- Alkyne gem-Hydrogenation: Formation of Pianostool Ruthenium Carbene Complexes and Analysis of Their Chemical Character
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Parahydrogen (p-H2) induced polarization (PHIP) NMR spectroscopy showed that [CpXRu] complexes with greatly different electronic properties invariably engage propargyl alcohol derivatives into gem-hydrogenation with formation of pianostool ruthenium carbenes; in so doing, less electron rich CpX rings lower the barriers, stabilize the resulting complexes and hence provide opportunities for harnessing genuine carbene reactivity. The chemical character of the resulting ruthenium complexes was studied by DFT-assisted analysis of the chemical shift tensors determined by solid-state 13C NMR spectroscopy. The combined experimental and computational data draw the portrait of a family of ruthenium carbenes that amalgamate purely electrophilic behavior with characteristics more befitting metathesis-active Grubbs-type catalysts.
- Biberger, Tobias,Gordon, Christopher P.,Leutzsch, Markus,Peil, Sebastian,Guthertz, Alexandre,Copéret, Christophe,Fürstner, Alois
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- A Novel Synthesis of Homologated Allylic Alcohols Using Dimethylsulphonium Methylide
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The reaction of excess dimethylsulphonium methylide with various aliphatic and aromatic ketones leads exclusively to homologated allylic alcohols in good yields.
- Harnett, J. J.,Alcaraz, L.,Mioskowski, C.,Martel, J. P.,Gall, T. Le,et al.
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- Allylic Alcohols by Methylene Transfer from N-Lithiomethyl-N,N',N'',N''-tetramethyldiethylenetriamine to Epoxides
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Allylic (homoallylic) alcohols are obtained from epoxides (and certain oxetanes) and N-lithiomethyl-N,N',N'',N''-tetramethyldiethylenetriamine.
- Schakel, Marius,Luitjes, Hendrikus,Dewever, Frank L. M.,Scheele, Jan,Klumpp, Gerhard W.
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- Antiandrogenic, maspin induction, and antiprostate cancer activities of tanshinone IIA and its novel derivatives with modification in ring A
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Expression of metastatic suppressor maspin is lost in advanced prostate cancer. Clinically relevant mutations in androgen receptor (AR) convert antiandrogens into AR agonists, promoting prostate tumor growth. We discovered tanshinone IIA (TS-IIA) is a potent antagonist of mutated ARs and induces maspin expression through AR. TS-IIA suppressed AR expression and induced apoptosis in LNCaP cells. Syntheses of TS-IIA derivatives (1-9) revealed that the 4,4-dimethyl group at ring A is important for TS-IIA's antiandrogenic and maspin induction activities.
- Liu, Weiguo,Zhou, Jinming,Geng, Guoyan,Shi, Qingwen,Sauriol, Francoise,Wu, Jian Hui
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- High Reactivity of Strained Seven-Membered-Ring trans-Alkenes
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trans-Oxasilacycloheptenes are highly reactive strained alkenes. Competition reactions showed that these seven-membered ring trans-alkenes underwent [4+2] cycloaddition reactions faster than a trans-cyclooctene. They also reacted with quinones and dimethyl acetylenedicarboxylate to form adducts with high diastereoselectivity. Kinetic studies showed that ring strain increases nucleophilicity by approximately 109. trans-Oxasilacycloheptenes are strained seven-membered-ring trans-alkenes that underwent [4+2] cycloaddition reactions faster than a bicyclic trans-cyclooctene. They also reacted with quinones and dimethyl acetylenedicarboxylate to form adducts with high diastereoselectivity. Kinetic studies showed that ring strain increases nucleophilicity by approximately 109.
- Sanzone, Jillian R.,Woerpel
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- Photochemical Organocatalytic Regio- and Enantioselective Conjugate Addition of Allyl Groups to Enals
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We report the first catalytic enantioselective conjugate addition of allyl groups to α,β-unsaturated aldehydes. The chemistry exploits the visible-light-excitation of chiral iminium ions to activate allyl silanes towards the formation of allylic radicals, which are then intercepted stereoselectively. The underlying radical mechanism of this process overcomes the poor regio- and chemoselectivity that traditionally affects the conjugate allylation of enals proceeding via polar pathways. We also demonstrate how this organocatalytic strategy could selectively install a valuable prenyl fragment at the β-carbon of enals.
- Berger, Martin,Carboni, Davide,Melchiorre, Paolo
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supporting information
p. 26373 - 26377
(2021/11/16)
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- Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
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Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
- Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
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supporting information
p. 5482 - 5488
(2021/02/03)
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- ETHERS AND ESTERS OF 1-SUBSTITUTED CYCLOALKANOLS FOR USE AS AROMA CHEMICALS
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The present invention relates to the use of an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use thereof for modifying the scent character of a fragranced composition; to an aroma chemical composition containing an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition. The invention further relates to specific ethers or esters of 1 -substituted cycloalkanols.
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- NiH-Catalyzed Proximal-Selective Hydroamination of Unactivated Alkenes
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Reported herein is a modular, NiH-catalyzed system capable of proximal-selective hydroamination of unactivated alkenes with diverse amine sources. The key to the successful implementation of this approach is the promotion of NiH insertion into even highly substituted olefins via coordination of the bidentate directing group to the nickel complex. A wide range of primary and secondary amines can be installed in both internal and terminal unactivated alkenes with excellent regiocontrol under the optimized reaction conditions. This protocol is flexible and general for the preparation of a variety of valuable β- and γ-amino acid building blocks that would otherwise be difficult to synthesize. The utility of this transformation was further demonstrated by the site-selective late-stage modification of complex and medicinally relevant molecules. Combined experimental and computational studies illuminate the detailed reaction mechanism.
- Jeon, Jinwon,Lee, Changseok,Seo, Huiyeong,Hong, Sungwoo
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supporting information
p. 20470 - 20480
(2020/11/27)
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- Sustainable Palladium-Catalyzed Tsuji-Trost Reactions Enabled by Aqueous Micellar Catalysis
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Palladium-catalyzed allylic substitution, or "Tsuji-Trost"reactions, can be run under micellar catalysis conditions featuring not only chemistry in water but also numerous combinations of reaction partners that require low levels of palladium, typically on the order of 1000 ppm (0.1 mol %). These couplings are further characterized by especially mild conditions, leading to a number of cases not previously reported in an aqueous micellar medium. Inclusion of diverse nucleophiles, such as N-H heterocycles, alcohols, dicarbonyl compounds, and sulfonamides is described. Intramolecular cyclizations further illustrate the broad utility of this process. In addition to recycling studies, a multigram scale example is reported, indicative of the prospects for scale up.
- Braga, Felipe C.,Gallou, Fabrice,Lee, Nicholas R.,Lippincott, Daniel J.,Lipshutz, Bruce H.,Moghadam, Farbod A.,Zhu, Bingchun
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supporting information
(2020/07/15)
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- Synthesis method of 2-(1-cyclohexenyl) ethylamine
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The invention belongs to the technical field of organic chemistry, and particularly relates to a synthesis method of a compound 2-(1-cyclohexenyl) ethylamine (I). Cyclohexanone (II) and a Grignard reagent are subjected to a Grignard reaction in an organic solvent to be converted into 1-vinyl cyclohexanol (III), the 1-vinyl cyclohexanol (III) and a chlorination reagent are subjected to a chlorination/rearrangement one-pot reaction in an organic solvent in the presence of organic alkali to prepare (2-chloroethylene methylene) cyclohexane (IV), the (2-chloroethylene methylene) cyclohexane (IV) and urotropine are subjected to quaternization in an organic solvent to form N-cyclohexylidene ethyl urotropine hydrochloride (V), and finally, hydrolysis rearrangement is carried out in a solvent in the presence of inorganic mineral acid to obtain the 2-(1-cyclohexenyl) ethylamine (I). The compound (I) has important industrial application value as an intermediate for synthesizing the antitussive drug dextromethorphan hydrobromide. The method has the advantages of cheap and accessible raw materials, mild reaction conditions, high yield and high product purity, is simple to operate, and is convenient for industrial production.
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Paragraph 0041-0043
(2020/11/02)
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- SUBSTITUTED IMIDAZOLECARBOXYLATE DERIVATIVES AND THE USE THEREOF
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A compound is shown in formula (I). The derivatives of the compound include a stereoisomer, a pharmaceutically acceptable salt, a solvate, a prodrug, a metabolite, a deuterated derivative. The compound is a structurally novel substituted imidazole formate derivative. Substituted imidazole formate derivatives are used in preparing a drug with sedative, hypnotic and/or anesthetic effects, as well as a drug that can control the state of epilepsy. The compound has a good inhibitory effect on the central nervous system, and provides a new option for clinical screening of and/or preparation of a drug with sedative, hypnotic and/or anesthetic effects and controlling the state of epilepsy.
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Paragraph 0903-0905
(2020/12/08)
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- Efficient synthesis of 3-sulfolenes from allylic alcohols and 1,3-dienes enabled by sodium metabisulfite as a sulfur dioxide equivalent
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We present herein an efficient and practical method for a gram scale synthesis of 3-sulfolenes using sodium metabisulfite as a safe, inexpensive, and easy to handle sulfur dioxide equivalent. Diversely-substituted 3-sulfolenes can be prepared by reacting a variety of 1,3-dienes or allylic alcohols with sodium metabisulfite in aqueous hexafluoroisopropanol (HFIP) or in aqueous methanol in the presence of potassium hydrogen sulfate. Advantageously, the method enables conversion of allylic alcohols directly to 3-sulfolenes, bypassing intermediate 1,3-dienes.
- Dang, Hang T.,Nguyen, Vu T.,Nguyen, Viet D.,Arman, Hadi D.,Larionov, Oleg V.
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supporting information
p. 3605 - 3609
(2018/05/26)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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supporting information
p. 3677 - 3686
(2018/06/04)
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- Prenyl Praxis: A Method for Direct Photocatalytic Defluoroprenylation
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The prenyl fragment is the quintessential constituent of terpenoid natural products, a diverse family which contains numerous members with diverse biological properties. In contrast, fluorinated and multifluorinated arenes make up an important class of anthropogenic molecules which are highly relevant to material, agricultural, and pharmaceutical industries. While allylation chemistry is well developed, effective prenylation strategies have been less forthcoming. Herein, we describe the photocatalytic defluoroprenylation, a powerful method that provides access to "hybrid molecules" that possess both the functionality of a prenyl group and fluorinated arenes. This approach involves direct prenyl group transfer under very mild conditions, displays excellent functional group tolerance, and includes relatively short reaction times (4 h), which is the fastest photocatalytic C-F functionalization developed to date. Additionally, the strategy can be extended to include allyl and geranyl (10 carbon fragment) transfers. Another prominent finding is a reagent-dependent switch in regioselectivity of the major product from para to ortho C-F functionalization.
- Priya, Sonal,Weaver, Jimmie D.
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supporting information
p. 16020 - 16025
(2018/11/27)
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- Accessing Frustrated Lewis Pair Chemistry through Robust Gold@N-Doped Carbon for Selective Hydrogenation of Alkynes
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Pyrolysis of Au(OAc)3 in the presence of 1,10-phenanthroline over TiO2 furnishes a highly active and selective Au nanoparticle (NP) catalyst embedded in a nitrogen-doped carbon support, Au@N-doped carbon/TiO2 catalyst. Parameters such as pyrolysis temperature, type of support, and nitrogen ligands as well as Au/ligand molar ratios were systematically investigated. Highly selective hydrogenation of numerous structurally diverse alkynes proceeded in moderate to excellent yield under mild conditions. The high selectivity toward the industrially important alkene substrates, functional group tolerance, and the high recyclability makes the catalytic system unique. Both high activity and selectivity are correlated with a frustrated Lewis pairs interface formed by the combination of gold and nitrogen atoms of N-doped carbon that, according to density functional theory calculations, can serve as a basic site to promote the heterolytic activation of H2 under very mild conditions. This "fully heterogeneous" and recyclable gold catalyst makes the selective hydrogenation process environmentally and economically attractive.
- Fiorio, Jhonatan Luiz,Gon?alves, Renato Vitalino,Teixeira-Neto, Erico,Ortu?o, Manuel A.,López, Núria,Rossi, Liane Marcia
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p. 3516 - 3524
(2018/04/14)
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- Ruthenium Catalysts Supported by Amino-Substituted N-Heterocyclic Carbene Ligands for Olefin Metathesis of Challenging Substrates
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N-Heterocyclic carbene (NHC) ligands IMes (Formula presented.) and IMes (Formula presented.) derived from the well-known IMes ligand by substituting the carbenic heterocycle with one and two dimethylamino groups, respectively, were employed for the synthesis of second-generation Grubbs- and Grubbs–Hoveyda-type ruthenium metathesis precatalysts. Whereas the stability of the complexes was found to depend on the degree of dimethylamino-substitution and on the type of complex, the backbone-substitution was shown to have a positive impact on their catalytic activity in ring-closing metathesis, with a more pronounced effect in the second-generation Grubbs-type series. The new complexes were successfully implemented in a number of challenging olefin metathesis reactions leading to the formation of tetra-substituted C=C double bonds and/or functionalized compounds.
- César, Vincent,Zhang, Yin,Ko?nik, Wioletta,Zieliński, Adam,Rajkiewicz, Adam A.,Ruamps, Mirko,Bastin, Stéphanie,Lugan, No?l,Lavigne, Guy,Grela, Karol
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supporting information
p. 1950 - 1955
(2017/02/15)
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- Gold-Ligand-Catalyzed Selective Hydrogenation of Alkynes into cis-Alkenes via H2 Heterolytic Activation by Frustrated Lewis Pairs
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The selective hydrogenation of alkynes to alkenes is an important synthetic process in the chemical industry. It is commonly accomplished using palladium catalysts that contain surface modifiers, such as lead and silver. Here we report that the adsorption of nitrogen-containing bases on gold nanoparticles results in a frustrated Lewis pair interface that activates H2 heterolytically, allowing an unexpectedly high hydrogenation activity. The so-formed tight-ion pair can be selectively transferred to an alkyne, leading to a cis isomer; this behavior is controlled by electrostatic interactions. Activity correlates with H2 dissociation energy, which depends on the basicity of the ligand and its reorganization on activation of hydrogen. High surface occupation and strong Au atom-ligand interactions might affect the accessibility and stability of the active site, making the activity prediction a multiparameter function. The promotional effect found for nitrogen-containing bases with two heteroatoms was mechanistically described as a strategy to boost gold activity. (Graph Presented).
- Fiorio, Jhonatan L.,López, Núria,Rossi, Liane M.
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p. 2973 - 2980
(2017/05/31)
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- Colloid and nanosized catalysts in organic synthesis: XI. Hydrogenation of alkynes catalyzed by nickel nanoparticles
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The reaction of alkynes with hydrogen under atmospheric pressure in the presence of nickel nanoparticles as a catalyst led to the exhaustive hydrogenation of the triple bond.
- Popov, Yu. V.,Mokhov,Nebykov
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- Application of Pd Nanoparticles Supported on Mesoporous Hollow Silica Nanospheres for the Efficient and Selective Semihydrogenation of Alkynes
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Herein, the preparation of a heterogeneous catalyst consisting of 1-2 nm sized Pd nanoparticles supported on amino-functionalized mesoporous hollow silica nanospheres and its use for the semihydrogenation of mono- And disubstituted alkynes is reported. By utilizing this Pd nanocatalyst together with the green poisoning agent DMSO, high yields of the desired alkenes could be achieved, while suppressing the degree of over-reduction to alkanes. To our delight, the Pd nanocatalyst displayed remarkable chemoselectivity towards the alkyne moiety, allowing the transformation to be carried out in the presence of other reducible functionalities, such as halogens, carbonyl, and nitro groups.
- Verho, Oscar,Zheng, Haoquan,Gustafson, Karl P. J.,Nagendiran, Anuja,Zou, Xiaodong,B?ckvall, Jan-E.
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p. 773 - 778
(2016/03/05)
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- Substrate-Controlled Product Divergence: Conversion of CO2 into Heterocyclic Products
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Substituted epoxy alcohols and amines allow substrate-controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach results in an unusual scope of CO2-derived products by initial activation of CO2 through either the amine or alcohol unit, thus providing nucleophiles for intramolecular epoxy ring opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile-assisted ring-opening step following an SNi pathway, and a 5-exo-tet cyclization, thus leading to heterocyclic scaffolds.
- Rintjema, Jeroen,Epping, Roel,Fiorani, Giulia,Martín, Eddy,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
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supporting information
p. 3972 - 3976
(2016/03/19)
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- Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: Efficient synthesis of 3-amino allylic alcohols
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An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination.
- Deng, Zhimin,Wei, Jialiang,Liao, Lihao,Huang, Haiyan,Zhao, Xiaodan
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supporting information
p. 1834 - 1837
(2015/04/27)
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- Congested C-C bonds by Pd-catalyzed enantioselective allyl-allyl cross-coupling, a mechanism-guided solution
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Under the influence of a chiral bidentate diphosphine ligand, the Pd-catalyzed asymmetric cross-coupling of allylboron reagents and allylic electrophiles establishes 1,5-dienes with adjacent stereocenters in high regio-and stereoselectivity. A mechanistic study of the coupling utilizing reaction calorimetry and density functional theory analysis suggests that the reaction operates through an inner-sphere 3,3′-reductive elimination pathway, which is both rate-defining and stereodefining. Coupled with optimized reaction conditions, this mechanistic detail is used to expand the scope of allyl-allyl couplings to allow the generation of 1,5-dienes with tertiary centers adjacent to quaternary centers as well as a unique set of cyclic structures.
- Ardolino, Michael J.,Morken, James P.
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supporting information
p. 7092 - 7100
(2014/06/09)
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- Isomerizing ethenolysis as an efficient strategy for styrene synthesis
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A shrinking chain: A bimetallic system consisting of [{Pd(μ-Br)(tBu 3P)}2] and a ruthenium metathesis catalyst has been found to efficiently promote the cross-metathesis between substituted alkenes and ethylene, while continuously migrating the double bond along the alkenyl chain (see scheme). When alkenylarenes, such as the natural products eugenol, safrol, or estragol, were treated with this catalyst under an ethylene atmosphere, they were cleanly converted into the corresponding styrenes and propylene gas. Copyright
- Baader, Sabrina,Ohlmann, Dominik M.,Goossen, Lukas J.
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supporting information
p. 9807 - 9810
(2013/08/23)
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- Manganese(III)-promoted tandem oxidation and cyclization of β-keto ester derivatives of terpenoids
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A new type of terpenoid cyclization directed by a β-keto ester moiety has been developed, which proceeded by manganese(III)-initiated oxidation of the β-keto ester, followed by an intramolecular hetero Diels-Alder reaction with the terpenoid chain. This reaction produces polycyclic dihydropyrans in high yields and stereoselectivities under mild conditions. Copyright
- Li, Zhilong,Jung, Heejung,Park, Mira,Lah, Myoung Soo,Koo, Sangho
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supporting information; experimental part
p. 1913 - 1917
(2011/10/08)
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- α-Aroyloxyaldehydes: Scope and limitations as alternatives to α-haloaldehydes for NHC-catalysed redox transformations
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α-Aroyloxyaldehydes are readily prepared bench stable synthetic intermediates. Their ability to act as α-haloaldehyde surrogates for NHC-promoted redox esterifications and in [4+2] cycloadditions is described.
- Ling, Kenneth B.,Smith, Andrew D.
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supporting information; experimental part
p. 373 - 375
(2011/02/24)
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- N-heterocyclic carbene-catalyzed hydrosilylation of styryl and propargylic alcohols with dihydrosilanes
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Reducing alkenes to tears: Addition of structurally diverse N-heterocyclic carbenes (NHCs) to silicon allows the reduction of propargylic and styryl alcohols through an organocatalyzed silylation/direct hydride transfer tandem reaction (see scheme). Catalytic turnover is enabled by the switch to and from hypervalent silicon. This provides a new synthetic application of NHC-main group element complexes. Copyright
- Zhao, Qiwu,Curran, Dennis P.,Malacria, Max,Fensterbank, Louis,Goddard, Jean-Philippe,Lacote, Emmanuel
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supporting information; experimental part
p. 9911 - 9914
(2011/10/05)
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- A novel one-pot conversion of allyl alcohols into primary allyl halides mediated by acetyl halide
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A new and simple method for the synthesis of the primary allyl chlorides and bromides 9-16 from the secondary or tertiary allyl alcohols 3-8 and acyl halide was developed (Scheme 2, Table 1). Non-commercially available secondary and tertiary allyl alcohols were synthesized from the related ketones and aldehydes via the addition of vinylmagnesium chloride. Mechanistic studies indicate that the alcohols were first acetylated by the acetyl halide and then protonated prior to substitution by the halide, Cl- or Br -, via an 5N2′ reaction, to yield the primary halides (Scheme 5).
- Kishali, Nurhan,Polat, M. Fatih,Altundas, Ramazan,Kara, Yunus
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- Synthesis of spirocyclic butenolides by ring closing metathesis
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Spirocyclic butenolides were efficiently prepared by a ring closing metathesis strategy.
- Albrecht, Uwe,Langer, Peter
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p. 4648 - 4654
(2007/10/03)
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- An efficient DABCO-catalyzed Ireland-Claisen rearrangement of allylic acrylates
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A novel DABCO-catalyzed Ireland-Claisen [3,3]-rearrangement of allylic acrylates to give α-methylene-γ,δ-unsaturated carboxylic acids in the presence of an excess of TMSCl and DBU in refluxing acetonitrile was developed. The protocol provides an easy entry to α-methylene-γ, δ-unsaturated carboxylic acids from allylic alcohols in good yields. Georg Thieme Verlag Stuttgart.
- Li, Yunxia,Wang, Quanrui,Goeke, Andreas,Fráter, Georg
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p. 288 - 292
(2007/10/03)
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- [(NHC)Au1]-catalyzed rearrangement of allylic acetates
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Equation Presented [(NHC)AuCl] complexes (NHC = N-heterocyclic carbene), in conjunction with a silver salt, were found to efficiently catalyze the rearrangement of allylic acetates under both conventional and microwave-assisted heating. The optimization of several reaction parameters (solvent, silver salt, and ligand) as well as a study of the reaction scope are reported. The steric hindrance of the ligand bound to gold was found crucial for the outcome of the reaction as only extremely bulky ligands permitted the isomerization.
- Marion, Nicolas,Gealageas, Ronan,Nolan, Steven P.
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p. 2653 - 2656
(2008/02/09)
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- Hydrovinylation of 1,3-dienes: A new protocol, an asymmetric variation, and a potential solution to the exocyclic side chain stereochemistry problem
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Cyclic and acyclic 1,3-dienes undergo efficient (substrate/catalyst = 72) heterodimerization with ethylene in the presence of a Ni catalyst prepared from [o-(PhCH2O)]C6H4PPh2, [(allyl)2NiBr]2, and Na+ BAr4- (Ar = 3,5-bis-trifluromethylphenyl), giving 1,2-addition products. Yields up to 99% can be realized for several 1-vinylcycloalkenes and 1-substituted 1,3-butadienes. Phospholanes with suitably placed hemilabile ligating groups and phosphoramidites derived from binaphthol are excellent ligands for an asymmetric variation of this reaction, the latter giving 99% yield and >95% ee's for selected substrates. An example of how an exocyclic chiral center can be used to install other stereo-centers in the ring (e. g., the carbon to which the side chain is attached) is also provided. These discoveries open an expeditious entry into several biologically relevant classes of compounds, especially those carrying tetrahydronaphthalene and related heterocyclic moieties. Copyright
- Zhang, Aibin,RajanBabu
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- DTBB-catalysed lithiation of 1,2-bis(phenylsulfanyl)ethene: Does 1-lithio-2-phenylsulfanylethene really exist?
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The reaction of (Z)- or (E)-1,2-bis(phenylsulfanyl)ethene (1) with an excess of lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 2.5 mol%) in the presence of a carbonyl compound as electrophile (Barbier conditions) in THF at -78°C leads, after hydrolysis with water at temperatures ranging between -78°C and rt, to a mixture of the corresponding (Z/E)-unsaturated 1,4-diols 2, the diastereomers ratio being independent of the stereochemistry of the starting materials. Allylic alcohols 3 are the main by-products, resulting from a lithium-hydrogen exchange on some of the lithiated intermediates along the whole process. A mechanistic explanation for the observed behaviour is given.
- Gómez, Cecilia,Maciá, Beatriz,Yus, Miguel
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p. 9325 - 9330
(2007/10/03)
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- Synthesis of carbo- and heterocyclic aldehydes bearing an adjacent donor group - Ozonolysis versus OsO4/KIO4-oxidation
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The synthesis of carbo- and heterocyclic aldehydes bearing an ipso-methoxy group is investigated. The synthetic sequence is based on an initial Grignard addition of an olefin to a cyclic ketone followed by methylation of the resulting tertiary alcohol. The terminal olefin serves as precursor for the aldehyde functionality. Oxidation by ozonolysis turned out to depend significantly on the distance of the donor methoxy group. The observed side reactions could be circumvented by applying a one-pot OsO4 mediated diol formation followed by Malaprade oxidation using KIO4. A series of carbo- and heterocyclic precursors were successfully converted to the title products. Springer-Verlag 2004.
- Mihovilovic, Marko D.,Spina, Markus,Mueller, Bernhard,Stanetty, Peter
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p. 899 - 909
(2007/10/03)
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- A modular and concise total synthesis of (±)-daurichromenic acid and analogues
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A modular and concise total synthesis of (±)-daurichromenic acid has been accomplished in four steps from ethyl acetoacetate, ethyl crotonate, and trans,trans-farnesal. A series of analogues of this natural product, which has potent anti-HIV activity, were also prepared from ethyl or methyl acetoacetate and a series of readily available α,β-unsaturated esters and aldehydes.
- Hu, Hongjuan,Harrison, Tyler J.,Wilson, Peter D.
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p. 3782 - 3786
(2007/10/03)
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- Ruthenium-catalyzed olefin metathesis double-bond isomerization sequence
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A novel ruthenium-catalyzed tandem ring-closing metathesis (RCM) double-bond isomerization reaction is described in this paper. The utility of this method for the efficient syntheses of five-, six-, and seven-membered cyclic enol ethers is demonstrated. It relies on the conversion of a metathesis-active ruthenium carbene species to an isomerization-active ruthenium-hydride species in situ. This conversion is achieved by using various additives. Scope and limitations of the different protocols are discussed, and some mechanistic considerations based on 31P and 1H NMR spectroscopic studies are presented.
- Schmidt, Bernd
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p. 7672 - 7687
(2007/10/03)
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- Synthesis of spirocyclic butenolides by ring closing metathesis
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Spirocyclic butenolides were efficiently prepared by a ring closing metathesis strategy.
- Langer, Peter,Albrecht, Uwe
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p. 1841 - 1842
(2007/10/03)
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- Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts
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Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated. Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated.
- Spee,Boersma,Meijer,Slagt,Van Koten,Geus
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p. 1647 - 1656
(2007/10/03)
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- Synthesis of spiro ethers by ring closing metathesis
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Starting from the cyclic ketones 1a-d, the dienes 3a-e were prepared. The ring closing metathesis reaction of these dienes using the Grubbs catalyst 5 provided the corresponding spiro ethers 4a-e in good yield. Force field calculations indicate that the conformer with the oxygen in axial position is favored.
- Maier, Martin E.,Bugl, Michael
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p. 1390 - 1392
(2007/10/03)
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- Indole derivatives as 5-HT1-like agonists for use in migraine
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The present invention relates to 3,5-disubstituted indole compounds which are selective agonists which act on 5-hdroxytryptamine receptors useful in the treatment of migraine.
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- One-pot transformation of p-toluenesulfonates of 2,3-epoxy alcohols into allylic alcohols
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A convenient and efficient method for the synthesis of synthetically useful non-racemic allylic alcohols from 4-methylbenzenesulfonates of non- racemic 2,3-epoxy alcohols is described. Satisfactory yields are obtained by treatment of 4-methylbenzenesulfonates of non-racemic 2,3-epoxy alcohols with potassium iodide followed by zinc powder and ammonium chloride in a one-pot manner. The method has been successfully applied to the synthesis of a key building block of C30-C37 botryococcenes.
- Habashita, Hiromu,Kawasaki, Takeshi,Akaji, Masako,Tamamura, Hirokazu,Kimachi, Tetsutaro,Fujii, Nobutaka,Ibuka, Toshiro
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p. 8307 - 8310
(2007/10/03)
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- Synthesis and Applications of Tetrahydrofuran-Stable Substituted (3-Lithioxyalkyl)- and (4-Lithioxyalkyl)lithiums, Modified with Magnesium 2-Ethoxyethoxide
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Substituted hydroxyalkyl phenyl sulfides 3 have been synthesized from the corresponding allylic or homoallylic alcohols 2. Regiospecific cleavage of the C - SPh bond of the sulfides 3 by lithium dispersion in tetrahydrofuran (THF) led to the synthesis of substituted (3-lithioxyalkyl)- and (4-lithioxyalkyl)lithiums 4, most of which share the ω carbon with a carbocyclic ring. The organolithiums were modified with magnesium 2-ethoxyethoxide in order to suppress their reactivity toward THF cleavage, thus offering the advantage of preparing storable ethereal solutions of certain types of (lithioxyalkyl)lithiums. This strategy appears to be of rather broad scope. The functionalized organolithiums prepared in this way react normally with electrophilic reagents with yields in the range 35-55%. Thus, carboxylations of 4 yielded lactones 5, some of which are natural products, while reactions of 4 with benzophenone and cyclic ketones yielded 1,4- and 1,5-diols 6 and 7, respectively.
- Kostas, Ioannis D.,Screttas, Constantinos G.
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p. 5575 - 5577
(2007/10/03)
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- Simple one-pot transformations of toluene-p-sulfonates of 2,3-epoxy alcohols into allylic alcohols
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A simple synthetic method for the preparation of scalemic allylic alcohols from toluene-p-sulfonates of scalemic 2,3-epoxy alcohols is reported. Satisfactory yields are obtained by treatment of toluene-p-sulfonates of 2,3-epoxy alcohols with potassium iodide followed by triphenylphosphine and iodine in a one-pot synthesis.
- Fujii, Nobutaka,Habashita, Hiromu,Akaji, Masako,Nakai, Kazuo,Ibuka, Toshiro,Fujiwara, Masahiro,Tamamura, Hirokazu,Yamamoto, Yoshinori
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p. 865 - 866
(2007/10/03)
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- Synthesis of spiranic heterocycles by induced decomposition of unsaturated peroxides
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Induced decomposition of unsaturated peroxides in a good hydrogen-donor solvent leads to the functionalization of the latter.If the peroxide contains a cycle on the carbon next to the O-O bond, the reaction gives spirans with an oxiran, an oxetan or a tetrahydrofuran ring in good or even excellent yields.Keywords: unsaturated peroxide / spiranic heterocycles / induced decomposition / homolytic intramolecular substitution / radical addition
- Montaudon, Evelyne,Kappes, Regina,Lemee, Laurent,Campagnole, Monique,Bourgeois, Marie-Josephe
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p. 253 - 261
(2007/10/02)
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- GRIGNARD REAGENTS AS POWDERS : PREPARATION AND REACTIVITY
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The TDA-1 chelating agent is able to complex Grignard reagents.This complexation leads to powders.The preparation is general and the complexes "RMgX/TDA-1" are easily prepared from every type of Grignard reagents.These solids are stable under nitrogen and can be titrated and used as Grignard reagents.The study of their chemical reactivity shows a behaviour comparable to that of conventional Grignard reagents, the rate of reactions however being decreased.Selective addition onto a mixture of aldehyde and ketone is possible.Interestingly the reactions can be performed in hydrocarbon solvents (toluene, light petroleum, cyclohexane).
- Boudin, Alain,Cerveau, Genevieve,Chuit, Claude,Corriu, Robert J.P.,Reye, Catherine
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p. 171 - 180
(2007/10/02)
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- Isomerisation de dienes-1,5 fonctionnalises par le fer pentacarbonyle
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A series of various, functionnalized 4-vinylcyclohexene derivatives, substituted with electron-withdrawing or -donating groups on the exocyclic double bond, have been isomerized by pentacarbonyliron, under thermodynamic control with heating, into a mixture of conjugated cyclohexadiene tricarbonyliron complexes, of which the 2-substituted derivative is the predominant.When ferrous chloride is used as the co-catalyst, the isomerisation proceeds under kinetic control to give the 1-substituted cyclohexadienetricarbonyliron complex as the major derivative.Reaction mechanisms, have been proposed for these isomerisation processes, which provide a new selective route to such derivatives.The formation of η4-1,4-cyclohexadienetricarbonyl complexes as intermediates has been excluded, and it is shown that the thermal isomerisation proceeds via η2-complexes that are formed by successive 1,3-hydrogen shifts.
- Rodriguez, J.,Brun, P.,Waegell, B.
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p. 343 - 370
(2007/10/02)
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- DIELS-ALDER REACTIONS OF 4,4-DIMETHYL-2-CYCLOHEXENONES. A DIRECT ROUTE TO THE 4,4-DIMETHYL-1-DECALONES
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Diels-Alder additions to enones 1 and 2, synthetic equivalents of the synthon 3, were studied using a variety of hydrocarbon dienes.The two enones have been shown to be effective and synthetically useful dienophiles.Spectroscopic (especially 1H and 13C magnetic resonance) and chemical techniques were used to define unambiguously the full structures of the adducts.The structures of the various reaction products were used to draw qualitative conclusions about the nature of the transition states involved and the various electronic and steric effects that play a role in the mechanistic course of the Diels-Alder reaction.
- Liu, Hsing-Jang,Browne, Eric N. C.
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p. 1262 - 1278
(2007/10/02)
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- ISOMERIZATION OF ALLYLIC ALCOHOLS CATALYZED BY VANADIUM OR MOLYBDENUM COMPLEXES.
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Isomerization of primary allylic alcohols proceeds in dichloromethane at 25 degree C in the presence of the catalyst prepared in situ from VO(acac)//2 or MoO//2(acac)//2, and Me//3SiOOSiMe//3 to give tertiary isomers in good yields. The catalysts are also effective for the rearrangements of sec. yields tert. allylic alcohols. The isomerization of an allenyl allylic alcohol, 6-methyl-1,2,5-heptatrien-4-ol, gives either (E)-2-methyl-3,5,6-heptarien-2-ol or (E)-6-methyl-3,5-heptadien-2-one selectively depending on the reaction conditions.
- Matsubara,Okazoe,Oshima,Takai,Nozaki
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p. 844 - 849
(2007/10/02)
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- Studies on the Occurrence of Hydrogen Transfer, 74. Electroreductive Hydrogenation Using Raney-Nickel-Powder as a Cathode
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Cathodically pretreated Raney-nickel-powder with a potential of -900 to -1000 mV (vs SCE) shows a positive potential shift of 200 to 300 mV in the presence of a hydrogen acceptor (coumarine or 1-ethinylcyclohexanol (1)).Pyridine and quinoline do not have any strong influence on the potential but retard the hydrogenation of coumarine.Acetylene derivatives as 1-ethinylcyclohexanol are hydrogenated in two steps applying a potential down to -1050 mV.At -1150 mV the selectivity is lost.With Raney-nickel-powder pretreated with pyridine or hydrogensulfide the two-step selectivity of the hydrogenation of 1 is preserved applying also a potential of -1200 mV. - Keywords: Heterogenous Hydrogenation Electrocatalysis, Electroreductive Hydrogenation, Raney-Nickel-Powder
- Horner, L.,Franz, Ch.
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p. 808 - 813
(2007/10/02)
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- Photooxygenation of 1-Vinylcycloalkenes. The Competition between "Ene" Reaction and Cycloaddition of Singlet Oxygen
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The competition between the "ene" reaction and 1,4-cycloaddition reaction of 1O2 in a series of 1-vinylcycloalkenes (n = 5-10, 12) and 1-isopropenylcycloalkenes (n = 6-8) was studied.Ring size had a profound effect.When n = 5 or 7, products of the "ene" reaction predominated, but as ring size increased cycloaddition competed closely with the "ene" process, the crossover being at ring size 10. 1-Vinylhexenes constituted an exception with 1,4-cycloaddition greatly predominant. "Ene" products were almost exclusively conjugated diene hydroperoxides or secondary products derived from them; small amounts of unconjugated diene hydroperoxides were formed only when n = 9, 10, or 12.The influence of ring size of the "ene" to cycloaddition product ratio is compared with the rates of photooxygenation and the degree of syn-regiospecificity exhibited by (Z)-1-methylcycloalkenes and attributed to the same mainly conformational factors, as is the geometry of the "ene" products.The 1,4-cycloaddition products were converted to furans by means of ferrous sulfate.
- Herz, Werner,Juo, Rouh-Rong
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p. 618 - 627
(2007/10/02)
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