- ISOMERIZATION OF ALKENES
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The present invention relates to an isomerization method for alkenes, comprising of reaction an alkene with a Ni(I)-compound. By this method, E-Alkenes are obtained in excellent yield.
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Page/Page column 20-21; 23
(2020/04/25)
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- Ru-catalyzed isomerization of ω-alkenylboronates towards stereoselective synthesis of vinylboronates with subsequent: In situ functionalization
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The stereoselective preparation of synthetically versatile vinylboronates from ω-alkenylboronates is achieved through a ruthenium-catalyzed isomerization reaction. A variety of di- A nd trisubstituted vinylboronates were conveniently produced and could be
- Ho, Guo-Ming,Marek, Ilan,Segura, Lucas
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p. 5944 - 5949
(2020/07/10)
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- Aliphatic α-Boryl-α-bromoketones: Synthesis and Reactivity
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A protocol for the preparation of α-boryl-α-bromoketones from alkenyl MIDA boronates was developed and applied to functionalized aliphatic derivatives. The reaction sequence included regioselective hydroxybromination of olefin moiety, followed by oxidation of alcohol group with Dess–Martin periodinane. The target trifunctional boronate-containing derivatives were obtained in up to 94 % yield over two steps starting from alkenyl MIDA boronates. In some cases, functional groups present in the substrate participated in the bromohydroxylation step via intramolecular nucleophilic attack at the bromonium cation leading to cyclic products. Additionally, the reactivity of aliphatic α-boryl-α-bromoketones was illustrated by nucleophilic substitution at the α-C atom and heterocyclization reactions.
- Ivon, Yevhen M.,Kuchkovska, Yuliya O.,Voitenko, Zoya V.,Grygorenko, Oleksandr O.
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p. 3367 - 3377
(2020/03/13)
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- E-Olefins through intramolecular radical relocation
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Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach.We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.
- Kapat, Ajoy,Sperger, Theresa,Guven, Sinem,Schoenebeck, Franziska
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p. 391 - 396
(2019/02/03)
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- Methylenespiro[2.3]hexanes via Nickel-Catalyzed Cyclopropanations with [1.1.1]Propellane
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[1.1.1]Propellane is a highly strained tricyclic hydrocarbon whose reactivity is dominated by addition reactions across the central inverted bond to provide bicyclo[1.1.1]pentane derivatives. These reactions proceed under both radical and two-electron pathways, hence, providing access to a diverse array of products. Conversely, transition metal-catalyzed reactions of [1.1.1]propellane are underdeveloped and lack synthetic utility, with reported examples generally yielding mixtures of ring-opened structural isomers, dimers, and trimers, often with poor selectivity. Herein, we report that nickel(0) catalysis enables the use of [1.1.1]propellane as a carbene precursor in cyclopropanations of a range of functionalized alkenes to give methylenespiro[2.3]hexane products. Computational studies provide support for initial formation of a Ni(0)-[1.1.1]propellane complex followed by concerted double C-C bond activation to give the key 3-methylenecyclobutylidene-nickel intermediate.
- Yu, Songjie,Noble, Adam,Bedford, Robin B.,Aggarwal, Varinder K.
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supporting information
p. 20325 - 20334
(2019/12/30)
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- Double-Bond Isomerization: Highly Reactive Nickel Catalyst Applied in the Synthesis of the Pheromone (9 Z,12 Z)-Tetradeca-9,12-dienyl Acetate
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A highly reactive nickel catalyst comprising NiCl2(dppp) or NiCl2(dppe) with zinc powder, ZnI2 and Ph2PH, was applied in the isomerization of terminal alkenes to Z-2-alkenes. The double-bond geometry of the 2-alkene can be controlled via the reaction temperature to yield the 2-Z-alkenes in excellent yields and high Z-selectivities. The formation of other constitutional isomers, such as 3-alkenes, is suppressed on the basis of the proposed mechanism via a 1,2-hydride shift from the metal to the Ph2P ligand. The nickel-catalyzed isomerization reaction was then applied in the synthesis of (9Z,12Z)-tetradeca-9,12-dienyl acetate, a pheromone with a 2Z,5Z-diene subunit.
- Weber, Felicia,Schmidt, Anastasia,R?se, Philipp,Fischer, Michel,Burghaus, Olaf,Hilt, Gerhard
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supporting information
p. 2952 - 2955
(2015/06/30)
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- Enantioselective syn and anti homocrotylation of aldehydes: Application to the formal synthesis of spongidepsin
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Whereas crotylboration has been a useful method for synthesis of stereochemically complex products, we have shown that homocrotylboration can be achieved with cyclopropanated crotylation reagents, and that the stereoselectivity of the reaction can be predicted by analogous models. This paper presents a full account of this work, including the first examples of asymmetric anti homocrotylation. The scope of this reaction is demonstrated with highly enantioselective homocrotylation of both aliphatic and aromatic aldehydes, as well as double diastereoselection studies. An application of the synthesis of the marine natural product spongidepsin is presented, as well as streamlined syntheses of homocrotylation reagents.
- Lin, Hongkun,Tian, Leiming,Krauss, Isaac J.
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supporting information
p. 13176 - 13182
(2015/10/28)
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- Synthesis of vinyl boronates from aldehydes by a practical boron-Wittig reaction
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A highly stereoselective boron-Wittig reaction between stable and readily accessible 1,1-bis(pinacolboronates) and aldehydes furnishes a variety of synthetically useful di- and trisubstituted vinyl boronate esters.
- Coombs, John R.,Zhang, Liang,Morken, James P.
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supporting information
p. 1708 - 1711
(2015/04/14)
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- Z -selective homodimerization of terminal olefins with a ruthenium metathesis catalyst
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The cross-metathesis of terminal olefins using a novel ruthenium catalyst results in excellent selectivity for the Z-olefin homodimer. The reaction was found to tolerate a large number of functional groups, solvents, and temperatures while maintaining excellent Z-selectivity, even at high reaction conversions.
- Keitz, Benjamin K.,Endo, Koji,Herbert, Myles B.,Grubbs, Robert H.
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supporting information; experimental part
p. 9686 - 9688
(2011/08/05)
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- PYRROLO [2, 3 - B] PYRAZINE - 7 - CARBOXAMIDE DERIVATIVES AND THEIR USE AS JAK AND SYK INHIBITORS
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The present invention relates to the use of novel pyrrolopyrazine derivatives of Formula (I), wherein the variables Q and R, R2, and R3 are defined as described herein, which inhibit JAK and SYK and are useful for the treatment of auto-immune and inflammatory diseases.
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Page/Page column 150-151
(2011/12/04)
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- Diastereoselective addition of zincated hydrazones to alkenylboronates and stereospecific trapping of boron/zinc bimetallic intermediates by carbon electrophiles
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Zincated hydrazones possessing a tert-butyl group on the zinc atom undergo addition to (E)- or (Z)-alkenylboronic acid pinacol esters to produce α-alkylated-γ-boryl-γ-zinciohydrazone intermediates with good to excellent diastereoselectivity (ds). The 1,1 -organodimetallic intermediate possessing a boron atom and a zinc atom in the position γ to the hydrazone group undergoes further C-C bond formation with a carbon electrophile to give a γ-boryl hydrazone possessing several contiguous stereogenic centers with up to 99% ds. The (S)-1-amino-2-methoxymethylpyrrolidine hydrazone shows a high level of asymmetric induction in the addition/trapping sequence. Density functional theory calculations on the pathways of the addition reaction revealed a metallo-ene mechanism consisting of the formation of a π complex between a zincated hydrazone and a vinylborane followed by a six-centered bond reorganization of a highly ordered boat conformation transition state. The calculations indicated that the use of the zinc atom together with the imine or hydrazone is the key for the success of the olefinic variant of the aldol reaction that has long been considered not to take place because of the endothermicity of the reaction and has never been examined with any seriousness by chemists. The steric repulsion caused by the bulky tert-butyl ligand on the zinc atom and the pinacol moiety of the vinylboronate substrates in the highly ordered transition structures gives rise to the observed high ds of the present carbozincation reaction.
- Hatakeyama, Takuji,Nakamura, Masaharu,Nakamura, Eiichi
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supporting information; experimental part
p. 15688 - 15701
(2009/03/12)
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- Sequential coupling of zincated hydrazone, alkenylboronate, and electrophile that creates several contiguous stereogenic centers
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A zincated N,N-dimethylhydrazone of a ketone undergoes stereospecific syn addition to E- or Z-alkenylboronate to generate a γ-Zn/B dimetallic intermediate, which reacts with a carbon electrophile to give a γ-borylhydrazone in good yield with excellent dia
- Nakamura, Masaharu,Hatakeyama, Takuji,Hara, Kenji,Fukudome, Hiroki,Nakamura, Eiichi
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p. 14344 - 14345
(2007/10/03)
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- Synthesis of functionalized vinyl boronates via ruthenium-catalyzed olefin cross-metathesis and subsequent conversion to vinyl halides
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Functionalized vinyl pinacol boronates suitable for Suzuki cross-coupling reactions are synthesized using ruthenium-catalyzed olefin cross-metathesis of 1-propenyl pinacol boronate and various alkenes, including functionalized and 1,1-disubstituted alkenes. The resultant boronate cross products are stereoselectively transformed into predominantly Z-vinyl bromides and E-vinyl iodides. The vinyl bromides may be synthesized in a two-step, one-pot synthesis from a variety of olefins, resulting in a Z-selective formal vinyl bromide cross-metathesis reaction.
- Morrill, Christie,Grubbs, Robert H.
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p. 6031 - 6034
(2007/10/03)
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