Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 36

September 12, 2005

Volume 44, Issue 36

Pages 5751–5903

    1. Cover Picture: Hexakis(trimethylsilyl)tetrahedranyltetrahedrane (Angew. Chem. Int. Ed. 36/2005) (page 5751)

      Masanobu Tanaka and Akira Sekiguchi

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200590120

      Extreme shortening of a C[BOND]C bond results from an increase in the s character of the bond orbitals, as is found in hexakis(trimethylsilyl)tetrahedranyltetrahedrane, which is depicted in the cover picture. Although a decade ago nobody assumed that such a derivative could be isolated, in their Communication on page 5821 ff. A. Sekiguchi and M. Tanaka describe the synthesis and characterization of this highly sought after target, which agrees perfectly with theoretical predictions.

    2. Protein Microarray Technology. Edited by Dev Kambhampati. (page 5770)

      Jörg Eppinger

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200485155

    3. Hydrogen Sponge? A Heteronuclear Cluster That Absorbs Large Quantities of Hydrogen (pages 5772–5774)

      Paul J. Dyson and J. Scott McIndoe

      Version of Record online: 18 AUG 2005 | DOI: 10.1002/anie.200501549

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      After a very long wait two arrive together: Following the recent highlight of a late-transition-metal octahedral cluster with 12 hydride ligands and 10 too few electrons, an equally remarkable highly electron-deficient pentanuclear cluster based on a triplatinum–dirhenium trigonal-bipyramidal core has been discovered which undergoes oxidative addition with three equivalents of H2 (see scheme)

    4. New Aspects of Soai's Asymmetric Autocatalysis (pages 5776–5777)

      Joachim Podlech and Timo Gehring

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/anie.200501742

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      Photolysis with circularly polarized light combined with Soai's asymmetric autocatalysis in the reaction of 2-(tert-butylethynyl)pyrimidine-5-carbaldehyde (1, R=C[TRIPLE BOND]CtBu) with iPr2Zn results in the amplification of ≈0.005 % ee to about 65 % ee in one step (see scheme). This reaction may serve as a model for how chiral amplification occurred in the prebiotic era.

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      The First Century of Ketenes (1905–2005): The Birth of a Versatile Family of Reactive Intermediates (pages 5778–5785)

      Thomas T. Tidwell

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200500098

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      An explosive history: Diphenylketene was isolated and identified by Staudinger (see photo) in 1905, as the first example of this class of highly reactive compounds. Others had previously generated these species, but missed the opportunity to claim their discovery. This Essay provides an enlightening view of the history behind these useful reagents.

    6. Protein-Reactive Natural Products (pages 5788–5809)

      Carmen Drahl, Benjamin F. Cravatt and Erik J. Sorensen

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200500900

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      Permanently arrested—that is, when small-molecule natural products inhibit enzymes by covalent modification of an amino acid residue in the active site. An example of this is the complex of human MetAP-2 (blue) with fumagillin (yellow) in which the natural product is linked to a histidine residue (cyan) of the protein by a C[BOND]N bond.

    7. Stimuli-Responsive Gels from Reversible Coordination Polymers (pages 5810–5814)

      Ho-Joong Kim, Jung-Hoon Lee and Myongsoo Lee

      Version of Record online: 30 AUG 2005 | DOI: 10.1002/anie.200501270

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      Sol–gel switching is triggered by counteranion guest exchange. The secondary structures of reversible coordination polymers can interconvert from a folded helical conformation (gel) into an unfolded zigzag conformation (sol) and back again in aqueous media (see picture).

    8. Porous Lanthanide–Organic Open Frameworks with Helical Tubes Constructed from Interweaving Triple-Helical and Double-Helical Chains (pages 5814–5817)

      Yan-Qiong Sun, Jie Zhang, Yong-Mei Chen and Guo-Yu Yang

      Version of Record online: 1 AUG 2005 | DOI: 10.1002/anie.200500453

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      Achiral channels as well as left- and right-handed helical tubes are present in novel lanthanide-organic frameworks prepared under hydrothermal conditions from lanthanide oxides. In the three-dimensional coordination polymers, the Ln atoms (Ln=Eu, Dy, Y, Pr, Nd, Sm, Gd, Tb, Er) are linked by 4,5-imidazoledicarboxylic acid ligands with skew coordination orientation (see picture).

    9. Molecular Engineering for Single-Chain-Magnet Behavior in a One-Dimensional Dysprosium–Nitronyl Nitroxide Compound (pages 5817–5821)

      Lapo Bogani, Claudio Sangregorio, Roberta Sessoli and Dante Gatteschi

      Version of Record online: 4 AUG 2005 | DOI: 10.1002/anie.200500464

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      Single-chain magnets: A rational approach to decrease magnetic dipolar interactions led to the chain compound [Dy(hfac)3{NIT(C6H4OPh)}] (see structure; NIT(R): 2-(4′-R)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), the first rare-earth-radical-based single-chain magnet. The compound shows slow relaxation behavior, a dynamical crossover resulting from finite-size effects, and a very rich static magnetic behavior.

    10. Hexakis(trimethylsilyl)tetrahedranyltetrahedrane (pages 5821–5823)

      Masanobu Tanaka and Akira Sekiguchi

      Version of Record online: 25 JUL 2005 | DOI: 10.1002/anie.200501605

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      On the short side: Hexakis(trimethylsilyl)tetrahedranyltetrahedrane (see formula) was synthesized by the oxidative coupling of tris(trimethylsilyl)tetrahedranyllithium via a cuprate complex. The exocyclic C[BOND]C bond between the two tetrahedrane units is the shortest known C[BOND]C single bond (1.436(3) Å) owing to the increased s character of the bond orbitals.

    11. Entangled Coordination Networks with Inherent Features of Polycatenation, Polythreading, and Polyknotting (pages 5824–5827)

      Xin-Long Wang, Chao Qin, En-Bo Wang, Yang-Guang Li, Zhong-Min Su, Lin Xu and Lucia Carlucci

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200501373

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      Caught in a net: Self-assembly of nickel salts with 4,4′-bipyridine and the long V-shaped 4,4′-oxybis(benzoate) ligand has led to three different coordination networks: a parallel polycatenation of nanotube motifs to give a layered framework (see picture), a 2D[RIGHTWARDS ARROW]3D polythreaded array involving five polymeric units at a time, and a 3D self-penetrating binodal network with an unprecedented (4.82)( topology.

    12. Carbon Dioxide Activation Assisted by a Bis(chlorodimethylsilyl)cyclopentadienyl Titanium Compound (pages 5828–5830)

      David Santamaría, Jesús Cano, Pascual Royo, Marta E. G. Mosquera, Tomás Cuenca, Luis M. Frutos and Obis Castaño

      Version of Record online: 4 AUG 2005 | DOI: 10.1002/anie.200500716

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      A helping hand: The assisted fixation of CO2 and its transformation into a carbonato ligand has been achieved using a di(silyl)cyclopentadienyl titanium(IV) complex. In the presence of water and under air, a dinuclear carbonato titanium(III) complex (see picture) is formed. Theoretical investigations into the electronic properties of this titanium(III) complex explain its high stability and diamagnetism.

    13. Solid/Solution-Phase Annulation Reagents: Single-Step Synthesis of Cyclic Amine Derivatives (pages 5830–5833)

      Roland E. Dolle, Calum MacLeod, Blanca Martinez-Teipel, William Barker, Pamela R. Seida and Torsten Herbertz

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/anie.200501665

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      Spanning the diversity gap: The conversion of primary amines into cyclic derivatives is achieved by using a family of amine-derivatizing reagents, termed SPAn reagents (see scheme). The reagents, which require no further chemical manipulation or activation, are used to prepare discrete compounds or a library collection of diverse heterocycles. SPAn reagents have application in finding new lead compounds and the development of structure–activity relationships.

    14. Highly Regio- and Enantioselective Asymmetric Hydroformylation of Olefins Mediated by 2,5-Disubstituted Phospholane Ligands (pages 5834–5838)

      Alex T. Axtell, Christopher J. Cobley, Jerzy Klosin, Gregory T. Whiteker, Antonio Zanotti-Gerosa and Khalil A. Abboud

      Version of Record online: 12 AUG 2005 | DOI: 10.1002/anie.200501478

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      Off the shelf: The commercially available ligand (R,R)-1,2-bis(2,5-diphenylphospholano)ethane ((R,R)-Ph-bpe) has been identified as an excellent ligand for asymmetric hydroformylation. State-of-the-art regio- and enantioselectivities are obtained for reactions with styrene, allyl cyanide, and vinyl acetate as substrates while high reaction rates (>4000 turnovers h−1) are maintained (see scheme; Ac=acetate, b/l=branched/linear).

    15. Highly Enantioselective Catalytic Thiolysis of Prochiral Cyclic Dicarboxylic Anhydrides Utilizing a Bifunctional Chiral Sulfonamide (pages 5838–5841)

      Takashi Honjo, Shigeki Sano, Motoo Shiro and Yoshimitsu Nagao

      Version of Record online: 4 AUG 2005 | DOI: 10.1002/anie.200501408

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      A catalytic desymmetrization is achieved for various prochiral dicarboxylic anhydrides with yields of 87–100 % and ee values of 83–98 % through the title reaction (see scheme; Bn=benzyl). The bifunctional effect of the chiral sulfonamide catalyst was clarified on the basis of unsuccessful asymmetric induction by using the related chiral sulfonamides.

    16. Two Molecular Tapes Consisting of Serial or Parallel Azido-Bridged Eight-Membered Copper Rings (pages 5841–5846)

      Yuan-Zhu Zhang, Hai-Yan Wei, Feng Pan, Zhe-Ming Wang, Zhi-Da Chen and Song Gao

      Version of Record online: 12 AUG 2005 | DOI: 10.1002/anie.200501327

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      Magnetic attraction: The exotic 1D molecular tapes [Cu4(N3)8(CH3CN)3(bzp)2]n (1) and [Cu5(N3)10(bzp)2]n (2) were obtained from a solution of methanol or methanol/acetonitrile (see scheme; bzp=2-benzoylpyridyl). The end-on azide bridges in 1 transmit ferromagnetic interaction, whereas in 2, the central copper center of a linear Cu5 unit is antiferromagnetically coupled with its neighboring Cu ions.

    17. The Cytoskyrin Cascade: A Facile Entry into Cytoskyrin A, Deoxyrubroskyrin, Rugulin, Skyrin, and Flavoskyrin Model Systems (pages 5846–5851)

      K. C. Nicolaou, Charles D. Papageorgiou, Jared L. Piper and Raj K. Chadha

      Version of Record online: 25 AUG 2005 | DOI: 10.1002/anie.200502011

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      Models revealed: A series of model systems, for example, for cytoskyrin and rugulin, were prepared from an anthraquinone (see scheme). The cascade sequence features Michael additions and oxidation reactions.

    18. New Iodination Reactions of Saturated Hydrocarbons (pages 5851–5854)

      José Barluenga, Esther Campos-Gómez, David Rodríguez, Francisco González-Bobes and José M. González

      Version of Record online: 10 AUG 2005 | DOI: 10.1002/anie.200501195

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      Unactivated C[BOND]H bonds react with iodine when exposed to trimethylsilyl azide in the presence of a hypervalent iodine reagent or, alternatively, to aqueous H2O2, acetic anhydride, and sodium azide (see scheme).

    19. PbTe Nanorods by Sonoelectrochemistry (pages 5855–5857)

      Xiaofeng Qiu, Yongbing Lou, Anna C. S. Samia, Anando Devadoss, James D. Burgess, Smita Dayal and Clemens Burda

      Version of Record online: 5 AUG 2005 | DOI: 10.1002/anie.200501282

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      Highly uniform, single-crystalline PbTe nanorods with a diameter of 7 nm and an aspect ratio of 7 can be obtained by using a sonoelectrochemical method. The metal ion/ligand ratio controls the purity of the PbTe nanostructures through the redox chemistry of the ions involved in the growth process. Transmission electron microscopy of the nanorods reveals the highly uniform morphology obtained (see picture).

    20. Domino Reaction of 2,3-Epoxy-1-alcohols and PIFA in the Presence of H2O and the Concise Synthesis of (+)-Tanikolide (pages 5857–5860)

      Yasuyuki Kita, Satoshi Matsuda, Eri Fujii, Mai Horai, Kayoko Hata and Hiromichi Fujioka

      Version of Record online: 11 AUG 2005 | DOI: 10.1002/anie.200501686

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      Lactols are prepared by a single operation, in which 2,3-epoxy-1-alcohols are treated with phenyliodine(III) bis(trifluoroacetate) (PIFA) in the presence of H2O. Thus, an efficient domino three- or four-step sequence has been developed and applied to the concise synthesis of (+)-tanikolide (see scheme).

    21. Stereospecific and Stereoselective Preparation of 2-(1-Hydroxyalkyl)-1-alkylcyclopropanols from α,β-Epoxy Ketones and Bis(iodozincio)methane (pages 5860–5863)

      Kenichi Nomura, Koichiro Oshima and Seijiro Matsubara

      Version of Record online: 9 AUG 2005 | DOI: 10.1002/anie.200501644

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      A coordinated attack: The reaction of α,β-epoxy ketones with bis(iodozincio)methane produces 2-(1-hydroxyalkyl)-1-alkylcyclopropanols diastereoselectively (see scheme). The reaction proceeds by the coordination and diastereoselective addition of the zinc reagent to the carbonyl group followed by a stereospecific intramolecular attack on the epoxide ring.

    22. Efficient One-Step Synthesis of Biologically Related Lariat RNAs by a Deoxyribozyme (pages 5863–5866)

      Yangming Wang and Scott K. Silverman

      Version of Record online: 5 AUG 2005 | DOI: 10.1002/anie.200501643

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      Closing the loop: The artificial 6BX22 deoxyribozyme (in green) synthesizes naturally occurring lariat RNAs in one step from readily available linear RNA substrates. The exquisite site selectivity of this macrocyclization reaction — which can form a 1597-membered ring in 72 % yield with <0.1 % side products — highlights the utility of catalytic DNA for transformations that are not possible with traditional synthetic methods.

    23. Stereoselective Synthesis of Highly Substituted Cyclopentenones through [4+1] Annulations of Trialkylsilyl Vinyl Ketenes with α-Benzotriazolyl Organolithium Compounds (pages 5867–5870)

      Christopher P. Davie and Rick L. Danheiser

      Version of Record online: 5 AUG 2005 | DOI: 10.1002/anie.200501579

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      Closing the ring: Highly functionalized cyclopentenones are prepared by the reaction of readily available metalated benzotriazole derivatives with trialkylsilyl vinyl ketenes (see scheme; Z=heteroatom substituent). Dienolate intermediates are generated which form the five-membered ring. Most transformations proceed with high stereoselectivity by a mechanism believed to involve stereospecific 4π-electrocyclic ring closure.

    24. Stabilization of Aryl–Calcium, –Strontium, and –Barium Compounds by Designed Steric and π-Bonding Encapsulation (pages 5871–5875)

      Sven-Oliver Hauber, Falk Lissner, Glen B. Deacon and Mark Niemeyer

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200501494

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      Pentafluorophenyl complexes of the heavier alkaline-earth metals (Ca, Sr, Ba) are stabilized by a novel sterically crowded triazenido ligand. The pendent arene rings of the aryl-substituted triazenide are π bonded to the alkaline-earth metal atoms, thereby suppressing decomposition pathways or ligand redistribution reactions and allowing the isolation of solvent-free derivatives (see picture; Ba: green; N: blue; F: light green; C: gray).

    25. Lithium Benzocyclobuteneoxide as a Precursor of a Vinylogous Enolate: Solvent-Controlled Synthesis of Highly Functionalized Seven-Membered Benzocarbocycles (pages 5875–5878)

      José Barluenga, Patricia García-García, Manuel A. Fernández-Rodríguez, Enrique Aguilar and Isabel Merino

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200501468

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      The reaction of alkynyl Fischer carbene complexes with the ortho-quinodimethane obtained from lithium benzocyclobuteneoxide leads to the preparation of highly functionalized seven-membered benzocarbocycles (see scheme). The position and the nature of the functional groups in the product are solvent controlled: benzocycloheptenones are selectively formed in THF, whereas benzocycloheptene ketals are exclusively synthesized in diethyl ether.

    26. 9/11 Mixed Helices in α/β Peptides Derived from C-Linked Carbo-β-Amino Acid and L-Ala Repeats (pages 5878–5882)

      Gangavaram V. M. Sharma, Pendem Nagendar, P. Jayaprakash, Palakodety Radha Krishna, K. V. S. Ramakrishna and Ajit C. Kunwar

      Version of Record online: 10 AUG 2005 | DOI: 10.1002/anie.200501247

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      A new twist: The α/β hybrid dipeptide repeats prepared from alternating C-linked carbo-β3-amino acid and L-Ala residues show a high propensity for mixed helices and produce hitherto unknown right-handed 11/9 and 9/11 helical structures (see picture).

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      Facile Synthesis of Chiral α-Difluoromethyl Amines from N-(tert-Butylsulfinyl)aldimines (pages 5882–5886)

      Ya Li and Jinbo Hu

      Version of Record online: 8 SEP 2005 | DOI: 10.1002/anie.200501769

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      Nucleophilic (phenylsulfonyl)difluoromethylation of (R)-(N-tert-butylsulfinyl)aldimines with difluoromethyl phenyl sulfone affords the corresponding products in excellent yields and with high diastereoselectivity (see scheme). The facile and convenient deprotection of both tert-butylsulfinyl and phenylsulfonyl groups affords the target α-difluoromethyl amines with high enantiomeric purity.

    28. Reversible, Strain-Controlled Haptotropic Shifts of Cyclopentadienyl Ligands in [1]- and [2]Metallocenophanes (pages 5886–5890)

      Makoto Tanabe, Sara C. Bourke, David E. Herbert, Alan J. Lough and Ian Manners

      Version of Record online: 10 AUG 2005 | DOI: 10.1002/anie.200501155

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      Slipping rings: A reversible shift from η5-Cp to η1-Cp and back has been established for ring-strained metallocenophanes (see scheme) and the dependence of the reversibility on the degree of ring strain has been probed. The presence of phosphane ligands has allowed the isolation of novel η1-Cp ring-slipped Fe and Ru complexes.

    29. Reversible Hydride Generation and Release from the Ligand of [Ru(pbn)(bpy)2](PF6)2 Driven by a pbn-Localized Redox Reaction (pages 5891–5894)

      Take-aki Koizumi and Koji Tanaka

      Version of Record online: 9 AUG 2005 | DOI: 10.1002/anie.200500760

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      Electrochemical reduction of [Ru(pbn)(bpy)2]2+ (1, pbn=2-(2-pyridyl)benzo[b]-1,5-naphthyridine, bpy=2,2′-bipyridine) in an acidic solvent gives [Ru(pbnH2)(bpy)2]2+ (2), which releases the hydrogen as “hydride” (see scheme). This catalytic system reduces substrates (for example, acetone) with two electrons and protons from water, and thus operates in a similar way to the NAD+/NADH redox couple.

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      Synthesis of a Lipomannan Component of the Cell-Wall Complex of Mycobacterium tuberculosis Is Based on Paulsen's Concept of Donor/Acceptor “Match” (pages 5894–5898)

      K. N. Jayaprakash, Jun Lu and Bert Fraser-Reid

      Version of Record online: 3 AUG 2005 | DOI: 10.1002/anie.200500505

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      The perfect match: A mannosidyl n-pentenylorthoester 1 is the sole donor and acceptor source for a branched oligomannan array (see picture). An iterative process of regioselective glycosidation of polyol acceptors virtually eliminates the need for protecting-group manipulations, thereby permitting a rapid, high-yielding route to the mycobacterial lipomannan phosphoinositide.

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