto-tandem, and assisted tandem catalysis. The proposed taxonomy, and the potential of tandem catalysis in organic synthesis, are illustrated with examples drawn from olefin metathesis and hydroformylation chemistry.
805 citations