Angewandte Chemie International Edition in English

Cover image for Vol. 28 Issue 9

September 1989

Volume 28, Issue 9

Pages 1147–1282

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 9/1989)

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911471

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      The cover illustration shows a space-filling model of a complex that may contribute to the understanding of biological nitrogen fixation. This process is catalyzed by nitrogenases, in all of which the dominant metal is iron surrounded by a coordination sphere of sulfur. Most nitrogenases also contain molybdenum, and some include vanadium. Recently, however, another type of nitrogenase has been characterized that contains only iron. In the model complex shown here, the extremely unstable molecule diazene (HN[DOUBLE BOND]NH) is bound to two iron atoms, each of which is pseudo-octahedrally coordinated to five donor atoms: four sulfurs and an amine nitrogen. Diazene is the first two-electron reduction product of N2. In addition to complexation and considerable steric blocking, diazene is here stabilized by powerful hydrogen bonding. More information regarding this bioinorganic model compound is presented by D. Sellmann et al. on p.1271 ff. (The current issue also contains other important contributions relevant to this subject).

    2. Graphical Abstract (Angew. Chem. Int. Ed. Engl. 9/1989)

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911472

  1. Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    5. Corrigenda
    1. Lipophilic Tartaric Acid Esters as Enantioselective Ionophores (pages 1147–1152)

      Prof. Dr. Vladimir Prelog, Dr. Miće Kovačević and Dr. Martin Egli

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911473

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      The ability of lipophilic esters 1 to distinguish hydrophilic ions of type 2 from their enantiomers was investigated by phase distribution experiments involving aqueous and lipophilic phases. The results have been interpreted on the basis of diamond-lattice sector models for the (nonisolable) complexes formed between 1 and 2.

    2. The Active Sites in Manganese-Containing Metalloproteins and Inorganic Model Complexes (pages 1153–1172)

      Prof. Dr. Karl Wieghardt

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911531

      The ultratrace element manganese is an essential component in, for example, the active center of photosystem II, and this has motivated inorganic chemists to synthesize and investigate two- and four-atom complexes of MnII, MnIII, MnIV, MnIIMnIII, and MnIIIMnIV with O, N donor atoms and O, N bridging ligands. In some cases, remarkable similarities have been observed between the electronic and spectroscopic properties of model compounds and those of manganoproteins. This article demonstrates in exemplary fashion the heights to which “bioinorganic chemistry” has risen.

    3. Cyclizations via Palladium-Catalyzed Allylic Alkylations [New Synthetic Methods (79)] (pages 1173–1192)

      Prof. Barry M. Trost

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911731

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      The synthesis of ring compounds has always fascinated organic chemists. Nevertheless, the investigation of carbocyclic and heterocyclic systems has been restricted by the availability of effective synthetic methods. In recent years, transition-metal catalysts—especially those containing palladium(0)—have greatly expanded the range of accessible cyclic systems. The title reactions (one example of which is shown below) now occupy an important place in the synthetic chemist's arsenal thanks to their extraordinary chemo-, regio-, and stereoselectivity and the resulting implications with respect to the development of enantioselective transformations.

    4. The Beginnings of Organic Photochemistry (pages 1193–1207)

      Prof. Dr. Heinz D. Roth

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198911931

      The interaction of light with matter is not limited to physical phenomena—light can also influence the chemical behavior of a substance. Three types of light-induced changes attracted the attention of early chemists: color changes, the appearance of gas bubbles, and the precipitation of photoproducts displaying lower solubilities than the starting material. A great many photochemical reactions were discovered during the 18th and 19th centuries. The name Ciamician is inseparable from the history of photochemistry; indeed, it was he who established photochemistry as an independent subdiscipline.

    5. Single-Source III/V Precursors: A New Approach to Gallium Arsenide and Related Semiconductors (pages 1208–1215)

      Prof. Alan H. Cowley and Prof. Richard A. Jones

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912081

      Can inorganic and organometallic chemists play a role in the further development of III/V semiconductors? The authors would answer “yes”, and they present here a series of III/V compounds that combine strong III/V-atom bonding with readily eliminated substituents. At the same time, the compounds are less pyrophoric and less toxic than reagents currently used, for example, in the manufacture of GaAs and InP. One case in point is [tBu2GaAsH2]3, which is stable as a solid at room temperature but decomposes smoothly in solution to finely divided, amorphous GaAs.

  2. Communications

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    5. Corrigenda
    1. Asymmetric Oligomerization of Propene and 1-Butene with a Zirconocene/Alumoxane Catalyst (pages 1216–1218)

      Prof. Dr. Walter Kaminsky, Dipl.-Chem. Aurelia Ahlers and Dipl.-Chem. Nico Möller-Lindenhof

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912161

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      Approximately 80 % stereoselectivity in the creation of the second chiral center is observed during olefin oligomerization when chiral zirconocene complex (S)-1 together with methylalumoxane is used as catalyst. The oligomerization product mixture can be largely restricted to dimers through pentamers by appropriate choice of catalyst-to-monomer concentration. Relatively straight forward access is thereby provided to alkyl-substituted 1-alkenes such as 2 and 3, which could be of interest in the synthesis of pheromones and other modestly functionalized chiral compounds. [Zr(CH2-indenyl)2{O2C[BOND]CH(OAc)Ph}2]

    2. Chain-Substituted Lipids as Substrates for Phospholipase A2 (pages 1218–1219)

      Prof. Fredric M. Menger and M. G. Wood Jr.

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912181

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      More stable liposomes for drug delivery, and substances for controlling prostaglandin levels, may result from the interesting observation reported here: phospholipids like 1, which contain bulky alkyl substituents in the first half of their fatty acid residues, are much less readily hydrolyzed by phospholipase A2 than distearoylphosphatidylcholine itself.

    3. Phosphonioboratoacetylenes: C2 Stabilized by Donor and Acceptor Molecules (pages 1219–1221)

      Prof. Dr. Hans Jürgen Bestmann, Dipl.-Chem. Harald Behl and Dipl.-Chem. Matthias Bremer

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912191

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      A complexed C2 molecule: that is one way of describing the C2 unit of the compound Ph3B⊖[BOND]C [TRIPLE BOND] C[BOND]⊕PMePh2 (1), which is derived from ethynyldiphenylphosphane, butyllithium, BPh3, and methyl iodide. The bulky substituents shield the C[TRIPLE BOND]C bond so effectively that 1 does not react with 1, 3-dipoles. At the same time, however, its P-CH3 group is transformed into P-C2H5 by deprotonation and methylation.

    4. [VO(O2CtBu)3] and [V6O6(μ-O)4(μ-O2CPh)9]. Structural Characterization of a Mononuclear Vv and a (2 + 4)-Nuclear VIVVmath image Carboxylato Complex. Models for Vanadate-Dependent Peroxidases (pages 1221–1222)

      Prof. Dr. Dieter Rehder, Dipl.-Chem. Wolfgang Priebsch and Margen von Oeynhausen

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912211

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      The two title compounds, prepared from VOC13 and the silver salts of pivalic and benzoic acids, are interesting models for the structure of the vanadium center in haloperoxidases from marine brown algae. The Vv center in crystalline pivalate complex 1 displays pentagonal-bipyramidal coordination. However, IR and 51V NMR data suggest that in solution the vanadium atom is only sixfold coordinated. The second title substance, which is hexanuclear, is an entirely new type of multinuclear oxovanadium compound with a twist-boat V6 structure.

    5. 3,3′:4,4′-Bis(thieno[2,3-b]thiophene): A Novel Fused Heteroarene (pages 1222–1224)

      Yasuhiro Kono, Hisakazu Miyamoto, Dr. Yoshio Aso, Prof. Dr. Tetsuo Otsubo, Prof. Dr. Fumio Ogura, Takanori Tanaka and Prof. Dr. Masami Sawada

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912221

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      The planar, centrosymmetric compound 1 is a promising electron-donating component for the synthesis of organic metals. Produced in up to 14 % yield by reductive dimerization of dibromothienothiophene, the compound can be reversibly oxidized electrochemically to a conducting polymer (κ = 0.06 S cm−1). In a 1:1 ratio with iodine it also forms a conducting complex (0.11 S cm −1).

    6. N-Cesiocarbazole ṁ pmdta and N-Potassiocarbazole ṁ pmdta (PMDTA = N,N,N′,N″,N″-Pentamethyldiethylenetriamine). Cation Size and Multihapto Bonding (pages 1224–1226)

      Dipl.-Chem. Karina Gregory, Dr. Matthias Bremer, Prof. Dr. Paul von Ragué Schleyer, Mr. Peter A. A. Klusener and Prof. Dr. Lambent Brandsma

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912241

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      Both σ and π interactions should characterize the solid-state structures of salts such as N lithiopyrrole. This prediction has been only partially confirmed in the case of the lower alkali metals, but carbazole salts of the higher homologues potassium and cesium indeed show multihapto coordinations of eight and nine/eight, respectively. The structure of the Ci-symmetrical dimer of the cesium salt is shown as an example.

    7. Very Short C[BOND]C Single Bonds and Their Origin. The Central Bond Length in Bitetrahedryl (pages 1226–1228)

      Prof. Dr. Paul von Ragué Schlever and Dr. Matthias Bremer

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912261

      A reduced C[BOND]C bond length and a lower rotational barrier: these are apparently the consequences of increasing the H[BOND]C[BOND]C bond angle in ethane according to ab initio calculation. An explanation is thereby provided for the abnormally short central C[BOND]C bond in compounds like bicubyl, in which this bond bears “bent-back” substituents. Since increasing the bond angle causes rehybridization and increased s character in the C[BOND]C bond, it is appropriate to compare the hybridization of the bond in bitetrahedryl (calculated length 1.438 Å) with that of the C[BOND]C single bond in butadiyne (1.384 Å).

    8. On the Stability of Trioxo(η5 -Cyclopentadienyl) Compounds of Manganese, Technetium, and Rhenium : An ab initio SCF Study (pages 1228–1231)

      Dipl.-Chem. Thomas Szyperski and Dr. Peter Schwerdtfeger

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912281

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      An isolobal analogy exists between the radicals TcO3, ReO3, and CH3, but not between MnO3 and CH3, according to ab initio SCF calculations. Consequently, compounds containing RTcO3 and RReO3 groups (where R is an organic or inorganic residue) should be stable. These results confirm calculations based on CpMO3 (1), which predict positive force constants for M [DOUBLE BOND] Tc or Re, but repulsion in the case M = Mn.

    9. P14iPr4 – The First Hexacyclic Organophosphane (pages 1231–1232)

      Prof. Dr. Marianne Baudler, Harald Jachow, Bernhard Lieser, Prof. Dr. Karl-Friedrich Tebbe and Dr. Magda Fehér

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912311

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      Compound 1 is made up of two norbornane like P7 units coupled in a unique way. It results from thermolysis of a mixture of bi-and tri-cyclic isopropylphosphanes and represents the first tetradecaphosphane to be characterized structurally. According to 1H{31P} NMR data, the configurational isomer present in the crystalline phase equilibrates in solution with two diastereomers.

    10. Unusual Geometry of a Sterically Congested Analogue of (CH)math image (pages 1232–1234)

      Prof. Dr. Günther Maier, Dipl.-Chem. Harald Rang and Dr. Hans-Otto Kalinowski

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912321

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      The tert-butyl-substituted cation 1 may be trigonal bipyramidal.13C NMR spectra reveal a temperature-dependent equilibrium linking three degenerate structures, with the average spectrum corresponding to the highly symmetrical structure 2.

    11. Sequence Dependence of Template-Directed Syntheses of Hexadeoxynucleotide Derivatives with 3′–5′ Pyrophosphate Linkage (pages 1235–1237)

      Dr. Günter von Kiedrowski, Dipl.-Chem. Britta Wlotzka and Dipl.-Chem. Jörg Helbing

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912351

      Self-replication in a minimal chemical system represents both a goal and a challenge for bioorganic chemistry, which concerns itself, among other things, with trying to understand the origin of life. A partial success can now be reported in the creation of a model system consisting of nucleic acid building blocks and capable of self replication under replicase-free conditions. This article presents evidence that a self complementary template can accelerate—in a highly selective way—the further incorporation of subunits into sequentially homologous oligonucleotides.

    12. A Base-Stabilized Ge–S Double Bond (pages 1237–1238)

      Prof. Dr. Michael Veith, Dipl.-Chem. Sabine Becker and Dr. Volker Huch

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912371

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      The Ge[BOND]S bond in 1 is only 2.06 Å long, ca. 0.2 Å less than would be expected for a Ge[BOND]S single bond. The monomeric form of 1 is apparently stabilized by an intramolecular N[BOND]Ge donor bond, which in solution at higher temperatures is fluxional on the NMR time scale. The analogous oxygen compound 2 is dimeric. Compounds 1 and 2 were prepared in 98 and 60 % yield, respectively, starting with germanediyl 3 and either S8 or O2.

    13. Double-Bond Geometry of Norbornene: Neutron Diffraction Measurement of a Derivative at 15 K (pages 1239–1241)

      Prof. Dr. Otto Ermer, Dipl.-Chem. Peter Bell and Dr. Sax A. Mason

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912391

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      The double bond in norbornene (1) is displaced nearly twice as far in the endo direction (χ = 7.4(2)°) as previously assumed, according to the results of a 15 K neutron diffraction study on the derivative 2. This discovery is important with respect to interpreting the double-bond reactivity of norbornene, which is characterized by a strong preference for exo attack, and it may mark the end of a very prolonged debate.

    14. equation image
      , the First Cyclized Lithium Amide Ladder: Synthesis and Structure of Hexamethyleneimidolithium (pages 1241–1243)

      Dr. Ronald Snaith, Dr. Donald Barr, Dominic S. Wright, Dr. William Clegg, Susan M. Hodgson, Glenn R. Lamming, Andrew J. Scott and Dr. Robert E. Mulvey

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912411

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      The title compound is best described not as two superimposed cyclic trimers, but rather as a “cyclic ladder” with six rungs. In crystalline form it exists as the hexamer 1. This is the first noncomplexed oligomeric lithium amide derivative with n > 4, as well as the first that does not consist of a simple, planar (NLi)n ring. Cryoscopic and 7Li NMR measurements verify that solutions of 1 contain not only the hexamer but also higher aggregates.

    15. Biomimetic Synthesis of an Inverted Porphyrinoid with Peripheral N Atoms (pages 1243–1245)

      Dr. Karl-Heinz Schumacher and Prof. Dr. Burchard Franck

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912431

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      Nitrogen atoms on the periphery rather than inside the molecule characterize inverted porphyrinoids. The first such species, 1, was synthesized in 71 % yield via a biomimetic route starting from hydroxymethylpyrrole 2.

    16. Binary Alloys of 2,5-Disubstituted DCNQI Radical Anion Salts of Copper and Their Electrical Conductivity (pages 1245–1246)

      Dr. Peter Erk, Prof. Dr. Siegfried Hünig, Dipl.-Chem. Hubert Meixner, Dipl.-Phys. Hans-Jörg Gross, Dipl.-Phys. Uwe Langohr, Dr. Hans-Peter Werner, Dr. Jost Ullrich von Schütz and Prof. Dr. Hans Christoph Wolf

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912451

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      Electrocrystallization or even reaction with a copper wire leads to conversion of two 2, 5-disubstituted DCNQIs (1 and 2) into the alloy 3. Such an alloy displays metallic conductivity. Moreover, the phase transformation that normally causes the pure components to become semiconductors upon cooling can be suppressed through alloy formation.

    17. Structure and Properties of the Cryptophane-E/CHCl3 Complex, a Stable van der Waals Molecule (pages 1246–1248)

      Dr. Josette Canceill, Dr. Michèle Cesario, Prof. Dr. André Collet, Dr. Jean Guilhem, Liliane Lacombe, Dr. Bénédicte Lozach and Dr. Claudine Pascard

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912461

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      In the absence of hydrophobic effects, the driving force for complexation between neutral host and guest molecules (e.g., cryptophane E and halomethanes) is a function of several factors. If size and form are suitable, as in the CHC13 complex 1, complexation is enthalpy driven, and stable supermolecules result (“van der Waals molecules”).

    18. Cryptophane Radical Cations as Components of Three-Dimensional Charge-Transfer Salts (pages 1249–1250)

      Dr. Anne Renault, Prof. Dr. Janine Lajzerowicz, Dr. Josette Canceill, Dr. Daniel Talham, Dr. Patrick Batail and Prof. Dr. André Collet

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912491

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      A delocalized quasi-free π electron is present in the radical cation of 1, according to ESR and measurements with a SQUID magnetometer. Electrochemical oxidation of 1 at a Pt wire produced salts of 1 in the form of blue-green single crystals. Based on cyclic voltammetric data, the dication 12⊕ is also relatively stable, perhaps with a triplet ground state.

    19. A Distillable C- and N-Silylated Nitrile Imine (pages 1250–1251)

      Florence Castan, Dr. Antoine Baceiredo and Dr. Guy Bertrand

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912501

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      Compound 1 should be regarded as the synthetic equivalent of

      . The Si[BOND]N bond is quite easily cleaved, and so is the Si[BOND]C bond. Thus, 1 rearranges photochemically to carbodiimide. Reaction with dipolarophiles at room temperature leads to the expected [2 + 3] adducts.

    20. Hg8 (“Mercubane”) Clusters in Rb15Hg16 (pages 1251–1252)

      Prof. Dr. Hans-Jörg Deiseroth and Dr. Axel Strunck

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912511

      Isolated, nearly cubic Hg8 clusters (“mercubanes”) have now been identified for the first time in the rubidium amalgam Rb15Hg16. Metallic, golden single crystals of this previously unknown compound were produced in the course of an unsuccessful attempt to synthesize RbHg. The geometry of the cluster suggests that electron transfer from the electropositive rubidium produces a chemical bond between mercury atoms that exhibits primarily σp (6p) character rather than the σs character familiar from the classical mercury polycations Hgmath image.

    21. Unsaturated 1,4-cis and 1,4-trans-Diaminotetradeoxycycloheptites—Enantiomerically Pure, Polyfunctionalized Tropa Derivatives by Enzymatic Hydrolysis (pages 1253–1255)

      Dipl.-Chem. Manuela Falk-Heppner, Dr. Manfred Keller and Prof. Dr. Horst Prinzbach

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912531

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      The compound anti-cis-diepoxycycloheptene alcohol 1 (R [DOUBLE BOND] H), prepared from tropilidene (tropone), is the starting material for an efficient synthesis of a variety of protected, enantiomerically pure 1, 4-diaminotetradeoxycycloheptites appropriate for glycosidation reactions. Enzymatic hydrolysis of the tropa-analogous meso-diacetate intermediates leads in 86–100% yield to monoacetates with ee values above 99%.

    22. Sulfur Cyanide Pentafluoride SF5 CN (pages 1255–1256)

      Dr. Oliver Lösking and Prof. Dr. Helge Willner

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912551

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      Two elusive but relatively simple SF5 compounds have been independently prepared by two research groups : SF5CN results from treatment of dirhodane with fluorine [Eq. (a)], and the structural isomer SF5NC can be obtained by debromination of SF5N = CBr2 [Eq. (b)]. The IR spectrum of the cyanide displays the characteristic CH stretching band at 2235 cm−1, while the corresponding band for the isocyanide is located at 2080 cm−1. Even though SF5NC isomerizes to SF5CN at room temperature and pressures < 50 Torr, the cyanide itself is remarkably stable. Both are gaseous, and they are expected to display unusual chemical and physical properties.

    23. Sulfur-Pentafluoride Isocyanide, SF5NC (pages 1256–1258)

      Prof. Joseph S. Thrasher and Krishnan V. Madappat

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912561

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      Two elusive but relatively simple SF5 compounds have been independently prepared by two research groups : SF5CN results from treatment of dirhodane with fluorine [Eq. (a)], and the structural isomer SF5NC can be obtained by debromination of SF5N = CBr2 [Eq. (b)]. The IR spectrum of the cyanide displays the characteristic CH stretching band at 2235 cm−1, while the corresponding band for the isocyanide is located at 2080 cm−1. Even though SF5NC isomerizes to SF5CN at room temperature and pressures < 50 Torr, the cyanide itself is remarkably stable. Both are gaseous, and they are expected to display unusual chemical and physical properties.

    24. Stereoregular Oligomerization by Repetitive Diels–Alder Reactions (pages 1258–1261)

      Peter R. Ashton, Dr. Neil S. Isaacs, Dr. Franz H. Kohnke, John P. Mathias and Dr. J. Fraser Stoddart

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912581

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      Highly stereoselective preparation of the oligomer 1 is possible “simply” by means of a structure-directed synthesis, that is, without any use of controlling reagents or catalysts. The 3 :2 Diets–Alder adduct of diene and dienophile has an all-syn configuration and is coiled in such a way that the two ends approach each other.

    25. Trinacrene – a Product of Structure-Directed Synthesis (pages 1261–1263)

      Peter R. Ashton, Dr. Neil S. Isaacs, Dr. Franz H. Kohnke, Prof. Guglielmo Stagno D'Alcontres and Dr. J. Fraser Stoddart

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912611

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      Trinacrene (1) is a promising—and very attractive-new cage compound with a name derived from an old designation for Sicily (Trinacrien). The synthesis of 1 was accomplished in two steps involving six (2 × 3) Diels–Alder reactions and highly symmetrical precursors, the second step being a high-pressure reaction (10 kbar). Compound 1 displays D3h symmetry and gives only the predicted five 1H NMR signals.

    26. Efficient Ion Exchangers and Receptors for Organic and Organometallic Cations (pages 1263–1265)

      Dipl.-Chem. Stefan Eller, Dipl.-Chem. Peter Brandt, Dipl.-Chem. Abdul K. Brimah, Peter Schwarz and Prof. Dr. R. Dieter Fischer

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912631

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      “Free” (CH3)3Sn ions can be exchanged with surprising ease in polymeric metal cyanides, as demonstrated by reactions (a) and (b). Host–guest complexes, in which an inorganic solid acts as host and an organometallic or organic cation is the guest, are of considerable interest with respect to the development of materials with nonlinear optical properties.

    27. Spontaneous Oxidation and in-situ Polymerization of Pyrrole in Channels of the Three-Dimensional Coordination Polymer [(Me3Sn)3FeIII(CN)6]∞ (pages 1265–1266)

      Dipl.-Chem. Peter Brandt, Prof. Dr. R. Dieter Fischer, Dr. Enrique Sanchez Martinez and Prof. Dr. Ricardo Diaz Calleja

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912651

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      Precursors to highly conducting polypyrrole (Ppy) are formed in the lipophilic channels of 1 subsequent to a spontaneous, strictly stoichiometric [N(Ppy)/Fe = 1/1] redox reaction. In view of the diameter of the channel (6.8 Å) the entrapped Ppy should be free of cross-linking (thus approximating a “molecular wire”).

    28. Isolation of a Zwitterion in a Diels–Alder Reaction with Inverse Electron Demand (pages 1267–1268)

      Dipl.-Chem. Klaus-Peter Hartmann and Priv.-Doz. Dr. Manfred Heuschmann

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912671

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      The Diels–Alder reaction between tetrazine 1 and the ketene-N,N acetal 2 is not concerted but rather a two-step process. At temperatures < −15 °C it proved possible to isolate the zwitterion 3, which reacted further to 4 upon warming. Previously confusing phenomena associated with such reactions now merit reconsideration and systematic investigation.

    29. 1-Phenalenol: Isolation and Disproportionation (pages 1268–1269)

      Dr. Yoshikazu Sugihara, Hidetoshi Kawanaka and Prof. Dr. Ichiro Murata

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912681

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      A large excess of reducing agent and high-dilution techniques permitted isolation of 1 in accordance with reaction (a). Disproportionation of 1 to phenalene and phenalenone is greatly accelerated by protic reagents : no reaction in CDCl3, but a half-life of only 30 min upon addition of HOAc (HOAC:1 = 1:30). Carbinols derived from stable carbenium ions are normally quite labile, so the procedure illustrated here is of general significance.

    30. Synthesis and Structure of [(C5H5)2TiS4AsCH3]—a New Reagent for the Synthesis of Sulfur-Rich Heterocycles (pages 1269–1271)

      Prof. Dr. Ralf Steudel, Dipl.-Chem. Birger Holz and Prof. Dr. Joachim Pickardt

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912691

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      The cleavage of binuclear titanocene polysulfide complexes [reaction (a)] is useful in the synthesis of the title compound 1. Reaction probably occurs in an analogous fashion with many elemental dihalides (ECl2 or RxEC12) and should therefore open the way to a wide variety of new titanocene complexes. Compound 1 contains a bimetallic heterocycle that functions as a transfer reagent for S4AsCH3.

    31. Nitrogenase Model Compounds: [μ-N2H2{Fe(“NHS4”)}2], the Prototype for the Coordination of Diazene to Iron Sulfur Centers and Its Stabilization through Strong N[BOND]H ⃛ S Hydrogen Bonds (pages 1271–1272)

      Prof. Dr. Dieter Sellmann, Dipl.-Chem. Wolfgang Soglowek, Dr. Falk Knoch and Dr. Matthias Moll

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912711

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      How are the energetically extremely unfavorable intermediates in nitrogenase reduction of N2 stabilized? By complexation, steric hindrance, and strong hydrogen bonding! At least this is the answer suggested by the complex 1. Diazene (HN [DOUBLE BOND] NH) is stabilized in 1 by bonding to Fe centers that are completely surrounded by biologically relevant donor atoms. Thus, 1 is a model complex for enzymatic nitrogen fixation in both a functional and a structural sense.

    32. A New Class of DNA-Cleaving Molecules: pH-Dependent DNA Cleavage by Propargylic and Allenic Sulfones (pages 1272–1275)

      Prof. K. C. Nicolaou, G. Skokotas, P. Maligres, G. Zuccarello, E. J. Schweiger, K. Toshima and S. Wendeborn

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912721

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      DNA-cleaving agents are of considerable interest in molecular biology and pharmaceutical chemistry. The Garrett–Braverman reaction sequence has now been utilized as a basis for developing the title compounds; l3 are examples. They are capable of cleaving ϕX174 DNA in a pH-dependent reaction with maximal activity at pH 8.5.

    33. Dithia Dications from Cyclic and Acyclic Precursors by Gas-Phase Oxidation (“Charge Stripping”) of 3e/2c-Radical Cations (pages 1275–1276)

      Dr. Thomas Drewello, Dr. Carlito B. Lebrilla, Prof. Dr. Klaus-Dieter Asmus and Prof. Dr. Helmut Schwarz

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912751

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      What cannot be accomplished in solution is readily achieved in the gas phase by “charge-stripping” mass spectrometry: generation of dications from radical cations of acyclic thioethers (e.g., 1 [RIGHTWARDS ARROW] 2). Ionization energies for the oxidation are in good agreement with the predictions of qualitative MO treatments of the bonding in three-electron two-center radical cations.

    34. Multiple “Remote Functionalization” of Different Sites in Flexible Molecules by “Anchored” Bare FeI Ions (pages 1277–1278)

      Dipl.-Chem. Gregor Czekay, Dipl.-Chem. Karsten Eller, Dipl.-Chem. Detlef Schröder and Prof. Dr. Helmut Schwarz

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912771

      Thumbnail image of graphical abstract

      Regiospecific, consecutive elimination of alkene and hydrogen—that turns out to be the pathway for what is formally an alkane elimination from the Fe complex of the α-branched carbonitrile 1. Both alkyl chains of 1 participate in this fragmentation, as shown by tandem MS experiments. R[DOUBLE BOND](CH2)5CD3, R′[DOUBLE BOND]C3H7.

    35. Does Cyanoacetylene Dimerize Thermally to 1,3-Cyclobutadiene-1,2-dicarbonitrile? (pages 1279–1280)

      Bernhard Witulski, Prof. Dr. Ludger Ernst, Prof. Dr. Peter G. Jones and Prof. Dr. Henning Hopf

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912791

      Thumbnail image of graphical abstract

      “Perhaps” is the answer to the question posed in the title. What is heating cyanoacetylene 1 to 160 °C in benzene leads to intermediates (2 a, b) that behave like cyclobutadiene-l, 2-dicarbonitrile. This has now been demon strated in the presence of the trapping reagent [2.2]paracyclophane, resulting in the Diels-Alder adducts of 2 a and 2b.

  3. Book Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    5. Corrigenda
  4. Corrigenda

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    5. Corrigenda
    1. You have free access to this content
      Corrigenda (page 1282)

      Article first published online: 30 DEC 2003 | DOI: 10.1002/anie.198912821

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