Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 34

September 5, 2003

Volume 42, Issue 34

Pages 3971–4107

    1. Cover Picture: Catalytic Reforming of Oxygenated Hydrocarbons for Hydrogen with Low Levels of Carbon Monoxide (Angew. Chem. Int. Ed. 34/2003) (page 3971)

      Rupali R. Davda and James A. Dumesic

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200390562

      CO-poor hydrogen can be produced by reforming oxygenates, such as ethylene glycol, in water over Pt catalysts. The expansion of the gas bubbles formed in the process by the vaporization of water results in a decrease in the partial pressures of H2 and CO2, thereby favoring the water–gas shift and lowering the CO concentration. This process leads to the production of fuel-cell-grade H2 at high pressures. For more information see the Communication by J. A. Dumesic and R. R. Davda on page 4068 ff.

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      Highly Enantioselective Construction of Quaternary Stereocenters on β-Keto Esters by Phase-Transfer Catalytic Asymmetric Alkylation and Michael Reaction (page 3981)

      Takashi Ooi, Takashi Miki, Mika Taniguchi, Misato Shiraishi, Mifune Takeuchi and Keiji Maruoka

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200390567

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      Lewis Acid Catalyzed Room-Temperature Michaelis–Arbuzov Rearrangement (page 3981)

      Pierre-Yves Renard, Philippe Vayron, Eric Leclerc, Alain Valleix and Charles Mioskowski

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200390569

    6. Web Site: Microarrays: Everything Counts in Large Amounts (page 3982)

      Holger Sültmann and Reiner Dahint

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200390565

    7. Recent Developments in the Synthesis of Helicene-Like Molecules (pages 3986–3989)

      Antonio Urbano

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200301667

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      Straightforward access to helicene-like molecules (see structure) is possible by short and efficient protocols that have emerged in the past few years. These transformations, as well as recent approaches to chiral nonracemic derivatives, constitute a significant advancement in synthetic methodology.

    8. Friedrich Wilhelm Ostwald (1853–1932), Now 150 Years Young… (pages 3990–3995)

      Regine Zott

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200330059

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      He counts as one of the co-founders of physical chemistry, contributor to scientific research and organization, scientific publicist, and color researcher. This year marks the 150th anniversary of the birth of Wilhelm Ostwald, Nobel Prize winner in 1909.

    9. Natural Product Hybrids as New Leads for Drug Discovery (pages 3996–4028)

      Lutz F. Tietze, Hubertus P. Bell and Srivari Chandrasekhar

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200200553

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      Unlimited options: The synthesis of natural product hybrids by combining structurally different, naturally occurring compounds that exhibit high biological activities appears to be a promising approach to increase the number and diversity of substances for pharmacological testing. An example is the hybrid of estrone and (−)-talaromycin (see picture).

    10. P42−: A 6π Aromatic Polyphosphide in Dicesium Cyclotetraphosphide–Ammonia (1/2) (pages 4030–4033)

      Florian Kraus, Jürgen C. Aschenbrenner and Nikolaus Korber

      Version of Record online: 14 AUG 2003 | DOI: 10.1002/anie.200351776

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      Aromatic P: Among the homoatomic polyanions of group 15 elements, Bi42− and Sb42− have been exotic curiosities for a long time, as they are potential 6π aromatic rings. As42− joined as the lighter congener as recently as 2002. Considering the diagonal relationship of P to C, the cyclobutadienediide analogue P42− would be expected naturally, but only now has it been prepared in the form of Cs2P4⋅2 NH3 from diphosphane(4).

    11. [3+3] Cyclizations of 1,3-Bis(silyl enol ether)s with 1,1-Diacetylcyclopentane and 1,1-Diacetylcyclopropane (pages 4033–4036)

      Peter Langer and Gopal Bose

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351263

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      Domino reactions of 1,3-bis(silyl enol ether)s with 1,1-diacetylcyclopentane and 1,1-diacetylcyclopropane (see scheme) allow a new and convenient one-pot synthesis of spiro[5.4]cyclodecenones, bicyclo[4.4.0]deca-1,4-dien-3-ones, and functionalized salicylates, which are versatile intermediates for the synthesis of pharmacologically relevant natural product analogues. MS=molecular sieves.

    12. Template Synthesis and Theoretical Investigation of [CuII2CuI3K66-Cl)(μ3-OtBu)12]: The First Mixed-Valence Copper Alkoxide (pages 4036–4039)

      Reinhart Ahlrichs, Christopher E. Anson, Dieter Fenske, Oliver Hampe, Alexander Rothenberger and Marek Sierka

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351395

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      A prismatic prison for chloride: Partial disproportionation of CuCl during the reaction with KOtBu leads to the formation of a mixed-valence CuI/CuII alkoxido complex. The trigonal prismatic K66-Cl) template in the middle of the complex is capped by two [CuII(OtBu)3] and three [CuI(OtBu)3] units (see picture, Cl green, Cu light blue, K yellow, O red).

    13. DFT Calculations on a New Class of C3-Symmetric Organic Bases: Highly Basic Proton Sponges and Ligands for Very Small Metal Cations (pages 4039–4042)

      Götz Bucher

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351648

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      Back to bases: What happens, if three nitrogen lone pairs are forced to interact with each other? An extraordinary increase in basicity. This conclusion is the result of DFT calculations which, for example, predict a pKa value (of the conjugate acid, in acetonitrile) of 30.2 for tris(8-quinolyl)borane 1. The basicity is due to a strongly destabilizing interaction between the three quinoline lone pairs in the free bases.

    14. Domino 1,4-Addition/Carbocyclization Reaction through a Radical–Polar Crossover Reaction (pages 4043–4046)

      Fabrice Denes, Fabrice Chemla and Jean F. Normant

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200250474

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      Radical processes explain the reactivity and selectivity observed in a one-pot, two- or three-component domino reaction, which consists of 1,4-addition, carbocyclization, and quenching with electrophiles. This radical–polar crossover reaction leads stereoselectively to 3,4-disubstituted 3-methoxycarbonylpyrrolidines (see scheme).

    15. Amine-Reactive Monolayers on Scribed Silicon with Controlled Levels of Functionality: Reaction of a Bare Silicon Surface with Mono- and Diepoxides (pages 4046–4049)

      Yit-Yian Lua, Michael V. Lee, William J. J. Fillmore, Reija Matheson, Amarchard Sathyapalan, Matthew C. Asplund, Steven A. Fleming and Matthew R. Linford

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200250846

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      The reaction of epoxides with a bare silicon surface is reported (see scheme). Diepoxides yield amine-reactive monolayers on scribed silicon. Controlled levels of epoxide functionality are obtained in mixed monolayers of 1,2-epoxyoctane and 1,2,7,8-diepoxyoctane.

    16. Generation, Trapping, and Dimerization of Pentacyclo[,10.03,7.04,9]dodeca-5,8,11-triene: An Uncatalyzed Thermal [2+2+2+2] Cycloaddition (pages 4049–4051)

      Pelayo Camps, José A. Fernández, Santiago Vázquez, Mercè Font-Bardia and Xavier Solans

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351070

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      Simultaneous formation of four C[BOND]C bonds and three rings occurs in the unique uncatalyzed thermal [2+2+2+2] cycloaddition to give the tridecacyclotetracosane derivative 2, which takes place when the highly pyramidalized alkene 1 is generated in the absence of a trapping agent (see scheme).

    17. The Role of Acyloxyphosphonium Ions and the Stereochemical Influence of Base in the Phosphorane-Mediated Esterification of Alcohols (pages 4051–4054)

      James McNulty, Alfredo Capretta, Vladimir Laritchev, Jeff Dyck and Al J. Robertson

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351209

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      Intimate details of the Mitsunobu mechanism: The trapping of an acyloxytributylphosphonium ion with a chiral secondary alcohol leads to either retention or inversion of stereochemistry in the resulting ester depending on the exclusion or inclusion of a base (see scheme). Insight into the mechanism of phosphorane-mediated esterification processes is presented.

    18. A Tris(carbene) Pincer Complex: Monomeric Platinum Carbonyl with Three Bound Carbene Centers (pages 4054–4057)

      Guanyang Lin, Nathan D. Jones, Robert A. Gossage, Robert McDonald and Ronald G. Cavell

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351320

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      Carbon monoxide replaces cod in the mono carbene phosphane imine complex 1 (see picture) to form, through a double silyl migration reaction, the remarkable complex 2 containing three carbene centers bound to platinum (cod=cycloocta-1,5-diene).

    19. Direct Formation of Mesostructured Silica-Based Hybrids from Novel Siloxane Oligomers with Long Alkyl Chains (pages 4057–4060)

      Atsushi Shimojima and Kazuyuki Kuroda

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351419

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      Lamellar and hexagonal structures of new silica-based hybrids were directly formed from newly designed alkylsiloxane oligomers 1. This approach based on the self-assembly of single precursors provides a novel pathway to ordered microporous silica as well as mesostructured silica-based hybrid materials (see scheme, 1) hydrolysis and polycondensation, 2) self-assembly).

    20. Fullerene-Terminated Dendritic Multiporphyrin Arrays: “Dendrimer Effects” on Photoinduced Charge Separation (pages 4060–4063)

      Myung-Seok Choi, Takuzo Aida, Hongxia Luo, Yasuyuki Araki and Osamu Ito

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351460

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      Energy funnels: A large dendritic zinc porphyrin heptamer (7PZn) in a C60-terminated electron-transfer relay system 7PZn-C60 (see picture) not only harvests visible light for the electron transfer to the C60 terminus, but also retards the back-electron-transfer process, thus resulting in a longer lifetime of the charge-separated state (7Pequation image-Cequation image).

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      Triplet Emission in Soluble Mercury(II) Polyyne Polymers (pages 4064–4068)

      Wai-Yeung Wong, Li Liu and Jian-Xin Shi

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351672

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      The light fantastic: The first examples of soluble high-molecular-weight d10 mercury(II) polyyne copolymers incorporating a 9,9-dialkylfluorene moiety have been prepared and photophysically characterized (see picture). These polymers have been shown to utilize a heavy-atom effect in exhibiting strong phosphorescence.

    22. Catalytic Reforming of Oxygenated Hydrocarbons for Hydrogen with Low Levels of Carbon Monoxide (pages 4068–4071)

      Rupali R. Davda and James A. Dumesic

      Version of Record online: 18 JUN 2003 | DOI: 10.1002/anie.200351664

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      Vaporization of water leads to low levels of CO: Now, it is possible to produce low-CO-containing, H2-rich streams by simple, aqueous-phase reforming of oxygenates. The schematic of ethylene glycol reforming on a Pt catalyst shows the composition of a gas bubble in the aqueous-phase reactor. Lowering the H2 and CO2 pressures, by increasing the water pressure, lowers the CO concentration in the product. WGS= water–gas shift.

    23. Synthesis and Characterization of Neutral, Homo and Heteronuclear Clusters with Unsubstituted Germanium or Tin Atoms (pages 4071–4074)

      Anne F. Richards, Håkon Hope and Philip P. Power

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351907

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      The first, well-characterized, polyhedral cluster with two different heavier group 14 elements is prepared (see picture). Low-valent group 14 halides are used to synthesize species in which the majority of the group 14 atoms carry no organic substituents.

    24. A New Catalytic C[BOND]C Bond-Forming Hydrogenation: Reductive Coupling of Dienes and Glyoxals under Catalytic Hydrogenation Conditions (pages 4074–4077)

      Hye-Young Jang, Ryan R. Huddleston and Michael J. Krische

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351986

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      Since the discovery of catalytic homogeneous hydrogenation in 1938, C[BOND]C bond formation has only been observed under hydrogenation conditions in alkene hydroformylation and Fischer–Tropsch-type processes, that is, in catalytic processes involving migratory insertion of carbon monoxide. As revealed in the present study, organometallic intermediates obtained upon diene hydrogenation are subject to electrophilic trapping by glyoxal partners, thus demonstrating catalytic C[BOND]C bond formation under hydrogenation conditions in the absence of carbon monoxide (see scheme). DCE: 1,2-dichloroethane. R=aryl, heteroaryl, alkyl.

    25. New Reactions of IBX: Oxidation of Nitrogen- and Sulfur-Containing Substrates To Afford Useful Synthetic Intermediates (pages 4077–4082)

      K. C. Nicolaou, Casey J. N. Mathison and Tamsyn Montagnon

      Version of Record online: 8 AUG 2003 | DOI: 10.1002/anie.200352076

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      New reactions for the synthetic toolbox: 2-Iodoxybenzoic acid (IBX) was employed to access a diverse array of useful synthetic intermediates. Among other transformations, the developed chemistry converts amines into imines, dithianes into carbonyl groups, N-heterocycles into N-heteroaromatic compounds, and hydroxylamines into oximes in high yields.

    26. Catalytic Enantioselective Synthesis of β-Lactams: Intramolecular Kinugasa Reactions and Interception of an Intermediate in the Reaction Cascade (pages 4082–4085)

      Ryo Shintani and Gregory C. Fu

      Version of Record online: 8 AUG 2003 | DOI: 10.1002/anie.200352103

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      A planar-chiral Cu/phosphaferrocene–oxazoline catalyst mediates intramolecular Kinugasa reactions to give tricyclic β-lactams with good enantioselectivity. A variant of the process, in which a postulated enolate intermediate is intercepted with an electrophile in a transformation that generates two C[BOND]C bonds, a C[BOND]N bond, two new rings, a carbonyl group, and adjacent tertiary and quaternary stereocenters (see scheme), supports the proposed mechanism.

    27. Columnar Supramolecular Architecture Self-Assembled from S4-Symmetric Coordination Nanotubes Encapsulating Neutral Guest Molecules (pages 4085–4089)

      Cheng-Yong Su, Mark D. Smith and Hans-Conrad zur Loye

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351353

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      Self-cyclization of four HgCl2 units and four ditopic 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (bbimms) ligands has resulted in the assembly of the neutral nanotube [Hg4Cl8(bbimms)4] containing two compartments which can accomodate DMF and DMSO guest molecules (see picture). Crystal packing arranges all the tubes into an extended pipeline structure.

    28. [{Zn2(HPO4)4}{Co(dien)2}]⋅H3O: A Zinc Phosphate with Multidirectional Intersecting Helical Channels (pages 4089–4092)

      Yu Wang, Jihong Yu, Min Guo and Ruren Xu

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351643

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      A twist in the tale: A racemic mixture of the chiral [Co(dien)2]Cl3 complex has been used as a template in preparing an open-framework zinc phosphate with multidirectional helical channels, consisting of alternate ZnO4 and PO4 tetrahedra. The framework contains 12-membered ring channels along the [100] direction, within which [Co(dien)2]3+ ions are located. Each channel is enclosed by chiral interpenetrating double helices (see picture; dien=diethylenetriamine).

    29. Preparation of Ruthenic Acid Nanosheets and Utilization of Its Interlayer Surface for Electrochemical Energy Storage (pages 4092–4096)

      Wataru Sugimoto, Hideki Iwata, Yutaka Yasunaga, Yasushi Murakami and Yoshio Takasu

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351691

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      A layered compound composed of crystalline ruthenic acid sheets interleaved with layers of water can be exfoliated (delaminated) to yield colloidal nanosheets. This material is a mixed conductor where the crystalline nanosheets contribute to the electron conductivity and the hydrous interlayer supplies proton transport (see diagram). A large active surface area and a high specific capacitance is promising for electrochemical supercapacitor applications.

    30. A [2]Pseudorotaxane-Based Molecular Machine: Reversible Formation of a Molecular Loop Driven by Electrochemical and Photochemical Stimuli (pages 4097–4100)

      Woo Sung Jeon, Albina Y. Ziganshina, Jae Wook Lee, Young Ho Ko, Jin-Koo Kang, Chongmok Lee and Kimoon Kim

      Version of Record online: 5 SEP 2003 | DOI: 10.1002/anie.200351925

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      Picking up the thread: A large, reversible change in size as well as shape is observed in a [2]pseudorotaxane-based molecular machine composed of cucurbit[8]uril (CB[8]; bead) and a hexamethylene-bridged bisviologen (thread, see schematic representation) on application of external stimuli. The key feature of the machinelike behavior is the reversible formation of a molecular loop by intramolecular pairing of the terminal viologen radical cation units inside CB[8] upon electrochemical or photochemical reduction.