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Graphical Abstract (Angew. Chem. Int. Ed. Engl. 31995)

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A Journal of the
Gesellschaft
Deutscher
Chemiker
International Edition in English
1995
3-413
Pages 249-368
COVER PICTURE
The cover picture shows an intramolecular electron-transfer reaction through duplex
DNA. The DNA has been covalently and site-specifically labeled with two different
redox-active ruthenium complexes to produce a donor-DNA-acceptor system.
After laser excitation, the kinetics of intramolecular electron transfer from Ru" to
Ru"' center through DNA was measured by transient-absorption techniques. This
system is designed to delineate the roles of base sequence and stacking in modulating the rates of long-range electron-transfer reactions. More about this elegant
method for providing well-defined model systems to probe the important and topical
issue of electron-transfer through DNA is reported by T. 5. Meade and J. F. Kayyem
on p. 352ff.
REVIEWS
Contents
If all atoms of the starting materials are found in the product and only catalytic
amounts of other reagents are needed, a reaction may be defined as ideal. A promising route to this ideal state is approached by the use of transition metal complexes
as catalysts for addition and isomerization reactions. In this way, for instance, seven
rings have been formed very efficiently from an acyclic precursor in a single step
according to Equation (a).
B. M. Trost* ..............................
259-281
Atom Economy-A Challenge for Organic
Synthesis: Homogeneous Catalysis Leads
the Way
77%
The analysis of the relation between configuration and action of steroids at the receptor
level has led to the discovery that--contrary to the ruling dogma-C/D-trans
steroids 1 of hormone type can improve cardiac contractility like the therapeutically
applied C/D-cis steroids 2 of digitalis type, and that the former may thus be used as
lead structures for the design of novel cardioactive drugs.
-
K. R. H. Repke,* R. Megges,
J. Weiland, R. Schon ................._282-294
Digitalis Research in Berlin- Buch-Retrospective and Perspective Views
2
~
~
~~
~~~~~~~~~
An@+<. Cheni. l n ~Ed.
. Engl. 1995, 34, No. 3
ci",VCH
Vertugs~e.reNs~'huJi
mhH, 0-69451 U'cinheim, 1995
0570-0833~95/0303-025/$10.00+ 2510
251
HIGHLIGHTS
Contents
Criteria for aromaticity-a topic with staying power! Planarity of the rings, bonds of
equal length, stabilization energies, and the number of TC electrons were considered
among the characteristics of the important phenomenon of aromaticity, but no one
of these features is generally valid. Schleyer et al. (p. 334 in this issue) have now
correlated the criteria with ab initio/IGLO calculations on five-membered heterocycles. In addition this highlight collates the synthesis methods and the chemical
properties of these interesting compounds.
By which route is monensin A biosynthesized? Is an (E,E,E) triene first epoxidized and
the polyepoxide then transformed into the natural product in a cascade of ring
openings and ring closures? O r does a (Z,Z,Z) triene undergo successive oxidative
cyclizations to give monensin A directly? New results from McDonald and Towne,
who carried out oxidations of ( 2 )dienes with pyridinium chlorochromate, support
the second route.
H. Grutzmacher* ......................
295-298
Five-Membered Aromatic and Antiaromatic Rings with Gallium, Germanium,
and Bismuth Centers: A Short March
through the Periodic Table
U. Koert* ..................................
298 -300
Oxidative Polycyclization versus the
“Polyepoxide Cascade”: New Pathways in
Polyether (Bio)synthesis?
rnonensin A
HO
COMMUNICATIONS
Alkyltrimethoxysilanes yield much
better host matrices for lipases than
tetramethoxysilane (see picture).
This is revealed by the esterifications
discussed herein catalyzed by lipases
that are immobilized in RSi(OMe),
gels. These heterogeneous biocatalysts are readily reusable and should
also be suitable for continuous processes.
/
Sixteen thiophene units make up the longest oligothiophene to date, the 64A-long oligomer 4. Like its
shorter homologues 1-3, 4 forms molecular structures on surfaces, which can be examined by scanning tunneling microscopy with submolecular resolution. Oligomers 1-4 can be considered components of “molecular wires” and serve as model
compounds for the study of charge transport in electrically conducting polymers.
A twelve-membered ring made up of Fez+ ions is
present in the cluster framework of 1 (shown on the
right without phenyl groups; Fe atoms are white, Se
atoms shaded). The Fez+ ions are located in the
centers of edge-sharing Se, tetrahedra, which in turn
form a ring. The shiny black needles of 1 are prepared from FeCI,, PPh,, and PhSeSiMe,, and decompose readily upon heating.
[Fe,,(SePh),,l
252
w,
I,
CH,,O.~,’~\S!-O,
SI
d
\
/‘o
CH,
I
b
,w, o,s:-o/si
cy
-CH,
o\2‘ w,!
wc“.
H o ~ - o , \ \ o ~ ~ SI
i o\
CH, m,
T o
\p
H
Cl2H25
1-4 ( n = 1 - 4)
”
M . T. Reetz,* A. Zonta,
J. Simpelkamp ..........................
301 -303
Efficient Heterogeneous Biocatalysts by
Entrapment of Lipases in Hydrophobic
Sol-Gel Materials
P. B5uerle,* T. Fischer, B. Bidlingmeier,
A. Stabel, J. P. Rabe* ................ 303-307
Oligothiophenes-Yet
Longer? Synthesis,
Characterization, and STM Images of
Homologous, Isomerically Pure
Oligo(alkylthiophene)s
D. Fenske,* A. Fischer .............. 307-309
New Selenolato-Bridged Clusters of Iron
and Nickel; the Structures of
[Fe, ,(SePh),,l and [Na,(POPh,),l“i*,Se,,(S~Me),,1
1
VCH ~,rlu~.sg~.rell.P~liirfi
mhH, 0-69451 Weinheim, 1995
0570-(i833jUSj03U3-0252 $ 10.00+ ,2510
Angrw. Chem. Inl. Ed. Engl. 1995, 34, N o . 3
Contents
A new structural type for polyrotaxanes (shown schematically on the right) results from the condensation
of an amino-substituted cyclodextrin semirotaxane
with the free acid groups of a dicarboxylic acid
group in the side chain of a polymethacrylate. The
structure of the novel polyrotaxane was determined unequivocally by NMR spectroscopic studies and by comparisons with a cyclodextrin-free model compound.
OH
Diacylated flavonol glycosides are the
response of Scots pine seedlings to
UV-B irradiation. The two induced
compounds 1 and 2 both have their
absorption maximum at 315 nm Ho
(6 = 50300) in the range of UV-B
6
radiation (290-320 nm), are compartmented in the epidermis, and offer much better protection than the
monoacylated analogues at the same
molarity.
M. Born, H. Ritter* ................. 309-311
Side-Chain Polyrotaxanes with a Tandem
Structure Based on Cyclodextrins and a
Polymethacrylate Main Chain
T. P. Jungblut, J.-P. Schnitzler,
W. Heller,* N. Hertkorn,
J. W. Metzger, W. Szymczak,
H. Sandermann, Jr. ................... 332-314
Structures of UV-B Induced Sunscreen Pigments of Scots Pine (Pinus sylvestris L.)
2:R=H
0
I. Dance,* P. Dean,
K. Fisher ...................................
Laser ablation of Zn(CN), and Cd(CN), gives rise to
a series of anions [Mx(CN)2x+l]-,which have helical structures according to density functional and
force-field calculations. M atoms with trigonal-planar coordination and each bearing a terminal CN
ligand are linked by linear M-CN-M bridges to form
helices. The supramolecular helices are stabilized by
interstrand coulombic interactions. The calculated
structure of [Zn,,(CN),,]- is shown on the right (0
314-316
Self-Assembled Helicates of Zinc and Cadmium Cyanides, [Mx(CN),.x+l]-,x 27
. @ = -
Clusters from lithium or sodium, phosphorus, and silicon form the frameworks of the
title compounds 1-4. Compound 2 consists of two clusters 1, which are “glued
together” by a (LiCI), ring. Compounds 3 and 4 form under the same conditions;
4 relieves the ring strain by opening the polyhedron. Two Na centers in 4 are each
q2-coordinated to one toluene (L) molecule. SiR, = SitBuIs, Is = 2,4,6-iPr3C,H,;
PR = PSiiPr,.
1
3
2
The paramagnetic hydroxo-bridged diplatinum complex 1 (X = C1) results from the reaction of the title
compound with 0, and triphenylphosphane. The
ferrocene unit in 1 not only fixes the two Pt atoms at
an appropriate distance but also functions as an
electron pool, as reactions with C 0 and pyridine
show.
Angim. Chem. lnr. Ed. Engl. 1995, 34, N o . 3
6
M. Dries,* G. Huttner, N . Knopf,
H. Pritzkow, L. Zsolnai ............. 316-318
Novel Alkali Metal Phosphanide Aggregates
4
PPh3
I
e P \ - x
Fe
,OH
T. Yoshida, S. Tanaka, T. Adachi,
T. Yoshida, K. Onitsuka,
K. Sonogashira* ........................
319-321
e 7 i - X
pph3
1
VCH Verlagsgesellschufr mbH, 0.69451 Weinheim,1995
Reactions of 1,l’-Ferrocenediylbis{chloro[ (1,2,5,6-q)-1,5-cyclooctadiene]}diplatinum
with Triarylphosphane and Molecular
Oxygen
057U-U833~95/0303-U253$
iO.OO+ .25/O
253
~
Contents
A cavity can be made to fit an aromatic guest molecule in certain polyazacyclophanes by contraction of
the inner volume, which is initiated by the binding of
metal cations. The anticipated cooperative effects
can be quantified by fluorescence spectroscopy with
suitable indicators, which opens new possibilities for
the detection of, for instance, zinc ions in aqueous solution. The ternary complex
formed from ligand, metal ion M, and guest G is depicted on the right.
Sterically demanding and carbanion-stabilizingsubstituents like SiMe, raise the barrier to the configurational inversion of a-thioalkyllithium compounds. With such
substituents these compounds can undergo, for example, electrophilic substitution
[Eq. (a)] without changes in configuration. Experiments with deuterated compounds
proved that alkyllithium intermediates from primary S-alkylthiocarbamates are
typically not configurationally stable.
The surprising thermal stability of the first monomeric, homoleptic diaryliron(I1)complex 1 arises because its Fe center is very well shielded by the sterically demanding ligands. The magnetic moment of
4.77 p, indicates a high-spin state of the highly soluble, air- and moisture-sensitive complex.
[Fe(2,4,6-1Bu,C,H,),]
I
Ei
I
R’
\;
B
**.
,.:H
325-327
1
la
B‘
\R
Me3Si
Me3Si--C- I
I
I“‘
B
cd;!=.:H
,b
\:
B .*
Et2B
Compounds with Planar Tetracoordinate
Boron Atoms: Anti van’t Hoff/Le Be1 Geometries without Metal Centers
\R’
T. S. Balaban, S. Schardt,
V. Sturm, K. Hafner* ................ 330-332
1,3,5,7-Tetra-terI-butykbaza- and 1,3,5,7Tetra-tert-butyl-4-phospha-s-indacene
1 (X=N)
2 (X=P)
A. K. Saxena, H. Zhang,
J. A. Maguire, N. S. Hosmane,”
A. H. Cowley* ...........................
332-334
A very short Ga-Ga bond, stabilized
by carborane moieties, is present in
the digallane I , which is air- and
moisture-sensitive, and soluble in
both polar and nonpolar organic solvents. The coordination of each Ga
atom to the respective C,B, carborane face is “slip distorted”. 0 = H,
o = SiMe,.
(CI VCH Verluzs,”r.;ells~hufimhH. 0-69451
M. Menzel, D. Steiner, H.-J. Winkler,
D. Schweikart, S. Mehle, S. Fau,
G. Frenking, W. Massa,
A. Berndt * .................................
327 -329
,
s-Indacenes reveal the limits of the Huckel rules:
These 12 n systems are formally antiaromatic, but
the results of more recent quantum mechanical calculations indicate n-electron delocalization. The
synthesis and spectroscopic investigation of the
non-electronically stabilized 4-hetero-s-indacenes 1
and 2 have now been achieved for the first time.
254
Preparation and Detection of Enantiomerically Enriched and Configurationally
Stable a-Thioalkyllithium Compounds
1
I”’
/,i
B. Kaiser, D. Hoppe* ................ 323-325
[Fe(2,4,6-tBu,C6H,),], a Monomeric Diaryl Complex with Two-Coordinate Iron(I1)
.
Me
Complexes from Polyazacyclophanes, Fluorescence Indicators, and Metal CationsAn Example of Allosterism through Ring
Contraction
H. Miiller, W. Seidel,*
H. Gorls ....................................
Electropositive elements are prerequisites for the formation of anti van’t Hoff/Le Be1
geometries, as evident in compounds 1, which contain planar tetracoordinate
boron atoms in the CB,H framework. These compounds extend the range of molecules of this structural type to include those without metal atoms. R = CH(SiMe,),
R’ = 2,3,5,6-Me,C6H.
Me
R. Baldes, H.-J. Schneider* ....... 321 -323
Surprising Formation of a Carborane-Substituted Digallane
1
Wriiiheim, 1995
0570-0R33/9510303-0254$ 10.00 t ,2510
Anzeu. Chem. Int. Ed. Engl. 1995, 34, N o . 3
Contents
b---T b--b
IGLO computations reveal the aromatic character of the
transition structures 1 a and 1 b for the Cope rearrangement
of 1 .S-hexadiene. In addition, high-level ah initio calculations favor a synchronous concerted mechanism via intermediates not having sigificant diradicaloid character.
Energetic, geometric, and magnetic criteria yield
quantitatively the same order of aromaticity (antiaromaticity) for the five-membered ring systems 1:
the aromatic 6 rt electron systems are stabilized, their
bond lengths are equalized, and the magnetic susceptibility exaltations are diamagnetic. In contrast,
the antiaromatic 47t electron systems are destabilized, double bonds are localized, and susceptibility
exaltations are paramagnetic.
--_
la
Ib
The Cope Rearrangement Transition
Structure Is Not Diradicaloid,
but Is It Aromatic?
P. von R. Schleyer,* P. K. Freeman,
H. Jiao, B. Goldfuss .................. 337-340
0
X
1, x = CH+(singlet), SiH+, BH,
CHZ,PH.SiH-, 0, S, NH, CH-
The potential of rigid macromolecules as building
blocks of supramolecular architectures is shown
here by the reactions in LB layers from cellulose
derivatives. With an appropriate sequence of layers,
a two-dimensional network is accessible by DielsAlder reaction between the side chains in the zones
of overlap shown schematically on the right.
Aromaticity and Antiaromaticity in FiveMembered C,H,X Ring Systems: "Classical" and "Magnetic" Concepts May Not Be
"Orthogonal"
M. Seufert, M. Schaub, G. Wenz,
G. Wegner* ...............................
340-343
Topochemical Aspects of the Formation of
Networks in Layered Langmuir -Blodgett
(LB) Assemblies
The Mn"'=O unit in the five-coordinate oxo(porphyrinato)manganese(rv) complex
2, which is formed by oxidation of the bromo(porphyrinato)manganese(m) complex
1 with potassium peroxycarbonate, was characterized by X-ray absorption spectroscopy. The relatively long Mn=O bond (1.69k0.03 A) is probably attributable
to the high-spin state and the low polarizability of the half-filled f:g subshell of
high-spin Mn"'.
1
H. Jiao, P. von R. Schleyer* ...... 334-337
...
K. Ayougou, E. Bill, J. M. Charnock,
C. D. Garner,* D. Mandon.
A. X. Trautwein,* R. Weiss,*
H. Winkler .................................
343-346
Characterization of an Oxo(porphyrinato)manganese(Iv) Complex by X-ray Absorption Spectroscopy
2
Twelve electrons more than the starting material, but
the same cluster framework-this modification was
achieved for the first time in the synthesis of the
Pt,Re clusters 1 (66e) from [Pt,{Re(CO),}(pdppm),]' (54e) and H,O, or propene sulfide. The
metal-oxygen units in 1 could serve as models for
the interactions between 0x0 ligands and metal clusters, which are important in oxide-supported Pt-Re
bimetallic catalysts.
L3
/& 1
p/-. 0
pp
,\.'
+
,..x..,
p o--:.p
i
p k p
L. Hao, J. Xiao, J. J. Vittal,
R. J. Puddephatt* ......................
346-348
Models for Bimetallic Catalysts: Multiple
Oxidation States in Pt,Re Cluster Cations
LPAJ
1: L = C O , X = 0: L = 0,x = 0.
L = co, x = s
The reversible photoisomerizationof the helical thioxanthenes 1 and 2 leads to photostationary states with large diastereomeric excesses. These compounds are promising
starting materials for optical data storage devices.
W. F. Jager, J. C. de Jong,
B. de Lange, N. P. M. Huck,
B. L. Feringa* ...........................
348-350
A Highly Stereoselective Optical Switching
Process Based on Donor-Acceptor Substituted Dissymmetric Alkenes
1(cis-nitro)
(90%1, 1 0% 2)
Angrir. C'kem. h i . Ed. Enh.1. 1995, 34. N o . 3
2 (trans-nitro)
(7Oo/o 2, 30%1)
C VCH
Vertugsgeseltschuft mhH. D-6945t Weinheim,1995
0570-0833i95/0303-02553 10.00f A ; f I
255
Contents
Anti-AIDS deoxynucleosides like stavudine (d4T, 3) are now accessible in a short
(five steps!) asymmetric synthesis. The "missing link" between the acyclic precursors
and the product is a Mo(CO),-catalyzed cycloisomerization. It yields the ether 2, the
saccharide building block for many nucleosides, from 1 in 80% yield. R = tBuCO.
''9
"MO(CO)~"
L
l
F. E. McDonald,*
M. M. Gleason ..........................
350-352
Asymmetric Syntheses of Stavudine (d4T)
and Cordycepin by Cycloisomerization of
Alkynyl Alcohols to Endocyclic Enol
Ethers
3
2
The rate of the electron transfer between two ruthenium centers at the ends of an
octanucleotide duplex (metal-to-metal distance = 21 .$) was determined to be
1.6(4) x lo6 s-'. By using automated DNA synthesis techniques, modified oligonucleotides were prepared with a protected phosphoroamidite of 2'-amino-2'-deoxyuridine. The NH,-modified oligonucleotides were hybridized with complementary DNA sequences to protect nucleotide bases, and then treated with ruthenium
complexes. In this way the ruthenium complex was bound only to the free NH,
group.
Important intermediates in catalytic hydrogenation, y2-dihydrogen complexes are
also appealing subjects for theoretical studies. The M -H, binding enthalpies for the
complexes [M(CO),(H,)] (M = Cr, Mo, W) were calculated at the CCSD(T)/MP2
level as 15.9 (M = Cr), 12.8 (M = Mo), and 16.3 kcalmol-' (M = W). Charge
decomposition analysis suggests that H , is a significant 0 donor and a moderate n
acceptor. The topological analysis of the electron density distribution indicates a
cyclic structure for the MH, moiety.
T. J. Meade,* J. F. Kayyem ........ 352-354
Electron Transfer through DNA: SiteSpecific Modification of Duplex DNA with
Ruthenium Donors and Acceptors
S. Dapprich, G. Frenking* ........ 354-357
Structure and Bonding of Transition Metal
Dihydrogen Complexes [M(CO),(H,)] (M
= Cr, Mo, W)
~
* Author
~~
~
to whom correspondence should be dddressed
BOOKS
Guardians of Science * Fairness and Reliability of Peer Review
Three-Dimensional Chemical Similarity Searching
The World of Physical Chemistry
Shikimic Acid
-
*
*
- H.-D. Daniel
C. Pepperrell
K. J. Laidler
E. Haslam
Shape in Chemistry. An Introduction to Molecular Shape and Topology
P. G. Mezey
M . Mahnig ........................................
359
D. H . Rouvray ...................................
359
H. Gerischer ( f ) ................................
360
J. Rohr ...............................................
361
D. H. Rouvray ...................................
362
New Books
363
~
Keyword Index 364
256
G YCH
Author Index 365
Y L i - l a ~ . ~ ~ ~ s e l l s mbH.
r h u f i D-69451 Wc,inhrim, 1995
0570-0833~95/0303-0256
$10.00+ ,2510
Preview 366
Angew,. Chem. Int.
Ed. Engl. 1995, 34, N o . 3
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