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Graphical Abstract (Angew. Chem. Int. Ed. Engl. 23241995)

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I\ /I I1 II 1
International Edition in English
A Journal
__ of the
Deutscher Chemiker
Pages 2571 -2796
The cover picture shows a ball-and-stick model of a multicyclophane described by an
achiral K 3 , stereoelement. K 3 . graphs consist of two sets of three points where each
point in one set is connected to every point in the other set. In the multicyclophane
shown. these six points are the red and blue benzene rings. J. S. Siege1 et al. report
more on pages 2657-2660 on this multicyclophane and its D,,-symmetric isomer,
which have dimensions on the order of nanometers in terms of length and kilodaltons in terms of weight. The picture was generated with the program QMView
developed by Kim K. Baldridge and Jerry Greenberg at the San Diego Supercomputer Center.
Owing to the ready availability of propargylic alcohols and their esters by the reaction
of terminal alkynes with carbonyl compounds, their Pd-catalyzed reactions hold
great potential in organic synthesis. For instance, the reaction of methyl carbonate
1 with methyl acrylate (2) leads to the coupling product 3. Many reactions, including
carbonylations, yield allenes that can be used in a range of subsequent reactions.
T H P = tetrahydropyranyl.
To imitate the way a chemist thinks in the planning of a synthesis is the goal of the
synthesis-planning program WODCA presented here. The system provides a variety
of tools to be selected by the knowledgeable chemist, which guide a synthesis plan
toward starting materials, exploiting long-range synthetically accessible structural
similarities. The way the program operates is demonstrated for the development of
suggestions for the synthesis of the calicheamicin precursors, ( + )-a-bisabolene, and
( + )-7,8-epoxy-2-basmen-2-one.
J. Tsuji,* T. Mandai .._..........._2589-2612
Palladium-Catalyzed Reactions of Propargylic Compounds in Organic Synthesis
W.-D. Ihlenfeldt,
J. Gasteiger * ..........................
Computer-Assisted Planning of Organic
Syntheses: The Second Generation of Programs
Pores with rotational symmetry, each formed from five transmembrane helices in
cytochrome c oxidase, form the postulated pathways for the protons required for the
biochemical reduction of 0 , as well as for the protons transported across the cell (or
inner niitochondrial) membrane resulting in 21 H gradient. The structures of cytochrome c oxidase from a bacterium recently described by Michel et a]. and from
bovine heart by Yoshikawa et al. corroborate many previous results on the structure
and function of this enzyme and disprove others.
Helical strands from Pz and P,,, units (see structure below). recently predicted by ab
initio calculations to be thermodynamically stable, and shortly thereafter discovered
as a structural element in (CuI),P,,, might be the major component of amorphous
red phosphorus. Radial distribution functions calculated on the basis of this struct u r d model are in very good agreement with experimentally determined diagrams.
B. Kadenbach* .._...._.._....__..__.
X-ray Crystal Structures of Cytochrome c
Oxidases from Pririicoccus denirr$cnns and
Bovine Heart and Their Implications for
the Molecular Mechanism of Cell Respiration
H. Hart]* ...............................
New Evidence Concerning the Structure of
Amorphous Red Phosphorus
High regioselectivity, good yields, and mild reaction conditions are the advantages of
the reaction of iminium salts 1 with imines 2 to afford the Mannich bases 3. Since
the amino group in 3 can be substituted readily, this approach enables the simple
regioselective functionalization of ketones-an important goal in synthesis.
M . Arend, N . Risch * ............. 2639-2640
Regio- and Diastereoselective Synthesis of
P-Amino Ketones by Addition of Imines to
Iminium Salts
With less than 1 mol% of a chiral vanadium catalyst and aqueous H,O, as oxidizing
agent, sulfides can be converted under the simplest of conditions into optically active
sulfoxides (with u p to 85% ee) [Eq. (a)]. R, R = alkyl, aryl.
chiral V catalvst
( S 1 mol %)
C. Bolm.* F. Bienewald .._....._2640-2642
Asymmetric Sulfide Oxidation with Vanadium Catalysts and H,O,
The mixed-valent Fe"Fe"' complex 1 (structure
shown on the right; the dashed line indicates a weak
hydrogen bond to one ClO, counterion) with the
ground state S, = 1/2 is the first functional model
for the mixed-valent form of the metalloprotein
hemerythrin. Like the protein, 1 disproportionates
autocatalytically in CH,CN to the Fe"Fe" and
F ~ I I I F ~ I I I forms. L = 1,4,7-trimethyl-l,4,7-triazacyclononane.
U. Bossek, H . Hummel, T. Weyhermuller,
E. Bill, K. Wieghardt* .........._ 2642-2645
The First p(0H)-Bridged Model Complex
for the Mixed-Valent Fe"Fe"' Form of
The first compounds of the type RSi(NH,), containing substituents R bound through
oxygen or nitrogen to silicon are presented herein. These compounds are expected,
like the isoelectronic silanetrioles RSi(OH),, to exhibit a wide range of reactivityselective substitutions have already been carried out-and should be ideal precursors for the preparation of dendrimers and ceramics.
K. Wraage, A. Kunzel,
M . Noltemeyer, H.-G. Schmidt,
H. W. Roesky* .......................
Synthesis and Structures of Triamino- and
Bridging by carbohydrate ligands instead of hydroxo
or 0x0 ligands causes the formation of small complexes instead of networks for the trivalent atoms in
the cornplcxes I ( M = Fe, V. Cr, Al, G a ; n z 13). At
slightly dkaline pH values all five acidic protons of
the furanose form of D-mannose are split off; this
pentaanion can then act as a pentadentate ligand.
The crystal structure of the anion in complex 1.
M = Fe. is displayed on the right.
J. Burger, C. Gack,
P. Klufers * ...........................
2647 - 2649
Fivefold Deprotonated u-Mannose as Ligand in Homoleptic Dinuclear Metalates of
Trivalent Iron, Vanadium. Chromium, A h minum, and Gallium
New uses for dad! Ideal examples of the flexible coordination of 1.4-diaza-1,3-butadiene (dad) ligands
are the novel niobium and tantalum (dad) complexes 1 and 2. As a result of the unusual p-g2,$ bridging function of two dad ligands in la,b, the lithium
ions are located within the ligand sphere of the complexes. Irrefutable evidence of the different coordination modes is provided by 2: three types are represented in this one dinuclear niobium complex.
B. Richter, J. Scholz, J. Sieler,
K.-H. Thiele* ........................ 2649-2651
dad Compounds of Niobium and Tantalum: Examples of the Structural Flexibility
of dad Ligands
la. M = N b : l h , M
Epoxidations of olefins and oxidations of alcohols can
be carried out in the presence of peroxides at relatively low temperatures with Cu2 histidine complexes that have been immobilized in zeolite cavities
(structure from molecular modeling shown on the
right). Combined diffuse reflectance and ESR spectroscopic studies reveal the presence of three nitrogen atoms in the first coordination sphere of C u z + .
B. M. Weckhuysen,* A. A. Verberckmoes,
I. P. Vannijvel, J. A. Pelgrims,
P. L. Buskens, P. A. Jacobs.
R. A. Schoonheydt ................ 2652--2654
More often than previously thought,
the solid-state structures of carboxylic acids display hydrogen
bonding motifs that differ from
those of the classic carboxylic acid
dimers. In studies aimed at engineering crystals with predictable structures. a specially designed tetracarboxylic acid was found to crystallize
with T H F to form a solid-state hostguest complex (clathrate); the host
lattice is shown on the right
S. V. Kolotuchin, E. E. Fenlon.
S. R. Wilson, C. J. Loweth,
S. C. Zimmerman* ................ 2654-2657
Topology is topical in supramolecular chemistry! Two new macrocyclophanes have
been prepared with novel architectures and relative molecular masses in the kilodalton range. One of them, the compound below, displays the K 3 , nonplanar molecular graph.
Zeolite Encaged Cu(Histidine) Complexes
as Mimics of Natural Cu Enzymes
Self-Assembly o f 1,3.5-Benzenetricarboxylic Acids (Trimesic Acids) and Several
Analogues in the Solid State
C.-T. Chen, P. Gantzel, J. S. Siegel,*
K. K. Baldridge,* R. B. English.
D. M. Ho ...............................
Synthesis and Structure of the Nanodimensional Multicyclophane "Kuratowski Cyclophane", an Achiral Molecule with Nonplanar K3, Topology
0 ’a
Bicyclic compounds can exist as in-out isomers,
which can interconvert when one chain passes ............
through the ring that it bridges, as shown schematiout-in isomer
cally on the right. A novel peptide macrobicycle ex- in-out isomer
hibits this property and two separate in-our isomers, which can be distinguished by
their NMR spectra because of stereocenters in one of the three chains, have been
separated and found to interconvert in solution over several days.
R. S. Wareham, J. D. Kilburn,*
D. L. Turner, N. H. Rees,
D. S. Holmes .........................
A potential single-source precursor for semiconducting cadmium phosphide phases, the title complex is prepared by nucleophilic substitution of
[Cd{N(SiMe,),},J with Ph,PLi. The adamantanoid
core of the dianion (shown on the right) contains
four Cd centers and six bridging phosphido ligands;
four terminal phosphides complete the coordination
spheres of the Cd atoms. (For clarity the substituents on phosphorus have been omitted.)
M. A. Beswick, P. R. Raithby,
C. A. Russell, A. Steiner,
K. L. Verhorevoort, G. N. Ward,
D. S. Wright* ........................
Homeomorphic Isomerism in a Peptidic
Synthesis and Structure of [Li(thf),],(Ph,P),,Cd,] Containing a Dianionic with
a Cd,P,, Adamantanoid Core
To correlate the electron transfer, electronic structure, and molecular structure of compounds with
their optical and electrochemical properties was
the motivation behind the synthesis and study of
donor/acceptor-substituted stilbenoids such as 1.
This particular compound displays electrochemically induced luminescence when the radical cation and
radical anion are formed sequentially.
A. Knorr, J. Daub* ............... 2664-2666
- e - \ Donor
Luminescence Stimulated by Electron
Transfer: Fluorescent Donor/AcceptorSubstituted Stilbenes Containing Pyrenoid
and Heteroaromatic Subunits
An efficient inhibitor of cell proliferation, the novel phospholipid 1 is not cytotoxic
and in contrast to other PC derivatives does not act by inhibition of the enzyme
protein kinase C. The title compound was synthesized in eight steps starting from
(R)-isopropylideneglyceraldehydein 22 % overall yield.
Glc-PC, a New Type of Glucosidic Phospholipid
M. Mickeleit, T. Wieder, K. Buchner,
C. Geilen, J. Mulzer,*
W. Reutter* ...........................
Reductive cleavage of the Se-Si bond in PhSeSiR, (R, = Ph,tBu) leads to the generation of the corresponding silyl radical and the anion PhSe- . These can be employed
in situ for a large number of cyclizations, as shown schematically below. X = CI, Br.
G. Pandey,*
K. S. S. P. Rao .......................
A New Dimension in Radical Chain
Group Transfer Reaction by Photosensitized
Electron Transfer (PET) Reductive Activation of PhSeSiR,
The reactivity of intradiol-cleaving catechol dioxygenases can be modeled with the
complex cation 1. The complex reacts nearly quantitatively with molecular oxygen
yielding 3,5-di-tert-butylmuconic anhydride (3) and 3,5-di-teri-butyI-S-carboxymethyl-2-furanone in a 1 :1 ratio. The catalytic oxygenation reaction of 2 [Eq. (a)]
gives 3 in 70% yield and with a turnover number of 54. dbcH, = 3,5-di-tert-butylcatechol; L-N,Me, = N,N’-dimethyl-2,1 I-diaza[3.3](2,6)pyridinophane.
W. 0. Koch, H.-J. Kriiger* .... 2671-2674
A Highly Reactive and Catalytically Active
Model System for Intradiol-Cleaving Catechol Dioxygenases: Structure and Reactivity of Iron(i1r) Catecholate Complexes of
N,N’-Dimethyl-2,11 -diaza[3,3](2,6)pyridinophane
VCH ~ , r l u ~ . ~ ~ P . r r l l s cmhH,
k n f i 0-69451 Weinhrrm, /YY5
(~570-0833rY5i3423-2576$ 10.00+ .25/0
Angew. Chem. Int. Ed. EngI. 1995, 34. N o . 23/24
J. Sadowski, M. Wagener.
J. Gasteiger* _..__.._......_........_
Kohonen neural networks have been used to show
that the cotnbinatorial libraries derived from 1 and
2 are very similar, whereas those obtained with 3 are
distinctly different. The depicted Kohonen map indicates that the libraries from 1 and 2 are so similar
that they need not both be synthesized for screening.
R ’ - R 4 : one of 18 possible amino acid residues.
R3& R4
Assessing Similarity and Diversity of Combinatorial Libraries by Spatial Autocorrelation Functions and Neural Networks
Two pyramidalized p,-phosphinidene units are
present in the cation 1 shown on the right. The complex I-BF,. formed by heating a solution of a
diphosphapalladacyclobutene in dichloromethane
to reflux in the presence of a diphosphirenium salt,
was characterized by an X-ray structure analysis.
R = iPr, R‘ = c-C,H,
A. Baceiredo, H. Gornitzka,
l+ Y.D.Canac.
Stalke, G . Bertrand* ........ 2677-2679
p h 3
The different environments for the two potassium ions in 1 justify its formulation as
a potassium salt o f a potassate. In an attempt to synthesize the analogous compound
containing [C(SiMe,),{SiMe,(HC=CH,))]- as anion, crystals of 2 were obtained
after four weeks, by the adventitious reaction with silicone grease.
[K(C,H,)][K (C(SiMe,),(SiMe,Ph)i,1
Synthesis of a Cationic 1,3-Diphospha-2.4dipallada(n)tricyclo[1.1.llpentane Derivative: The First Structurally Characterized
Pyramidal p,-Phosphinidene
C. Eaborn, P. B. Hitchcock, K. Izod,
J. D. Smith* ...........................
Two Diorganopotassates: Crystal Structure
of [K(C6H6)][K{C(SiMe,),(SiMe2Ph)J 21
Fixed in the SiO, cage at temperatures below 485 K,
the [CoCp,]’ ion in the cobaltocenium fluoride
nonasil 1 exhibits no rotational disorder. This unusual structural feature for clathrasils is attributed
to strong C-- H . . . 0 - S i interactions, among them
hydrogen bonds with a H . ‘ 0distance of 2.31 A.
P. Behrens,* G. van de Goor,
C. C. Freyhardt ....._......_......_.
Structure-Determining C-H . ’ . 0-Si Hydrogen Bonds in Cobaltocenium Fluoride
[COCP,l+ F - [SIOZII2 1
Complex molecules can be made in short order, as shown in a concise synthesis of the
antitumor agent (20s)-camptothecin (1 with R‘ = R2 = H), which relies on a cascade radical reaction [Eq. (a)]. This approach also provides a straightforward route
to substituted analogs (R’ = H, Et; RZ = OMe, OH), which are immediate precursors of compounds that have better properties for pharmaceutical applications and
are currently in clinical trials
, .,
~3 VCH
Cascade Radical Reactions of Isonitriles: A
Second-Generation Synthesis of (20s)Camptothecin, Topotecan, Irinotecan, and
OH 0
The first report of the formal potentials of a series of solid metal hexacyanometalates
(M+),M’[M”(CN),] is given (M’= Li’, K’, Na’, Rb’, Cs’; M’ = Ag, Al, Cd,
Co, Cr, Cu, Fe, Ga, In, Mn, Ni, Pb; M” = Cr, Fe, Mn). A linear correlation exists
between the ionic potential @ = z/rerfof the nitrogen-bonded M‘ ions and the formal
potentials of the hexacyanometalate ions. This results from increased x back bonding when the acid-base interaction between the nitrogen atom of the cyanide ions
and the M’ ions is stronger.
An,q(”!, Clieiir. lirr Ed C I g l 1995. 34, N o . 23/24
D. P. Curran,* S.-B. KO,
H. Josien ................................
Vrrlugsgrsrllschufi mhH, 0-69451 Wririhron. 1995
F. Scholz,* A . Dostal ....._.._....
The Formal Potentials of Solid Metal
0570-0833:95:3423-2577 X 10.00+ 25.11
Small but powerful! Nitromethane serves as a nucleophile in palladium-catalyzed
allylic substitutions with allylic carbonates 1 giving nitro compounds 2 with high
enantioselectivities. A new mechanism is in action in addition to the known one
when R = alkyl; mechanistic details are not yet known.
Complexes of the type [PtCl,(PEt,)(azacrown)I can
be obtained by the substitution of the ammine
ligand in trans-[PtCl,(PEt,)(NH,)] for azacrown
ethers. These transition metal containing host molecules form adducts with the cations NH; and
rBuNH: and the neutral complex truns-[PtCl,(PEt,)(NH,)]. As an X-ray structural study shows,
the latter complex is bound to the host by hydrogen
bonds (schematic representation shown on the right,
R = PtCI,(PEt,)).
[RKI(PPhdd Meq'/QMe3
Palladium Complex Catalyzed Asymmetric
Allylic Substitutions with Nitromethane:
Enantioselectivities Exceeding 99.9 % ee
B. R. Cameron, S. S. Corrent,
S. J. Loeb* .............................
Transition Metal Complexes as Both Host
and Guest: Second-Sphere Coordination
between a Pt-Azacrown Ether Host and a
Pt-NH, Guest
Both q2- and q4-coordinated (vinylallene)rhodium(I)complexes can be obtained by
ligand exchange with vinylallenes, depending on the substitution at the allene terminus. Vinylallenes like 1 react with CO via q4 complexes in a new Rh'-catalyzed
[4 + l]cycloaddition to give cyclopentenones 2.
H. Rieck, G. Helmchen * ....... 2687-2689
M. Murakami,* K. Itami,
Y. Ito* .
A Study on Rhodium-Vinylallene Complexes Leading to a New Reaction,
Rhodium-Catalyzed Carbonylative [4 13Cycloaddition
2691 - 2694
At least four types of silanol groups are present in
MCM-41, a novel silicate with uniform mesopores, according to IR spectroscopy. Isolated
silanol groups (type 1 in the picture on the right)
............ 2694-2696
Distinguishing the Silanol Groups in the
Mesoporous Molecular Sieve MCM-41
trimethylsilane (CTMS) and chlorotriphenylsilane (CTPS). Isolated silanol groups are
accessible for both CTMS and the bulkier CTPS.
thus where it always is for fluorine
chemists-sits one of the fluorine
atoms of the PF, unit in the twelvemembered heterocycle P6N6FT3
(structure shown on the right). However, in the eight-membered ring in
the P4N4F; ion, the corresponding
fluorine atom interacts with the three
other phosphorus centers and forms
the apex of a highly distorted square
A significant extension of the field of two-phase catalysis is achieved through the use of ionic liquids such
as 1. In this way substrates, complexes, and ligands
that are poorly soluble or unstable in water can be
employed for this industrially important variant of
homogeneous catalysis.
Fluorophosphazenate Ions: A Route to
Complexation of Fluoride Ions
[ Me,NTN,nBj
A-= BF4; PF;, SbFg
................ 2698-2700
A Novel Class of Versatile Solvents for
Two-Phase Catalysis : Hydrogenation, Isomerization, and Hydroformylation of Alkenes Catalyzed by Rhodium Complexes in
Liquid 1,3-Dialkylimidazolium Salts
VCH,echujtmhH, 0-69451 Wrinherm. I995
0570-0X33i95,3423-2578 5 10.00 + 25:O
A n g n i . Chenl. In!. Ed. EngI. 1995, 34, N o . 231'24
The tripodal hexathiol ligand H,-1 is accessible for the first time by coupling 3,3dimercaptobenzoic acid (2) to 1,3,5-tris(aminomethyl)benzene.The hexadentate
ligand H,-1 forms ;i trinuclear complex with [(C5H,),TiCI,] and the complex
[Mo(I)] with [Mo(O),(acac),].
F. E. Hahn,* W. W. Seidel
_. . ..
2700 ~ ~ 2 7 0 3
Synthesis and Coordination Chemistry of
orzlio-Functionalized Dimercaptobenzene:
Building Blocks for Tripodal Hexathiol
Hg- 1
T. Degen, B. Harbrecht* __.....2703-2705
Channels more than 0.6 nm wide run through the tantalum partial structure of Ta,(S,Te), (section of
structure shown on the right). The microporous
structure results from the penetration and linkage of
Ta,, icosahedra and icosahedral hypho-Ta,, and
uruc,hno-Ta, fragments. The chalcogen atoms cover
the walls of the pores.
Ta,(S,Te),: Microporous Tantalum with
Chalcogen-Coated Inner Surfaces
Alkynes are effective promoters of light-induced electron, hole, and energy transfer
between metal centers in a rnultinuclear complex. Studies on Zn”, Fe”. and Co”
complexes of type 1 led to this and other conclusions.
V. Grosshenny, A. Hariman.*
R. Ziessel* ..............................
Towards the Development of Molecular
Wires: Electron Localization, Exchange,
and Transfer in Alkyne-Bridged Multinuclear Complexes
1, n = 1, 2
In only four steps starting from commercially available alkynols, acceptor-substituted butatrienes 1 are
accessible in good yields. The key feature of this
synthesis is the “cumulation” of the allene function.
R’ = H, Me,Et;
R. W. Sadfrank,* A. Welch,
M. Haubner .................... ...... 2709-2710
Butatrienes by
R2 = Et, Me
Biological activity and surprisingly good solubility in water are the properties of the
fluorescein-labeled taxol 1 that make visible the attack of the antitumor agent taxol
on the microtubule system in cell cultures.
A. A. Souto, A. U . Acufia,
J. M. Andreu, I. Barasoain. M. Abal,
F. Amat-Guerri* ..........._....... 2710-2712
New Fluorescent
Block by block the carbohydrate amino acids can be peptidically coupled to form
oligosaccharide mimetics, thus providing a simple approach to a novel class of
compounds that has great significance for physiological processes. The feasibility of
the approach is demonstrated by the block synthesis of tetramer 1 .
H . P. Wessel,* C. M. Mitchell.
C. M. Lobato, G. Schmid ...... 271 2-272 3
Saccharide- Peptide Hybrids as Novel
Oligosaccharide Mimetics
A rigid molecular framework with hydrophilic and
hydrophobic substituents is found in the macrocyclic amphiphile 1, which can be prepared in
gram quantities. An X-ray structure determination of crystals of 1 obtained from pyridine
shows that the polar phenoxy groups point toward the outside and that the macrocycle has a
hydrophobic interior.
S. Hoger,* V. Enkelmann ...... 2713-2716
Synthesis and X-ray Structure of a ShapePersistent Macrocyclic Amphiphile
Parallel layers of Fe and 0 atoms are found in the
core of the decairon(n1) complex 1 (dbm = dibenzoylmethane) (structure shown on the right), which
is prepared by controlled hydrolysis of FeCI, . The 0
atoms in 1 display the same cubic closest packing
arrangement as that found in some iron oxides and
hydroxides. The layered arrangement of iron ions
may suggest a possible mechanism for the growth of
bulk oxides from smaller aggregates
A. Caneschi, A. Cornia, A. C. Fabretti,
D. Gatteschi* ........................
Structure and Magnetic Properties of a Decanuclear Oxoiron(1ir) Cluster: A Further
Step to Understanding Iron Aggregation
Mixtures of a cationic surfactant containing an activated amide function and the
anionic surfactant hexadecanoate ion in aqueous buffer at pH 8 and 25.0“C produce
anion -cation aggregates rather than the “fast amide cleavage under mild conditions” reported by Menger et al. last year in Angewandte Chemie.
W. K. Fife,* S. Liu ................. 2718-2720
“Fast Amide Cleavage” or Reproducible,
Concentration- and Time-Dependent Aggregation of Anionic and Cationic Surfactants?
Six at one blow! The creation of small oligosaccharide libraries was achieved by a
new strategy of random glycosylation of nonprotected sugars. With tri-0-benzyl-Lfucopyranosyl trichloroacetimidate as donor and PGal(1 + n)PGlcNAc-OR
(n = 3, 4, 6; R = (CH,),OC,H,-p-OMe) as acceptors, all six trisaccharides form in
D M F in roughly equal quantities. It is astounding that all free OH groups are
fucosylated at a similar rate.
0. Kanie, F. Barresi, Y. Ding, J. Labbe,
A. Otter, L. S. Forsberg, B. Ernst,
0. Hindsgad* .......................
Polyfunctional dialkylzinc compounds and primary alkyl iodides bearing a remote
double bond undergo nickel-catalyzed cross-coupling even at - 35 “C within a few
hours, as shown in the example below. The resulting polyfunctional products are
formed in good yield. NMP = N-methyl-2-pyrrolidinone, acac = acetylacetonate.
Piv = pivaloyl.
A. Devasagayaraj, T. Stiidemann,
2723 -2725
P. Knochel * ...........................
[Ni(acac)~](7 rnol % )
-35’C,15 h
A Strategy of “Random Glycosylation” for
the Production of Oligosaccharide Libraries
A New Nickel-Catalyzed Cross-Coupling
Reaction between sp3 Carbon Centers
T VCH Vrrlag~gerellrchaffmhH. 0-69451 Wemheim 1995
73 %
O570-0833/95/3423-2580 $ 10 OO+ 2510
Angen Chem Int Ed Engl 1995, 34, No 23/24
The redox behavior is markedly different t'br thc \econd generation dendrinicr 1 (clcpicted on the right) from
that ofthe first generation dendrimer
w i t h o u t the densely packed dendritic
structure. The unusually positive
Fc"':Fe" redox potential of 1 in water ( + O . 19 V L'S. SCE) is attributable
to the strong shielding of the heme
core from the surrounding solvent by
the dendritic cnvironrnent.
P. J. Dandliker. F. Diederich.*
J.-P. Gisselbrecht. A . Louiiti.
M. Gross* ...____...............
...... 2725-2728
Water-Soluble Dendritic 1 ron Porphyrins:
Models of Globular Heme
M. T. Reetz,* S. A. Quaiser.
R. Breinbauer, B. Tesche ._._.__
Without appreciable migration into the pores of the
support (A1203),preformed and size-selectively synthesized metal clusters (e.g. Pd or Ni) and bimetal
clusters (e.3. Pt/Sn) stabilized by ammonium salts
can be placed specifically on the outer surface and
immobilized (see schematic representation on the
right: black: metal cluster, gray: support particles).
Initial experiments indicate that such cortex catalysts show increased activities in hydrogenation reactions.
A New Strategy in Heterogeneous Catalysis: The Design of Cortex Catalysts
Under kinetic control, the dimerization of the title allene proceeds with participation
of on(' phenyl group. Only on thermolysis of the dimer 1 is the thermodynamically
favored dimer 2 formed, which, unlike the dimers of known cycloallenes with eightmembered or smaller rings. has a cis configuration.
M. Christl,* M. Rudolph.
E.-M. Peters, K. Peters.
H. G. von Schnering .............. 2730-2732
1-Phenyl-I ,2-cyclooctadiene Dimerizes in
an Unusual Manner
Ph Ph
* Author to whom correspondence should be addressed
Events 2582
New Books 2733
Keyword Index 2734
Cumulative Indexes: Reviews and Highlights 2741
Author Index 2735
Preview 2736
Authors 2745
Subjects 2757
Chemistry-A European Journal may be found after page 2798 with its
own table of contents and separate pagination.
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