Angewandte Chemie International Edition

Cover image for Vol. 45 Issue 14

March 27, 2006

Volume 45, Issue 14

Pages 2149–2313

    1. Cover Picture: Autonomous Fueled Mechanical Replication of Nucleic Acid Templates for the Amplified Optical Detection of DNA (Angew. Chem. Int. Ed. 14/2006) (page 2149)

      Yossi Weizmann, Zoya Cheglakov, Valeri Pavlov and Itamar Willner

      Version of Record online: 17 MAR 2006 | DOI: 10.1002/anie.200690048

      A catalytic cutter for the sensitive detection of a target DNA, a Tay–Sachs disorder mutant, is described by I. Willner and co-workers in their Communication on page 2238 ff. As the cover picture shows, a tailored nucleic acid hairpin probe (top) is opened upon hybridization with the analyte DNA, activating the formation of the DNA cutter (central structure), which initiates the autonomous scission of a fuel substrate that leads to the replication of the catalytic cutter and to the formation of a fluorescent product as an optical readout signal.

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    4. Organocatalytic Enantioselective Photoreactions (pages 2168–2171)

      Pablo Wessig

      Version of Record online: 24 FEB 2006 | DOI: 10.1002/anie.200503908

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      Light at the end of the tunnel. The reports on organocatalytic photoreactions that are also enantioselective are few and far between. Recently published work now highlights a breakthrough. When special catalysts derived from Kemp's triacid were used, selectivities of up to 70 % ee were achieved (see scheme; PET=photoinduced electron transfer).

    5. Construction of Asymmetric Fluorinated Carbon Centers (pages 2172–2174)

      G. K. Surya Prakash and Petr Beier

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503783

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      Various choices: Recent advances in the construction of asymmetric fluorinated carbon centers are discussed. Special attention is called to catalytic enantioselective reactions such as electrophilic fluorination (top) and decarboxylative allylation (bottom) of fluorinated substrates.

    6. Metal Vinylidenes and Allenylidenes in Catalysis: Applications in Anti-Markovnikov Additions to Terminal Alkynes and Alkene Metathesis (pages 2176–2203)

      Christian Bruneau and Pierre H. Dixneuf

      Version of Record online: 7 MAR 2006 | DOI: 10.1002/anie.200501391

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      Versatile key intermediate metal vinylidenes and allenylidenes participate in numerous catalytic processes such as alkene metathesis, coupling reactions, and anti-Markovnikov additions to alkynes. The formation of a metal vinylidene intermediate in a catalytic reaction (see scheme) was first reported 20 years ago, and much development in the field has since taken place.

    7. Sequential Self-Assembly of a DNA Hexagon as a Template for the Organization of Gold Nanoparticles (pages 2204–2209)

      Faisal A. Aldaye and Hanadi F. Sleiman

      Version of Record online: 27 FEB 2006 | DOI: 10.1002/anie.200502481

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      Six of one and half a dozen of the other: A cyclic hexamer of six gold nanoparticles was sequentially and selectively self-assembled by labeling each particle (red sphere) with a DNA-containing molecule (colored block), which serves to dictate its ultimate location within the final construct. This method may be used to construct any discrete well-defined pattern of nanoparticles.

    8. Expanding the Utility of One-Pot Multistep Reaction Networks through Compartmentation and Recovery of the Catalyst (pages 2209–2212)

      Nam T. S. Phan, Christopher S. Gill, Joseph V. Nguyen, Z. John Zhang and Christopher W. Jones

      Version of Record online: 10 MAR 2006 | DOI: 10.1002/anie.200503445

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      Controlled catalysis: The combination of magnetically and gravimetrically recoverable catalysts such as the nanoparticle-bound base (see picture; blue) and the resin-bound acid (green), respectively, allow the application of non-complementary catalysts to multistep, one-pot reaction cascades (e.g. A[RIGHTWARDS ARROW]B[RIGHTWARDS ARROW]C). The catalysts are recovered after reaction and reused in subsequent, unrelated reactions.

    9. Imaging Proteins in Membranes of Living Cells by High-Resolution Scanning Ion Conductance Microscopy (pages 2212–2216)

      Andrew I. Shevchuk, Gregory I. Frolenkov, Daniel Sánchez, Peter S. James, Noah Freedman, Max J. Lab, Roy Jones, David Klenerman and Yuri E. Korchev

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503915

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      Do not touch! The surface of a living cell is soft and responsive and therefore high-resolution imaging of the cell membrane has not been possible to date. Now noncontact imaging of protein complexes in the plasma membrane of living cells has been demonstrated (see picture) and has been used to follow the cells' structural reorganization. This breakthrough opens up a wealth of new experiments in membrane and cell biology.

    10. Magnetic Behavior of a 1D Molecular-Oxygen System Included within a Transformable Single-Crystal Adsorbent (pages 2216–2221)

      Satoshi Takamizawa, Ei-ichi Nakata and Takamasa Akatsuka

      Version of Record online: 2 MAR 2006 | DOI: 10.1002/anie.200501639

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      Sheer magnetism: The phase transitions and magnetic behavior of included oxygen in a single crystal were studied at low temperature. The system exhibits three correlated structural and magnetic phases. The distinct middle-temperature phase shows a one-dimensional-chain arrangement of oxygen trimers with an anomalous magnetization response to external magnetic fields.

    11. Colloidal CdSe Nanocrystals Passivated by a Dye-Labeled Multidentate Polymer: Quantitative Analysis by Size-Exclusion Chromatography (pages 2221–2224)

      Mingfeng Wang, Tieneke E. Dykstra, Xudong Lou, Mayrose R. Salvador, Gregory D. Scholes and Mitchell A. Winnik

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200502538

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      Hold on tight: Pyrene-labeled poly(dimethylaminoethyl methacrylate) (Pyr-PDMAEMA) was synthesized as a multidentate ligand for CdSe nanocrystals (NCs, see picture). The mean number of polymers that bind to each NC can be determined by a quantitative analytical method based on size-exclusion chromatography. Spectroscopic characterization of the eluted particles shows that Pyr-PDMAEMA binds tightly to these NCs.

    12. DNA Sequencing Based on Intrinsic Molecular Charges (pages 2225–2228)

      Toshiya Sakata and Yuji Miyahara

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503154

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      In charge: Label-free DNA sequencing can be performed by using a field-effect transistor to detect the intrinsic molecular charges (see picture). Oligonucleotide probes are immobilized on the Si3N4 gate surface, and complementary target DNA is hybridized with them. The change in charge density on the Si3N4/SiO2 gate caused by each single-base extension can be measured as a shift in the threshold voltage. VG=gate voltage.

    13. A Caged Doxycycline Analogue for Photoactivated Gene Expression (pages 2229–2231)

      Sidney B. Cambridge, Daniel Geissler, Sandro Keller and Beate Cürten

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503339

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      High potential: High-resolution transgene expression in two biological applications demonstrates the potential of a photoactivated gene-expression technique. Irradiation of one half of a transgenic tobacco leaf produced a sharp boundary of reporter gene expression between photoactivated tissue and nonirradiated tissue (see picture). This method was established by synthesis of a photosensitive doxycycline analogue.

    14. A Subtle End-Group Effect on Macroscopic Physical Gelation of Triblock Copolymer Aqueous Solutions (pages 2232–2235)

      Lin Yu, Huan Zhang and Jiandong Ding

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503575

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      In the end: Alkyl end groups can induce a thermoreversible sol–gel transition in an otherwise sol-like suspension by affecting the macroscopic self-assembly behavior. The picture shows PLGA-PEG-PLGA triblock copolymer/water mixtures in the sol (polymer a), gel (polymers b and c), and precipitation states (polymer d). PLGA=poly(lactic acid-co-glycolic acid), PEG=poly(ethylene glycol).

    15. Asymmetric Retro-[1,4] Brook Rearrangement and Its Stereochemical Course at Silicon (pages 2235–2238)

      Atsuo Nakazaki, Takeshi Nakai and Katsuhiko Tomooka

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503734

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      Taking the silyl group a step further: An unprecedented rearrangement in an anion derived from an allyloxysilane occurs by a [1,4] shift of the silyl group (see scheme). The asymmetric synthesis of enantiomerically enriched γ-functionalized allylsilanes with Si stereocenters can be accomplished with this retro-[1,4] Brook rearrangement. E=electrophile.

    16. Autonomous Fueled Mechanical Replication of Nucleic Acid Templates for the Amplified Optical Detection of DNA (pages 2238–2242)

      Yossi Weizmann, Zoya Cheglakov, Valeri Pavlov and Itamar Willner

      Version of Record online: 2 MAR 2006 | DOI: 10.1002/anie.200503810

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      Fuel for a DNA machine: A FokI enzyme/DNA scission machine is triggered by the hybridization of its DNA hairpin structure with a target nucleic acid. The machine is fueled by a secondary fluorophore (F)- and quencher (Q)-functionalized nucleic acid 2. Scission of 3 leads to replication of the machinery cutter 1 and yields a fluorescent product 6, which provides an optical output for the machine (see scheme).

    17. Efficient Phenanthrene, Helicene, and Azahelicene Syntheses (pages 2242–2245)

      David C. Harrowven, Ian L. Guy and Lana Nanson

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200504287

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      Homolytic aromatic substitution reactions are used for the efficient regioselective synthesis of helicenes, phenanthrenes, and azahelicenes. The use of halo and alkoxy substituents to control the stereochemical outcome of this approach and X-ray studies of the resulting helicenes are described (see structure; red O, gray C).

    18. Isolation of a 1,2-Dialuminacyclobutene (pages 2245–2247)

      Chunming Cui, Xiaofei Li, Chunhua Wang, Jianying Zhang, Jinpei Cheng and Xiaoqing Zhu

      Version of Record online: 6 MAR 2006 | DOI: 10.1002/anie.200504329

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      Aluminum siding: Reduction of Ar′AlI2 (Ar′=2,6-Dipp2C6H3, Dipp=2,6-iPr2C6H3) in the presence of Me3SiCCSiMe3 afforded (Ar′Al)2(CSiMe3)2 (see picture), a dialuminum-substituted cyclobutene analogue. The central four-membered Al2C2 ring adopts a folded geometry and is isoelectronic with aromatic cyclobutadiene dications.

    19. Low-Surface-Free-Energy Materials Based on Polybenzoxazines (pages 2248–2251)

      Chih-Feng Wang, Yi-Che Su, Shiao-Wie Kuo, Chih-Feng Huang, Yuung-Ching Sheen and Feng-Chih Chang

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503957

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      How low can you go? Polybenzoxazines can display surface free energies which are even lower than that of pure poly(tetrafluoroethylene). The contact angles and surface free energies were monitored during the polymerizations (see graph for an example). These materials are cheaper to prepare and easier to process than fluoropolymers.

    20. Synthesis of Stable Super Water- and Oil-Repellent Polythiophene Films (pages 2251–2254)

      Mael Nicolas, Frédéric Guittard and Serge Géribaldi

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503892

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      A cauliflowerlike surface (see picture, scale bar: 8 μm) and perfluorocarbon chains on the polymer backbone result in super water and oil repellency of a film of the fluorinated polythiophene shown that was electrochemically deposited on an indium tin oxide surface. The inset shows a camera image of a water droplet on the surface (contact angle>150°).

    21. High Substrate/Catalyst Organocatalysis by a Chiral Brønsted Acid for an Enantioselective Aza-Ene-Type Reaction (pages 2254–2257)

      Masahiro Terada, Kyoko Machioka and Keiichi Sorimachi

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503477

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      Lowering the load: A very small amount of a binaphthol-derived monophosphoric acid organocatalyst accelerates an aza-ene-type reaction of N-benzoylimines with enecarbamates to provide β-aminoimines with high enantiomeric purity. This catalysis with a high substrate/catalyst(S/C) ratio provides a practical route to 1,3-diamine derivatives of synthetic and biological importance.

    22. Ab Initio MO Analysis of the Excited Electronic States of High-Spin Quintet 2-Methylphenylene-1,3-dinitrene (pages 2257–2260)

      Kenji Sugisaki, Kazuo Toyota, Kazunobu Sato, Daisuke Shiomi and Takeji Takui

      Version of Record online: 6 MAR 2006 | DOI: 10.1002/anie.200502695

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      The concept of orbital correlations between the benzene skeleton and the nitrene moieties of 2-methylphenylene-1,3-dinitrene was used to interpret the energy levels and characters of the excited electronic states of this typical high-spin quintet molecule by high-level ab initio MO calculations. Thus, the UV/Vis absorption spectrum of this dinitrene was assigned theoretically for the first time (see stick spectrum in the picture).

    23. Asymmetric Hydrogenation of Quinolines and Isoquinolines Activated by Chloroformates (pages 2260–2263)

      Sheng-Mei Lu, You-Qing Wang, Xiu-Wen Han and Yong-Gui Zhou

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503073

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      Active ingredient: Optically active tetrahydroquinolines and tetrahydroisoquinolines can be obtained by the asymmetric hydrogenation of quinolines and isoquinolines with chloroformates as the activating reagent (e.g., ClCO2Bn, see scheme). The method has been applied to the asymmetric synthesis of several naturally occurring alkaloids. Bn=benzyl.

    24. Synthesis of Macrocyclic Poly(ε-caprolactone) by Intramolecular Cross-Linking of Unsaturated End Groups of Chains Precyclic by the Initiation (pages 2264–2267)

      Haiying Li, Antoine Debuigne, Robert Jérome and Philippe Lecomte

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503961

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      Biodegradable cyclic polyesters are synthesized by using an ε-caprolactone polymerization initiated by a cyclic tin alkoxide, followed by the addition and sequential polymerization of a few units of α-(1-acryloxyethyl)-ε-caprolactone. Tadpole-shaped polyesters with two tails of controllable length are readily prepared by this procedure (see picture).

    25. Nanoparticle-Assisted Visualization of Binding Interactions between Collagen Mimetic Peptide and Collagen Fibers (pages 2267–2270)

      Xiao Mo, Yoojin An, Chang-Soo Yun and Seungju M. Yu

      Version of Record online: 2 MAR 2006 | DOI: 10.1002/anie.200504529

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      Collagen treatment: Gold nanoparticles conjugated with collagen mimetic peptide (CMP) form stable adducts with collagen fibers (see picture) that are visible by transmission electron microscopy, thereby allowing the study of binding interactions between CMPs and type I collagen fibers. This labeling technique may potentially be used to identify structural abnormalities in collagen fibers that are related to diseases.

    26. Regio- and Stereoselective Decarbonylative Carbostannylation of Alkynes Catalyzed by Pd/C (pages 2271–2274)

      Yoshiaki Nakao, Jun Satoh, Eiji Shirakawa and Tamejiro Hiyama

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200504283

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      Out with the CO: The highly regio- and stereoselective aryl-, alkenyl-, and alkylstannylation of alkynes was achieved by the decarbonylative carbostannylation of propargyl 2-furoates in the presence of Pd/C. Various functionalized alkenylstannanes were obtained that contain nucleophilic alkenylstannane and electrophilic allyl furoate moieties, which can be transformed by coupling reactions.

    27. Highly Diastereoselective One-Pot Synthesis of Spirocyclic Oxindoles through Intramolecular Ullmann Coupling and Claisen Rearrangement (pages 2274–2277)

      Hiroshi Miyamoto, Yoichiro Okawa, Atsuo Nakazaki and Susumu Kobayashi

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200504247

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      An efficient and convenient approach to the synthesis of spirocyclic oxindoles from iodoindoles involves a sequential intramolecular C[BOND]O Ullmann coupling reaction and Claisen rearrangement (see scheme). The one-pot procedure affords 3-spiro-2-oxindoles in good yield with excellent diastereoselectivities.

    28. An Unprecedented Example of a Hetero-trimetallic Main-Group [L2Al2Ge4Li2S7] Cluster Containing a GeII[BOND]GeII Donor–Acceptor Bond (pages 2277–2280)

      Zhi Yang, Xiaoli Ma, Rainer B. Oswald, Herbert W. Roesky, Chunming Cui, Hans-Georg Schmidt and Mathias Noltemeyer

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503940

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      Donations accepted: The reaction of [{LAl[(SLi)2(thf)2]}2] (L=HC(CMeNAr)2, Ar=2,6-iPr2C6H3) with GeCl2⋅dioxane yields the novel GeII[RIGHTWARDS ARROW]GeII-containing hetero-trimetallic [L2Al2Ge4Li2S7] cluster, which has a crablike structure (Al gray, Ge magenta, Li orange, S yellow, O green, N blue, C light gray). This cluster is the first aluminum-containing hetero-trimetallic sulfide.

    29. Label-Free Affinity Assays by Rapid Detection of Immune Complexes in Submicrometer Pores (pages 2281–2285)

      Jeffrey D. Uram, Kevin Ke, Alan J. Hunt and Michael Mayer

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200502862

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      Resistance movement: A submicrometer conical pore was used for the single-aggregate detection and characterization of immune complexes consisting of proteins such as staphylococcal enterotoxin B and antibodies. The developed assay is rapid, label-free, requires no immobilization or modification of the antibody or antigen, and can be performed with antibodies or proteins in serum.

    30. On the Issue of the Deactivation of Au–Ceria and Pt–Ceria Water–Gas Shift Catalysts in Practical Fuel-Cell Applications (pages 2285–2289)

      Weiling Deng and Maria Flytzani-Stephanopoulos

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503220

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      A small amount of gaseous oxygen (air) added to the feed gas stabilizes nanostructured Au–ceria and Pt–ceria catalysts for the water–gas shift (WGS) reaction in H2-rich gases and start/stop operation. Au–ceria materials emerge as practical alternatives to expensive Pt-based catalysts for total CO removal from reformate gas mixtures for fuel-cell use. PROX=preferential oxidation of CO.

    31. Annulative Tandem Reactions Based on Pd0/tBu3P-Catalyzed Cross-Coupling and C(sp3)[BOND]H Bond Activation (pages 2289–2292)

      Cheng-Guo Dong and Qiao-Sheng Hu

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200504310

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      All together now: Pd0/tBu3P-catalyzed annulative tandem reactions of 1,2-dihalobenzenes were carried out with hindered Grignard reagents. This new type of tandem reaction is believed to occur through cross-coupling followed by cyclization with C(sp3)[BOND]H bond activation as the key step and allows one-step access to potentially useful substituted fluorenes in high yield from readily available 1,2-dibromobenzenes and 1-bromo-2-iodobenzene.

    32. Synthesis of a “Half”-Parent Phosphasilene R2Si[DOUBLE BOND]PH and Its Metalation to the Corresponding P-Zinciophosphasilene [R2Si[DOUBLE BOND]PM] (pages 2293–2296)

      Matthias Driess, Stefan Block, Markus Brym and Michael T. Gamer

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200504145

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      Remarkably stable—even with a hydrogen atom at the low-coordinate phosphorus center! A straightforward synthesis provides the thermally robust phosphasilenes (E)/(Z)-1, which have a terminal PH group. These compounds can be cleanly metalated with dimethylzinc in the presence of tmeda (tetramethylethylenediamine) to afford exclusively the P-zincio-substituted phosphasilene 2 with E configuration. R=2,4,6-triisopropylphenyl.

    33. Nonribosomal Peptide Biosynthesis: Point Mutations and Module Skipping Lead to Chemical Diversity (pages 2296–2301)

      Silke C. Wenzel, Peter Meiser, Tina M. Binz, Taifo Mahmud and Rolf Müller

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503737

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      Big effects from small changes: In a comparative analysis of the nonribosomal peptide synthetases (NRPSs) from the biosynthetic pathways of two highly related myxobacterial lipopeptides, module skipping and point mutations are directly correlated to structural variations in these natural products. The skipping process during myxochromide S biosynthesis was characterized biochemically and represents the first example of a module skipping in NRPS systems.

    34. Synthesis of Macrocyclic Aluminum–Phosphorus and Gallium–Phosphorus Compounds (pages 2302–2305)

      Carsten von Hänisch and Sven Stahl

      Version of Record online: 28 FEB 2006 | DOI: 10.1002/anie.200503531

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      A 16-membered ring consisting of eight aluminum or gallium atoms and eight phosphorus atoms is the central structural motif in the polycyclic compounds formed through the reaction of the diphosphanyldisiloxane O(SiiPr2PH2)2 with MEt3 (M=Al, Ga; see the heteroatom framework of the gallium compound).

    35. Catalytic Activation of N[BOND]N Multiple Bonds: A Homogeneous Palladium Catalyst for Mechanistically Unprecedented Reduction of Azo Compounds (pages 2305–2308)

      Kilian Muñiz and Martin Nieger

      Version of Record online: 3 MAR 2006 | DOI: 10.1002/anie.200503875

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      Just two oxidation states are involved in the homogeneous reduction of azo compounds at a single palladium catalyst site. The reaction proceeds through an intermediate state in which the catalyst displays a novel palladadiaziridine structure, and ethanol or related alcohols can be employed as the terminal reducing agent (see scheme).

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