Chemistry - A European Journal

Cover image for Vol. 10 Issue 22

November 19, 2004

Volume 10, Issue 22

Pages 5557–5874

    1. Cover Picture: Efficient and Mild Copper-Catalyzed N- and C-Arylations with Aryl Bromides and Iodides (Chem. Eur. J. 22/2004) (page 5557)

      Henri-Jean Cristau, Pascal P. Cellier, Jean-Francis Spindler and Marc Taillefer

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/chem.200490074

      The cover picture shows the very broad application field of new catalytic systems for the N-, O- and C-arylations of various nucleophiles (the background represents crystals of the catalyst Cu2O). These systems, which result from combinations of copper salts with a set of original chelating ligands not previously known to promote such reactions, are unique in terms of versatility. Mildness, low-cost, experimental simplicity, and the ability to work at low catalyst loading are features of this methodology, which make it particularly well suited for industrial-scale syntheses for which financial and environmental issues are of greater concern. Consequently, it should find applications very soon for the synthesis of industrially important synthetic targets, found in a range of pharmaceuticals, agrochemicals and natural products. For mote details see the article by M. Taillefer, H.-J. Cristau et al. on p. 5607 ff.

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      Final Elucidation of the Absolute Configuration of the Signal Metabolite Hormaomycin (page 5568)

      Boris D. Zlatopolskiy, Karin Loscha, Petra Alvermann, Sergei I. Kozhushkov, Sergej V. Nikolaev, Axel Zeeck and Armin de Meijere

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/chem.200490076

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    4. Nanoparticles: Scaffolds for Molecular Recognition (pages 5570–5579)

      Ulf Drechsler, Belma Erdogan and Vincent M. Rotello

      Version of Record online: 2 SEP 2004 | DOI: 10.1002/chem.200306076

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      Nano-scaffolding: Nanoparticles provide scaffolds for the attachment of molecular recognition elements (illustrated here schematically). Integration of the methodologies and insight developed in the field of supramolecular chemistry with the diverse array of available nanoparticle platforms provides new directions for the creation of devices and the assembly of nanocomposite materials.

    5. New Uses for the Burgess Reagent in Chemical Synthesis: Methods for the Facile and Stereoselective Formation of Sulfamidates, Glycosylamines, and Sulfamides (pages 5581–5606)

      K. C. Nicolaou, Scott A. Snyder, Deborah A. Longbottom, Annie Z. Nalbandian and Xianhai Huang

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400503

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      The Burgess reagent (1) is remarkably effective at accomplishing a number of non-dehydrative synthetic tasks when applied to appropriate substrates, such as the formation of sulfamidates from 1,2-diols or epoxyalcohols, α- and β-glycosylamines from carbohydrates, and cyclic sulfamides from 1,2-aminoalcohols. This article delineates the power of these new reaction manifolds and demonstrates how the use of novel Burgess-type reagents extends the scope of these transformations even further.

    6. Highly Efficient and Mild Copper-Catalyzed N- and C-Arylations with Aryl Bromides and Iodides (pages 5607–5622)

      Henri-Jean Cristau, Pascal P. Cellier, Jean-Francis Spindler and Marc Taillefer

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400582

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      Cheap and copper! Ullmann-type N- and C-arylations of various nucleophiles were found to occur with high yields under particularly mild conditions by using inexpensive and air-stable catalytic systems; these systems are composed of a combination of catalytic copper salts with a set of chelating ligands still not known to promote such reactions. The catalyst generated from chelating Schiff base 1 c is unique in terms of versatility. EWG=electron-withdrawing group, EDG=electron-donating group.

    7. An Insight into a Novel Class of Self-Assembled Porphyrins: Geometric Structure, Electronic Structure, One- and Two-Photon Absorption Properties (pages 5623–5631)

      Xin Zhou, Ai-Min Ren and Ji-Kang Feng

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400251

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      A series of butadiyne-linked porphyrin derivatives that exhibit large two-photon absorption (TPA) cross sections in the visible-IR range were investigated theoretically. The dimer with two porphyrins linked at meso-positions by a butadiyne linkage (see picture) exhibits a maximum TPA cross section (79.35×10−48 cm4 s per photon). Porphyrins with the similar structure would be a promising direction for further development of novel TPA materials.

    8. The Control of the Cholesteric Pitch by Some Azo Photochemical Chiral Switches (pages 5632–5639)

      Silvia Pieraccini, Giovanni Gottarelli, Riccardo Labruto, Stefano Masiero, Omar Pandoli and Gian Piero Spada

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400463

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      Chiral bis(azo) photoswitches that contain a binaphthyl moiety (e.g. 1 and 2) can transform nematic phases into cholesteric phases with reflection bands in the visible region. The reflection colours can be changed reversibly by photoisomerisation of the azo groups.

    9. Cobalt-Catalyzed Cross-Coupling Reactions of Alkyl Halides with Allylic and Benzylic Grignard Reagents and Their Application to Tandem Radical Cyclization/Cross-Coupling Reactions (pages 5640–5648)

      Hirohisa Ohmiya, Takashi Tsuji, Hideki Yorimitsu and Koichiro Oshima

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400545

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      Superior to reactions with palladium, nickel, or copper catalysts, cobalt-catalyzed cross-coupling reactions between alkyl halides and allylic Grignard reagents allow secondary and tertiary (as well as primary) alkyl halides to be employed as the coupling partners (see scheme). In addition, benzylmagnesium chloride can couple with alkyl halides. The reaction should begin with the generation of alkyl radical from the parent alkyl halide, suggesting a tandem radical cyclization/cross-coupling reaction with [CoCl2(dppp)] catalysis.

    10. Total Synthesis of Salicylihalamides A and B (pages 5649–5660)

      Christian Herb, Alexander Bayer and Martin E. Maier

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400617

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      Running rings around enamides: By use of a new enamide synthesis, salicylihalamide 2 was prepared from the macrolactone 1. This macrolactone could either be reached by Mitsunobu macrolactonization or classical ring-closing metathesis.

    11. 2,5-Diphenyl-3,4-bis(2-pyridyl)cyclopenta-2,4-dien-1-one as a Redox-Active Chelating Ligand (pages 5661–5670)

      Ulrich Siemeling, Imke Scheppelmann, Jürgen Heinze, Beate Neumann, Anja Stammler and Hans-Georg Stammler

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400465

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      Why always cling to ferrocene and quinone derivatives? The cyclopentadienone 1 has been established as a redox-active ligand in coordination chemistry; it forms a series of N,N chelates. It represents a new and convenient ligand platform for use in redox switches and sensors. Its versatility as a ligand is enhanced by the fact that its binding characteristics can be modulated through coordination of the cyclopentadienone π system to another metal atom.

    12. Electron Delocalization in Linearly π-Conjugated Systems: A Concept for Quantitative Analysis (pages 5671–5680)

      Maria Grazia Giuffreda, Maurizio Bruschi and Hans Peter Lüthi

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400313

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      A novel computational approach based on deletion and on second-order orbital interaction energies in a natural bond orbital (NBO) scheme is presented to quantitatively assess electron delocalization in linearly π-conjugated systems (see figure). This approach was applied to butadiene as an illustration, and more extensively to unsubstituted and substituted tetraethynylethenes (TEEs) with donors and acceptors. By means of this method we were able to understand why certain paths favor conjugation more than others, to quantify the effect of the substituents on the backbone, and to predict how to enhance delocalization.

    13. Rhodium-Catalyzed Intramolecular Hydroacylation of 5- and 6-Alkynals: Convenient Synthesis of α-Alkylidenecycloalkanones and Cycloalkenones (pages 5681–5688)

      Kenzo Takeishi, Koudai Sugishima, Kaori Sasaki and Ken Tanaka

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400679

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      A novel intramolecular hydroacylation of 5- and 6-alkynals leading to α-alkylidenecycloalkanones (see scheme) was accomplished by using a cationic rhodium(I)/BINAP complex. For all cyclizations described, a single (E)-olefin isomer was obtained. At elevated temperature, hydroacylation and double bond migration of 5- and 6-alkynals proceeded in a one-pot reaction to give cycloalkenones. This method represents an attractive new route to highly functionalized α-alkylidenecycloalkanones and cycloalkenones.

    14. Hydrogen Bonding of Water Confined in Mesoporous Silica MCM-41 and SBA-15 Studied by 1H Solid-State NMR (pages 5689–5696)

      Bob Grünberg, Thomas Emmler, Egbert Gedat, Ilja Shenderovich, Gerhard H. Findenegg, Hans-Heinrich Limbach and Gerd Buntkowsky

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400351

      Waterlogged: The adsorption of water in two mesoporous silica materials with cylindrical pores of uniform diameter, MCM-41 and SBA-15, is studied by solid-state NMR spectroscopy. All observed hydrogen atoms are either surface [BOND]SiOH groups or hydrogen-bonded water molecules. For low-filling degrees, a partial-monolayer coverage of the surface is observed. At higher water contents, a diameter-dependent filling of the pores is observed. In small-diameter MCM-41 pore filling is by pore condensation (axial-pore-filling mode), and in large-diameter SBA-15 layered-pore filling is observed.

    15. RNA Is More UV Resistant than DNA: The Formation of UV-Induced DNA Lesions is Strongly Sequence and Conformation Dependent (pages 5697–5705)

      Lal Mohan Kundu, Uwe Linne, Mohamed Marahiel and Thomas Carell

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200305731

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      The formation of UV-induced cancerous and age-inducing lesions in small DNA and RNA hairpins was investigated (see scheme). Surprisingly large differences depending on the sequence and the conformation (DNA versus RNA) were observed.

    16. Gaseous H5P2O8 Ions: A Theoretical and Experimental Study on the Hydrolysis and Synthesis of Diphosphate Ion (pages 5706–5716)

      Federico Pepi, Andreina Ricci, Marzio Rosi and Marco Di Stefano

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400293

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      Insight into the mechanism of diphosphate ion hydrolysis and synthesis is afforded from the study of gaseous H5P2O8 ions generated from the chemical ionization (CI) of an H4P2O7/H2O mixture and from electrospray ionization (ESI) of CH3CN/H2O/H4P2O7 solutions. These ions were structurally characterized by mass spectrometric and theoretical techniques as a mixture of gaseous [H3P2O7⋅⋅⋅H2O], [H3PO4⋅⋅⋅H2PO4], and [PO3⋅⋅⋅H3PO4⋅⋅⋅ H2O] clusters (see picture).

    17. Regioselectivity in Iron-Catalyzed [2+2+1] Cycloadditions: A DFT Investigation of Substituent Effects in 1,4-Diazabutadienes (pages 5717–5729)

      Wolfgang Imhof and Ernst Anders

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400215

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      The π-donor ability of the substituents at the imine carbon atoms to contribute to a delocalized π system incorporating the adjacent imine moiety is the main reason for the observed regioselectivities in the iron-catalyzed [2+2+1] cycloaddition of 1,4-diazabutadienes with different substituents at the imine carbon atoms, carbon monoxide, and ethylene (see scheme).

    18. Oxidation of CS2 by AsBr4+: The Unexpected Formation of the Simple CS2Br3+ Carbenium Ion (pages 5730–5736)

      Marcin Gonsior and Ingo Krossing

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400046

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      By serendipity we synthesized the novel CS2Br3+carbenium ion through the 4 e oxidation of CS2 with AsBr4+[Al(OR)4] (R=C(CF3)3) (see scheme). This is the first structure of a carbocation with a C[BOND]S[BOND]X bond (X=halogen). Electronically it is closely related to the CBr3+ ion. CS2Br3+ is best viewed as a planar 10 π cation.

    19. Readily Prepared Metallo-Supramolecular Triple Helicates Designed to Exhibit Spin-Crossover Behaviour (pages 5737–5750)

      Floriana Tuna, Martin R. Lees, Guy J. Clarkson and Michael J. Hannon

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400518

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      Spin-crossover behaviour is introduced into readily prepared dinuclear metallo-supramolecular triple-helicates by using a bis-imidazolimine ligand system. The imidazole NH groups engage in hydrogen bonding to anions and solvents; in the case of the iron(II) tetrafluoroborate complex this hydrogen bonding links supramolecular cylinders into an extended two-dimensional array as shown here. Consistent with this, a sharp spin-crossover transition is observed for this compound. More subtle anion effects are indicated in the perchlorate salt, which gives a two step spin conversion thereby displaying tristability.

    20. In Search of Ultrastrong Brønsted Neutral Organic Superacids: A DFT Study on Some Cyclopentadiene Derivatives (pages 5751–5760)

      Robert Vianello, Joel F. Liebman and Zvonimir B. Maksić

      Version of Record online: 14 OCT 2004 | DOI: 10.1002/chem.200400337

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      Pentasubstituted cyclopentadienes such as (NC)5C5H, (NO2)5C5H, and (CN)5C5H containing strongly electron-withdrawing groups are neutral organic superacids of unprecedented strength according to the DFT calculations presented here. The origin of the highly pronounced acidity of these compounds was analyzed by using the recently developed triadic formula, which showed that high Koopmans' ionization energies of the conjugate bases (see picture) exerts a decisive influence on acidity. It is fair to say that high acidity is a consequence of the final state effect.

    21. Novel Metathesis Catalysts Based on Ruthenium 1,3-Dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: Synthesis, Structure, Immobilization, and Catalytic Activity (pages 5761–5770)

      Liangru Yang, Monika Mayr, Klaus Wurst and Michael R. Buchmeiser

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400278

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      Highly active metathesis catalysts [RuX2(NHC){[DOUBLE BOND]CH-2-(2-PrO)-5-NO2-C6H3}] (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; X=Cl (1), CF3COO (2)) were synthesized and structurally characterized (structure of 2 depicted). Supported analogues of 2 were prepared by immobilization on a hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization. Compounds 1 and 2 and the supported versions of 2 showed high reactivity in ring-closing metathesis and ring-opening cross-metathesis.

    22. Injecting Electronic Excitation Energy into an Artificial Antenna System through an Ru2+ Complex (pages 5771–5775)

      Olivia Bossart, Luisa De Cola, Steve Welter and Gion Calzaferri

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400743

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      Well and truly stoppered! An Ru2+ complex was electrostatically bound to the negatively charged channel entrances of a dye loaded zeolite L as a functional stopcock molecule. Impressive electronic excitation energy transfer from the stopcock to the acceptor dyes located inside the channels can be observed when the Ru2+ complex is selectively excited (see figure).

    23. Multiple Binding Modes of the Camptothecin Family to DNA Oligomers (pages 5776–5787)

      Wojciech Bocian, Robert Kawȩcki, Elzbieta Bednarek, Jerzy Sitkowski, Agnieszka Pietrzyk, Michael P. Williamson, Poul Erik Hansen and Lech Kozerski

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200305624

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      A novel combination of experimental and theoretical methods dealing with the conformational ensemble of drug/biomolecule complexes exemplified by topotecan (TPT)/DNA interaction is presented (see scheme).

    24. Chemoenzymatic Preparation of Optically Active trans-Cyclohexane-1,2-diamine Derivatives: An Efficient Synthesis of the Analgesic U-(−)-50,488 (pages 5788–5794)

      Javier González-Sabín, Vicente Gotor and Francisca Rebolledo

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400607

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      Stereospecific then stereoselective: Optically active trans-2-(N,N-dialkylamino)cyclohexanamines and their acetamide and carbamate derivatives were obtained in very good chemical yields and with ee values of 92–99 % through chemoenzymatic methodology (see scheme). The utility of these compounds was shown by the preparation of the analgesic U-(−)-50,488. CAL-B=Candida antartica lipase B, Cbz=benzyloxycarbonyl.

    25. From Allylic Alcohols to Aldols by Using Iron Carbonyls as Catalysts: Computational Study on a Novel Tandem Isomerization–Aldolization Reaction (pages 5795–5803)

      Vicenç Branchadell, Christophe Crévisy and René Grée

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400466

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      Carbonyl-ene-type condensation of formaldehyde with the free enol follows an enol/allyl alcohol ligand-exchange process (see scheme) in the mechanism of a tandem isomerization–aldolization reaction between allyl alcohol and formaldehyde mediated by [Fe(CO)3] according to B3LYP DFT calculations.

    26. Lanthanide(III) Complexes of DOTA–Glycoconjugates: A Potential New Class of Lectin-Mediated Medical Imaging Agents (pages 5804–5816)

      João P. André, Carlos F. G. C. Geraldes, José A. Martins, André E. Merbach, Maria I. M. Prata, Ana C. Santos, João J. P. de Lima and Éva Tóth

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400187

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      A suitable glycodendrimer architecture made it possible to obtain a new class of stable hydrophilic glycoconjugates. The synthesis of the glycodendrimers by using different carbohydrates (glucose, galactose and lactose) is reported, as well as their SmIII, EuIII and GdIII complexes. The in vitro relaxivity of the GdIII–glycoconjugates such as 1 was studied by 1H nuclear magnetic relaxation dispersion (NMRD).

    27. C[BOND]C Double- and Triple-Bond Formation from Reactions of B Atoms with CO: Experimental and Theoretical Characterization of OBBCCO and OBCCBO Molecules in Solid Argon (pages 5817–5822)

      Mingfei Zhou, Ling Jiang and Qiang Xu

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400474

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      All change! Reactions of boron atoms with CO molecules in solid argon formed the boron–boron triple-bonded OCBBCO molecule, which underwent a photochemical rearrangement where CO was activated to form the OBBCCO and OBCCBO molecules, as shown in the equation.

    28. Room-Temperature Surface-Erosion Route to ZnO Nanorod Arrays and Urchin-like Assemblies (pages 5823–5828)

      Zhengquan Li, Yue Ding, Yujie Xiong, Qing Yang and Yi Xie

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400498

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      Manipulation makes the difference: A solution surface-erosion route was successfully employed to produce one-dimensional ZnO nanostructures. ZnO nanorod arrays (see figure) and three-dimensional urchinlike assemblies were selectively obtained with a simple surface-erosion process at room temperature.

    29. Noncovalent Anchoring of Asymmetric Hydrogenation Catalysts on a New Mesoporous Aluminosilicate: Application and Solvent Effects (pages 5829–5835)

      Chrétien Simons, Ulf Hanefeld, Isabel W. C. E. Arends, Roger A. Sheldon and Thomas Maschmeyer

      Version of Record online: 7 OCT 2004 | DOI: 10.1002/chem.200400528

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      Excellent activities and enantioselectivities (up to >98 %) in the hydrogenation of methyl 2-acetamidoacrylate were achieved by using new heterogeneous catalysts that were prepared by noncovalent anchoring of two well-established asymmetric catalysts, [RhI(cod){(R,R)-MeDuPHOS}]BF4 (1) and [RhI(cod){(S,S)-DiPAMP}]BF4 (2), to a new aluminosilicate (AlTUD-1; see scheme). Interestingly, the solvent played an important role in hydrogenations with these catalysts.

    30. Some Novel Binuclear Group 13 Metal Tin Hydrides Formed in Ar Matrices Following the Codeposition of the Metal Vapor with SnH4 (pages 5836–5847)

      Benjamin Gaertner, Hans-Jörg Himmel, Victoria A. Macrae, Jennifer A. J. Pardoe, Paul G. Randall and Anthony J. Downs

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/chem.200400564

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      Novel mixed-metal hydrides HMSnH3 (1) and H2M(μ-H)2Sn (2), produced thermally or photolytically on co-condensation of Al or Ga (M) atoms with SnH4 in an excess of Ar, have been characterized by their IR spectra and by appropriate quantum chemical calculations.

    31. Self-Assembly of Human Serum Albumin (HSA) and l-α-Dimyristoylphosphatidic Acid (DMPA) Microcapsules for Controlled Drug Release (pages 5848–5852)

      Zhihua An, Gang Lu, Helmuth Möhwald and Junbai Li

      Version of Record online: 13 OCT 2004 | DOI: 10.1002/chem.200400090

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      Multilayered microcapsules: Human serum albumin (HSA) and l-α-dimyristoylphosphatidic acid (DMPA) were used as coating materials to encapsulate ibuprofen crystals by a process based on the layer-by-layer technique for drug release (see figure). The controllable release of the drug was confirmed.

    32. Hydrogen-Bonded Polyrotaxane-like Structure Containing Cyclic (H2O)4 in [Zn(OAc)2(μ-bpe)]⋅2 H2O: X-ray and Neutron Diffraction Studies (pages 5853–5859)

      Meng Tack Ng, Theivanayagam C. Deivaraj, Wim T. Klooster, Garry J. McIntyre and Jagadese J. Vittal

      Version of Record online: 14 OCT 2004 | DOI: 10.1002/chem.200400551

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      A 24-membered O[BOND]H⋅⋅⋅O hydrogen-bonded ring and cyclic (H2O)4 units are the key features of the one-dimensional ribbon-like polymer [Zn(OAc)2(μ-bpe)]⋅2 H2O (see picture). bpe=4,4′-bipyridylethane.

    33. By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes? (pages 5860–5870)

      Luís F. Veiros, Georg Dazinger, Karl Kirchner, Maria José Calhorda and Roland Schmid

      Version of Record online: 14 OCT 2004 | DOI: 10.1002/chem.200400523

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      Alkyne to cyclobutadiene transformations: DFT/B3LYP calculations led us to propose two distinct pathways for the formation of η4-cyclobutadiene complexes from metallacycles generated by oxidative coupling of two acetylenes with the fragments CpRuCl, [CpRu(PH3)]+, CpCo, and CpRh. Both a multistep reaction mechanism via a cyclopropenyl carbene and a tetrahedrane-type intermediate, and a direct one-step transformation (depicted for CpCo; values in kcal mol−1) are discussed.

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      Preview: Chem. Eur. J. 22/2004 (page 5874)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/chem.200490077

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