- Synthesis of functional olefin copolymers with controllable topologies using a chain-walking catalyst
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The branching topology of ethylene polar copolymers was for the first time successfully controlled by copolymerization of ethylene with polar olefins using a palladium-bisimine chain-walking catalyst, in which ethylene pressure and comonomer concentration were used to control the competition between isomerization (chain-walking) and monomer insertion processes. Although the overall branching density changes very slightly, the topology of the copolymers becomes more dendritic as the ethylene pressure and comonomer feed concentration are decreasing. This provides a straightforward one-pot synthesis to access a full range of functional copolymers having controllable branching topologies. To demonstrate the utility of this methodology, dendritic functional copolymers having hydroxyl, epoxide, and carbohydrate groups were prepared in a one-pot polymerization as potential functional materials.
- Chen, Guanghui,Ma, Xun S.,Guan, Zhibin
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- Palladium(II) Complexes derived from the Potentially Chelating Ligands 2,2,NN-Tetramethylpent-4-enylamine and 2,2-Dimethylpent-4-enyl Methyl Sulphide. Crystal Structures of Dichloropalladium(II) and Chloro<1-3-η-syn-1-(1,1'-dimethyl-2'-met...
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Reaction of PdX2.2PhCN (X=Cl or Br) with 2,2,NN-tetramethylpent-4-enylamine (1a) gives complexes (2) of stoicheiometry PdX2.(1a) in which Pd-X has added to the olefinic bond to generate a seven-membered chelate ring.In contrast, 2,2-dimethylpent-4-enyl methyl sulphide (1b) initially gives labile olefinic complexes, which readily rearrange to the derivatives (5a) and (5b) of 2,2-dimethylpent-(E)-3-enyl methyl sulphide (13).Variable-temperature 1H n.m.r. studies show that at low temperatures (5a) and (5b) exist in solution as pairs of epimers at sulphur, while heating leads first to equilibration of the epimers and then to labilisation of the metal-olefin bond.The ?-allyl species (6a) and (6b) have been prepared from (5a) and (5b).X-Ray structures of (5a) and (6a) are reported.Crystals of (5a) are monoclinic, space group P21/n with Z=4 in a unit cell of dimensions a=8.365(2), b=15.068(2), c=9.595(1) Angstroem, and β=94.00(1) deg.Crystals of (6a) are monoclinic, space group P21/c, with Z=4 in a unit cell of dimensions a=6.583, b=12.462, c=12.859(6) Angstroem, and β=96.20(5) deg.Both structures have been solved by the heavy-atom method and refined by full-matrix least-squares calculations to R=0.023 for 2 414 reflections for (5a) and to R=0.046 for 2 515 reflections for (6a).The five-membered chelate rings in (5a) and (6a) have C(2)-envelope conformations.In (5a) principal dimensions are Pd-Cl 2.313 and 2.320(1), Pd-S 2.269(1), and Pd-C 2.195 and 2.231(3) Angstroem, and the interplanar angle between the PdCl2S plane and the Pd-ethylenic carbon plane is 96.0 deg.In (6a) dimensions are Pd-Cl 2.381(1), Pd-S 2.364(1), Pd-C 2.089,2.120, and 2.173(5) Angstroem; the plane of the allyl moiety forms a dihedral angle of 116.4 deg with the PdSClC(5) plane.
- McCrindle, Robert,Alyea, Elmer C.,Ferguson, George,Dias, Shelton A.,McAlees, Alan J.,Parvez, Masood
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- The use of chiral diferrocenyl diselenidcs for highly selective asymmetric intramolecular selenocyclisation
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Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral 2-[1-(dimethylamino)ethyl]ferrocenylselenenyl cations proceeds smoothly to give the corresponding organoselenenyl moiety-containing lactones, cyclic ethers and N-heterocycles, respectively, in good to excellent chemical yields (up to 97%) with very high diastereoselectivities (up to 98% de). The nature of the counter anions of the selenenylating agents affected remarkably the diastereoselectivity of the cyclisation, PF6- and BF4- being revealed to be the best for alkenoic acids and alkenols, and alkenyl urethanes, respectively. A plausible reaction scheme for the cyclisation is presented where a chiral selenenylating agent approaches the carbon-carbon double bond of the substrate from the less sterically-congested direction to afford a chiral episelenonium ion followed by an intramolecular back side attack of a nucleophile.
- Takada, Hiroya,Nishibayashi, Yoshiaki,Uemura, Sakac
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- SYNTHESIS OF (+/-)-6-PROTOILLUDENE AND (+/-)-3-EPI-6-PROTOILLUDENE BY INTRAMOLECULAR MAGNESIUM-ENE- AND KETENE/ALKENE ADDITION REACTIONS
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The sesquiterpene (+/-)-6-protoilludene (1) and its C(3)-epimer 11 were synthesized from aldehyde 5.The key steps are a regio- and stereo-selective type-I-magnesium-ene reaction 4 -> 3 and an intramolecular vinylketene/alkene addition 2 -> 9a + 9b.
- Oppolzer, Wolfgang,Nakao, Akio
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- A One-Pot Intramolecular Tandem Michael-Aldol Annulation Reaction for the Synthesis of Chiral Pentacyclic Terpenes
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A chiral tricyclic terpene possessing a 6,6,6-tricyclic framework and a 3,3-dimethyl-7-oxooctylidenyl side chain undergoes a double ring-closing reaction to give two chiral pentacyclic terpenes in a ratio of 4:3 via an intramolecular Michael addition followed by aldol condensation under basic conditions. Three new stereogenic centers are introduced in the initial Michael annulation reaction. Stereoselective installation of an ethoxycarbonyl group at C17 of the two pentacyclic terpenes separately gives the corresponding highly functionalized pentacyclic terpenoids with seven stereogenic centers. The structures and stereochemistry of key intermediates and products are established through X-ray crystallographic analysis. A mechanism is proposed for explaining the stereochemistry in the Michael annulation reaction.
- Lu, Jianyu,Koldas, Serkan,Fan, Huafang,Desper, John,Day, Victor W.,Hua, Duy H.
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- Radical Aryl Migration from Boron to Carbon
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Radical aryl migration reactions represent a unique type of organic transformations that involve the intramolecular migration of an aryl group from a carbon or heteroatom to a C- or heteroatom-centered radical through a spirocyclic intermediate. Various elements, including N, O, Si, P, S, Sn, Ge, and Se, have been reported to participate in radical aryl migrations. However, radical aryl migration from a boron center has not been reported to date. In this communication, radical 1,5-aryl migration from boron to carbon in aryl boronate complexes is presented. C-radicals readily generated through radical addition onto alkenyl aryl boronate complexes are shown to engage in 1,5-aryl migration reactions to provide 4-aryl-alkylboronic esters. As boronate complexes can be generatedin situby the reaction of alkenylboronic acid esters with aryl lithium reagents, the aryl moiety is readily varied, providing access to a series of arylated products starting from the same alkenylboronic acid ester via divergent chemistry. Reactions proceed with high diastereoselectivity under mild conditions, and also the analogous 1,4-aryl shifts are feasible. The suggested mechanism is supported by DFT calculations.
- Daniliuc, Constantin G.,Mück-Lichtenfeld, Christian,Studer, Armido,Wang, Dinghai
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supporting information
p. 9320 - 9326
(2021/07/19)
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- Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH2CMe2CH2CH= CH2]2in Solution and the Origin of Rapid Nucleation
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The compound cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum, Pt[CH2CMe2CH2CH= CH2]2 (3), is a recently discovered chemical vapor deposition (CVD) precursor for the deposition of highly smooth platinum thin films without nucleation delays on a variety of substrates. This paper describes detailed mechanistic studies of the pathway by which 3 reacts upon being heated in solution. In various solvents between 90 and 130 °C, 3 decomposes to generate ~1 equiv of 4,4-dimethylpentenes by addition of a hydrogen atom to the pentenyl ligands in 3. The "extra"hydrogen atoms arise by dehydrogenation of other pentenyl ligands; some of these dehydrogenated ligands are released as methyl-substituted methylenecyclobutanes and cyclobutenes. A combination of isotope labeling and kinetic studies suggests that 3 decomposes by C-H activation of both allylic and olefinic C-H bonds to give transient platinum hydride intermediates, followed by reductive elimination steps to form the pentene products, but that the exact mechanism is solvent-dependent. In C6F6, solvent association occurs before C-H bond activation, and the rate-determining step for thermolysis is most likely the formation of a Pt σ complex. In hydrocarbon solvents, the solvent is little involved before C-H bond activation, and the rate-determining step is most likely the formation of a Pt σ complex only for γ-C-H and ?-C-H bond activation, but cleavage or formation of a C-H bond for δ-C-H bond activation. A comparison of the thermolysis reactions under CVD conditions and in solution suggests that the high smoothness of the CVD-grown films is due in part to rapid nucleation (which is a consequence of the availability of low-barrier C= C bond dissociation pathways) and in part to the formation of carbon-containing species that passivate the Pt surface.
- Liu, Sumeng,Zhang, Zhejun,Abelson, John R.,Girolami, Gregory S.
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supporting information
p. 3817 - 3829
(2020/11/13)
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- Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
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The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)-italicene.
- Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
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supporting information
p. 8135 - 8148
(2019/05/29)
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- Copper-Catalyzed Modular Amino Oxygenation of Alkenes: Access to Diverse 1,2-Amino Oxygen-Containing Skeletons
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Copper-catalyzed alkene amino oxygenation reactions using O-acylhydroxylamines have been achieved for a rapid and modular access to diverse 1,2-amino oxygen-containing molecules. This transformation is applicable to the use of alcohols, carbonyls, oximes, and thio-carboxylic acids as nucleophiles on both terminal and internal alkenes. Mild reaction conditions tolerate a wide range of functional groups, including ether, ester, amide, carbamate, and halide. The reaction protocol allows for starting with free amines as the precursor of O-benzoylhydroxylamines to eliminate their isolation and purification, contributing to broader synthetic utilities. Mechanistic investigations reveal the amino oxygenation reactions may involve distinct pathways, depending on different oxygen nucleophiles.
- Hemric, Brett N.,Chen, Andy W.,Wang, Qiu
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supporting information
p. 1468 - 1488
(2019/01/25)
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- Rhodium-Catalyzed Cyclization of O,ω-Unsaturated Alkoxyamines: Formation of Oxygen-Containing Heterocycles
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O,ω-Unsaturated N-tosyl alkoxyamines undergo unexpected RhIII-catalyzed intramolecular cyclization by oxyamination to produce oxygen-containing heterocycles. Mechanistic studies show that an aziridine intermediate seems to be responsible for the formation of the heterocycles, possibly via a RhV species.
- Escudero, Julien,Bellosta, Véronique,Cossy, Janine
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supporting information
p. 574 - 578
(2018/02/21)
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- Br?nsted Acid Catalysis in Visible-Light-Induced [2+2] Photocycloaddition Reactions of Enone Dithianes
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1,3-Dithiane-protected enones (enone dithianes) were found to undergo an intramolecular [2+2] photocycloaddition under visible-light irradiation (λ=405 nm) in the presence of a Br?nsted acid (7.5–10 mol %). Key to the success of the reaction is presumably the formation of colored thionium ions, which are intermediates of the catalytic cycle. Cyclobutanes were thus obtained in very good yields (78–90 %). It is also shown that the dithiane moiety can be reductively or oxidatively removed without affecting the photochemically constructed ring skeleton.
- Brenninger, Christoph,P?thig, Alexander,Bach, Thorsten
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supporting information
p. 4337 - 4341
(2017/04/04)
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- TETRAHYDRONAPHTHALENE DERIVATIVES THAT INHIBIT MCL-1 PROTEIN
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Provided herein are myeloid cell leukemia 1 protein (Mcl-1) inhibitors, methods of their preparation, related pharmaceutical compositions, and methods of using the same. For example, provided herein are compounds of Formula I, (I) and pharmaceutically acceptable salts thereof and pharmaceutical compositions containing the compounds. The compounds and compositions provided herein may be used, for example, in the treatment of diseases or conditions, such as cancer.
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Page/Page column 105
(2016/03/22)
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- Z -selective alkene isomerization by high-spin cobalt(II) complexes
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The isomerization of simple terminal alkenes to internal isomers with Z-stereochemistry is rare, because the more stable E-isomers are typically formed. We show here that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer. The catalysis proceeds via an "alkyl" mechanism, with a three-coordinate cobalt(II) alkyl complex as the resting state. β-Hydride elimination and [1,2]-insertion steps are both rapid, as shown by isotopic labeling experiments. A steric model explains the selectivity through a square-planar geometry at cobalt(II) in the transition state for β-hydride elimination. The catalyst works not only with simple alkenes, but also with homoallyl silanes, ketals, and silyl ethers. Isolation of cobalt(I) or cobalt(II) products from reactions with poor substrates suggests that the key catalyst decomposition pathways are bimolecular, and lowering the catalyst concentration often improves the selectivity. In addition to a potentially useful, selective transformation, these studies provide a mechanistic understanding for catalytic alkene isomerization by high-spin cobalt complexes, and demonstrate the effectiveness of steric bulk in controlling the stereoselectivity of alkene formation.
- Chen, Chi,Dugan, Thomas R.,Brennessel, William W.,Weix, Daniel J.,Holland, Patrick L.
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supporting information
p. 945 - 955
(2014/02/14)
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- PROCESS AND INTERMEDIATES FOR PREPARING MACROLACTAMS
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The present invention relates to macrolactam compounds, intermediates useful in the preparation of macrolactams, methods for preparing the intermediates, and methods for preparing and modifying macrolactams. One use of the compounds and methods described herein is in the production of macrolactam compounds able to inhibit HCV NS3 protease activity. An example of an HCV inhibitory compound that can be synthesized using the procedures described herein is Compound A and derivative thereof.
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Paragraph 0266-0269
(2013/10/22)
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- Copper(I)-catalyzed borylative exo -cyclization of alkenyl halides containing unactivated double bond
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A borylative exo-cyclization of alkenyl halides has been reported. The reaction includes the regioselective addition of a borylcopper(I) intermediate to unactivated terminal alkenes, followed by the intramolecular substitution of the resulting alkylcopper(I) moiety for the halide leaving groups. Experimental and theoretical investigations of the reaction mechanism have also been described. This reaction provides a new method for the synthesis of alkylboronates containing strained cycloalkyl structures from simple starting materials.
- Kubota, Koji,Yamamoto, Eiji,Ito, Hajime
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supporting information
p. 2635 - 2640
(2013/03/29)
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- Enantioselective intramolecular [2+2] photocycloaddition reactions of 4-substituted coumarins catalyzed by a chiral Lewis acid
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Eight coumarins, which carry a terminal alkene tethered by a CH 2XCH2 group to their 4-position (X=CH2, CMe2, O, S, NBoc, NZ, NTs, NBn), were synthesized in overall yields of 51-80 %. Starting materials for the syntheses were either commercially available 4-hydroxycoumarin or 4-formylcoumarin. The intramolecular [2+2] photocycloaddition of these coumarins gave diastereoselectively products with a tetracyclic 3,3a,4,4a-tetrahydro-1H-cyclopenta[2,3]cyclobuta[1,2-c]chromen-5(2H) -one skeleton. Direct irradiation at λ=300 nm in dichloromethane (c=10 mM) led to product formation in good yields for most substrates, presumably via a singlet excited state intermediate. Due to the low coumarin absorption at λ >350 nm the photocycloaddition was slow upon irradiation at λ=366 nm. Addition of a chiral oxazaborolidine-based Lewis acid (50 mol %) increased the reaction rate at λ=366 nm and induced a significant enantioselectivity in the [2+2] photocycloaddition. Six out of eight coumarin substrates (X=CH2, CMe2, O, NBoc, NZ, NTs) gave the respective products in yields of 72-96 % and with 74-90 % enantiomeric excess (ee) upon irradiation in dichloromethane (c=20 mM) at -75 °C. The Lewis acid presumably acts by coordination to the coumarin carbonyl oxygen atom, which leads to a bathochromic shift (redshift) of the UV absorption and which increases the singlet state lifetime. A second electrostatic interaction of the hydrogen atom at C3 with the oxygen atom of the oxazaborolidine is likely. Copyright
- Brimioulle, Richard,Guo, Hao,Bach, Thorsten
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supporting information; experimental part
p. 7552 - 7560
(2012/07/30)
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- Intramolecular hydroalkoxylation in Bronsted acidic ionic liquids and its application to the synthesis of (±)-centrolobine
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The SO3H-tethered imidazolium and triazolium salts, nonvolatile and recyclable Bronsted acidic ionic liquids, efficiently mediate intramolecular hydroalkoxylations of alkenyl alcohols. They have been successfully employed in the synthesis of (±)-centrolobine.
- Jeong, Yunkyung,Kim, Do-Young,Choi, Yunsil,Ryu, Jae-Sang
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supporting information; experimental part
p. 374 - 378
(2011/02/28)
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- Discovery of novel thieno[2,3-d]pyrimidin-4-yl hydrazone-based cyclin-dependent kinase 4 inhibitors: synthesis, biological evaluation and structure-activity relationships
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The design, synthesis, and evaluation of novel thieno[2,3-d]pyrimidin-4-yl hydrazone analogues as cyclin-dependent kinase 4 (CDK4) inhibitors are described. In continuing our program aim to search for potent CDK4 inhibitors, the introduction of a thiazole group at the hydrazone part has led to marked enhancement of chemical stability. Furthermore, by focusing on the optimization at the C-4′ position of the thiazole ring and the C-6 position of the thieno[2,3-d]pyrimidine moiety, compound 35 has been identified with efficacy in a xenograft model of HCT116 cells. In this paper, the potency, selectivity profile, and structure-activity relationships of our synthetic compounds are discussed.
- Horiuchi, Takao,Takeda, Yasuyuki,Haginoya, Noriyasu,Miyazaki, Masaki,Nagata, Motoko,Kitagawa, Mayumi,Akahane, Kouichi,Uoto, Kouichi
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experimental part
p. 991 - 1002
(2011/10/02)
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- MASKED CARBOXYLATE NEOPENTYL SULFONYL ESTER CYCLIZATION RELEASE PRODRUGS OF ACAMPROSATE, COMPOSITIONS THEREOF, AND METHODS OF USE
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Masked carboxylate neopentyl sulfonyl ester prodrugs of acamprosate, pharmaceutical compositions comprising such prodrugs, and methods of using such prodrugs and compositions thereof for treating diseases are disclosed. In particular, acamprosate prodrugs
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Page/Page column 51-52
(2009/04/24)
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- Gem-dimethyl 4-pentenyl glycosides: Novel glycosylating agents and anomeric protecting groups
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Image Persented Two classes of gem-dimethyl 4-n-pentenyl glycosides (i.e., C2-series and C3-series) have been prepared and studied in both the glycosylation and hydrolysis manifolds utilizing NBS as the sole stoichiometric activator. These novel glycosyla
- Fortin, Michael,Kaplan, Justin,Pham, Khoa,Kirk, Sharon,Andrade, Rodrigo B.
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scheme or table
p. 3594 - 3597
(2011/02/23)
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- EXTERNALLY MASKED NEOPENTYL SULFONYL ESTER CYCLIZATION RELEASE PRODRUGS OF ACAMPROSATE, COMPOSITIONS THEREOF, AND METHODS OF USE
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Masked nitrogen-substituted and oxygen-substituted neopentyl sulfonyl ester prodrugs of acamprosate, pharmaceutical compositions comprising such prodrugs, and methods of using such prodrugs and compositions thereof for treating diseases are disclosed. In particular, acamprosate prodrugs exhibiting enhanced oral bioavailability and methods of using acamprosate prodrugs to treat neurodegenerative disorders, psychotic disorders, mood disorders, anxiety disorders, somatoform disorders, movement disorders, substance abuse disorders, binge eating disorder, cortical spreading depression related disorders, tinnitus, sleeping disorders, multiple sclerosis, and pain are disclosed.
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Page/Page column 46
(2009/04/24)
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- Internally Masked Neopentyl Sulfonyl Ester Cyclization Release Prodrugs of Acamprosate, Compositions Thereof, and Methods of Use
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Internally masked neopentyl sulfonyl ester prodrugs of acamprosate, pharmaceutical compositions comprising such prodrugs, and methods of using such prodrugs and compositions thereof for treating diseases are disclosed. In particular, acamprosate prodrugs
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Page/Page column 46
(2009/04/24)
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- HCV NS3 protease inhibitors
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The present invention relates to macrocyclic compounds of formula (I) that are useful as inhibitors of the hepatitis C virus (HCV) NS3 protease, their synthesis, and their use for treating or preventing HCV infections.
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Page/Page column 76-77
(2008/06/13)
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- ORGANIC COMPOUNDS
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Compounds of the formula are inhibitors of protein tyrosine phosphatases (PTPases) and, thus, may be employed for the treatment of conditions mediated by PTPase activity. The compounds of the present invention may also be employed as inhibitors of other enzymes characterized with a phosphotyrosine binding region such as the SH2 domain. Accordingly, the compounds of formula (I) may be employed for prevention and/or treatment of insulin resistance associated with obesity, glucose intolerance, diabetes mellitus, hypertension and ischemic diseases of the large and small blood vessels, conditions that accompany type-2 diabetes, including hyperlipidemia, hypertriglyceridemia, atherosclerosis, vascular restenosis, irritable bowel syndrome, pancreatitis, adipose cell tumors and carcinomas such as liposarcoma, dyslipidemia, and other disorders where insulin resistance is indicated. In addition, the compounds of the present invention may be employed to treat and/or prevent cancer (such as prostate or breast cancer), osteoporosis, neurodegenerative and infectious diseases, and diseases involving inflammation and the immune system.
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Page/Page column 80
(2010/11/27)
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- Reaction of γ-hydroy-N-[1-(dimethylcarbamoyl)ethyl]butanamides under the 'direct amide cyclization' conditions
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The preparation of the title compounds was achieved via the 'azirine/oxazolone method' starting from the corresponding γ-hydroxy acids. Upon subjecting the γ-hydroxy-N-[1-(dimethylcarbamoyl)-ethyl] butanamides 4 to the so-called 'direct amide cyclization' (DAC) conditions, chlorinated acids 11 or imino lactones 12 were obtained as the sole products instead of the expected cyclodepsipeptides A or their cyclodimers (Scheme 4). Variation of the substituents in 4 did not affect the outcome of the reaction and a mechanism for the formation of both products from the intermediate oxazolone 13 has been proposed. Under the acidic conditions of the DAC, the imino lactones are formed as their HCl salts 12, which, in polar solvents or on silica gel, reacted further to give the chlorinated acids 11. Stabilization of the imino lactones was achieved by increasing the substitution in the five-membered ring, and their structure, in the form of the hydrochlorides, was established independently by X-ray crystallography (Fig. 4). A derivative 15 of the imino lactone 12a was prepared by the reaction with the 2H-azirin-3-amine 10a; its structure was also established by an X-ray crystal-structure determination (Fig. 3). Furthermore, the structures of the ω-chloro acids 11a and 11b were determined by X-ray crystallography (Fig. 2).
- Iliev, Boyan,Linden, Anthony,Heimgartner, Heinz
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p. 153 - 175
(2007/10/03)
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- New silicon-mediated, sequential ring expansions of n-sized 2-cycloalkenones into hydroxyolefinic n + m + p medium-sized lactones: Short synthesis of (-)-phoracantholide-J
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(Chemical Equation Presented) In only four steps from 2-cyclopentenone and 2-cyclohexenone, sequential three- or four-atom and then one- to three-atom ring enlargements produce nine- to 12-membered hydroxyolefinic lactones on a gram scale. 2-Cyclopentenon
- Posner, Gary H.,Hatcher, Mark A.,Maio, William A.
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p. 4301 - 4303
(2007/10/03)
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- Sulfone derivatives as 5-HT7 receptor ligands
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The present invention relates to sulfone derivatives of formula (I): Ar—SO2—CR2R3-L-N(R1)2??I wherein Ar, L, R1, R2 and R3 are as defined herein, and pharmaceutically
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Page/Page column 9
(2010/02/09)
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- Direct lactonization of alkenols via osmium tetroxide-mediated oxidative cleavage
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(Matrix presented) A highly efficient, mild, and simple protocol is presented for the tandem OsO4-mediated oxidative cleavage/oxidative lactonization of alkenols to lactones. The protocol couples the OsO 4-catalyzed oxidative cleavage of olefins with Oxone as the co-oxidant with the direct oxidation of aldehydes in alcoholic solvents to their corresponding esters.
- Schomaker, Jennifer M.,Travis, Benjamin R.,Borhan, Babak
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p. 3089 - 3092
(2007/10/03)
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- POLYMERIZATION OF OLEFINS
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Olefins containing selected functional groups such as silyl, ether and alkenyl, and often containing a blocking group, may be copolymerized with unsubstituted olefins such as ethylene and propylene in the presence of certain coordination compounds of nickel or palladium. The resulting polymers are useful as molding resins, elastomers, in adhesives and for films.
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- An amino alcohol ligand for highly enantioselective addition of organozinc reagents to aldehydes: Serendipity rules
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(matrix presented) Amino alcohol 4 (or its enantiomer) is prepared in two simple steps. Commercial (1R,2S)-2-amino-1,2-diphenylethanol is dialkylated with bis(2-bromoethyl) ether. Subsequent hydrogenation over 5% Rh on alumina in the presence of morpholine unexpectedly stops at the hexahydro derivative 4. Amino alcohol 4 promotes the enantioselective addition of diethylzinc to aldehydes at room temperature in up to 99% enantiomeric excess.
- Nugent, William A.
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p. 2133 - 2136
(2007/10/03)
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- Intramolecular functionalisation by a methylene radical of a 1,2-diol and a vicinal amino alcohol: Models for coenzyme B12-dependent diol dehydratase and ethanolamine ammonia lyase
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Coenzyme B12-dependent diol dehydratase converts 1,2-diols (e.g. propane-1,2-diol) into the corresponding aldehyde and water. The similar enzyme ethanolamine ammonia lyase transforms vicinal aminoalcohols (e.g. 2-aminoethanol) into the corresponding aldehyde and ammonia. Model systems have been developed that replicate key features of the putative enzymatic mechanism, i.e. removal of a hydrogen atom from the CH2OH group of a 1,2-diol or vicinal aminoalcohol by a methylene radical derived from an alkylcobalt compound, and conversion of a 1,2-diol or vicinal aminoalcohol into a carbonyl compound and water or ammonia triggered by such a methylene radical. The models are based on alkyl(pyridine)bis(dimethylglyoximato)cobalt complexes [alkyl(pyridine)cobaloximes, Cbx], which were synthesised from appropriate organic precursors using standard methodology. The complexes contain a 1,2-diol [as in 4,5-dihydroxy-2,2-dimethylpentyl(pyridine)cobaloxime] or vicinal aminoalcohol [as in 6-amino-5-hydroxy-2,2-dimethylhexyl(pyridine)cobaloxime] tethered to the cobalt by a carbon chain. Photolysis or thermolysis of 4,5-dihydroxy-2,2-dimethylpentyl(pyridine)cobaloxime at pH 3 or 9 gave 4,4-dimethylpentanal. It is proposed that homolysis of the Co-C bond of 4,5-dihydroxy-2,2-dimethylpentyl(pyridine)cobaloxime induced by photolysis or thermolysis affords the 1,2-dihydroxy-4,4-dimethyl-l-pentyl radical via a 1,5-H shift, which is converted into the 4,4-dimethyl-1-oxo-2-pentyl radical, and hence 4,4-dimethylpentanal. The pathway for formation of the aldehyde was diagnosed using the specifically deuteriated analogue [5,5-2H 2]-4,5-dihydroxy-2,2-dimethylpentyl(pyridine)-cobaloxime, which gave [1,5-2H2]-4,4-dimethylpentanal accompanied by 3,3-dimethylbutanal on thermolysis or photolysis at pH 3. The protected model compound 2a was hydrolysed to 6-amino-5-hydroxy-2,2-dimethylhexyl(pyridine)cobaloxime, which was heated at pH 3 or 9 to give 5,5-dimethylhexan-2-one and ammonia. The Royal Society of Chemistry 2000.
- Andersen, Rosaleen J.,Ashwell, Susan,Garnett, Ian,Golding, Bernard T.
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p. 4488 - 4498
(2007/10/03)
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- Complete relative stereochemistry of maitotoxin
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By addressing the relative stereochemistry of the four acyclic portions via organic synthesis, the complete relative stereochemistry of maitotoxin (MTX) has been established as 1B. The relative stereochemistry of the C.1-C.15 portion was elucidated via a two-phase approach: (1) the synthesis of the eight diastereomers possible for model C, representing the C.1-C.11 portion, and the eight diastereomers possible for model D, representing the C.11-C.15 portion, and the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 9 and 35 represent the relative stereochemistry of the corresponding portions of MTX; (2) the synthesis of the two remote diastereomers 51 and 52, and comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 51 represents the relative stereochemistry of the C.1-C.15 portion of MTX. The relative stereochemistry of the C.35-C.39, C.63-C.68, and C.134-C.142 acyclic portions was established via (1) the synthesis of the 8, 8, and 16 diastereomers possible for models E, F, and G, respectively, and (2) the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 81, 117, and 187, respectively, represent the relative stereochemistry of the corresponding portions of MTX. Some biogenetic considerations have been given to speculate on the absolute configuration of MTX. The vicinal proton coupling constants observed for models 51, 81, 117, and 187 were used to elucidate their preferred solution conformation. Assembling the preferred solution conformations found for the four acyclic portions allows one to suggest that the approximate global conformation of MTX is represented by the shape of a hook, with the C.35-C.39 portion being its curvature. MTX appears to be conformationally relatively rigid, except for conformational flexibility around the C.7-C.9 and C.12-C.14 portions. On the basis of the experimental results gained in the current work, coupled with those in the AAL-toxin/fumonisin area, it has been pointed out that the structural properties of 51, 81, 117, 187 and their diastereomers are inherent to the specific stereochemical arrangement of the small substituents on the carbon backbone and are independent from the rest of the molecule. Thus, it has been suggested that each of these diastereomers has the capacity to install a unique structural characteristic through a specific stereochemical arrangement of substituents on the carbon backbone, and that fatty acids and related classes of compounds may be able to carry specific information and serve as functional materials in addition to structural materials.
- Zheng,DeMattei,Wu,Duan,Cook,Oinuma,Kishi
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p. 7946 - 7968
(2007/10/03)
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- Heterocyclic pesticidal compounds
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Compounds of the formula (I) STR1 which contain between 10 and 27 carbon atoms, and wherein m and n are independently selected from 0, 1 and 2; R2a is hydrogen, methyl, or ethyl; R2b is acetylene or contains between 3 and 18 carbon atoms and is a group R7, wherein R7 is a C1-13 non-aromatic hydrocarbyl group, optionally substituted by a cyano or C1-4 carbalkoxy group and/or by one or two hydroxy groups and/or by one to five halo atoms which are the same or different and/or by one to three groups R8 which are the same or different and each contain one to four hetero atoms, which are the same or different and are chosen from oxygen, sulphur, nitrogen and silicon, 1 to 10 carbon atoms and optionally 1 to 6 fluoro or chloro atoms or R2b is a 6-membered aromatic ring substituted by cyano and/or by one to three groups R8 and/or by a group --C CH, --C C-R7 or C C-halo and/or by one to five halo atoms and/or by one to three C1-4 haloalkyl groups wherein R7 and R8 are as hereinbefore defined; R4 and R6 are the same or different and are chosen from hydrogen, methyl, trifluoromethyl or cyano; and R5 is hydrogen or methyl provided that R2b is not propyl or butyl are described which have pesticidal activity, particularly against arthropod pests. Pesticidal formulations containing the compounds of the formula (I), their use in the control of pests and method for their preparation are also disclosed.
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- Synthesis of medium-sized lactones by the copper(I)chloride/2,2′-bipyridine-catalyzed cyclization of di- and trichloroacetates
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Medium-sized lactones (eight- to eleven-membered rings) are efficiently formed by Cu(bpy)Cl catalyzed cyclization of various alkenyl di- and trichloroacetates at temperatures between 80 and 190°C in 1,2-dichloroethane or benzene as solvents. The mechanism of the alkene addition reaction is best understood as a chlorine atom transfer process through radical type intermediates. Exclusive endo-cyclization is observed in all cases. Ten and eleven-membered lactones are only accessible by the 'rigid chain' approach, in which an alkyne or alkene function is incorporated in the chain connecting the reaction centres, thus reducing the flexibility of the molecule.
- Pirrung, Frank O. H.,Hiemstra, Henk,Speckamp, W. Nico,Kaptein, Bernard,Schoemaker, Hans E.
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p. 12415 - 12442
(2007/10/02)
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- A Formal Synthesis of Aplysiatoxin: Enantioselective Synthesis of Kishi's Aldehyde
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This paper describes the enantioselective synthesis of key fragments (12,18,24, and 35) for the synthesis of aplysiatoxin (1a), a potent cancer promoter, and their convergent assembly to Kishi's aldehyde (2).Since 2 has already been transformed into 1a in
- Okamura, Hiroaki,Kuroda, Satoru,Ikegami, Satoru,Tomita, Kenji,Sugimoto, Yu-ichi,et al.
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p. 10531 - 10554
(2007/10/02)
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- Process for producing vitamin A aldehyde
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The invention provide a process for producing vitamin A aldehyde in high yield by oxidizing vitamin A with a aldehyde of the general formula (1) STR1 wherein R1, R2 and R3 are the same or different and respectively represents a lower alkyl group or a lower alkenyl group in the presence of aluminum alkoxide in a catalytic amount.
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- Conformational Analysis and Stereodynamics of Primary Acyclic Alkyl Radicals by EPR Spectroscopy
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The EPR spectra of n-alkyl, 2-methylalkyl, 2,2-dimethylalkyl, 2,2,3-trimethylbutyl, and 2,2,3,3-tetramethylbutyl radicals indicate that at 90 K they exist in "rigid" conformations with respect to rotation about the Cβ-Cγ bonds.The preferred conformations about the Cα-Cβ and Cβ-Cγ bonds were deduced by analysis of the β- and γ-H hyperfine splittings (hfs). 2,2,3,3-Tetramethylbutyl radicals, the only radicals with a CH3 group approximately all-trans with respect to the semioccupied p-orbital, were also the only radicals to show resolved δ-hfs.The barriers to internal rotation of the methyl groups in n-propyl, isobutyl, neopentyl, 2,2-bis(trideuteriomethyl)butyl, and 2,2,3,3-tetramethylbutyl radicals were obtained by line shape analysis; the ethyl rotation barrier in 2,2-bis(trideuteriomethyl)butyl and the tert-butyl rotation barrier in 2,2,3,3-tetramethylbutyl radicals were estimated in a similar way.The experimental hfs of trans γ-hydrogens were shown to fit a relationship of the form aHγ = 0.1 +7.9 cos2 Φ, where Φ is the dihedral angle between the SOMO and the plane through Cα, Cβ, and Cγ.Trends in the internal rotation barriers of the alkyl groups were adequately accounted for in terms of steric effects.
- Ingold, K. U.,Nonhebel, D. C.,Walton, J. C.
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p. 2859 - 2869
(2007/10/02)
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- An Investigation of the Thermal Decomposition of the Methohydroxides and Methodeuterio-oxides of Some 5-N,N-Dimethylaminopent-1-enes
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The base-catalysed thermal decomposition of a number of quaternary bases of the type (R1)2C=CH(R2)2C(R3)2CH2N+Me3X- (R1 = H, Me; R2 = H, 2H; R3 = H, 2H, Me; X = OH, O2H) has been investigated.It is shown that the reaction is initiated by attack of base (OH-, O2H-, ylide) on an allylic proton or .A mechanism for the reaction is suggested.
- Cocker, Wesley,Geraghty, Niall W. A.,McMurry, T. Brian H.,Shannon, Patrick V. R.
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p. 2245 - 2254
(2007/10/02)
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- Reactions of Methyl-Substituted Hex-5-enyl and Pent-4-enyl Radicals
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Relative and absolute kinetic data have been determined for ring closure of methyl-substituted hex-5-enyl radicals: 2-methyl-(10a), 3-methyl-(4a), 4-methyl-(5a), 2,2-dimethyl-(10c), 3,3-dimethyl-(4c) and 4,4-dimethyl-hex-5-enyl (5c) radicals, generated by interaction of tributylstannane with the corresponding bromides (1a)-(3a) and (1c)-(3c).Each radical undergoes regiospecific or highly regioselective 1,5-cyclization more rapidly than does the unsubstituted radical (4d).The rate enhancements, which arise mainly from lowering of the activation energy, can be rationalized in terms of the gem-dimethyl effect. 1,5-Ring closures of monosubstituted species are stereoselective: 2-methyl- and 4-methyl-hex-5-enyl radicals (10a) and (5a) give mainly trans products, whereas 3-methylhex-4-enyl radical gives mainly the cis.This behaviour reflects the effect of the substituent on the stabilities of cyclic transition complexes in chair-like conformations.Ring closure of 2,2-dimethylpent-4-enyl radical or of 3,3-dimethylpent-4-enyl radical (19) could not be detected.
- Beckwith, Athelstan L. J.,Easton, Christopher J.,Lawrence, Tony,Serelis, Algirdas K.
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p. 545 - 556
(2007/10/02)
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- Cyclometallation of Dialkylbis(triethylphosphine)platinum(II) Complexes: Formation of Pt,Pt-Bis(triethylphosphine)platinacycloalkanes
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The thermal decompositions of three analogues of bis(triethylphosphine)dineopentylplatinum(II) (L2Pt2 (1)) - L2Pt2 (3), L2Pt2 (5), and L2Pt2 (7) - have been examined.Compounds 3 and 7 decompose more rapidly than 1 by a factor of ca. 104 to give as products Pt,Pt-bis(triethylphosphine)-3,3-dimethylplatinacyclohexane (4) and Pt,Pt-bis(triethylphosphine)-3,3,5,5-tetramethylplatinacyclohexane (8), respectively, and 1 equiv of the corresponding alkane.Compound 5 decomposes at a rate ca. 50 times faster than 1 to yield Pt,Pt-bis(triethylphosphine)-2,4,4-trimethylplatinacyclopentane (6a), -3-methyl-3-n-propylplatinacyclobutane (6b), and -3,3-dimethylplatinacyclohexane (6c).The conversion of 3 to 4 and 5 to 6a proceeds by dissociation of triethylphosphine, intramolecular oxidative addition of a δ carbon-hydrogen bond of the alkyl groups to platinum, and reductive elimination of alkane.The decomposition of L2Pt2 (11) proceeds by β-hydride elimination rather than cleavage of a carbon-hydrogen bond and formation of platinacycloalkane.The difference in the free energies of activation for reactions which form four- and five-membered platinacycloalkanes is small (ΔΔG(excit.) ca./= 4 kcal mol-1); that for reactions wich form four- and six-membered rings is smaller (ΔΔG(excit.) ca./= 0 kcal mol-1).We identify these values of ΔΔG(excit.) with estimates of the strain energies of these rings, assuming the strain energy of the platinacyclohexane is small.The important conclusion from these studies is that the strain energy of the platinacyclobutane studied here is small (-1).
- DiCosimo, Robert,Moore, Stephen S.,Sowinski, Allan F.,Whitesides, George M.
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p. 124 - 133
(2007/10/02)
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- gem-Dimethyl Effect in a Grignard Reagent Cyclization-Cleavage Rearrengament
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(2,2-Dimethyl-4-penten-1-yl)magnesium bromide (1) is in equilibrium with its cyclic isomer, magnesium bromide (2).The equilibrium constant for this cyclization has a value of 2E-3.The gem-dimethyl substitution leads to an increase of a factor of about 22 in the equilibrium constant and also retards the rate of cleavage of 2.The sources of the gem-dimethyl effect in this system are discussed.
- Hill, Alexander E.,Link, Daniel C.,Donndelinger Peter
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p. 1177 - 1182
(2007/10/02)
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