bluuebunny/crossref_metadata_2025 huggingface dataset:
Pseudoasymmetrie in der organischen Chemie
Authors: Prelog V. , Helmchen G.
Published: December 2004

The geometrical foundations of ‘pseudoasymmetry’ and several other related concepts of organic stereochemistry such as ‘prochirality’ and ‘propseudoasymmetry’ in two‐ and three‐dimensional space have been explored. As a consequence some modifications of the R,S system for specification of molecular chirality and stereoisomerism are proposed.
Umlagerung von Allyl‐aryläthern und Allyl‐cyclohexadienonen mittels Bortrichlorid
Authors: Borgulya J. , Madeja R. , Fahrni P. , Hansen Hans‐Jürgen , Schmid Hans , Barner R.
Published: December 2004

Allyl aryl ethers which have no strongly electron attracting substituents undergo a charge‐induced [3 s, 3 s] sigmatropic rearrangement in the prescence of 0.7 mole boron trichloride in chlorobenzene at low temperature, to give after hydrolysis the corresponding o‐allyl phenols (Tables 1 and 2). The charge induction causes an increase in the reaction rate relative to the thermal Claisen rearrangement of ∼1010. With the exception of allyl 3‐methoxyphenyl ether (5), m‐substituted allyl aryl ethers show similar behaviour (with respect to the composition of the product mixture) to that observed in the thermal rearrangement (Table 3). The rearrangement of allyl aryl ethers with an alkyl group in the o‐position, in the prescence of boron trichloride, yields a mixture of o‐ and p‐allyl phenols, where more p‐product is present than in the corresponding product mixture from the thermal rearrangement (Table 4). This ‘para‐effect’ is especially noticeable for o‐alkylated α‐methylallyl aryl ethers (Table 5 ).

With boron trichloride, 2,6‐dialkylated allyl aryl ethers give reaction products which arise, in each case, from a sequence of an ortho‐Claisen rearrangement followed by a [1,2]‐, [3,3]‐ or [3,4]‐shift of the allyl moiety (Tables 6 and 7). Ally1 mesityl ether (80), with boron trichloride, gives pure 3‐ally1 mesitol (95). From phenol, penta‐ally1 phenol (101) can be obtained by a total of five O‐allylations followed by three thermal and two boron trichloride‐induced rearrangements.

The sigmatropic rearrangements of the ethers studied, using D‐ and 14C‐labelled compounds, are collected in scheme 2; only the reaction steps indicated by heavy arrows are of importance.

With protic acids, there is a [3,3]‐shift of the allyl group in 6‐allyl‐2,6‐disubstituted cyclohexa‐2,4‐dien‐l‐ones, while with boron trichloride the [3,3]‐reaction is also observed along with the much less important [1,2]‐ and [3,4]‐transformations (Table 8). 4‐Allyl‐4‐alkyl‐cyclohexa‐2,5‐dien‐1‐ones give only [3,3]‐rearrangements with boron trichloride (Table 9). As expected, the naphthalenone 112, which is formed by allowing boron trichloridc to react for a short time with allyl (1‐methyl‐2‐naphthyl) ether (111), undergoes only a [3,4] rearrangement (Scheme 3).

Representations of how, in our opinion, the complex behaviour of allyl aryl ethers and allyl cyclohexadienones under the influence of boron trichloride, can be rationalized are collected together in Schemes 4 and 5.

In the last part of the discussion section, the steric factors leading to the appearance of the ‘para‐effect’, are dealt with (Scheme 6).
Russula‐Farbstoffe: Zur Struktur von Russupteridin‐sIII
Authors: Iten Peter Xaver , Arihara Shigenobu , Eugster Conrad Hans
Published: December 2004

Der rote Hauptfarbstoff aus den zu den Basidiomyceten gehörenden Pilzen Russula emetica Fr., R. sardonia Fr. em. Rom. und anderen Spezies, das sog. Russupteridin‐sIII, ist ein «dimeres» Lumazinderivat. Nach Säurehydrolyse konnte Ribose, bzw. Furfurol nachgewiesen werden, neben dem tricyclischen 2,10‐Dihydro‐4,6,8‐trihydroxy‐10‐ribityl‐2‐oxo‐pyrimido[5,4‐g]pteridin (2). Spaltung mit 2proz. Essigsäure unter Sauerstoffausschluss im geschlossenen Rohr lieferte die N‐Ribityllumazine 3a, 3b und 4, nebst weiteren, bisher nicht identifizierten Verbindungen.

Verschiedene Russula‐Arten können, da sie verhältnismässig viel Riboflavin enthalten, als flavinogene Organismen angesprochen werden. Wir postulieren einen Zusammenhang zwischen der Entstehung der roten Russupteridine und der Biosynthese von Riboflavin.
Relationships Between Acidity Functions, Rates of Reactions of Formaldehyde with Cellulose and of Cellulose Hydrolysis. 28th communication on investigations in textile chemistry
Authors: Mohn‐Wehner Angelika , Rouette H. K. , Zollinger H.
Published: December 2004

The rates of hydrolysis of cellulose and the rates of formation of cellulose formal were measured in heterogeneous systems consisting of cotton cellulose and solutions of formaldehyde in aqueous hydrochloric acid and in solutions of hydrochloric acid in various water/acetic acid mixtures. The rates were related to the acidity functions (Ho) of the solutions. Although fairly good linear relationships between the logarithms of the rates and Ho were obtained in most cases, no conclusions concerning the reaction mechanism could be drawn.
Die Elektronenstruktur des Dicyclohepta[c d, g h]pentalens
Authors: Müllen Klaus , Reel Henning
Published: December 2004

Dicyclohepta[cd, gh]pentalene is shown by ESR.‐ and NMR.‐spectroscopic evidence to be best represented as a perturbed [14] annulene. The orbital interaction between the π‐perimeter and the ethylene‐“bridge” is discussed.
Elektrophile und nucleophile Substitution partiell hydrierter Nicotinsäure‐Derivate. 11. Mitt. über synthetische Indol‐Verbindungen
Authors: Troxler F.
Published: December 2004

1‐Methyl‐1,4‐dihydronicotinamide (1)2 reacts with gramines to the corresponding 1‐methyl‐5‐skatyl‐1,4‐dihydronicotinamides (3), the structures of which have been proved by conversion of 6, a homologue of 3, into dimethyl pyridine‐3,5‐dicarboxylate (11). Palladium/H1 reduces 3 to the 1,4,5,6‐tetrahydronicotinamides 12, which are hydrogenated with platinum/H1 to a mixture of the diastereomeric 1‐methyl‐5‐skatyl‐nipecotinamides 14 and 15. Alkaline hydrolysis converts the trans‐amide 15 to the cis‐carboxylic acid 16. Enamine alkylation of 1 with benzylbromide and subsequent catalytic reduction leads in low yield to 5‐benzyl‐1‐methyl 1,4,5,6‐tetrahydronicotinamide (18). 1‐Substituted 1,4,5,6‐tetrahydronicotinic acid derivative 19 are alkylated by strong electrophilic halides to iminium salts 20, which, after catalytic reduction form 3,3‐disubstituted piperidines 21 generally in high yield. The factors influencing the enamine alkylation are discussed. The addition of nucleophiles to iminium salts 20 has been studied. Thus the 1‐methyl‐hexahydro‐2H‐pyrrolo[3.4‐b]pyridines 32 und 33 were prepared by treatment of 20 with cyanide, followed by reduction with LiAlH4 in the case of 33. Intramolecular addition of nucleophiles onto 20 formed the pyrido[2 3‐a]carbazole 35, the indolo[2.3‐a]quinolizines 37 and the benzopyrano[2.3‐b]pyridines 43, 44 and 46. It has been shown that in the iminium salts 20 the group X can eliminate either, if X  CONH2, by a fragmentation mechanism or, if X  CX by nucleophilic attack.
Synthese der Sequenz 1‐34 von menschlichem Parathormon. Vorläufige Mitteilung
Authors: Andreatta R. H. , Hartmann A. , Jöhl A. , Kamber B. , Maier R. , Riniker B. , Rittel W. , Sieber P.
Published: December 2004

Brewer et al. [1] have established sequence I for the first 34 amino acid residues of human parathyroid hormone. It differs in 6 and 5 positions respectively from the corresponding bovine [2] [3] and porcine [4] hormone sequences. The synthesis of the protected tetratriacontapeptide II by the fragment‐coupling approach and its purification by counter‐current distribution are described. Removal of the protecting groups by acidolysis then gave I in high purity.

I displays hypercalcemic activity in the thyroparathyroidectomized rat indicating that the amino terminal part also constitutes the hormonally active region of human parathyroid hormone.
Über thermische, eine Amino‐Claisen‐Umlagerung einschliessende. Reaktionen von N‐Propargyl‐naphthylaminen
Authors: Scheurer H. , Zsindely J. , Schmid H.
Published: December 2004

N‐Propargyl‐1‐naphthylamine (1), the corresponding N‐butinylcompound 5 and N‐propargyl‐2‐naphthylamine (2) ‐ unlike N‐propargyl‐anilines ‐ on heating to 250° are converted to a mixture of py‐tetrahydro‐benzoquinolines and benzoquinolines (scheme 1). The mechanism of these reactions which are induced by a [3s, 3 s] rearrangement of the propargyl group and include a [1,5s] H‐shift is depicted in scheme 4. N‐Methylation of 1 and 2 reduces for steric reasons the rate of the [1,5s] H‐shifts; therefore ring closure of the allenylnaphthylamine intermediates to indols 13 and 14 is favoured (schemes 2 and 5).
Organic Phosphorus Compounds 59. A new method for the synthesis of phosphonic dichlorides
Authors: Maier Ludwig
Published: December 2004

Heating of thiophosphonic dichlorides, RP(S)Cl2, R  CH3, C2H3, C2H5, with a molar equivalent of SOCl2 under pressure at 150° for 5 to 8 h yields phosphonic dichlorides in quantitative yield. In addition sulfur and sulfur dichloride is formed according to the equation:

This method is particularly useful for the preparation of CH3P(O)Cl2 since it was observed that chlorination of CH3P(O)(OCH3)2 with PCl5 yields CH3OP(O)Cl2 as a by‐product which is difficult to separate from CH3P(O)Cl2. On the other hand chlorination of methylphosphonic acid with PCl5 also gives pure CH3P(O)Cl2

.
The Conversion of Isoindolobenzazepines into Dibenzazecines: A new Synthesis of α‐Allocryptopine from Schöpf's Base VI
Authors: Teitel S. , Borgese J. , Brossi A.
Published: December 2004

Der Hofmann'sche Abbau des Brommethylates 1 der « Schöpf‐Base VI » gibt zwei ungesättigte Basen, für welche die Strukturen 2 und 3 abgeleitet wurden. Das 10gliedrige ces‐Dibenzazecin 3 konnte in schlechter Ausbeute in das Protopinalkaloid α‐Allocryptopin 6 übergeführt werden.
Identifizierung von sechs Komponenten des Spurpheromons der Ameisenart Lasius fuliginosus. Vorläufige Mitteilung
Authors: Huwyler Siegfried , Grob Kurt , Viscontini Max
Published: December 2004

Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid are components of the trail pheromone of the ant species Lasius fuliginosus. The acids were extracted from the contents of the rectal ampullae and identified by the mass spectra and gas chromatographic retention times of the corresponding methyl esters.
Metal Complexes of Free Radicals. Part III: Triplet state ESR. of magnesium(glyoxal‐bis‐N‐t‐butylimine)2
Authors: Clopath Peter , Zelewsky Alexander V.
Published: December 2004

The preparation and the ESR. spectra of a 1 : 2 complex of Mg2+ with the radical anion of glyoxal‐bis‐N‐t‐butylimine (GLI) are reported. The ESR. spectrum of Mg(GLIR)2 in 2‐methyl‐tetrahydrofuran at −165° is interpreted as due to a randomly oriented molecular triplet. The magnetic dipole‐dipole interaction of the two unpaired electrons in Mg(GLIR)2 can be interpreted by an axially symmetric fine structure term with D = 0.021 cm−1.
Über die Wirkung von Auxochromen in Flavyliumsalzen, III. 7‐Dimethylamino‐flavyliumsalze
Authors: Kokkinos Konstantinos , Wizinger Robert
Published: December 2004

The absorption maximum at longest wave lengths of the 7‐dimethylaminoflavylium perchlorate being shifted by 121 nm to longer wave lengths than the maximum of the flavylium perchlorate and yet the auxochromes in 4′‐position having a less strong effect in the 7‐dimethylamino‐flavylium salts than in the flavylium salts, the absorption maxima of both series converge strongly. In the case of the 4′‐dimethylamino derivatives the convergence reaches the high value of 61 nm.
Die Geometrie des aktivierten Komplexes der thermischen und ladungsinduzierten aromatischen para → ortho ‐ Claisen‐Umlagerung
Authors: Wunderli Alfred , Zsindely Janos , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

Pure 10β‐(trans‐2′‐butenyl)‐17β‐hydroxy‐estra‐1,4‐dien‐3‐one (6), 10‐(trans‐2′‐butenyl)‐2‐oxo‐Δ1(9),3(4)‐hexahydronaphthalene (13), trans‐2′‐butenyl 17β‐hydroxy‐3‐estra‐1,3,5‐(10)‐trienyl ether (12) and trans‐2′‐butenyl 5,6,7,8‐tetrahydro‐2‐naphthyl ether (14) were prepared by direct C‐ and O‐alkylation, respectively, of the corresponding phenols (cf. [3] [10]), namely estra‐3, 17β‐diol and 5,6,7,8‐tetrahydro‐2‐naphthol.

The Claisen rearrangement of the ether 14 (200°, 12 h) yielded 53% 1‐(1′‐methylallyl)‐ and 34% 3‐(1′‐methylallyl)‐5,6,7,8‐tetrahydro‐2‐naphthol (15 and 16, respectively), whereas in the thermal (120°, 14 h) and in the acid‐catalysed (boron trifluoride in ether, 20°, 20 min) reaction of the corresponding dienone 13 nearly equal amounts of 15 (53–54%) and 16 (46%) were formed by thermal and charge‐induced aromatic [3s, 3s]‐sigmatropic rearrangements [2].

The steroid dienone 6, on heating at 120°, was rearranged by [3s, 3s]‐sigmatropic processes to form 52% of 2‐(1′‐methylallyl)‐ and 48% of 4′‐(1′‐methylallyl)‐3, 17β‐dihydroxy‐estra‐1,3,5,(10)‐triene (7 and 8, respectively). The steroid phenols 7 and 8 were carefully separated; subsequent hydrogenation (Raney‐Ni in alcohol) and ozonolysis yielded 2‐methylbutyric acid (9): from 7, S‐(+)‐9, and from 8, R‐(−)‐9, obtained in 88,5 and 88,0% optical purity (cf. [4a]). This means (cf. scheme 2 and Table 2) that both phenols are formed to the extent of at least 94% via a chair‐like activated complex, and of at most 6% via a both‐like activated complex (ΔΔG = 2.15 kcal/mol). Similarly, the boron trifluoride‐induced rearrangement of 6 (born trifluoride in ether, 0°, 45 min) yielded 7 and 8, from which S‐(+)‐9 and R‐(−)‐9 were respectively obtained in 89% and 98% optical purity. For these induced rearrangements this corresponds to at least 94,5 and 99%, respectively, of the chair‐like, and to only 5.5 and 1% of the boat‐like activated complex (ΔΔG = 1.5–2.5 kcal/mol). These results demonstrate that the activated complexes of both [3s,3s]‐sigmatropic processes, i.e. the pure thermal reaction at 120° and the charge‐induced reaction occurring at 0°, must be very similar. Thus, the boron trifluoride accelerates the Cope‐like reactions 6 → 7 + 8, but does not influence the geometries of their transition states.

The Claisen rearrangement of the steroid ether 12 (200°, 15 h), yielding 7 and 8, was not influenced by the chiral steroid skeleton, because no optical induction was observed (both phenols, 7 and 8, yielded on degradation racemic 2‐methylbutyric acid (9)).
Hormone: Receptor Interactions. Biological activities of [phenylalanine2, norvaline4]‐adrenocorticotropin‐(1‐24)‐tetrakosipeptide and its 4,5‐dehydro‐4,5‐ditritio‐norvaline4 analogue in isolated rat lipocytes and adrenal cortex cells: Lipolysis, corticosterone and cyclic adenosine‐3′,5′‐monophosphate production
Authors: Lang Ursula , Karlaganis Georg , Seelig Steven , Sayers George , Schwyzer Robert
Published: December 2004

[Phenylalanin2, norvalin4]‐adrenocorticotropin‐(1‐24)‐tetrakosipeptid und sein 4,5‐dehydro‐4,5‐ditritio‐Derivat sind in isolierten Ratten‐Lipocyten und ‐Nebennierenrindenzellen biologisch gleich aktiv. In Bezug auf Lipolyse, Corticosteron‐ und cyclo‐AMP‐Produktion zeigen sie gleiche intrinsische Aktivität wie das Adrenocorticotropin‐(1‐24)‐tetrakosipeptid mit der natürlichen Aminosäurensequenz, müssen aber zur Erzielung desselben Effektes in ca. 8–12mal höheren Dosen angewandt werden.
Die Deprotonierung von Metallaquoionen II: Aquochrom(III)‐ion. Zur Struktur aktiver Chromhydroxide
Authors: von Meyenburg Urs , Široký Otokar , Schwarzenbach Gerold
Published: December 2004

On alkalinization of solutions of the chromiun(III)‐aquo ion simple deprotonation takes place first. The degree of hydroxylation nOH however can be brought up to only about 1 (the exact value depending on the total concentration [Cr]t), before the uncharged complex Cr(OH)3(OH2)3 is precipitated. The structure of the very sparingly soluble complex (solubility ∼10−7M) is held together by hydrogen bonds of type I between the molecules, so that its formula may be written as Cr(OH)2H6/2‐lattice. The formation of the well ordered structure is extremely fast. On aging, the metallic centers become connected by μ‐hydroxo‐bridges (type II) and the substances become amorphous and very insoluble. magnified image The dinuclear (H2O)4Cr(OH)2Cr(OH2)44+ behaves similar on deprotonation. Concerning the various equilibria constants see Table 1.
Etude du comportement électrochimique du manganèse dans le tampon borate
Authors: Painot J. , Monnier R. , Augustynski J.
Published: December 2004

The anodic behavior of the manganese electrode in borate buffer solutions have been studied by potentiostatic and galvanostatic electrochemical techniques. Three distinct steps determined on the charging curves are attributed to the formation of Mn (OH)2, MnOOH and MnO2. The manganese dioxide formed anodically in pH 11 borate solution may be reduced cathodically with high faradaic efficiency.
The Dehydrogenation of 1,4‐Cyclohexadienes with 2,3‐Dichloro‐5,6‐dicyanobenzoquinone and Triphenylmethylfluoroborate
Authors: Müller Paul
Published: December 2004

The dehydrogenation of 1,4‐cyclohexadiene (1) cis‐3,6‐dimethyl‐1,4‐cyclohexadiene (2) and trans‐3,6‐dimethyl‐1,4‐cyclohexadiene (3) with triphenylmethylfluoroborate in acetonitrile or 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) proceeds in the same reactivity sequences 2 > 1 > 3. The mechanism of the dehydrogenation of 1,4‐cyclohexadienes with triphenylmethylfluoroborate and DDQ is discussed in the light of these results and in view of the kinetic isotope effects.
A. New Synthesis of Triasteranedione
Authors: McDonald Ian A. , Dreiding André S. , Hutmacher Hans‐Martin , Musso Hans
Published: December 2004

Bromierungen von Bicyclo[3.3.1]nonan‐3, 7‐dion (6) mit vier Äquivalenten Brom oder Phyenyltrimethylammonium‐tribromid lieferten zwei Tetrabromide, deren Zusammensetzung (Hydrat) und IR.‐Spektren (keine CO, dafür OH‐Banden) zeigten, dass neben der Bromierung noch eine Cyclisierung unter Anlagerung von Wasser an die beiden Carbonylgruppen zu einem Oxa‐adamantan‐System stattgefunden hatte. Die Ausbildung der eher seltenen α,α′‐Dihydroxyäther‐Funktion wird der kooperativen Wirkung des induktiven Effekts der vier Bromatome, der räumlichen Nähe der beiden Carbonylgruppen und der Stabilität des Adamantangerüstes zugeschrieben. Die NMR.‐spektren mit den zahlreichen Fernkopplungen bestätigen, dass es sich um zwei stereomere 4,8,9,10‐Tetrabrom‐1,3‐dihydroxy‐2‐oxa‐adamantane handelt. Die Zahl der HC(Br)‐Signale sowie deren Fernkopplungsmuster erlauben die Ableitung der 4β, 8β, 9β, 10α‐Konfiguration für das eine Isomere (8), Smp. 177°, und der 4β, 8β, 9β, 10β‐Konfiguration für das andere (9), Smp. 180°E.

Dehydrobromierung der rohen Tetrabromierungsprodukte von 6 mit Triäthylamin ergab in 80% Ausbeute ein 1:1‐Gemisch von 2,6‐ und 2,4‐Dibrom‐triasteran‐3, 7‐dion (10 und 11), aus dem sich nur das erstere (10) in reiner Form, Smp. 212°, isolieren liess. Die Lagen der Bromatome wurden aus den NMR.‐Spektren abgeleitet. Als Nebenprodukt entstand auch ein wenig 2‐Brom‐triasteran‐3, 7‐dion (12), Smp. 172°.

Die drei Brom‐triasteran‐3, 7‐dione (10, 11 und 12) liessen sich mit Tri‐n‐butyl‐zinnhydrid in 50% Ausbeute zu Triasterandion (7), Smp. 154°, reduktive debromieren. Triasterandion (7) wurde auch direkt aus dem rohen Tetrabromierungsgemisch von Bicyclo[3.3.1]nonan‐3, 7‐dion (6) durch Erhitzen mit Kupferpulver in 31% Ausbeute hergestellt.
Homopolar‐ and Heteropolar Bond Dissociation Energies and Heats of Formation of Radicals and Ions in the Gas Phase. I. Data on organic molecules
Authors: Egger Kurt W. , Cocks Alan T.
Published: December 2004

The literature data on heteropolar and homopolar 2‐center bond dissociation energies in organic molecules in the gas phase and the corresponding heats of formation of radicals and ions have been critically evaluated. Data for more than 500 bonds are represented in tabular form together with the pertinent literature references.

Selected electron affinities and π‐bond dissociation energies have also been incorporated. The follow‐up paper will discuss some empirical general aspects of these data particularly regarding the effect of structure on the bond dissociation energies.
Spectre de Resonance Paramagnétique Electronique de la Diphénylthiophosphine cristalline irradiée aux rayons X
Authors: Geoffroy Michel
Published: December 2004

The electron spin resonance spectra of X‐irradiated diphenylphosphine sulfide monocrystal and powder are reported. The results show that the radical Φ2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm P}\limits^{.} $\end{document}S is mainly produced. The values and directions of the principal components of ḡ and 31P‐hyperfine tensors are determined.
‘Lone pair’ Electronic Structure, Conformation and Oxidation Behaviour of Diaziridines
Authors: Haselbach Edwin , Mannschreck Albrecht , Seitz Werner
Published: December 2004

Photoelectron spectroscopic investigations indicate that (i) monocyclic diaziridines prefer a trans‐conformation of the nitrogen‐lone pairs, and (ii) the interaction between these is comparable to that exhibited by open‐chain analogues, i.e. alkyl‐substituted hydrazines. The chemical experience concerning the particular case of NHNH→NN oxidation of diaziridines can therefore not be accounted for by a prevailing unfavorable ‘lone pair’ interaction. Thermochemical as well as entropy arguments may serve as an explanation. A rather unsatisfactory agreement between predictions from various theoretical procedures and experimental results for the ionization potentials of ‘lone pair’ MO electrons is noted.
Metallbindungsphänomene: Alkoholat‐Aggregate als unmittelbare Teilnehmer an Eliminierungsreaktionen
Authors: Schlosser Manfred , Jan Gérald , Byrne Edeline , Sicher Jiři
Published: December 2004

In solvents of low polarity it is neither a monomolecular nor a dissociated alcoholal species which effects dehydrohalogenation of vic‐dihaloalkanes and vic‐dihalocycloalkanes but rather a dimeric, trimeric or tetrameric alcoholate aggregate. This behavior has important implications for the stereochemical outcome of such elimination reactions.
Intermediaires organiques du germanium divalent: III obtention de germylenes γ‐hydroxyles à partir de 3‐chlorohydrogermyl‐1‐propanols et de 3‐methoxyhydrogermyl‐1‐propanols
Authors: Barrau Jacques , Satgé Jacques , Massol Michel
Published: December 2004

3‐chlorohydrogermyl‐1‐propanols ClH2Ge(CH2)3OH and Cl2HGe (CH2)3OH are synthesized by action of mercury (II) chloride, in tetrahydrofuran, on 3‐germyl‐1‐propanol H3Ge(CH2)3OH. By thermal effect these halohydrides released hydrochloric acid, with formation of oxagermacyclopentanes
equation image
(R = H or Cl); these derivatives decomposed by α‐elimination with formation of γ‐hydroxy divalent species of germanium RGe(CH2CH2)3 OH (R = H or Cl).

‘Chlorine‐methoxy’ exchange using tributylmethoxygermane on Cl2HGe(CH2)3OH leads to the 3‐methoxyhydrogermyl‐1‐propanols (MeO)ClHGe(CH2)3OH and (MeO)2HGe(CH2)3OH; α‐decomposition on the germanium atom in these latter compounds leads to the formation of the same γ‐hydroxypropylgermylenes. These functional divalent germanium species were characterized by insertion into some σ‐bonds.
Synthese von 1α‐Hydroxycholecalciferol. Vorläufige Mitteilung
Authors: Fürst Andor , Labler Ludvik , Meier Werner , Pfoertner Karl‐Heinz
Published: December 2004

1α‐hydroxycholesterol (4a) was synthesized from cholesterol and transformed via its diacetyl derivative 4b into 1α, 3β‐diacetoxycholesta‐5, 7‐diene (6b). Irradiation of the ring‐B‐diene 6b followed by thermal isomerization and saponification gave 1α‐hydroxycholecalciferol (7).
Intramolecular Diels‐Alder reactions: Construction of aza‐ and diaza‐steroid type skeletons
Authors: Gschwend Heinz W.
Published: December 2004

The preparation of 2‐(4‐phenyl)butadienyl‐piperidine 5 is described. An intramolecular Diels‐Alder reaction of the intermediately formed fumaramide thereof produces stereoselectively the tricyclic lactam 6. Its structure, as well as the configurational relationship of its 5 asymmetric centers, is corroborated on the basis of the NMR.‐data. Cycloacylation of the thermodynamically stable precursors 13 and 20 leads to pentacyclic aza‐ or diaza‐steroid type skeletons. Their structures (14, 16, and 21) and in particular their relative configurations are elaborated. A few qualitative kinetic aspects of this intramolecular (4+2)‐cycloaddition are presented.
Über Pterinchemie. 43. Mitteilung [1]. Synthese von D‐Neopterin‐3′‐phosphat und D‐Neopterin‐2′, 3′‐cyclophosphat. Betrachtungen über die Biopterin‐Biogenese
Authors: Viscontini Max , Furuta Yoshiteru
Published: December 2004

Die Synthese des D‐Neopterin‐3′‐phosphates (II) und des entsprechenden Cyclophosphates III wird beschrieben. Bei der Behandlung von D‐Neopterin mit Polyphosphorsäure in der Wärme tritt Cyclisierung der Trihydroxypropyl‐Kette mit dem N(5)‐Atom unter Verlust von zwei Molekeln Wasser ein. Ein möglicher Zusammenhang zwischen dieser leichten Wasserabspaltung und der Biogenese des Sepiapterins bzw. Biopterins wird diskutiert.
Säurekatalysierte Dienon‐Phenol‐Umlagerungen von 6‐Propargyl‐6‐methyl‐cyclohexa‐2,4‐dien‐1‐onen; ladungskontrollierte, aromatische [1s, 2s]‐ und [3s, 4s]‐sigmatropische Reaktionen
Authors: Widmer Ulrich , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

The acid catalysed dienone‐phenol rearrangement of methyl substituted o‐propargyl‐cyclohexadienones (scheme 3) was investigated. The rearrangements were carried out in acetic anhydride containing about 10/00 sulfuric acid. Under these conditions acetoxy benzenium ions are formed as intermediates. These then undergo charge‐controlled [3s, 4s]‐ and [1s, 2s]‐sigmatropic rearrangements. Thus, the [3s, 4s]‐process leads to the formation of the corresponding allenyl‐phenol acetates (19, 21, 23, 25, 28, 30) whereas the [1s, 2s]‐process yields propargyl‐phenol acetates (20, 22, 24, 26, 29), respectively (cf. scheme 4).
Etude calorimétrique de complexes à transfert de chargeinterhalogène‐quinoléine en solution. (Communication préliminaire)
Authors: Biselx Charles , Schaer Jean‐Jacques , Janjic Désimir
Published: December 2004

A calorimetric study has been made for the determination of K and ΔH for quinolineinterhalogen complexes in carbon tetrachloride. The order of stabilities of the complexes with respect to halogens does not agree very well with their acid strength.
Nucleophilic Reactions at Tertiary Carbon. Part 2. σ‐ and π‐routes to the 8‐hydrindanyl cation
Authors: Becker Konrad B. , Boschung André F. , Grob Cyril A.
Published: December 2004

Stereoisomeric ion pairs are implicated as intermediates in the solvolysis of cis and trans‐8‐hydrindanyl chloride 3, whereas 4‐(cyclopenten‐1‐yl)butyl tosylate 5 appears to cyclize by way of an unsymmetrically solvated 8‐hydrindanyl cation. This follows from the solvolysis products and rates of these compounds in aqueous solvents.

The rate and equilibrium constants of the chlorides 3 show that the transition state for the trans‐isomer is more stable by 0.5 kcal than the one for the cis‐isomer. By inference the intermediates differ by a similar amount of energy.

Experimental results are not explained satisfactorily by conformationally isomeric 8‐hydrindanyl cations, as suggested in the literature.
3‐Amino‐3‐desoxyverbindungen von Uzarigenin, Oleandrigenin, Gitoxigenin und Digoxigenin. Partialsynthetische Versuche in der Reihe der Herzgifte, 6. Mitt.
Authors: Hauser Emil , Boffo Ursula , Meister Lotte , Sawlewicz Ludwika , Linde Horst H. A. , Meyer Kuno
Published: December 2004

Es werden die Partialsynthesen der 3‐Aminoverbindungen der im Titel genannten Cardenolide beschrieben.
Contribution à la phytochimie du genre Gentiana, VI. Etude des xanthones dans les feuilles de Gentiana bavarica L.
Authors: Hostettmann Kurt , Tabacchi Rafaël , Jacot‐Guillarmod André
Published: December 2004

Ten tetraoxygenated xanthones (1‐hydroxy‐3, 7, 8‐trimethoxyxanthone I; 1, 7‐dihydroxy‐3, 8‐dimethoxyxanthone II; 1, 7, 8‐trihydroxy‐3‐methoxyxanthone III; 1, 3, 7, 8‐tetrahydroxyxanthone IV; 3, 7, 8‐trimethoxyxanthone‐1‐O‐primeveroside V; 7‐hydroxy‐3, 8‐dimethoxyxanthone‐1‐O‐primeveroside VI; 1, 8‐dihydroxy‐3‐methoxyxanthone‐7‐O‐acetylrutinoside VII; 7, 8‐dihydroxy‐3‐methoxyxanthone‐1‐O‐primeveroside VIII; 3, 7, 8‐trihydroxyxanthone‐1‐O‐primeveroside IX; 3, 7, 8‐trihydroxyxanthone‐1‐O‐glucoside X) have been isolated from leaves of Gentiana bavarica L. by means of column chromatography on polyamid. Among these xanthones, VI, VII, VIII and IX were not encountered before in nature.
Dediazoniations of Arene Diazonium Ions in Homogenous Solution. Part IV: Change‐over from a heterolytic to a homolytic mechanism in 2,2,2‐trifluoroethanol pyridine mixtures
Authors: Burri Peter , Loewenschuss Hana , Zollinger Heinrich , Zwolinski Gene K.
Published: December 2004

There are only two dediazoniation products of benzenediazonium tetrafluoroborate in 2,2,2‐trifluoroethanol (TFE), namely phenyl 2,2,2‐trifluoroethyl ether (1) and fluorobenzene (2). The reaction kinetics are strictly first‐order with respect to the diazonium salt. The addition of increasing amounts of pyridine to the system results in a gradual decrease in the yields of 1 and 2 and an increase in the yields of the homolytically formed products, benzene (3), biphenyl (4), isomeric phenylpyridines (5) and diazo tar (6). The reaction kinetics show that the rate of dediazoniation of the benzene diazonium salt increases with increasing amounts of pyridine. The reaction with added pyridine is no longer first‐order with respect to the diazonium ion.

The product analyses and the kinetic data are consistent with the view that in pure TFE this diazonium salt decomposes completely by a heterolytic mechanism. The addition of pyridine brings about a competitive homolytic mechanism which becomes increasingly dominant as the concentration of pyridine increases.
5‐(1‐Alkenyl)‐1, 3, 4‐oxadiazol‐2(3H)‐one
Authors: Rüfenacht Kurt
Published: December 2004

3‐(2‐alkenoyl)‐thiocarbazic acid O‐methyl esters 1 are desulfurated by bromine and the unknown intermediates are transformed by alkali to 5‐(1‐alkenyl)‐1, 3, 4‐oxadiazol‐2(3H)‐ones (2). This type of oxadiazolone substitution is not realizable by the common ring closure of hydrazides with phosgene due to pyrazolidinone ring closure of unsaturated acids with hydrazine.
Der Einfluss von Substituenten in Stellung 4 auf das n‐Ionisationspotential des Chinuclidins
Authors: Bieri Gerhard , Heilbronner Edgar
Published: December 2004

The vertical ‘lone‐pair’ ionization potentials Iv(n) of fifteen 4‐substituted quinuclidines, of aza‐adamantane and of aza‐twistane have been determined by photoelectron spectroscopy. It is shown that the dependence of Iv(n) on the nature of the substituent S can be rationalized in terms of the contribution to the local potential at the ionization site (i.e. the nitrogen centre) by the dipole of S. Both the solution pK's and Iv(n) correlate with classical substituent parameters (e. g. σ* or F) and with each other. However, no conclusions can be drawn from such regressions concerning a close relationship between the electronic mechanisms responsible for the observed changes in pK or Iv(n).
Transposition bis‐homoallénylique: solvolyse de γ‐tosylates alléniques
Authors: Ragonnet Bernard , Santelli Maurice , Bertrand Marcel
Published: December 2004

Cyclisation (formation of derivatives of 2‐methylidene‐cyclopentanol or cyclohexanone) with inversion of configuration and retention of optical activity is observed during the solvolysis of secondary γ‐allenic tosylates.

Steric factors rather than electronic ones control the participation of one of the double bonds in the allenic system. Kinetic results and product distribution are discussed.
Stoffwechselprodukte von Mikroorganismen. 130. Mitteilung. Synthese des δ‐N‐Hydroxy‐L‐arginins
Authors: Widmer Jörg , Keller‐Schierlein Walter
Published: December 2004

A synthesis of the antibiotically active amino acid, δ‐N‐hydroxy‐L‐arginine, starting from L‐ornithine is described. In addition a new synthesis of δ‐N‐hydroxy‐L‐ornithine, an important building stone of many sideramines, is given.
Effect of Pressure in the Gamma Radiolysis of Cyclohexane in the Vapor Phase
Authors: Milon Hubert , Gäumann T.
Published: December 2004

The vapor phase γ‐radiolysis of cyclohexane has been investigated as a function of pressure, from 100 to 0.5 Torr, in vessels of different dimensions. With decreasing pressure, the yield of hydrogen and substituted cyclohexanes is decreased and the formation of molecules having less than six carbon atoms is enhanced. The curves of yield vs. pressure have a sigmoïd shape from which we define a transition pressure depending only on the dimensions of the vessels, the variation of the yield of a given product being the same for all the vessels. We propose and discuss a simple model of competition between the neutralization of the ions in the volume and their diffusion to the surface where they are neutralized. From the slope of the curve of the inverse of the transition pressure vs. the square of the characteristic diffusion length, we evaluate a maximum life‐time of 68 ms for the ions, using a calculated value of the cyclohexane ions diffusion coefficient.
Isomerisierungen und Umlagerungen in Bicyclischen Systemen via cyclopropan‐carbaldehyd‐enamine
Authors: Rey Max , Dreiding André S.
Published: December 2004

The pyrrolidino‐aminal (4) of bicyclo[3.1.0]hex‐2‐ene‐6‐endo‐carbaldehyde (3) underwent a facile (80°), mildly acid catalyzed isomerization to the corresponding exo‐aminal (6), which was characterized by hydrolysis to bicyclo[3.1.0]hex‐2‐ene‐6‐exo‐carbaldehyde (7).

At higher temperatures (140°), the two aminals 4 and 6 were converted smoothly to a 1:1 mixture of syn‐ and anti‐4‐(pyrrolidino‐methylidene)‐bicyclo[3.1.0]hex‐2‐ene (syn‐ and anti‐7‐pyrrolidino‐homofulvene1) 8 and 9. The structures of 8 and 9 were derived from spectral data. This corrects a previous interpretation by Cook et al.

The endo → exo‐aminal isomerization (4 → 6) is considered to occur via the enamine (5) of bicyclo[3.1.0]hex‐2‐ene‐6‐carbaldehyde (3 or 7), with which the aminals (4 and 6) are in equilibrium. The same enamine (5), a methylidene cyclopropane derivative, is thought to be the intermediate in the aminal (4 or 6) → amino‐homofulvene (8 and 9) conversion, which, therefore, belongs to the vinyl‐methylidene‐cyclopropane rearrangement type.

A cationic mechanism for the endo → exo‐aminal isomerization is excluded by the discrepancy in this reaction of the pyrrolidino‐aminals (13 and 15) of 6‐exo‐methyl‐bicyclo[3.1.0]hex‐2‐ene‐6‐endo‐carbaldehyde (12) and of bicyclo[3.1.0]hexane‐6‐endo‐carbaldehyde (14). While the former aminal (13) is stable even under acid catalysis and at higher temperatures, the latter (15) isomerizes readily to the exo‐aminal 16.

The three endo‐aldehydes 3, 12 and 14 were prepared by the alkali catalyzed rearrangement of the three chlorohydrins 7‐endo‐chloro‐bicyclo[3.2.0]hept‐2‐en‐6‐endo‐ol (20ac), 7‐endo‐chloro‐7‐exo‐methyl‐bicyclo[3.2.0]hept‐2‐en‐6‐endo‐ol (20ad) and 7‐endo‐chloro‐bicyclo[3.2.0]heptan‐6‐endo‐ol (20bc) according to the method of Brook.

The configurations of the unsaturated endo‐aldehydes 3 and 12 followed from their equilibria with the corresponding 2‐oxa‐bicyclo[3.2.1]octa‐3,6‐diene systems (23) and those of the saturated aldehydes 14 and 17 from oxidations to the corresponding carboxylic acids. The endo‐ and exo‐ isomers of the aldehydes and aminals treated in this work were readily distinguished by certain highly characteristic NMR.‐signals.
Die Addition von Imidazolderivaten an DCCI; eine Nebenreaktion bei der Synthese von Histidinpeptiden
Authors: Rink Hans , Riniker Bernhard
Published: December 2004

In the synthesis of histidine peptides by means of the carbodiimide method the formation of Nim‐amidino‐histidine derivatives as secondary products has been observed. The reaction of imidazoles with DCCI leading to such compounds and their cleavage have been investigated. The significance of this side‐reaction in peptide synthesis is discussed.
Surface Chemistry of Polymers Physical Adsorption of Nitrogen, Argon, Sulfur Dioxide and Neopentane on Polyvinylidene Fluoride
Authors: Houriet Jean‐Philippe , Ghiste Patrick , Stoeckli Fritz
Published: December 2004

The adsorption of nitrogen, argon, sulfur dioxide and neopentane on polyvinylidene fluoride has been measured by static methods and by gas‐solid chromatography. The polymer has a homogeneous surface of low energy, which is not significantly affected by heating.
A Stereospecific Synthesis of (E, Z)‐α, β‐γ, δ‐Diunsaturated Aldehydes, Ketones, and Esters Using the Benary Reaction
Authors: Näf Ferdinand , Decorzant René
Published: December 2004

The reaction between (Z)‐1‐alkenyllithium and (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenals, (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenones or (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenoic esters yields mainly (E, Z)‐α, β‐γ, δ‐diunsaturated aldehydes, ketones, or esters and is therefore highly stereospecific.
Stereoselective Ring Closure of Methyl‐5‐hexenyl‐aluminium Systems
Authors: Stefani Annibale
Published: December 2004

A remarkable intramolecular stereoselectivity was observed in the ring closure reactions of 1‐, 2‐, 3‐, and 4‐methyl‐5‐hexenyl‐aluminium systems. The possible relationship between this stereoselectivity and the relative thermodynamic stabilities of the conformers involved in the cyclization reactions, is discussed.
Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen an Carbonsäurechloride. 35. Mitteilung über Photoreaktionen
Authors: Schmid Ursula , Gilgen Paul , Heimgartner Heinz , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

Irradiation of 2, 3‐diphenyl‐2H‐azirine (1a) and 1‐azido‐1‐phenyl‐propene, the precursor of 2‐methyl‐3‐phenyl‐2H‐azirine (1b), in benzene, with a high pressure mercury lamp (pyrex filter) in the presence of acid chlorides yields the oxazoles 5a–d (Scheme 2). Photolysis of 2, 2‐dimethyl‐3‐phenyl‐2H‐azirine (1c) under the same conditions gives after methanolysis the 5‐methoxy‐2, 2‐dimethyl‐4‐phenyl‐3‐oxazolines 7a, b, d, while hydrolysis of the reaction mixture leads to the formation of the 1, 2‐diketones 8a, c, d (Scheme 4). The suggested reaction path for all these reactions is a 1, 3‐dipolar cycloaddition of the photochemically generated benzonitrilemethylides 2 to the carbonyl double bond of the acid chlorides to give the intermediates 4, followed by either elimination of hydrogen chloride or solvolysis (Schemes 2 and 4).

Irradiation of 1c in the presence of acetic acid anhydride leads via the intermediate 9 to the 5‐hydroxy‐3‐oxazoline 10 and the 5‐methylidene‐3‐oxazoline 11 (Scheme 5).
Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit Triphenyl‐vinylphosphoniumbromid. 36. Mitteilung über Photoreaktionen
Authors: Gakis Nikolas , Heimgartner Heinz , Schmid Hans
Published: December 2004

On irradiation in acetonitrile 3‐phenyl‐2H‐azirines of type 1 react with triphenyl vinyl phosphonium bromide to form in approximative 50% yield 2H‐indoles of type 4 (Scheme 1). In analogy to other photochemical reactions with 2H‐azirines [2] [3] it is assumed that the photochemically generated dipoles 2 react with the triphenyl vinyl phosphonium salt (Scheme 1). The conversion of 1 to 4 represents a new synthesis for 2H‐pyrroles.
Radical Anion of Azuleno[5.6.7‐cd]phenalene, a Failure of the Simple HMO Model
Authors: Gerson Fabian , Jachimowicz Joanna , Jutz Christian
Published: December 2004

Hyperfine proton coupling constants are reported for the radical anions of azuleno‐[5.6.7‐cd]phenalene (I), 6‐phenylazulene (II) and the corresponding 1,3‐dideuterio‐derivatives (I‐d2 and II‐d2). The singly occupied orbitals of both I⊖ and II⊖ are found to be symmetric with respect to the mirror plane perpendicular to the plane of the molecule. In the case of I, surprisingly, such an orbital corresponds not to the first, but to the second lowest antibonding HMO. A correlation diagram for the relevant orbitals of I and II indicates that the correct energy order in the HMO model of I can be achieved by a decrease in the absolute value of the parameter βμν for the bonds 4a–5, 6–6a, 9a–10 and 11–11a.
Stoffwechselprodukte von Mikroorganismen. 139. Mitteilung. Synthesen in der Sideramin‐Reihe: Rhodotorulasäure und Dimerumsäure
Authors: Widmer Jörg , Keller‐Schierlein Walter
Published: December 2004

t‐Butyl (E)‐O‐acetyl‐Δ2‐anhydromevalonate could be prepared. by a Reformatsky reaction of 4‐acetoxybutan‐2‐one and t‐butyl bromoacetate. Condensation of its activated derivatives with the diketopiperazine of N5‐hydroxy‐L‐ornithine led to di‐O‐acetyl dimerumic acid, which could be transformed, by ammonolysis, to dimerumic acid, identical with the natural compound. The corresponding acetohydroxamic acid, prepared by acetylation of the diketopiperazine, was identical with natural rhodotorulic acid.
Dielectric Properties of Apolar Micelle Solutions Containing Solubilized Water
Authors: Eicke Hans‐Freidrich , Shepherd John C. W.
Published: December 2004

Varying amounts of water have been solubilized in a micelle solution of sodium di‐2‐pentyl–sulfoscuccinate in benzene and the complex permittivity has been observed in the range 200 KHz to 10 MHz. Part of a dielectric dispersion is seen, which extends to higher frequencies with a broad distribution of relaxation times. Due to association processes, the static dielectric increment is found to vary non‐linearly with hydrated micelle concentration and with the amount of solubilized water, whereas a linear variation with micelle concentration is found if no water is added. These effects are explained on the assumption that part of the solubilized water increases the dipole moment of the micelle.

Additionally, at higher water concentrations, a sudden increase in the conductivity of the solution is observed, which is taken to indicate a conformational change of the solubilized micelle.
Terpenoids Derived from Linalyl Oxide. Part 3. The isolation, structure, absolute configuration and synthesis of the davanafurans, nor‐sesquiterpenes isolated from Artemisia Pallens
Authors: Thomas Alan F. , Dubini Renée
Published: December 2004

The novel nor‐sesquiterpenoids, the davanafurans, have been isolated from the oil of Artemisia pallens, the principal component being the cis, threo‐isomer (1a). The absolute configuration of this isomer, and the relative stereochemistry of the other isomers, have been established by synthesis from linalool oxides of known configuration.
The Wall Effect on Hydrogen Formation in the Vapour‐Phase Radiolysis of c‐C6D12 and n‐C7D16
Authors: Fujisaki Noboru , Gäumann Tino
Published: December 2004

Vapour‐phase radiolysis of c‐C6D12 and n‐C7D16 leads to a relatively large HD yield, up to ∼ 20% of the total hydrogen, which cannot be accounted for by incomplete deuteration of c‐C6D12 and n‐C7D16. In order to elucidate the mechanism of the HD formation, we have examined the effect of additives and of physical conditions on the HD yield. By coating the vessel with a layer of Aquadag the HD yield is greatly decreased without appreciable variation of the total hydrogen yield. The HD yield from nontreated vessels also decreases remarkably with increasing total dose; it is increased upon the addition of traces of water; and is less affected by small amounts of c‐C6H12. The addition of SF6 selectively reduces the HD yield. These experimental results lead us to conclude that inert hydrocarbon ions react by proton transfer with water desorbed from the vessel wall to give hydronium ions which yield HD on subsequent neutralization.
1,2,3,4,5‐Pentamethyl‐5‐acetyl‐cyclopentadien‐1,3, ein ungewöhnliches Keton
Authors: Burger Ulrich , Delay Arlette , Mazenod François
Published: December 2004

It has been shown that the reaction of the title ketone with phosphorous pentachloride leads to regiospecific chlorine transfer to the diene moiety of the molecule, leaving the carbonyl function intact. Attempted acetalization with ethylene glycol did not give the dioxolane but rather 1,2,3,4,5‐pentamethylcyclopenta‐1, 3‐diene in quantitative yield. An independent synthesis of this hydrocarbon, previously available only by lengthy multistep synthesis, has also been described. The only normal carbonyl reaction of the permethyl‐acetyl‐cyclopentadiene observed was the reduction by metal hydrides.
FIR.‐Spektren von Übergangsmetallkomplexen mit orthogonalem Ligandensystem. I. Halogeno‐Kupfer(II)‐Komplexe methylsubstituierter Pyridine
Authors: Stieger Hans‐Rudolf , Ludwig Werner
Published: December 2004

Far‐infrared spectra (400–40 cm−1) have been studied for orthogonal systems CuL2X2 (L = pyridine, mono‐, di‐, tri‐methylsubstituted pyridine and X = Cl, Br). Assignements are suggested for the four bands of the molecular vibrations which form a stable region within the spectra of the complex series. Relations between number and position of bands and structural data are discussed.
Energy Sequence of the Lowest Antibonding Orbitals in Symmetrical Didehydro[n]annulenes with n = 4N+2
Authors: Gerson Fabian , Jachimowicz Joanna , Nakagawa Masazumi , Iyoda Masahiko
Published: December 2004

A model of a perturbed n‐membered perimeter (n = 4N + 2) is used to interpret the ESR.‐data for the radical anions of symmetrical tetra‐t‐butyl‐didehydro[n]annulenes with n = 14, 18, 22 and 26 (N = 3, 4, 5 and 6). The singly occupied orbital of such radical anions correlates with one of the doubly degenerate, lowest antibonding perimeter MO's which have been classified as symmetric (ΨS) or antisymmetric (ΨA) with respect to the mirror plane passing through two opposite centres and perpendicular to the plane of the perimeter. The relevant MO is ΨS for n = 14 (N = 3) and 22 (N = 5), but ΨA for N = 18 (N = 4) and 26 (N = 6), in accordance with the prediction of the model. It has been shown that the introduction of two symmetrically placed triple bonds into a (4N + 2)‐membered perimeter should stabilize ΨS and destabilize ΨA when N is odd, whereas the reverse should hold when N is even.
The Gas‐Solid Interface Calculations of Adsorption Potentials in Slot‐Like Pores of Molecular Dimensions
Authors: Stoeckli Fritz
Published: December 2004

Two theoretical models are presented for the calculation of adsorption potentials in slot‐like pores of molecular dimensions, with respect to the adsorption by a single flat surface. The cases of continuous and layer‐like solids are considered, with interatomic pair‐potentials of the 6:12 type, and for pore widths ranging from two to four times the equilibrium distance of adsorption. Both models give good results for the adsorption of simple molecules by microporous carbons and graphitized carbon blacks.
Die Konfiguration der stereoisomeren Tris(glycinato)‐Kobalt(III)‐Komplexe
Authors: Gerlach Hans , Müllen Klaus
Published: December 2004

It is shown that the stereoisomeric tris(glycinato)cobalt(III) complexes, first prepared by Ley & Winkler, differ in their molecular symmetry. Based on this difference it is possible to assign by 13C‐NMR. spectroscopy the facial configuration to the red β‐complex and the peripheral configuration to the violet α‐isomer.
Synthesen der Nonactinsäure
Authors: Gerlach Hans , Wetter Hansjürg
Published: December 2004

Two stereoselective syntheses of nonactic acid I, the building block of the macrotetrolide antibiotic nonactin are described. The characteristic cis‐configuration of the 2,5‐substituents on the tetrahydrofuran ring of I is obtained in the first synthesis by catalytic hydrogenation of the furan derivative X. This key intermediate possesses the carbon skeleton and correct distribution of oxygen functions for conversin into nonactic acid. It is synthesized by an electrophilic substitution of 2‐acetonylfuran (VI) with the N‐cyclohexyl‐N‐propenyl nitrosonium ion (V) generated from the corresponding α‐chloronitrone (VII) and silver fluoroborate, followed by hydrolysis and oxidation of the aldehyde group.

The second synthesis starts with a diol already having the correct configuration of the side chain that contains the hydroxyl group. For this purpose threo‐1‐octen‐5,7‐diol (XV) is synthesized from acetylacetone in two steps. Oxidative cleavage of the terminal double bond of this threo‐diol yields an aldehyde which is converted by a Wittig reaction, with the carbanion, obtained from diethyl α‐methoxycarbonylethyl phosphonate, into the open chain intermediate, 2‐methyl‐6,8‐dihydroxy‐2‐nonenoic acid methylester (XVIII). Base‐catalyzed cyclisation of this α,β‐unsaturated dihydroxy ester yields the methyl ester of nonactic acid (I) as the main product.