bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Pyridoxal Phosphate in the Catalysis of Glycogen Phosphorylases
Authors: Helmreich Ernst J. M. , Klein Helmut W.
Published: December 2003

Glycogen phosphorylases catalyze the degradation of glycogen by phosphate (or arsenate) to glucose 1‐phosphate (or glucose + arsenate). All glycogen phosphorylases that have been studied so far contain pyridoxal 5′‐phosphate, a vitamin B6‐derivative, as cofactor. Removal of the cofactor results in an inactive apoenzyme. However, reduction of the azomethine bond linking pyridoxal phosphate to an ϵ‐aminolysyl side chain of the enzyme with NaBH4 does not inactivate glycogen phosphorylase. If therefore the cofactor should be involved in catalysis in glycogen phosphorylase it must function differently from all other classical pyridoxal phosphate dependent enzymes, for these are inactivated by reduction. 31P‐NMR spectroscopy has revealed that the 5′‐phosphate group of pyridoxal phosphate is present in catalytically active forms of glycogen phosphorylases as dianion in a hydrophobic environment shielded from aqueous solvent. Covalent and/or allosteric activation of muscle glycogen phosphorylases is accompanied by a transition of the monoprotonated form to the dianionic form of the phosphate group of the cofactor. We now report on such ionization changes in unregulated active potato‐ and E. coli maltodextrin phosphorylases on binding of glucose and oligosaccharides and following catalytic turnover, i.e. arsenolysis of α‐1,4‐glycosidic bonds. (Like glycogen phosphorylases, maltodextrin phosphorylases belong to the class of α‐glucan phosphorylases.) The results of experiments carried out by our group together with recent findings on the three dimensional structure of crystalline muscle glycogen phosphorylases indicate a participation of the dianionic phosphate group as proton acceptor for the glucosyl transfer to and from the glucosyl acceptor. Although other interpretations are not excluded, at present little doubt remains that in the case of glycogen phosphorylases the dianionic phosphate group of the cofactor functions in catalysis.
Molecular and Crystal Structure of β‐SeBr
Authors: Katryniok Detlef , Kniep Rüdiger
Published: December 2003

A contribution to the structural chemistry of compounds of type A2B2 (A = S, Se; B = F, Cl, Br) is provided by the X‐ray structure analysis of β‐SeBr at −80°C. The BrSeSeBr molecules (SeSe = 2.241 Å; dihedral angle 93.58°) are arranged in the crystal in such a manner that some of the Se…Br contacts are significantly closer than the sum of the van der Waals radii.
Photophysical and Photochemical Processes in Micellar Systems
Authors: Turro Nicholas J. , Grätzel Michael , Braun André M.
Published: December 2003

A fascinating feature inherent to aqueous surfactant solutions is the phenomenon of self‐organization: above a certain critical concentration (the critical micelle concentration, CMC) detergent molecules associate spontaneously to build up structural entities of colloidal dimensions called micelles. The architecture of these agglomerates is such that the interior contains the hydrophobic alkyl chain of the amphiphile while the hydrophilic head groups are located at the surface and are in contact with bulk water. In the case of ionic micelles the interface is charged giving rise to an electrical double layer and a potential difference of up to several hundred millivolts between the micellar pseudophase and water. Thus micellar systems are microheterogeneous in character: the electrostatic potential and polarity prevailing in the interior of the aggregate differ from those of the bulk aqueous phase. A particularly attractive aspect of photochemical studies in micellar systems is the possibility of organizing the reactants at a molecular level: by comparison of the data in micelles with similar data in homogeneous solution one can learn about the molecular details of a given reaction and establish which conditions favor one pathway or another. In simple surfactant systems differences in rate and efficiency of a reaction will often be controlled by local electrostatic potentials and the compartmentalization of the reagents within the surfactant aggregates. Through the latter effect the statistics of probe distribution over the micelles becomes important in controlling fast photochemical events. Functional micelles are distinguished by the fact that the surfactant molecule contains a group which itself participates in the photoprocess. These units are unique in that self‐assembly often introduces striking cooperative effects.
Dehydroxylation of Hydrogen Zeolites: Conditions for the Preparation of Thermally Stable Catalysts
Authors: Marosi Laszlo
Published: December 2003

The elimination of water from hydrogen zeolites proceeds in two steps: (i) between ca. 320 and 550°C water is eliminated from hydroxy groups coordinated to adjacent framework aluminum atoms; (ii) between ca. 550 and 630°C water elimination proceeds via migration of framework aluminum atoms into the intracrystalline pore system. Suitable choice of conditions, especially in the last stage, provides a means of influencing the quality of the resulting zeolite catalysts. Too fast a heat‐up rate between 500 and 600°C causes the crystal lattice to collapse.
Mechanistic Aspects of Diels‐Alder Reactions: A Critical Survey
Authors: Sauer Jürgen , Sustmann Reiner
Published: December 2003

The question of concerted or consecutive bond formation arises in all types of cycloaddition reactions. Stereochemical investigations and studies of regiospecificity as well as intensive kinetic investigations with regard to substituent and solvent effects, and the dependence of the reaction on temperature and pressure permit in many cases mechanistic conclusions concerning the Diels‐Alder reaction. Efforts towards a theoretical interpretation, ab initio and semiempirical calculations, the application of frontier molecular orbital theory (FMO) as well as thermochemical measurements permit a description of the energy hypersurface of these [4+2]‐cycloadditions. An attempt is made here to draw a line of distinction between the mechanistic alternatives—one‐step reaction versus two‐step reaction—considering all experimental and theoretical criteria.
Chemistry in Compressed Solutions
Authors: le Noble William J. , Kelm Hartwig
Published: December 2003

Contrary to “common sense” impression, modest pressures often have quite large effects on reactions in solution.—The volume profile of a chemical reaction in solution is easily measurable with considerable precision by means of the effect of pressure on the rate and equilibrium constant. The factors that govern the magnitude of these pressure effects are similar to those that affect the entropy changes and there is a rough correlation between them; however, the volume parameters are much less subject to apparently random fluctuations, have much greater appeal to the solution chemist's intuition, and most important, the activation volume is the only transition state property that can readily be determined in absolute terms (rather than as a difference value). In this paper we outline the experimental approach to the measurement of volume changes in wet chemical reactions, interpret the volume quantities, discuss a number of simple model equilibria and reactions, point out a number of contributions in both mechanistic and synthetic chemistry, and make an attempt to foresee future developments.
Chemoselective and Position Specific Methylation of tert‐Alkyl Halides with Methyltitanium(IV) Chlorides
Authors: Reetz Manfred T. , Westermann Jürgen , Steinbach Rainer
Published: December 2003

Methylation with methyltitanium reagents promises to have a wide range of application, not least because of its chemoselectivity. In the tert‐alkyl chlorides studied, which additonally contained a primary‐or sec‐alkyl chloride unit or an olefinic double bond, only the tert‐C‐atom was methylated under favorable conditions.
Separation of the Enantiomers of 2‐Hydroxycarboxylic Acids on Optically Active Stationary Phases
Authors: König Wilfried A. , Sievers Susanne , Schulze Uwe
Published: December 2003

The gas chromatographic separation of enantiomeric 2‐hydroxycarboxylic acids has been achieved for the first time on novel stationary phases. The acids are separated as O‐trifluoroacetylated isopropyl estes. Examples for the phases are (S)‐mandelic acid (S)‐α‐phenylethlamide and O‐benzyloxycarbonyl‐(S)‐mandelic acid tert‐butylamide.
Synthesis of Alternating Depsipeptides with the 4‐Methylthiophenoxycarbonyl Group as Protecting and Activating Group for the Amino Function
Authors: Kunz Horsi , Lorenz Klaus
Published: December 2003

Depsipeptides with alternating amino and hydroxy acid units are obtainable with the aid of the new protecting group p‐MeSC6H4OCO (Mtpc) and its oxidation product p‐Me—SO2—C6H4OCO (Mspc). The Mtpc‐Leu‐Lac‐OtBu half of the educt is hydrolyzed; the other half oxidized. These products react to give the teradepsipeptide (1). The reaction sequence is repeatable.
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N‐(Amidosulfonyl)hydroxylamine, H2NSO2NHOH
Authors: Boldhaus Michael , Brink Klaus , Bliefert Claus
Published: December 2003

The first unsubstituted amide of a hydroxylaminosulfonic acid, the title compound, has now been synthesized via the route given below. Its alkaline hydrolysis yields, as expected, sulfite, ammonia, and HNO (→ 1/2 N2O + 1/2 H2O).
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Reversible Topotactic Redox Reactions of Solids by Electron/Ion Transfer
Authors: Schöllhorn Robert
Published: December 2003

Solids having suitable structural and electronic properties are able to form intercalation compounds by reversible redox reactions at room temperatureviatopotactic electron/ion transfer processes. The host lattices range from inorganic solids with different structural dimensionality to organic molecular solids. Similarly, depending on the host lattice type, the guest species may vary from protons and metal ions to large inorganic and organic molecular ions. The possibilities of a systematic “tailoring” of new stable or metastable compounds, the controlled modification of physical properties of solids, and the technical application of electronic/ionic conductors, provide a wide and attractive field for academic and applied research in an interdisciplinary area that involves solid state chemistry and physics, molecular chemistry, electrochemistry, and interface science.
Template Synthesis of Clusters using the Tripod Ligand HC(PPh2)3 Ni3(CO)6(tripod)
Authors: Osborn J. A. , Stanley George G.
Published: December 2003

The stepwise synthesis of the nickel cluster (3) from Ni(CO)4 and the “Tripod” ligand illustrates a possible application of this tris(phosphane). The first trinuclear nickel(0) complex is formed via (1) (with chelated Ni(CO)2 and a free PPh2 group) and (2) (with Ni(CO)3 attached to this group).
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Homoatomic Bonding of Main Group Elements
Authors: von Schnering Hans Georg
Published: December 2003

Clusters of main group elements are not rare. On the contrary, it is becoming difficult to avoid the discovery of new substances of this type. Clusters are the natural intermediate stages between an element and its isolated atoms or ions. In the form of polycations and polyanions they offer models for the stepwise oxidation and reduction of an element and represent a bridge between the elements. The great majority of homonuclear bonded structures are already present in the solid phases of simple systems. Mobilization of these clusters as molecules represents a great challenge.
Ternary Sulfides: Model Compounds for the Correlation of Crystal Structure and Magnetic Properties
Authors: Bronger Welf
Published: December 2003

Relationships between crystal structure and magnetic properties enable an insight into the nature of the binding of atoms or ions in the solid state. Suitable as model substances are transition metal compounds in which the collective bonds that are generally present are directively degraded by incorporation of diamagnetic cations. This requirement of progressive degradation is met with in sulfides of the general composition AxMySz, where A ≙ alkali metal and M ≙ transition metal.
Crystal Structure of P4O7
Authors: Jansen Martin , Voss Marlen
Published: December 2003

P4O7, a new phosphorus oxide, was obtained by reaction of P4O6 with alkali metal oxides A2O. P4O7 has an adamantane‐like structure with one terminal O atom. However, the idea that these molecules are constructed, in a building‐block manner, from P4O6 and P4O10 units, with retention of the PO bond lengths is not entirely reconcilable with the structural findings.
Negative Ion Field Desorption Mass Spectrometry (NFD‐MS) of Salts
Authors: Ott Karl H. , Röllgen Franz W. , Zwinselman Jan J. , Fokkens Roel H. , Nibbering Nico M. M.
Published: December 2003

The mass spectrometric analysis of salts can be carried out by dissolving the material of interest and polyethylene oxide 4000 (approx. 1:1) in water, applying the mixture to the emitter and introducing the latter into the field‐desorption source of a conventional mass spectrometer. After the application of 4 kV across the emitter, a negative‐ion mass spectrum can be recorded. The method has been applied to a considerable number of inorganic and organic salts.
Toxication of Foreign Substances by Conjugation Reactions
Authors: Reichert Dieter
Published: December 2003

Elucidation of the metabolic pathways of foreign compounds in mammalian organisms contributes substantially to the understanding of toxic effects and is therefore a basic component of every risk analysis. The abundance of chemical reactions which take part in metabolic transformations allows one to speculate that we, with our present state of knowledge, are just at the beginning of a development which will help explain the interplay between chemical structure, biochemical transformation and toxic effects. This applies in particular to the conjugation of foreign compounds with structures and molecules endogenous to the body. Until recently it was thought that these conjugation reactions lead to chemically and biologically inert products, which could be easily eliminated by the organism. Using new biological testing procedures and sensitive methods of analysis, this assumption has been refuted. The fact is, that highly toxic, mutagenic and carcinogenic products can result from the chemical interactions of foreign substances with endogenous substrates.
Advances in Organophosphorus Chemistry Based on Dichloro(methyl)phosphane
Authors: Weissermel Klaus , Kleiner Hanns‐Jerg , Finke Manfred , Felcht Utz‐Hellmuth
Published: December 2003

Besides phosphorus trichloride and phosphane, dichloro(methyl)phosphane is gaining importance as a starting material for the synthesis of organophosphorus compounds. It provides ready access to phosphonic, phosphinic and phosphonous acid derivatives, as well as their secondary products. The synthetic and application potential of organophosphorus compounds—based on industrially produced dichloro(methyl)phosphane—is illustrated by means of numerous examples.
Polymethinic Ring Compounds and the Polymethinic Carbonyl Group
Authors: Kulpe Siegfried
Published: December 2003

For corrigendum see DOI:10.1002/anie.198104121
Photochemical Hydroformylation
Authors: Mirbach Manfred J. , Topalsavoglu Nicholaos , Phu Tuyet Nhu , Mirbach Marlis F. , Saus Alfons
Published: December 2003

UV irradiation favors the hydroformylation of alkenes in the presence of some cobalt or rhodium catalysts. For example, propene can be hydroformylated to butyraldehyde with CO/H2 (1:1), 85 bar at 85 °C on Co(OAc)2/P(nBu)3‐catalysis in methanol; the selectivity is ⩾99%. Under these conditions the reaction proceeds thermally. A high stereoselectivity ( ≈ 90%) with respect to the linear chain products is also found photochemically in the case of 1‐octene.
Ca3AlAs3—An Intermetallic Analogue of the Chain Silicates
Authors: Cordier Gerhard , Schäfer Herbert
Published: December 2003

Chains of AlAs4 tetrahedra have been detected in the intermetallic compound Ca3AlAs3. Hence, it could be shown for the first time that such groups of chains also occur in Zintl phases—and not only in silicates and polyphosphates.
Stable Metal‐Phthalocyanines as Poison‐Resistant Catalysts in Homogeneous Catalysis: Reduction of Organic Compounds with NaBH4
Authors: Eckert Heiner , Kiesel Yvonne
Published: December 2003

The metal phthalocyanines MPc (M = VO, Mn, Fe, Co, Pd) related to vitamin B12 are stable reduction catalysts having advantageous properties and also potential industrial applications. These compounds are soluble (MPc⊖) during the reduction (with NaBH4) and insoluble (MPc) under non‐reducing conditions. They enable selective reductions and are not, or rarely, poisoned by SH⊖, CN⊖, or I⊖.
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Molecular Self‐Organization and the Origin of Life
Authors: Kuhn Hans , Waser Jürg
Published: December 2003

The sequence of many small physically and chemically plausible steps that lead to self‐organization of matter are considered. These are governed by periodic temperature changes and a multi‐faceted spatial environment, both of which occurred in suitable locations on the primordial planet. The specific model described reveals the logical framework of this process, the nature and locations of fundamental difficulties as well as the means by which they might be overcome. The barriers that must be surmounted are mostly related to an accumulation of copying errors. An early stagnation barrier was hurdled by aggregate formation, by means of which erroneous copies are rejected; a further barrier was overcome by the evolution of machinery capable of synthesizing “cellular” envelopes which confine the building components. A system evolved which produced a primitive “replicase” that stabilized a rudimentary genetic code. A later stagnation phase ended when the functional system was reorganized by the evolution of separate machinery for replication and for translation of genetic information. — The purpose of this account is to stimulate experiments and theoretical efforts towards the improvement, refinement, and expansion of the model described. It also demonstrates the fruitfulness of the present style of approach that leads to assertions about the prerequisites, logical framework, and organizational structure of evolutionary processes.
Intermolecular Forces—An Example of Fruitful Cooperation of Theory and Experiment
Authors: Schuster Peter
Published: December 2003

New experimental techniques and extensive ab initio calculations have rendered it possible to gain a detailed knowledge of aggregates of atoms, small ions and/or small molecules in the vapor phase which are held together by intermolecular forces. Theory and experiment are often complementary regarding reliable predictions. The results obtained for complexes of three or more constituents are still fragmentary; nevertheless, they can be used to explain some properties of the condensed phase.
Redox Reltionship between Carbeneiron and σ‐Alkyliron Porphyrins
Authors: Lexa Doris , Savéant Jean‐Michel , Battioni Jean‐Paul , Lange Marc , Mansuy Daniel
Published: December 2003

σ‐Alkyliron porphyrins, both with FeII as well as with FeIII can be generated from carbeneiron (II) porphyrins by cyclovoltammetric reduction. (TPP) Fe(HCCPh2)—a σ‐vinyl‐FeII complex–was also independently synthesized from (TPP)Fe(ClO4) and BrMgCHCPh2; its properties resemble those of the product of the (2e + H⊕)‐reduction of (TPP) Fe(:CCPh2).
Facile Nucleophilic Silylation Reactions at Carbonyl Functionalities Using Trimethylsilylaluminum Compounds
Authors: Rösch Lutz , Altnau Gerald , Otto Wolfgang Helmut
Published: December 2003

In order to check whether organic compounds can be nucleophilically silylated with Me3SiAl compounds such as (1) and (2), the latter were allowed to react with an aldehyde, a ketone, and an acid. Complexing agents like diethyl ether and AlCl3 have considerable influence on the reactions. Summary: Reagents (1) and (2) can be used for the directed nucleophilic silylation of carbonyl compounds; α‐hydroxytrimethylsilyl derivatives are formed. An advantage is the absence of undesirable by‐products.
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The Philosophy of Science: Its Possibilities and Limits
Authors: Wieland Wolfgang
Published: December 2003

Science in the modern world has long since become a factor in the production and reproduction of goods and a condition of life in this world. At the same time, however, it is more than this. Science has therefore become caught‐up in an orientation crisis ever since scientists became aware that science can no longer be pursued merely for the sake of pure knowledge, the ideal from ancient times which had been held to be the proper guide for science in its quest for self‐understanding. Is the philosopher of science capable of providing the researcher with an answer to the questions what it is he does, and whether or not he is deceiving himself in regard to science and his relationship to it? The philosophy of science has revealed areas which demonstrate that our science is never the smooth and elegant construction composed of observation, experiments, and mathematical and formal techniques which it has often been held to be. It is not the least of the modern philosophy of science's achievements to have demonstrated that science cannot teach man what he should do with it and its results.
Gas Chromatographic Separation of Carbohydrate Enantiomers on a New Chiral Stationary Phase
Authors: König Wilfried A. , Benecke Ingrid , Bretting Hagen
Published: December 2003

The direct separation of simple, volatile derivatives of enantiomeric sugars has been achieved for the first time by glass‐capillary gas chromatography of trifluoroacetyl derivatives on a temperature‐stable, chiral stationary phase. The usefulness of the new method was demonstrated on an hydrolyzate of the galactan of the snail Helix pomatia.
Direct and Inverse Reactivity‐Selectivity Relationship in the [1.2]‐Addition of Singlet Carbenes to Olefins
Authors: Schoeller Wolfgang W.
Published: December 2003

The selectivity of carbenes on addition to olefins can—contrary to common belief—increase with increasing reactivity. On the basis of the frontier orbital model two classes of carbenes can be differentiated: those with direct and those with inverse reactivity‐selectivity relationship.
Syntheses of Pyrethroid Acids
Authors: Arlt Dieter , Jautelat Manfred , Lantzsch Reinhard
Published: December 2003

In the course of the last decade the chemistry of insecticides was expanded with the discovery of new cyclopropanecarboxylic acid esters of specific structure, far superior in action to the hitherto known insecticides of other substance classes or the natural prototypes from the group of pyrethrum constituents. The discovery quickly precipitated a host of wide‐ranging studies on the synthesis of these compounds. The development of selective methods of synthesizing complicated small rings called for a comprehensive repertoire: thus, synthesis of the compounds on an industrial scale makes use of sigmatropic rearrangement, radical addition, and nucleophilic ring closure with carbanions. These new industrial syntheses have acquired particular topicality because of their use of stereospecific and enantioselective methods.
Inorganic Pigments: Bases for Colored, Uncolored, and Transparent Products
Authors: Hund Franz
Published: December 2003

Colored and uncolored inorganic pigments have been obtained since prehistoric times from natural minerals, at first empirically, then by specially developed methods. Since the beginning of the 18th century they have also gradually come to be studied scientifically, and today such research makes use of the latest techniques of solid‐state physics and chemistry. On the basis of our knowledge of technically and aesthetically important properties, it has been possible in the last seventy years to make synthetic pigments superior to the natural ones, to increase production drastically while maintaining the pigment properties unchanged or improving them, and to broaden the range by the addition of new synthetic pigments. Nowadays it is in principle possible to write down a specification for many fields of application, taking into account aesthetic, technical, economic, and ecological aspects, and to make the corresponding inorganic pigment in adequate amounts. In what follows I shall discuss the dependence of the scattering and absorption constants of pigments on the refractive index, the wavelength of the light and the particle size, the properties of pigmented systems that depend on the particle geometry, and also some of the optical characteristics determined by the arrangement of the atoms in the crystal lattice.
A Mild and Effective Method for the Reactivation or Maintenance of the Activity of Heterogeneous Catalysts
Authors: Tiltscher Helmut , Wolf Helmut , Schelchshorn Joachim
Published: December 2003

The influence of increasing the pressure into the supercritical region on heterogeneous catalysts has been investigated, for example, on the isomerization of 1‐hexene in the presence of 2‐chlorohexane (500:1) on γ‐Al2O3. On increasing the pressure the catalyst could even be reactivated when covered with volatile substances or when specific catalyst poisons had been added.
ETC: A Mechanistic Concept for Inorganic and Organic Chemistry
Authors: Chanon Michel , Tobe Martin L.
Published: December 2003

The concept of electron transfer catalysis (ETC), or more specifically “Double Activation Induced by Single Electron Transfer” (DAISET) gives an opportunity to connect experimental facts never previously correlated. The first activation results from the transfer of an electron to (or from) a molecular species; the second activation results from the build‐up of a reaction chain able to reproduce the species formed in the first step. The starting point of this review is the SRN1 mechanism where principle and experimental diagnostic criteria are critically discussed. The thermal and photochemical exchange and substitution reactions of PtIVcomplexes are then reviewed together with the exchange reaction [AuCl4]−/Cl−, reactions with Grignard reagents and other organometallic reagents, as well as the redox behavior of electronically excited organic compounds. Photochemical applications, including solar energy conversion are discussed. New aspects are also presented for the mechanistic problem “SN2 reaction or SET process?” Moreover, the concept has significance for SH2 reactions at metal centers, molecule‐induced homolyses, reactions of complexes, as well as electrochemical processes.–Unless otherwise specified, only double activation (DAISET) processes will be discussed in this article.
The Chemistry of Acyl Cyanides
Authors: Hünig Siegfried , Schaller Rainer
Published: December 2003

Through improved and novel syntheses, acyl cyanides—especially aliphatic acyl cyanides—have become so readily accessible that numerous synthetic applications present themselves. The present review surveys the development of the chemistry of the acyl cyanides during the last 25 years. The syntheses and most important reaction possibilities of RCOCN are outlined in four large schemes: reactions of the CO‐ and CN‐groups—in each case with preservation of the carbon skeletal framework—as well as acylations with cleavage of cyanide ions.
2,4,6‐Cycloheptatrienylidenemalondialdehyde(8,8‐Diformylheptafulvene)
Authors: Reichardt Christian , Yun Kyeong‐Yeol
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 113. DOI:10.1002/anie.198201130
1,3‐Cyclooctadien‐6‐yne—An Isolable Bishomodehydrobenzene
Authors: Meier Herbert , Echter Toni
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 91. DOI:10.1002/anie.198200910
Regioselective Opening of α‐ and β‐Alkoxyepoxides with Trimethylaluminum
Authors: Pfaltz Andreas , Mattenberger Anton
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 161. DOI:10.1002/anie.198201610
Oxanickelacyclopentene Derivatives from Nickel(0), Carbon Dioxide, and Alkynes
Authors: Burkhart Georg , Hoberg Heinz
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 147. DOI:10.1002/anie.198201470
Lewis Acid Induced α‐Alkylation of Carbonyl Compounds
Authors: Reetz Manfred T.
Published: December 2003

Carbonyl compounds undergo α‐alkylation via the corresponding silyl enol ethers using SN1 active alkyl halides or acetates in the presence of Lewis acids. This methodology extends the scope of carbonyl chemistry considerably, since SN1 active alkylating agents are generally base sensitive and therefore unsuitable for reactions with enolate anions or nitrogen analogs. A prime example is the α‐tert‐alkylation of aldehydes, ketones and esters.
Bridged C5Me5CoII Complexes— Reactive Intermediates in the Cyclopentadienylation of Cobalt(II) Halides
Authors: Kölle Ulrich , Khouzami Fouad , Fuss Bernhard
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 230. DOI:10.1002/anie.198202300
The Dianion 1,2‐Diphenylbenzocyclobutadienediide
Authors: Boche Gernot , Etzrodt Heinz , Marsch Michael , Thiel Walter
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 345. DOI:10.1002/anie.198203450
Efficient Synthesis of 8‐Oxabicyclo[3.2.1]oct‐6‐en‐3‐ones, Preparatively Useful [4 + 3]‐Cycloadducts
Authors: Föhlisch Baldur , Gehrlach Eberhard , Herter Rolf
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 241. DOI:10.1002/anie.198202410
Ambivalent Coordination Behavior of Lithium Aluminum Hydride in Electron Transfer Reactions
Authors: Kaim Wolfgang
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 298. DOI:10.1002/anie.198202980
Synthesis of a Dicyanocobalt(III) D‐Didehydrocorrinate and Its Reduction to the Dicyanocobalt (III) Corrinate
Authors: Kräutler Bernhard , Hilpert Kurt
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 305. DOI:10.1002/anie.198203050
Synthesis and Structure of Triply Coordinated Sulfur Anions
Authors: Roesky Herbert W. , Schmieder Wilfried , Isenberg Wilhelm , Böhler Dieter , Sheldrick George M.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 269. DOI:10.1002/anie.198202690
Single‐Phase Polymer Alloys of Polyvinyl Chloride and New Polymers
Authors: Hardt Dietrich , Süling Carlhans , Lindner Christian , Morbitzer Leo
Published: December 2003

Polymer alloying is acquiring ever increasing significance for the modification of polymeric materials. Polymer alloys are defined by their phase character, which in turn is determined by the mutual compatibility or incompatibility of the components. Suitable techniques for the analysis of the phase character include,inter alia, dynamic‐mechanical methods, according to which a polymer alloy may be considered in a simplified manner as single‐phase when onlyoneglass transition is observed, even if it extends over a broader temperature range than in the case of the pure components. Aliphatic (polyester)‐polycarbonates and tetramethylbisphenol‐A polycarbonate are new, PVC‐compatible, polymer modifiers. The (polyester)‐polycarbonates (from adipic acid, hexane‐1,6‐diol, neopentanediol, and diphenyl carbonate) yield with PVC single‐phase alloys that at temperatures above the glass transitions of the mixture display the characteristics of soft PVC and that are tough far below this temperature. The special high‐temperature properties of the resin‐like tetramethylbisphenol‐A polycarbonate permits the preparation of alloys with increased dimensional stability under heat (higher deflection temperatures under load).
Two‐Step Sigmatropic RearrangementversusAldol Addition of Ammonioimides
Authors: Gompper Rudolf , Kohl Bernhard
Published: December 2003

The complete manuscript of this communication appears in:Angew. Chem. Suppl. 1982, 405. DOI:10.1002/anie.198204050
Novel Synthesis of Spiro[1,8a]dihydroindolizines; A New Photochemically Reversible System
Authors: Gross Hubert , Dürr Heinz
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 559. DOI:10.1002/anie.198205590
[2 + 2]‐Cycloreversions
Authors: Schaumann Ernst , Ketcham Roger
Published: December 2003

Four‐membered rings can be cleaved thermally, Photochemically, or catalytically into two π bonded fragments. Theoretical calculations, kinetic studies, and investigations of stereo‐ and regioselectivity have been undertaken to clarify the question of whether the reaction involves one or two steps and to permit predictions on its course. [2 + 2]‐Cycloreversions have been used to clarify the structure of four‐membered rings, to prepare highly reactive π electron‐systems and–in combination with a [2 + 2]‐cycloaddition–to protect double bonds. The combination of a cycloaddition and‐reversion can be used to convert a carbonyl group into an olefin. Starting with compounds containing annelated four‐membered rings, compounds with two functional groups or large ring systems can be prepared. [2 + 2]‐Cycloreversions have also been discussed in connection with storage of solar energy.
Synthesis and Reactions of 4‐Chromanones
Authors: Kabbe Hans‐Joachim , Widdig Arno
Published: December 2003

Many natural products, such as the plant insecticides rotenone and ageratochromene (precocene), some fungitoxic phytoalexins, hashish constituents, vitamin E, and plant pigments, contain the chroman ring system as common structural unit. Some years ago we discovered a particularly simple entry to this class of heterocyclic compounds: The condensation of o‐hydroxyacetophenones with aliphatic aldehydes and ketones in the presence of pyrrolidine leads to 4‐chromanones in good yields. The scope of application and limitations as well as modification of this versatile synthesis are outlined; the accompanying tables give a good indication of the wealth and variety of possible substituents. The reaction of o‐hydroxyacetophenone, e. g. with glyoxylic acid or with α,β‐unsaturated ketones, proceeds atypically. The majority of the new chromanones can be used, inter alia, for the preparation of chromones, chromones and chromons, and for the synthesis of tricyclic and larger ring systems.
λ3‐Phosphazenes as Bridging η1‐Ligands
Authors: Scherer Otto J. , Konrad Rainer , Guggolz Ernst , Ziegler Manfred L.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 730. DOI:10.1002/anie.198207300
Active Transport of Amino Acid Anions by a Syntheic Metal‐Complex Carrier
Authors: Tsukube Hiroshi
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 575. DOI:10.1002/anie.198205750
Transition Metal Complexes with cyclo‐Triphosphorus (η3‐P3) and tetrahedro‐Tetraphosphorus (η1‐P4) Ligands
Authors: Vaira Massimo Di , Sacconi Luigi
Published: December 2003

Salts of 3d, 4d, and 5d metals in the presence of the ligands 1,1,1,‐tris(diphenylphosphinomethyl)ethane (triphos) or tris (2‐diphenylphosphinoethyl) amine (np3) react with white phosphorus P4 (or yellow As4) to produce several mononuclear sandwich and dinuclear triple‐decker sandwich complexes, which contain the unprecedented cyclo‐triphosphorus (or cyclo‐triarsenic) unit acting as a trihapto‐ligand. In these complexes the metal atoms are bonded to the there phosphorus atoms of the phosphane ligand and to the three atoms of the cyclo‐P3 or cyclo‐As3 unit. The complexes are diamagnetic or have μeff‐values corresponding to one or two unpaired electrons. The cyclo‐P3 ligand is coordinatively unsaturated as proved by the fact that the mononuclear sandwich compounds may form Lewis‐base adducts with electron‐acceptor fragments. Reaction of the complexes (np)3M (M = Ni, Pd) with white P4 leads to formation of diamagnetic compounds [(np3)M(η1‐P4)], in which the metal atom is bonded to the three phosphorus atoms of the np3‐ligand and in addition to one P atom of the intact P4 molecule, which behaves as a monohapto‐ligand. This article contains a review of the syntheses and structures of these complexes as well as a unified, albeit qualitative, approach to their bonding and properties.
Light‐Induced Activation of 7‐Dehydrocholesterol
Authors: Schmitt‐Rau Karlheinz , Wilk Manfred
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 846. DOI:10.1002/anie.198208460
Oxidation with Palladium Salts: Stereo‐ and Regiospecific Acetoxylation of 4‐Vinylcyclohexene Derivatives
Authors: Heumann Andreas , Reglier Marius , Waegell Bernard
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 922. DOI:10.1002/anie.198209220
λ3‐Phosphorins by [4 + 2]‐Cycloaddition of α‐Pyrones and Cyclopentadienones with H5C6—CP
Authors: Märkl Gottfried , Jin Gui Yu , Silbereisen Ernst
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 881. DOI:10.1002/anie.198208810
β,ε‐Dioxophosphonates by Reductive Nucleophilic Acylation of 1,3‐Dioxo Compounds: Facile Synthesis of Jasmones
Authors: Altenbach Hans‐Josef , Korff Rainer
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 777. DOI:10.1002/anie.198207770
Synthesis and Structure of the First Transition Metal Complex of a Phosphorus Compound with a Direct λ3P—λ5P Bond
Authors: Gilje John W. , Sheldrick William S. , Weferling Norbert , Schmutzler Reinhard
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 907. DOI:10.1002/anie.198209070
A Novel Bischelating Ligand with Two Tetradentate N,N,O,S Subunits–Synthesis and Properties of a Dinuclear CuII Complex
Authors: Girerd Jean Jacques , Kahn Olivier
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 953. DOI:10.1002/anie.198209530
Which Factors Determine the Reactivity and Regioselectivity of Free Radical Substitution and Addition Reactions?
Authors: Tedder John M.
Published: December 2003

The relative importance of bond strength, steric effects, and polarity in determining the rate and orientation of free radical subsitution and free radical addition reaction is considered. The factors which control substitution reaction (radical transfer reaction) are gathered together as five “rules”, and a similar five “rules” are proposed for addition rections. These “rules” are shown to be special cases of two “laws” which govern all free radical reactions.
Dependence of the Enantioselectivity on the Relative Concentration of Substrate in an NADH Model Reaction
Authors: Baba Naomichi , Oda Jun'ichi , Inouye Yuzo
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1021. DOI:10.1002/anie.198210210
Photochemical Evolution of H2 in the System Methyl Viologen/MnII‐meso‐Tetraphenylporphyrintrisulfonic Acid/Mercaptoethanol/Hydrogenase
Authors: Okura Ichiro , Kim‐Thuan Nguyen , Takeuchi Makoto
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1004. DOI:10.1002/anie.198210040
A Spirocyclic Diphosphirane
Authors: Clegg William , Haase Martin , Hesse Michael , Klingebiel Uwe , Sheldrick George M.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1009. DOI:10.1002/anie.198210090
2‐Aminobenzothiazoles by Oxidative Cyclization of Arylthioureas with Sulfinyl Chloride
Authors: Papenfuhs Theodor
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1155. DOI:10.1002/anie.198211550
Cyclopentadienone Complexes as Synthons: Ring‐ and Regiospecific Nucleophilic Additions to Cobaltocenium Salts—Synthesis of Substituted Cyclopentadienes and Cyclopentenones
Authors: Tane Jeffrey P. , Vollhardt K. Peter C.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1360. DOI:10.1002/anie.198213600
Intramolecular Diels‐Alder Reaction of Allenecarboxanilides
Authors: Himbert Gerhard , Henn Lothar
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1473. DOI:10.1002/anie.198214730
Functionalization at Proanomeric Centres by Photobromination: A Novel Access to Oxo‐ and Acyloxyimino‐glycosyl Bromides
Authors: Lichtenthaler Frieder W. , Jarglis Pan
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1449. DOI:10.1002/anie.198214490
New Method for the Synthesis of N‐Vinylamides.
Authors: Schmitt Günter , Ebertz Wolfgang
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1440. DOI:10.1002/anie.198214400
Kinetic Acidity of Methine Protons and Carbonyl‐Activated Methylene Protons
Authors: Miyata Okiko , Schmidt Richard R.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1398. DOI:10.1002/anie.198213980
The Unambiguous Specification of the Steric Course of Asymmetric Syntheses
Authors: Seebach Dieter , Prelog Vladimir
Published: December 2003

The nomenclature of organic chemistry has not kept pace with the staggering advances made in asymmetric syntheses over the last 15 years. Efforts to specify the steric course of stereoselective reactions by use of the terms erythro and threo, and by other descriptors have led to ambiguous notation and consequently to an almost Babylonic confusion. We propose here a method, based on the CIP‐(Cahn‐Ingold‐Prelog) system, for the unambiguous specification of the steric course and the product configuration of diastereoselective reactions. The reflection‐invariant relative topicity of approach of reactants is defined as like (lk) and unlike (ul) if the corresponding descriptor pairs are Re*, Re*. or R*, Re*, and Re*, Si*, or R*, Si*, respectively. The descriptor pair notations (lk and ul) of reactants disclose related steric courses of reactions more often than do the relative configurations of their products, for which the configurational notation l=R*, R* and u=R*, S* is proposed. The advantage of specifying the relative topicity is demonstrated by means of a series of recent examples of importance to the synthetic organic chemist taken from the literature and from our own work.
The Thermal Conversion of 1, 5, 9‐Triynes into Arenes: [2 + 2 + 2]‐Cycloadditions or Sigmatropic Rearrangements?
Authors: Dower William V. , Vollhardt K. Peter C.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1545. DOI:10.1002/anie.198215450
From cis,trans,cis‐1,2,3,4‐Tetravinylcyclobutane to Cyclododecatetraene—Two Consecutive Cope Rearrangements
Authors: Gubernator Klaus , Gleiter Rolf
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1491. DOI:10.1002/anie.198214910
Easy Rotation about the Carbon‐Carbon Bond in Lithium Cyclopentadienyl (Ester‐)Enolates
Authors: Boche Gernot , Eiben Robert , Thiel Walter
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1535. DOI:10.1002/anie.198215350
A Novel Method for the Synthesis of Thiiranimines
Authors: Schaumann Ernst , Nimmesgern Hildegard , Adiwidjaja Gunadi
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1567. DOI:10.1002/anie.198215670
Alkyl‐Substituted 3,4‐Dihydro‐2H‐pyrans: Mass Spectroscopy, Synthesis, and Identification as Insect Constituents
Authors: Francke Wittko , Mackenroth Wolfgang
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1556. DOI:10.1002/anie.198215560
Synthesis of Primary Alkylarenes without Benzene via Olefin Metathesis
Authors: Warwel Siegfried , Ridder Heinz , Winkelmüller Wolfgang
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1525. DOI:10.1002/anie.198215250
Polarity of Binary Liquid Mixtures
Authors: Langhals Heinz
Published: December 2003

In contrast to the thoroughly studied plarity properties of pure liquids, only little is known about the polarity of mixtures of liquids, although the majority of machanistic and preparative work is not carried out in pure phases. Using a widely applicable two‐parameter equation, polar behavior of binary liquid mixtues can be described quantitatively as a function of their composition. Based on this equation, satisfactory explanations are found for deviations observed for binary solvent mixtures from the linear correaltion of polarity scales, as well as for the unusual activation parameters estimated byWinsteinfor solvolysis oftert‐butyl chloride. Applications of the equation range from a rapid test for determining water contents of solvents, the study of reaction mechanisms, to polymer chemistry.
Synthesis and Structure of [Zn(S2N2CO)6][AsF6]2—Sulfur‐Nitrogen Rings as Ligands in Coordination Compounds
Authors: Roesky Herbert W. , Thomas Manfred , Noltemeyer Mathias , Sheldrick George M.
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1813. DOI:10.1002/anie.198218130
CrTe3—A Novel Transition‐Metal Polytelluride
Authors: Klepp Kurt O. , Ipser Herbert
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 2004. DOI:10.1002/anie.198220040
Chloro(phenoxy)carbene—A Nucleophilic Carbene having Temperature‐Dependent Selectivity
Authors: Brück Wolfgang , Dürr Heinz
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 2030. DOI:10.1002/anie.198220300
1,2‐Dihydropentalene from 1,6‐Cyclooctadien‐3‐yne
Authors: Hanold Nobert , Molz Thomas , Meier Herbert
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 2050. DOI:10.1002/anie.198220500
Tetra‐tert‐butylallene and Its Radical Cation
Authors: Bolze Rudolf , Eierdanz Horst , Schlüter Kaspar , Massa Werner , Grahn Walter , Berndt Armin
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 2039. DOI:10.1002/anie.198220390
Novel Facile Synthesis of Multiplyortho‐Bridged Phane‐Hydrocarbons and of Dihydrocyclobutabenzenes
Authors: Klieser Brigitte , Vögtle Fritz
Published: December 2003

The complete manuscript of this communication appears in:Angew. Chem. Suppl. 1982, 1956. DOI:10.1002/anie.198219560
“μ‐C3” Trisphosphanes by Direct Phosphane/Allylphosphane Coupling
Authors: Arpac Ertugrul , Dahlenburg Lutz
Published: December 2003

The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1950. DOI:10.1002/anie.198219500
Synthetic Gene Fragments in Genetic Engineering—The Renaissance of Chemistry in Molecular Biology
Authors: Davies Julian E. , Gassen Hans Günter
Published: December 2003

Chemistry and biology paved the way for a new scientific discipline, molecular genetics. The breathtaking progress in deciphering the genetic machinery of a living being within the last 20 years may be attributed mainly to the experimental skill and ingenuity of molecular biologists. Chemists lost interest in the investigation of biological problems. The advances in genetic engineering exemplify the new demands chemists are confronted with in contemporary science. Following a short introduction on the genetics of bacteria, the articles deals with the molecular basis of gene cloning, which is subdivided into in vitro recombination of nucleic acids and in vivo transformation of cells. Next, the criteria for the selection of passenger DNA, vectors, and host cells are discussed. Recombination and transformation are easy‐to‐learn experimental techniques, whereas the search for the positive clone requires detailed knowledge of microbiology and the ability to handle of a battery of modern biochemical techniques. Finally, the automated chemical synthesis of gene fragments serves to demonstrate that chemistry is starting to make its comeback into molecular biology.