Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 11

March 4, 2005

Volume 44, Issue 11

Pages 1573–1739

    1. Cover Picture: Iron-Catalyzed Aryl–Aryl Cross-Couplings with Magnesium-Derived Copper Reagents (Angew. Chem. Int. Ed. 11/2005) (page 1573)

      Ioannis Sapountzis, Wenwei Lin, Christiane C. Kofink, Christina Despotopoulou and Paul Knochel

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200590033

      Aryl–aryl cross-couplings are among the most important C[BOND]C bond-forming reactions. Catalysts for this reaction tend to be expensive (Pd) or toxic (Ni). Fe salts are not usually employed as they promote homocoupling of the aryl magnesium reagent. In their Communication on page 1654 ff., P. Knochel and co-workers report an efficient and environmentally benign [Fe(acac)3]-catalyzed cross-coupling of organocopper species ArCu(CN)MgCl with aryl iodides to give a wide range of polyfunctional biphenyl compounds in 50–93 % yield.

    2. Squaring the Interface: “Surface-Assisted” Coordination Chemistry (pages 1594–1596)

      Mario Ruben

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200462064

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      Coming to the surface: A straightforward approach for the generation of gridlike modular structures composed of metal ions and ligands on surfaces (see picture) was developed by the research groups led by K. Kern, J. V. Barth, and N. Lin. This Highlight hails a novel, “surface-assisted” coordination chemistry.

    3. Comments on “How Single and Bifurcated Hydrogen Bonds Influence Proton-Migration Rate Constants, Redox, and Electronic Properties of Phenoxyl Radicals” (pages 1598–1599)

      Ian J. Rhile and James M. Mayer

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200461977

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      Mechanistic reinterpretation of cyclic voltammetry data on hydrogen-bonded phenols precludes the stepwise electron- then proton-transfer pathway suggested by F. Thomas et al. Thermochemical and kinetic results indicate that the phenoxyl–ammonium product is formed directly in the anodic process (see scheme).

    4. Asymmetric Multicomponent Reactions (AMCRs): The New Frontier (pages 1602–1634)

      Diego J. Ramón and Miguel Yus

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200460548

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      Some of the many advantages of asymmetric multicomponent reactions over classical divergent synthesis include superior atom economy, simple procedures, savings in solvent, time, and energy, simple equipment and manipulation, as well as lower costs. Besides these advantages, this new strategy has reached excellent levels of stereoselectivity in many processes.

    5. Real-Time Spectroscopic and Chemical Probing of Reductive Electron Transfer in DNA (pages 1636–1639)

      Peter Kaden, Elke Mayer-Enthart, Anton Trifonov, Torsten Fiebig and Hans-Achim Wagenknecht

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200462592

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      Highly acceptable: DNA is a flexible medium with a range of conformational states. Thus, in investigations of the DNA-mediated reductive electron transfer using a modified DNA duplex containing 5-bromo-2′-deoxyuridine (red in picture) as the electron acceptor and pyren-1-yl-2′-deoxyuridine (blue) as the electron donor, a distribution of electron-transfer rates has been observed.

    6. Self-Assembly of Bidentate Ligands for Combinatorial Homogeneous Catalysis Based on an A–T Base-Pair Model (pages 1640–1643)

      Bernhard Breit and Wolfgang Seiche

      Version of Record online: 9 FEB 2005 | DOI: 10.1002/anie.200462499

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      The odd couple: Inspired by the principle of DNA base pairing a conceptually new approach for the generation of a heterobidentate-ligand library based on self-assembly through hydrogen-bonding is realized. From a 4×4 library a catalyst that shows outstanding activity and excellent regioselectivity could be identified (see scheme; FGR=functional group, Do=donor group).

    7. Derivatives of the Simplest Polyhedral Carborane Anion: Structures at the Borderline between Two- and Three-Dimensional Aromatic Compounds (pages 1643–1646)

      Yüksel Sahin, Carsten Präsang, Matthias Hofmann, Gertraud Geiseler, Werner Massa and Armin Berndt

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200462397

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      Borderline aromatics: The series of compounds of composition CBnHn+1 is now completed with the simplest three-dimensional aromatic 1. The precursor 2, a two-dimensional aromatic, and the product of protonation, 3, a homoaromatic, display partially nonclassical σ frameworks. R=SiMe3, Dur=2,3,5,6-tetramethylphenyl.

    8. Bond-Selective H Ion Abstraction from Thymine (pages 1647–1650)

      Sylwia Ptasińska, Stephan Denifl, Verena Grill, Tilmann D. Märk, Paul Scheier, Sascha Gohlke, Michael A. Huels and Eugen Illenberger

      Version of Record online: 9 FEB 2005 | DOI: 10.1002/anie.200461739

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      The attachment of free electrons to thymine in the gas phase leads to the abstraction of H ions and a broad, structured feature in the energy range between 5 and 12 eV (see picture). In experiments with partly deuterated thymine the different peaks in the H ion yield were shown to be associated unambiguously with abstraction from the different molecular positions. This reaction may be an important initial step towards DNA strand breaks.

    9. An Orthogonal Double-Linker Resin Facilitates the Efficient Solid-Phase Synthesis of Complex-Type N-Glycopeptide Thioesters Suitable for Native Chemical Ligation (pages 1650–1654)

      Stefano Mezzato, Manuela Schaffrath and Carlo Unverzagt

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200461125

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      A safety catch combined with a Rink-amide linker allowed convenient monitoring (LC–MS) and optimization of several key reactions in a solid-phase synthesis of the building block A for the glycoprotein RNase B. The native chemical ligation of A and B delivered the glycosylated RNase B fragment 30–68.

    10. Iron-Catalyzed Aryl–Aryl Cross-Couplings with Magnesium-Derived Copper Reagents (pages 1654–1658)

      Ioannis Sapountzis, Wenwei Lin, Christiane C. Kofink, Christina Despotopoulou and Paul Knochel

      Version of Record online: 30 DEC 2004 | DOI: 10.1002/anie.200462013

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      Well-matched couples: Functionalized aryl and heteroaryl copper species obtained from the corresponding magnesium derivatives undergo Fe-catalyzed cross-coupling reactions with aryl iodides that bear keto, ester, triflate, or nitrile groups (see scheme).

    11. Boron as a Bridging Ligand (pages 1658–1661)

      Holger Braunschweig, Krzysztof Radacki, David Scheschkewitz and George R. Whittell

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200463026

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      Getting boron into line: The reaction of the dichloroboryl complex 1, with Na[Fe(CO)4]2− yields [{(η5-C5Me5)Fe(CO)2}(μ2-B){Fe(CO)4}] (2; see scheme green B). Na2[Cr(CO)5] reacts analogously with 1 to give [{(η5-C5Me5)Fe(CO)2}(μ2-B){Cr(CO)5}] (3). Both compounds 2 and 3 contain an unprecedented linearly bridging “naked” boron atom.

    12. “True” Chirality Transfer from Silicon to Carbon: Asymmetric Amplification in a Reagent-Controlled Palladium-Catalyzed Hydrosilylation (pages 1661–1664)

      Martin Oestreich and Sebastian Rendler

      Version of Record online: 2 MAR 2005 | DOI: 10.1002/anie.200462355

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      Borne by silicon: A silicon reagent with Si-centered chirality induces C-centered chirality in C[BOND]Si bond formation. All of the stereochemical information stems from the chiral silane. This first “true” chirality transfer from silicon to carbon has been realized in a Pd-catalyzed hydrosilylation of a prochiral alkene. Moreover, this reagent-controlled process displays an unusual positive nonlinear effect (see Scheme).

    13. Cu(OTf)2 as an Efficient and Dual-Purpose Catalyst in the Regioselective Reductive Ring Opening of Benzylidene Acetals (pages 1665–1668)

      Chi-Rung Shie, Zheng-Hao Tzeng, Suvarn S. Kulkarni, Biing-Jiun Uang, Ching-Yun Hsu and Shang-Cheng Hung

      Version of Record online: 31 JAN 2005 | DOI: 10.1002/anie.200462172

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      Reducing the choices. Cu(OTf)2 is an efficient and dual-purpose catalyst for the highly regioselective reductive ring openings of benzylidene acetals with either BH3 or Me2EtSiH to give the corresponding primary and secondary alcohols (see scheme). Isotope studies have confirmed that both modes of ring cleavage proceed by an SN1 reaction pathway when borane or silane attack the acetal carbon center.

    14. C3 Chirality in Polymerization Catalysis: A Highly Active Dicationic Scandium(III) Catalyst for the Isoselective Polymerization of 1-Hexene (pages 1668–1671)

      Benjamin D. Ward, Stéphane Bellemin-Laponnaz and Lutz H. Gade

      Version of Record online: 14 FEB 2005 | DOI: 10.1002/anie.200462804

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      A tactical approach: C3-chiral ancillary ligands such as tris(oxazolinyl)ethane allow stereocontrol in olefin polymerization (see scheme). An alkyl ScIII catalyst polymerizes 1-hexene with activities ranging from 2000 to 36 000 kg mol−1 h−1 (at −30 to +21 °C) and good tacticity control at low temperatures.

    15. Hybrid Solution/Solid-Phase Synthesis of Oligosaccharides by Using Trichloroacetyl Isocyanate as Sequestration-Enabling Reagent of Sugar Alcohols (pages 1672–1676)

      Alessandro Dondoni, Alberto Marra and Alessandro Massi

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462422

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      An excess of glycosyl acceptor is used in the solution-phase synthesis of oligosaccharides and any unconverted acceptor is removed by using trichloroacetyl isocyanate. A levulinoyl (Lev) ester group is then used as a masked tag in the following “resin-capture–release” purification strategy (see scheme).

    16. Conformationally Restricted Aza-Bodipy: A Highly Fluorescent, Stable, Near-Infrared-Absorbing Dye (pages 1677–1679)

      Weili Zhao and Erick M. Carreira

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200461868

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      To dye for: A highly fluorescent, photostable aza-dipyrromethene dye 1 (λem=751 nm) with sharp and intense absorption (full width at half maximum height=30.4 nm; ε=159 000) in the near-infrared (NIR) region (λmax=740 nm) is reported. The dye is insensitive to solvent polarity, meets the requirements of a NIR chromophore, and has potential use in biological probes.

    17. Nanofabrication: Reversible Self-Assembly of an Imbedded Hexameric Metallomacrocycle within a Macromolecular Superstructure (pages 1679–1683)

      Pingshan Wang, Charles N. Moorefield and George R. Newkome

      Version of Record online: 31 JAN 2005 | DOI: 10.1002/anie.200462379

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      Turned inside out: The construction of a peripheral 114-membered macrocycle by a Grubbs-catalyzed metathesis reaction facilitates the self-assembly of a terpyridine-based FeII hexamer. The quantitative, base-promoted removal of the FeII centers allows the reversible disassembly of the metalated complex (see scheme, gray metal).

    18. The Natural LewisX-Bearing Lipids Promote Membrane Adhesion: Influence of Ceramide on Carbohydrate–Carbohydrate Recognition (pages 1683–1687)

      Christine Gourier, Frédéric Pincet, Eric Perez, Yongmin Zhang, Zhenyuan Zhu, Jean-Maurice Mallet and Pierre Sinaÿ

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200461224

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      Tight vesicles: Two glycosphingolipids, CerLLeX (see picture) and CerLLea (Cer=ceramide, L=lactose, LeX=LewisX determinant, Lea=Lewis a determinant) are used to study the Ca2+-mediated specific adhesion of natural LeX-bearing molecules inserted in fluid bilayer membranes. Vesicle adhesion energy experiments show that LeX–LeX recognition is highly sensitive to molecular structure.

    19. Practical Synthesis of Enantiopure γ-Amino Alcohols by Rhodium-Catalyzed Asymmetric Hydrogenation of β-Secondary-Amino Ketones (pages 1687–1689)

      Duan Liu, Wenzhong Gao, Chunjiang Wang and Xumu Zhang

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462178

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      Another way to antidepressants: A series of β-secondary-amino ketone hydrochlorides (e.g. 1) were hydrogenated with remarkably high enantioselectivities by using a Rh complex containing P-chiral bisphospholane 2. These results establish a short and practical means for the synthesis of enantiopure N-monosubstituted γ-amino alcohols (e.g. 3), which are key intermediates in the synthesis of important antidepressants. (nbd=norbornadiene; TON=turnover number).

    20. A Cyclohexyl-1,2-diamine-Derived Bis(binaphthyl) Macrocycle: Enhanced Sensitivity and Enantioselectivity in the Fluorescent Recognition of Mandelic Acid (pages 1690–1693)

      Zi-Bo Li, Jing Lin and Lin Pu

      Version of Record online: 2 FEB 2005 | DOI: 10.1002/anie.200462471

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      Optically active cyclohexanediamine-based bis(binaphthyl) macrocyle (S)-1 shows a highly sensitive and enantioselective fluorescent recognition of mandelic acid: That is, while the R enantiomer of mandelic acid causes little change in the fluorescence of the macrocycle, the S enantiomer enhances the fluorescence by over 20-fold.

    21. Synthesis of (E)-1,2-Diphosphanylethene Derivatives from Alkynes by Radical Addition of Tetraorganodiphosphane Generated In Situ (pages 1694–1696)

      Akinori Sato, Hideki Yorimitsu and Koichiro Oshima

      Version of Record online: 2 FEB 2005 | DOI: 10.1002/anie.200462603

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      E-asy radical addition: A tetraorganodiphosphane, generated in situ from a diorganophosphane and a chlorodiorganophosphane in the presence of triethylamine, adds to terminal alkynes by a radical process (see scheme) to afford (E)-diphosphanylethene derivatives in excellent yields. The reaction conditions are mild enough to tolerate many functional groups.

    22. Synthesis of Functionalized Salicylate Esters and Amides by Photochemical Acylation (pages 1696–1699)

      Omid Soltani and Jef K. De Brabander

      Version of Record online: 31 JAN 2005 | DOI: 10.1002/anie.200462577

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      Functionalized salicylates in a flash: Photolysis of functionalized benzodioxinones in the presence of alcohols or amines is a powerful method for the synthesis of sterically hindered salicylic esters and amides (see scheme). This reaction tolerates a broad range of functional groups and efficiently engages a wide range of acylation substrates, including sterically hindered nucleophiles that are inert to other acylation methods.

    23. A Stable P-Heterocyclic Carbene (pages 1700–1703)

      David Martin, Antoine Baceiredo, Heinz Gornitzka, Wolfgang W. Schoeller and Guy Bertrand

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462239

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      A stable diphosphorus analogue of Enders' N-heterocyclic carbene has been prepared by taking advantage of the inherent π-donor capabilities of phosphorus, which are as good as, or better than, those of nitrogen. The P-heterocyclic carbene (see figure; C gray, N blue, P red) behaves as a strong donor ligand and forms transition-metal complexes that are thermally and air stable.

    24. An Aerobic, Organocatalytic, and Chemoselective Method for Baeyer–Villiger Oxidation (pages 1704–1706)

      Yasushi Imada, Hiroki Iida, Shun-Ichi Murahashi and Takeshi Naota

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462429

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      Highly chemoselective Baeyer–Villiger oxidations can be performed in the presence of other reactive functionalities such as alcohols, olefins, and sulfides, which would undergo electrophilic oxidation under conventional conditions (see scheme). [DMRFlEt]+[ClO4] (depicted blue) is a new class of flavin compound that catalyzes aerobic Baeyer–Villiger oxidations in the presence of Zn dust as the electron source.

    25. Reevaluation of the Mechanism of the Baylis–Hillman Reaction: Implications for Asymmetric Catalysis (pages 1706–1708)

      Varinder K. Aggarwal, Sarah Y. Fulford and Guy C. Lloyd-Jones

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462462

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      One step beyond: Proton transfer (step 3, see scheme), not C[BOND]C bond formation (step 2) as previously thought, is the rate-limiting step (RLS) in the initial stage of the Baylis–Hillman reaction, which involves the amine-catalyzed addition of an aldehyde to an activated alkene to generate an allylic alcohol. This finding has considerable implications for asymmetric catalysis of the reaction.

    26. Redox-Induced Collapse and Regeneration of a Pincer-Type Complex Framework: A Nonplanar Coordination Mode of Palladium(II) (pages 1709–1711)

      Christian M. Frech, Linda J. W. Shimon and David Milstein

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462386

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      Unequal partners: One-electron reduction of a pincer-type palladium complex 1 results in collapse of the pincer system and formation of a novel bimetallic diamagnetic complex containing a linearly coordinated 14 e Pd0 center and a nonplanar PdII unit (2). The reaction is reversed by oxidation with Ag+ or organic halides. The catalytic activity of 2 is investigated for the Heck reaction.

    27. A Metal-Based Lumophore Tailored To Sense Biologically Relevant Oxometalates (pages 1712–1714)

      Anna F. A. Peacock, Helen D. Batey, Claudia Raendler, Adrian C. Whitwood, Robin N. Perutz and Anne-K. Duhme-Klair

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462306

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      Oxometalate detection: A new catechol–[ReI(2,2′-bpy)(py)(CO)3]+ (bpy=bipyridine, py=pyridine) conjugate has been prepared which signals the presence and concentration of molybdate, vanadate, and/or tungstate ions in solution in aqueous acetonitrile by efficient quenching of the Re-based luminescence (see picture).

    28. Synthesis of a Metallophilic Metallamacrocycle: A HgII⋅⋅⋅CuI⋅⋅⋅HgII⋅⋅⋅HgII⋅⋅⋅CuI⋅⋅⋅HgII Interaction (pages 1715–1717)

      Upali Patel, Harkesh B. Singh and Gotthelf Wolmershäuser

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462487

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      Complexation of a CuIion in a mercuramacrocycle demonstrates the potential of metal–metal interactions in a preorganized system to trap metal ions. The molecular structure of the CuI complex is presented and shows Hg⋅⋅⋅Cu heterometallic and Hg⋅⋅⋅Hg homometallic d10⋅⋅⋅d10 interactions (see figure).

    29. Colloidally Stable Amphibious Nanocrystals Derived from Poly{[2-(dimethylamino)ethyl] Methacrylate} Capping (pages 1717–1720)

      Hongwei Duan, Min Kuang, Dayang Wang, Dirk G. Kurth and Helmuth Möhwald

      Version of Record online: 31 JAN 2005 | DOI: 10.1002/anie.200461023

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      Polymer brushes are grown on both hydrophobic and hydrophilic nanocrystals by surface-initiated atom-transfer radical polymerization. The poly{[2-(dimethylamino)ethyl] methacrylate}-coated nanocrystals are well dispersed in both water and most organic solvents without detectable aggregation and deterioration of their intrinsic properties. This methodology paves a simple and efficient way to direct nanocrystals into specific media.

    30. Heterobimetallic Main-Group–Transition-Metal Paddle-Wheel Carboxylates (pages 1721–1724)

      Evgeny V. Dikarev, Thomas G. Gray and Bo Li

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462433

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      Bismuth(II) tetra(trifluoroacetate) acts as a metalloligand toward transition-metal units to yield heterobimetallic homoleptic carboxylates [BiM(O2CCF3)4] (M=Rh, Ru; see picture). The heterometallic molecules maintain a paddle-wheel structure, with a single bond between bismuth and the transition-metal atom, and behave as one-ended Lewis acids in solution and in the solid state.

    31. Direct Localization of Atoms in Mixed-Occupancy Powders by Resonant Contrast Diffraction (pages 1725–1729)

      Herve Palancher, Jean-Louis Hodeau, Christophe Pichon, Jean-François Bérar, John Lynch, Bernadette Rebours and Juan Rodriguez-Carvajal

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200461642

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      Spot on! Resonant scattering enables accurate localization of the individual cations in powders by the routine use of “anomalous differential patterns” and “dispersive difference maps” (see picture), as demonstrated for (Sr,Rb) zeolite X, a sample of potential industrial interest.

    32. Catalytic Dehydrative Allylation of Alcohols (pages 1730–1732)

      Hajime Saburi, Shinji Tanaka and Masato Kitamura

      Version of Record online: 3 FEB 2005 | DOI: 10.1002/anie.200462513

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      An environmentally benign synthesis of allyl ethers has been developed which can be applied to a highly chemoselective protection of hydroxyl groups. A highly efficient [CpRu]–2-quinolinecarboxylic acid (L) catalytic system was successfully employed for the dehydrative allylation of various alcohols without additional activators and solvent (see scheme; R=alkyl, aryl, multifunctional alkyl, Cp=C5H5).

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      Direct Synthesis of (+)-Erogorgiaene through a Kinetic Enantiodifferentiating Step (pages 1733–1735)

      Huw M. L. Davies and Abbas M. Walji

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462227

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      The combined approach of C[BOND]H activation and a Cope rearrangement catalyzed by a rhodium catalyst [Rh2(R-dosp)4] (dosp=(N-dodecylbenzenesulfonyl)prolinate) is shown to be a very effective method for the construction of the three stereogenic centers (marked in red, see scheme) present in the diterpene erogorgiaene (1).

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