bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolierung, Molekulargewichtsbestimmung und alkalischer Abbau von Drosopterin und Isodrosopterin ‐ Augenpigmente der Fruchtfliege Drosophila melanogaster. Pteridine, LII
Authors: Schlobach Heinrich , Pfleiderer Wolfgang
Published: December 2004

The isolation of the eye pigments drosopterin and isodrosopterin from Drosophila melanogaster, their molecular weight determination and the alkaline degradation of the pigments is described. The identification of 6 hydrolysis products leads to the proposal of a new structural formula for the drosopterins as atropisomeric dipterinyl‐methane dyestuffs (13).
Synthese und Reaktionen von Droso‐ und Isodrosopterin. Pteridine, LIV
Authors: Schlobach Heinrich , Pfleiderer Wolfgang
Published: December 2004

The synthesis of the Drosophila pigments droso‐ and isodrosopterin (7) from 7.8‐dihydropterin (3) and 2‐hydroxy‐3‐oxobutyric acid (4) is described. A reaction mechanism is discussed and proven by isotope experiments. Droso‐ and isodrosopterin form in weak acidic medium in the presence of NH ions two red reaction products each one of which seems to be identical with neodrosopterin.
The Ring Expansion ‐ Ring Contraction Dichotomy in Aromatic Nitrene and Carbene Reactions II. Hetarylnitrenes. Preliminary communication
Authors: Wentrup C. , Thétaz C. , Gleiter R.
Published: December 2004

15N‐labelling experiments and energy calculations on nitreno‐azines and ‐diazies are in agreement and lead to the theory that both ring contraction and ring expansion in hetarylnitrenes can be one‐step processes which are governed mainly by the energy differences between the reacting species and the products.
Eine einfache Darstellungsmethode für Nucleosid‐5′amidophosphorsäurediester
Authors: Kvita Vratislav , Baschang Gerhard
Published: December 2004

The reaction of phosphites with derivatives of 5′‐azido‐uridine and 5′‐azidoadenosine in the presence of nucleophiles is a simple method to obtain the corresponding 5′‐amidophosphoric esters. The dependency of heterocyclic alkylation of reaction temperature and solver has been investigated.
Säurekatalysierte Dienon‐Phenol‐Umlagerungen von Allylcyclohexadienonen; ladungsinduzierte und ladungskontrollierte sigmatropische Reaktionen
Authors: Widmer U. , Zsindely J. , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

The rearrangement of 10‐allyl‐2‐oxo‐Δ1(9), 3‐hexahydronaphthalene (12) catalysed by trifluoroacetic acid and other Bronsted acids yielded almost exclusively the [3s, 3s]‐products, 1‐ and 3‐allyl‐5,6,7,8‐tetrahydro‐2‐naphthol (16 and 15, respectively). The rearrangement of 12 with trifluoroacetic anhydride or acetic anhydride/sulfuric acid, yields, besides 15 and 16, appreciable amounts of the [1s, 2s]‐rearrangement product, 4‐allyl‐5,6,7,8‐tetrahydro‐2‐naphthol (14) (table 1).

The CF3COOH catalysed dienone‐phenol‐rearrangement of 6‐ally‐5,6‐dimethyl‐cyclohexa‐2,4‐dien‐l‐one (11) in hexane at 0° yields4‐allyl‐2,3‐dimethyl‐phenol (19). Rearrangement of d3‐ll containing a specifically deuteriated allyl group proves that the formation of d3‐19 occurs via a [3s, 3s]‐sigmatropic reaction. On the other hand, treatment of 11 with (CF3CO)2O at 0° in hexane gives (after saponification) 4‐allyl‐, 5‐allyl‐ and 6‐allyl‐2,3‐dimethyl‐phenol (19, 20 and 21, respectivcly). This reaction occurs via an acyloxybenzenium‐ion intermediate. The reactions performed with d3‐11 demonstrate that the formation of d3‐19 occurs both by a direct [3s, 3s]‐shift and by a twofold [1s, 2s]‐shift, respectively. d3‐20 is formcd by a [3s, 4s]‐sigmatropic reaction. d3‐21 is obtained with about 95% inversion of the carbon skeleton of the allyl group. Thus d3‐21 is mainly formed by a [1s, 2s]‐ followed by a [3s, 4s]‐sigmatropic rearrangement.

6‐Allyl‐6‐niethyl‐cyclohexa‐2,4‐dien‐1‐one (4) yields with CF3COOH in hexane 4‐allyl‐2‐methyl‐phenol (5), whereas with (CF3CO)2O in hexane 5, 3‐allyl‐ and 5‐allyl‐2‐methyl‐phenol (24 and 25, respectively) are formed in comparable amounts. As a minor product 6‐allyl‐2‐methyl‐phenol (26) was observed.

Based on these observations, the concept of charge‐induced, e.g. schemes 2 and 3, and charge‐controlled, e.g. scheme 7, sigmatropic reactions, has been elaborated. In the former, the charge serves only to accelerate appreciably thermal orbital‐symmetry allowed reactions, whereas in the latter, the charge determines the course of the transformations according to the Woodward‐Hoffmann rules.

Especially in acetylating systems, allylcyclohexdienones undergo charge‐induced and charge‐controlled reactions simultaneously.
Zinkchloridkatalysierte, thermische Umlagerungen von N‐Allyl in C‐Allyl‐aniline; ladungsinduzierte, aromatische Amino‐Claisen‐Umlagerungen
Authors: Schmid M. , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

N‐Allyl‐2‐methylaniline (12) forms on heating at 140° in xylene in the presence of zinc chloride 2‐allyl‐6‐methylanline (19) as major compound and 4‐allyl‐2‐methylaniline (20) as well as 2,7‐dimethyl‐indoline (21) as minor products. Compound 21 is also formed when 19 is heated in the presence of zinc chloride (scheme 2). That 19 arises from a charge‐induced [3s, 3s] sigmatropic rearrangement of 12 – and 20 from two consecutive [3s, 3s]‐sigmatropic transformations – follows from the reaction of N‐crotyl‐2‐methylaniline (13) in the presence of zinc chloride at 140°. 2‐(1′‐Methylallyl)‐6‐methylaniline (22) and 4‐crotyl‐2‐methylaniline (23) are formed exclusively. Small amounts of 2,3,7‐trimethyl‐indoline (24) and 2‐(cis‐ and trans‐1′‐methyl‐propenyl)‐6‐methylaniline (cis‐ and trans‐25) are observed as by‐products. Compound 24 arises from 22 in the presence of zinc chloride (scheme 3). Similar results are obtained when N‐allyl and N‐(2′‐methylallyl)‐N‐methyl‐aniline (14 and 15, respectively) are heated in the presence of zinc chloride. Whereas 14 gives nearly exclusively 2‐allyl‐N‐methyl‐aniline (28) and only small amounts of the corresponding 1, 2‐dimethyl‐indoline (29) and of 2‐(cis‐ and trans‐propenyl)‐N‐methyl‐aniline (cis‐ and trans‐27), 15 forms comparable amounts of 2‐(2′‐methylallyl)‐N‐methyl‐aniline (30), 1,2,2‐trimethyl‐indoline (31), and 2‐isobutenyl‐N‐methyl‐aniline (32) (scheme 4). Compound 30, and also 32, are transformed into 31 on heating in the presence of zinc chloride.

Charge‐induced aromatic amino‐Claisen rearrangements are also observed when N‐allylated anilinium tetraphenylborates are heated at 100–105° in hexamethyl phosphoric acid triamide. Thus, N‐allyl‐ and N‐crotyl‐N, N‐dimethyl‐anilinium tetraphenylborate (16 and 17, respectively) yield 2‐allyl‐ and 2‐(1′‐methylallyl)‐N,N‐dimethyl‐aniline (33 and 34, respectively) besides small amounts of N, N‐dimethyl‐aniline. N‐Cinnamyl‐N, N‐dimethyl‐anilinium tetraphenylborate (18) gives, besides appreciable amounts of N,N‐dimethyl‐aniline, a mixture of 2‐(1′‐phenylallyl)‐,2‐cinnamyl‐, and 4‐cinnamyl‐N, N‐dimethyl‐aniline (35, 36, and 37, respectively) in which the first two compounds predominate.
Photochemische Reaktionen. 71. Mitteilung. Die Photoisomerisierung eines spirocyclischen α, β‐Epoxyketons
Authors: Wüthrich H. J. , Siewinski A. , Schaffner H. , Jeger Oskar
Published: December 2004

On direct UV. irradiation and on triplet sensitization with acetophenone the spirocyclic epoxyketone (R)‐(−)‐9 undergoes racemization (Φ313/334 0.014, ΦSens 0.0060) and rearrangement to the enantiomeric spiro‐β‐diketones (R)‐(+)‐14 (Φ313/334 0.068, ΦSens 0.0037) and (S)‐(−)‐14 (Φ313/334 0.024, ΦSens 0.0023). The quantum yield data show that triplet reaction due to intersystem crossing is unimportant on direct irradiation, and they exclude that one common diradical intermediate of type d (Scheme 8) for the three reaction paths is involved in both the singlet and the triplet reaction. The postulate of photolytic CαO epoxide cleavage to intermediates of type d for the rearrangement requires that the rate of rearrangement is greater than the rate of rotation around the CαCβ; bond in a given d, and that the rate difference is greater in singlet‐generated d than in the triplet analogue. Reclosure of diradicals d and/or photolytic CαCβ cleavage to diradical e and reclosure can account for the racemization of 9.

The optically active spiro‐β‐diketone 14 was found to racemize also on direct irradiation and on triplet sensitization. Furthermore, both 14 and the isomeric β‐diketone 20, which was obtained by UV. irradiation of the homocyclic epoxyketone 19, photochemically isomerize to the enol lactones 23 and 21, respectively.
A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.). III. Structure Determination and Synthesis of 5‐(4‐Methyl‐2‐furyl)‐6‐methylheptan‐2‐one (“Solanofuran”) and of 3,4,7‐Trimethyl‐1,6‐ dioxa‐spiro[4.5]dec‐3‐en‐2‐one (“Spiroxabovolide”), Two New Flavour Components of Burley Tobacco
Authors: Demole E. , Demole C. , Berthet D.
Published: December 2004

Two novel constituents of Burley tobacco condensate were shown to be 5‐(4‐methyl‐2‐furyl)‐6‐methylheptan‐2‐one (solanofuran, 4) and 3,4,7‐trimethyl‐1,6‐dioxa‐spiro[4.5]‐dec‐3‐en‐2‐one (spiroxabovolide, 6). These structures were deduced from spectral data and confirmed by synthesis.

Solanofuran (4) was prepared via the dye‐sensitized photo‐oxygenation of solanone (1). This type of reaction involving the uncommon ‘diene‐addition’ of 1O2 to a conjugated acyclic diene system was thus applied for the first time to the synthesis of a terpenoid furan, a route that might have some biogenetic significance.

Both solanofuran (4) and spiroxabovolide (6) display interesting organoleptic properties. Identification of these compounds increases to 210 the total number of Burley tobacco flavour constituents so far characterized in this laboratory.
Near Cancellation of Through Space and Through Bond Interaction in bicyclo[3.2.2]nona‐6,8‐diene
Authors: Goldstein M. J. , Natowsky S. , Heilbronner Edgar , Hornung V.
Published: December 2004

The photoelectron spectra of bicyclo[3.2.2]nonane and its five dehydrogenated analogues are reported. Analysis of the π‐bands reveals that the unsymmetrical diene 5 retains the ‘natural order’ of the π‐orbitals present in the lower homologues, i. e. the in‐phase below the out‐of‐phase combination of the basis π‐orbitals πa and πc. The isomeric diene 4 is the first member of the symmetrical homologous series (I), which inverts this order, so that a1(π) (in phase!) lies above b2(π) (out‐of‐phase!).
13C‐ and 1H‐NMR. Spectra of ortho‐benzoquinones. On the assignment problem in 13C spectra
Authors: Hollenstein R. , Von Philipsborn Wolfgang
Published: December 2004

13C‐ and 1H‐NMR. spectra of ortho‐benzoquinone 1 and its methyl derivatives have been analysed. By means of heteronuclear double resonance experiments it is shown that assignments given in the literature for the olefinic carbon resonances of 1 and of a series of substituted ortho‐benzoquinones have to be inverted. 13C‐carbonyl frequencies of various six‐membered cyclic ketones are presented.
N, N′‐Alkylidenpeptide: Peptidsynthese‐Nebenprodukte bei Einwirkung von Carbonylverbindungen
Authors: Cardinaux F. , Brenner M.
Published: December 2004

Byproducts of peptide synthesis, formed in the course of accidental attack by Pd‐activated oxygen on ethanol and triethylamine in reaction media, have been identified as products of condensation between peptides and acetaldehyde, and demonstrated to represent N,N′‐alkylidenepeptides, i.e. derivatives of 4‐imidazolidinones. The same products are obtained by direct action of acetaldehyde on the respective peptides, and analogs resulted in some cases when acetaldehyde was replaced by formaldehyde or acetone. The condensation is reversible, imidazolidinone stability depending on structural features of both the involved peptide and carbonyl compound. There are evidently implications of these findings with respect to the chemistry and biochemistry of peptides and proteins.
Methode zur Konstitutionsaufklärung von Celluloseformalen von niedrigem Substitutionsgrad. 29. Mitteilung über textilchemische Untersuchungen
Authors: Heinisch K. A. , Katayama A. , Rouette H. K. , Zollinger H.
Published: December 2004

A method is described which allows the determination of the hydroxyl group(s) in glucose units of cellulose which react with formaldehyde at low degrees of substitution (0.2 to 1.5% CH2O on cellulose). It consists of permethylation of the cellulose by a sequence of two methylations with dimethylsulfate and NaOH (without solvent) followed by 2 exchange methylations with methyl iodide and sodium n‐butoxide and further steps described earlier [2]. The results demonstrate that the use of the new permethylation method leads to a loss of material of less than 5%.
Zur Konfiguration der 2,4,6,8‐Tetrabrom‐cyclooctan‐1,5‐dione Reduktion des β‐Isomers durch Natrium‐borhydrid
Authors: Heller Jürg E. , Dreiding André S.
Published: December 2004

Of the two previously described 2,4,6,8‐tetrabromo‐cyclooctane‐1,5‐diones, the higher melting β‐isomer, mp. 226°, was treated with sodium borohydride to give: (1) by a double reduction and an intramolecular SN2‐reaction two epimeric alcohols, namely the 2‐exo‐hydroxy‐ (6) and 2‐endo‐hydroxy‐ (7) isomers of 3‐exo,5‐exo,7‐endo‐tribromo‐9‐oxa‐bicyclo[4.2.1]nonane, and (2) by a single step reduction a hemiketal, 1‐hydroxy‐2‐exo,4‐exo,6‐endo,8‐endo‐tetrabromo‐9‐oxa‐bicyclo[3.3.1]nonane (8).

The structures of these three hydroxy‐compounds (6, 7 and 8) were derived from their properties, especially from complete analyses of their NMR.‐spectra, which led to deductions of all configurations and conformations. Of special interest is the preferred existence of the 9‐oxa‐bicyclo[3.3.1]norane derivative 8 in a chair‐chair conformation.

The derivation of the configurations of the three hydroxy‐compounds 6, 7 and 8 is tantamount to establishing the 2,4‐cis, 4,6‐trans, 6,8‐cis‐configuration (5) of the β‐isomer of 2,4,6,8‐tetrabromocyclooctane‐1,5‐dione, mp. 226°.
Neuartige Cycloadditionsreaktionen von 2‐ und 4‐Vinylpyridin mit N‐Alkyl‐maleinimiden
Authors: Wagner‐Jauregg Th. , Ahmed Q. , Pretsch E.
Published: December 2004

4‐Vinylpyridine (1a) combines with 3 moles of dienophilic N‐alkyl‐maleinimides (2) in the presence of polymerization inhibitors. The first step of the reaction probably consists of 1:1‐addition with participation of an aromatic double bond, comparable to the analogous behavior of styrene and its derivatives under similar conditions. The unstable intermediates 3, like other Schiff bases (imines), add 2 further moles of the N‐alkyl‐maleinimides forming the spiro compounds 4. These are split in an acidic medium into the N‐alkyl‐5,6,7,8‐tetrahydroisoquinoline‐7,8‐dicarboximides (5), and N,N′‐dialkyl‐2‐butene‐1,2,3,4‐tetracarboxylic 1,2,:3,4‐diimides (6). LiAlH4 reduction of these two types of compounds leads to N‐alkyl‐1 H‐(3,4‐d)‐pyrrolo‐2,3,3a,4,5,9b‐hexahydroisoquinolines (7) and to N,N′dialkyl‐3,3′‐bipyrrolidyls (8A) and their dehydro‐products 8B, respectively.

From the reaction of 2‐vinylpyridine (1b) with N‐alkyl‐maleinimides (2) the 1:2‐addition products 9 can be isolated in the presence of polymerization inhibitors, which are derivatives of N‐alkyl‐5,6,7,8‐tetrahydroquinoline‐5,6‐dicarboximides (9). This again corresponds to the reaction type of cycloadditions with styrene. Furthermore 1:3 adducts are formed which according to 1H‐ and 13C‐NMR.‐data most likely have the structure 10, representing a new type of cycloaddition involving the pyridine nitrogen.
Hydride Abstraction from Benzocyclopropene. Preliminary communication
Authors: Müller Paul
Published: December 2004

The reaction between benzocyclopropene (1) and triphenylmethyl fluoroborate in acetonitrile shows an isotope effect of 6.7 and the isolation of the resulting triphenylmethane and benzaldehyde has been effected. A mechanism for the formation of the latter is proposed, involving an intermediate benzocyclopropenium ion (2).
Chemically Induced Dynamic Nuclear Polarization XI. Intermediary vinyl alcohol during photochemical reactions of acetaldehyde and of acetoin
Authors: Blank B. , Fischer H.
Published: December 2004

Vinylalcohol, formed by disproportionation of α‐hydroxyethyl radicals, is detected by NMR. spectroscopy during photoreactions of acetaldehyde and acetoin in solution and slowly tautomerizes to acetaldehyde.
Eine kinetische Studie über Ligandenverdrängungsreaktionen von π‐ Allyl‐π‐cyclopentadienyl‐Metallkomplexen
Authors: Harder Viktor , Werner Helmut
Published: December 2004

The kinetics of the reactions of the complexes C3H5MC5H5 (M  Ni, Pd) with tertiary phosphites P(OR)3 to give M[P(OR)3]4 have been investigated. For M  Ni and R  C2H5, there results a third‐order rate law whereas for M  Pd and R  C6H5 a second‐order rate law is observed. Possible mechanistic implications of the kinetic data will be discussed.
Flash Photolysis Studies of Reversible Photoprocesses V. Photochromism and triplet states in the dianthrone system
Authors: Gschwind Kurt H. , Wild Urs P.
Published: December 2004

The kinetics of the formation of the photochromic forms B and C of tetramethyl‐dianthrone has been studied in triacetin and methylcyclohexane/2‐methylpentane at several temperatures. A flash spectroscopy method was developed, which allows the recording of the transient behaviour of the sample as function of both – wavelength and time – using a single photoflash for excitation. The results show that the photochromic forms B and C are directly populated from the excited singlet state. In addition a new triplet‐triplet absorption band in the near infrared region was detected.
Fulvene, VII. Analyse der 13C‐ und 1H‐NMR.‐Spektren
Authors: Hollenstein Roger , von Philipsborn Wolfgang , Vögeli Rudolf , Neuenschwander Markus
Published: December 2004

Carbon‐13 and proton NMR. spectra of pentafulvene and of a series of 6‐substituted fulvenes have been analysed and assigned by homo‐ and heteronuclear double resonance and with the aid of iterative computation. 13C and 1H chemical shifts are interpreted in terms of substituent effects and compared with π‐electron charges calculated for the unsubstituted fulvene. From 13C shifts a 10 percent contribution of dipolar structures to the electronic configuration of fulvene may be estimated. All long‐range proton‐proton coupling constants including relative signs and some proton‐carbon couplings in the fulvene spin system have been determined and assigned.
Über die Synthesen von Maytenin, N‐Methylspermidin und N‐Methylsaytenin
Authors: Schlittler Emil , Spitaler Ulrich , Weber Nikolaus
Published: December 2004

Maytenine and N‐methylmaytenine were synthesized and the structure of maytenine definitively proved.
Indices de rétention de cycloalcanes, cycloalcènes, bicycloalkyles, cycloalkyl‐cycloalcényles et bicycloalcényles en chromatographie en phase gazeuse
Authors: Besson Richard , Gäumann Tino
Published: December 2004

The retention indices for cycloalkanes, cycloalkenes and bicyclic compounds have been measured as a function of temperature for different liquids phases. The diastereomeric bicycloalkenyl‐2 were separated. Some rules concerning the indices are given.
The Gas‐Chromatographic Retention Indices of Deuterated Compounds
Authors: Gäumann Tino , Bonzo Reipso
Published: December 2004

Die Änderung des Retentionsindex mit dem Deuterierungsgrad einiger Verbindungen wurden als Funktion der Temperatur und der stationären Phase untersucht. Er zeigt grosse Regelmässigkeiten in der Abhängigkeit von der Anzahl der Deuteriumatome in der Molekel und von der stationären Phase. Die Resultate gestatten eine Abschätzung der relativen Flüchtigkeit α einer deuterierten Verbindung und der Änderung der thermodynamischen Zustandsfunktionen bei der Deuterierung.
Synthesis of ‘Pear Ester’. A novel synthesis of 2,4‐diolefinic aldehydes and esters
Authors: Ohloff Günther , Pawlak Manfred
Published: December 2004

Vinylogous epoxyaldehydes undergo stereospecific Wittig condensations in high yields. The resulting diolefinic epoxides are cleaved at the C(1)–C(2) single bond, when treated with periodic acid, to give the corresponding aldehydes. Direct transformation into the corresponding ethyl‐ester leads to an efficient synthesis of the ‘pear ester’.
Dérivés C‐Glycosyliques XIV. Synthèse de Glycosyl‐5‐Δ2‐Isoxazolines
Authors: Tronchet Jean M. J. , Jaccard‐Thorndahl Sonia , Faivre Liliane , Massard Robert
Published: December 2004

Treatment of terminal‐unsaturated sugars with stable aromatic nitrile oxides led to the expected Δ2‐isoxazolines, obtained as a mixture of two diastereoisomers epimeric at the new asymmetric carbon. One isomer (and in some cases both) has been isolated in a pure state. These compounds are potentially useful in the drug‐design of therapeutically active molecules.
Imidazole als Induktoren der Cyclo‐Oligomerisation von N‐Alkyl‐maleinimiden und der cis‐trans, Umlagerung von Maleinsäure‐dimethylester
Authors: Wagner‐Jauregg Th. , Ahmed Q. , Pretsch E.
Published: December 2004

N‐Methylimidazole (N–M), in boiling acetonitrile, catalyzes the oligomerization of N‐alkyl maleimides (2) to tri‐, tetra‐, penta‐ and hexamers. In the presence of small amounts of hydroquinone the trimers of 2 are formed, which have the structure of N,N′,N″‐trialkyl‐cyclohexane‐1,2,3,4,5,6‐hexacarboxy‐1,2:3,4:5,6‐tri‐midies (6). A possible mechanism of this catalytic cyclo‐oligometization is discussed. Dependant from the chemical nature of the N‐alkyl substituent of the maleimides, imidazole or benzimidazole and some of its C‐substituted products also can function as oligomerization catalysts. However in this case the normal 1:1 addition is the main reaction, as observed also with pyrazoles plus 2. Maleic dimethylester was isomerized to fumaric dimethylester in the presence of N‐methylimidazol. These observations reveal additional catalytic functions to the well known hydrolysis catalyzing properties of imidazoles.
The Preparation of Merrifield‐Resins Through Total Esterification With Cesium Salts
Authors: Gisin B. F.
Published: December 2004

The reaction of chloromethylated polystyrene‐co‐1%‐divinylbenzene resin with the cesium salts of N‐protected amino acids proceeds fast and without side reactions to give N‐protected amino acyl resin esters free of quaternary ammonium sites or reactive chloride.
Chlorosulfates d'alkyle
Authors: Doucet‐Baudry Mme Ginette , Perrot M. Roger
Published: December 2004

IR.‐ and UV.‐spectra of some alkylchlorosulphates are described.
Reinvestigation of the Classical Synthesis of Cinchona Alkaloids. II. The synthesis of quinine and its naturally occurring diastereomers from quinotoxine
Authors: Gutzwiller Jürg , Uskoković Milan R.
Published: December 2004

Stereoselektive Synthesen der Cinchona Alkaloide Chinin (6) und seiner natürlich vorkommenden Diastereomeren 7, 8 und 9, ausgehend von Chinotoxin (2), werden beschrieben. Reduktion der Ketone 4 und 5 mit DIBAL ergibt ausschliesslich die C(8)–C(9) erythro‐Verbindungen Chinin und Chinidin, während Reduktion von 5 mit Natriumborhydrid ausnahmslos zu den epi‐Verbindungen 8 und 9 führt. Die letztgenannten Verbindungen werden selektiv auch auf einem anderen Weg über die erythro‐Epoxide 20 und 21 erhalten.
Modellreaktionen zur Biosynthese von Verbindungen der Damascon‐Reihe und ihre präparative Anwendung
Authors: Ohloff Günther , Rautenstrauch Valentin , Schulte‐Elte Karl H.
Published: December 2004

We report a new general synthesis of damascones. In the presence of acids, 7, 8‐dehydro‐β‐ionole (10) or the related diols 11 are converted into a mixture of β‐damascone (2) and the 7, 8‐dehydrotheaspiranes (19). In the same way the 6‐hydroxy‐7, 8‐dehydro‐α‐ionoles 12 are transformed into a mixture of β‐damascenone (3) and the 8‐oxatheaspiranes (20). The reaction Provides access to damascone derivatives 4–7 which have been found in nature.

These synthetic experiments lend support to our hypotheses concerning the biogenesis of damascones from suitable carotenoids or their metabolites.
C(8) Epimeric 8‐Hydroxy‐erythromycins‐B
Authors: Kurath Paul , Martin Jerry R. , Tadanier Jack , Goldstein Alma W. , Egan Richard S. , Dunnigan Daniel A.
Published: December 2004

Die gepufferte m‐Chlorperbenzoesäure‐Epoxydation von 8, 9‐Anhydroerythromycin‐B‐6, 9‐hemiacetal liefert nach der Reduktion der N‐Oxidgruppe stereoselektiv das (8S, 9S)‐8, 9‐Anhydro‐erythromycin‐B‐6, 9‐hemiacetal‐8, 9‐epoxid nebst einer geringen Menge des 8‐epi‐(8 R, 9R)‐8, 9‐Anhydro‐erythromycin‐B‐6, 9‐hemiacetal‐8, 9‐epoxids. Die beiden Epoxide reagieren in wässeriger Essigsäure‐Lösung unter Wasseranlagerung stereospezifisch zum entsprechenden (8S)‐8‐Hydroxy‐erythromycin‐B, beziehungsweise zum 8‐epi‐(8R)‐8‐Hydroxy‐erythromycin‐B.
Synthese und Eigenschaften einiger neuer Mono(π‐cyclopentadienyl)‐Nickel‐Komplexe
Authors: Harder Viktor , Werner Helmut
Published: December 2004

During studies on the mechanism of ligand displacement reactions of nickelocene non‐ionic monocyclopentadienylnickel complexes of the type πC5H5Ni[P(OP)3]X with X = Cl and P(O) (OR)2 have been obtained. The new compounds have been characterised by means of their IR., UV., NMR. and Mass spectroscopic data. The phosphonate ligands are bonded with the phosphorus atom to the transition metal.
Thermische Zerfallsreaktionen von Nitroverbindungen in Stosswellen. III: Dissoziation von 1‐Nitropropan und 2‐Nitropropan
Authors: Glänzer K. , Troe J.
Published: December 2004

The pyrolysis of 1‐ and 2‐nitropropane highly diluted in Ar has been studied in shock waves at temperatures K 915 < T < 1200 K and total gas concentrations 7 · 10−6 mol cm−3 < [Ar] < 1.5 · 10−4 mol cm−3. The reactions behind the shock waves have been followed by recording light absorption‐time profiles of the decomposing molecules and the produced NO2 Under the conditions of the experiments, the primary reaction step in both cases is the CN bond:fission: \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{rcl} {\rm 1} - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & n - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.3 \cdot 10^{15} {\rm exp }(- 55{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ 2 - {\rm C}_{\rm 3} {\rm H}_{\rm 7} {\rm NO}_{\rm 2} {\rm (} + {\rm M)} &\to & i - {\rm C}_{\rm 3} {\rm H}_{\rm 7} + {\rm NO}_{\rm 2} {\rm (} + {\rm M)\quad k} = 2.4 \cdot 10^{15} {\rm exp }(- 54{\rm kcal mol}^{ - 1} /{\rm RT}){\rm s}^{ - 1} \\ \end{array} $\end{document} (first order rate constants k measured at concentrations of [Ar] ≃ 10−4 mol cm−3).

At these concentrations the reactions are near to the high pressure limit. By varying the Ar‐concentrations over one order of magnitude, only a slight pressure dependence was found. Reaction mechanisms which account for NO2 removal are discussed.
Nuclear Quadrupole Resonance and Stereochemistry I. α – Chloro ethers
Authors: Ardalan Ziba , Lucken Edwin A. C.
Published: December 2004

35Cl nuclear quadrupole resonance spectra of cyclic α‐chloro ethers of known configuration are presented. The resonance frequencies of chlorine atoms in equatorial positions are in every case some 2.5 MHz higher than those of corresponding chlorine atoms in axial positions. Similar results are obtained for open‐chain trichloromethyl ethers and the effect is sufficiently well‐defined to distinguish between configurational isomers and establish their conformation. These results may be rationalised in terms of a model in which the lone‐pair electrons on the oxygen atom hyperconjugate with the electrons of the CCl bond.
Le mécanisme de la réduction polarographique des dérivés ditosyloxylés et son implication en électrochimie préparative
Authors: Gerdil Raymond
Published: December 2004

The cleavage of a single SO2O bond occurs during the polarographic reduction of a tosyloxy group (pCH3C6H4SO2O = TsO) in aprotic medium and intramolecular cyclisation may ensue when a second TsO group is present on the same molecule. The polarographic behaviour of aliphatic ditosyloxy derivatives is discussed on the assumption that oriented vicinal derivatives at the interface assume a conformation which resembles the geometry of the transition state for an intramolecular elimination with anchimeric assistance of one of the tosyloxy groups. This situation favours the electron transfer, whereas the same geometric requirements hinder the intramolecular interaction of the TsO groups of the oriented non‐vicinal derivatives. This interpretation agrees well with the fact that the large scale electrolysis of vicinal ditosyloxy derivatives give much higher yield of cyclic ethers than the higher homologues. It is also shown that intramolecular interaction between TsO groups can occur through an intervening double bond in a non‐vicinal derivative.
Thermal and Photochemical Rearrangements of Divinylcyclopropanes to Cycloheptadienes. ‐ A model for the biosynthesis of the cycloheptadiene derivatives found in a seaweed (Dictyopteris). Preliminary communication
Authors: Pickenhagen Wilhelm , Näf Ferdinand , Ohloff Günther , Müller Paul , Perlberger Jean‐Claude
Published: December 2004

The activation parameters of the thermal rearrangements of the trans‐divinylcyclopropanes 1 and 2, and of cis‐divinylcyclopropane 3 to give cycloheptadiene 5 have been determined. In addition it has been shown that trans‐divinylcyclopropane‐cycloheptadiene rearrangements also occur under irradiation by a mercury lamp in benzene at 40°. These low‐temperature in vitro rearrangements suggest that the biosynthesis of the cycloheptadienes in Dictyopteris (dictyopterenes C′ and D′) may proceed by the same reaction(s).
Circulardichroismus. 62. Mitteilung. Chiroptische Eigenschaften einiger Trimethylcyclohexen‐Derivate: Die Jonone, Irone und Abszisinsäuren
Authors: Ohloff Günther , Otto Eberhard , Rautenstrauch Valentin , Snatzke Günther
Published: December 2004

The absolute configuration of (+)‐α‐ionone 3 (R), the absolute configurations at C(6) of (+)‐cis‐α‐irone 5 (6S) and (−)‐trans‐α‐irone 6 (6R), and the absolute configurations of (+)‐cis‐abscisic acid 10 (S) and (+)‐trans‐abscisic acid 11 (S) are deduced from the CD.‐spectra.
Steroide und Sexualhormone. 248. Mitteilung. Die Partialsynthese von 5α‐Dihydrohirundigenin und von 5α‐dihydroanhydrohirundigenin
Authors: Imhof René , Marti Franz , Schaffner Beat P. , Wehrli Hansuli
Published: December 2004

A partial synthesis of dihydroanhydrohirundigenin (4), a hydrogenation product of naturally occurring anhydrohirundigenin (2) is described. Furthermore 4 is transformed into the formal dihydroderivative 14 of hirundigenin (1).
Die Photoelektronen‐Spektren des Tricyclo[4.2.1.02,5]nonadiens und seines 3,4‐Diaza‐Analogons. Ein Beitrag zur Kenntnis der Wechselwirkung zwischen den einsamen Elektronenpaaren der cis‐konfigurierten Azogruppe
Authors: Brogli Franz , Eberbach Wolfgang , Haselbach Edwin , Heilbronner Edgar , Hornung Volker , Lemal David M.
Published: December 2004

A comparative photoelectron spectroscopical investigation of the title compound (11) and its 3,4‐ and 7,8‐dihydro derivatives (9 and 10) indicates that a considerable ‘through bond’ interaction exists between the π‐orbitals in 11. The PE. spectra of the 3,4‐diaza‐analogue of 10 and 11, which contain a cis azo group in a four‐membered ring, yield a splitting Δn (4‐memb. ring) = 1.55–1.60 eV between the nitrogen lone‐pair orbital energies. This value contrasts with those obtained for a three‐membered ring analogue (3,3‐dimethyldiazirine (5), Δn (3‐memb. ring) = 3.55 eV) and for a five‐membered ring analogue (2,3‐diazanorbornene (7) Δn(5‐memb. ring) = 3.10 eV). The sequence Δn (3‐memb. ring) > Δn (4‐memb. ring) Δn (5‐memb. ring) is satisfyingly reproduced by MINDO/2‐ and EHT‐calculations for the model systems with n = 3,4,5. A similar trend can be deduced from MINDO/2‐calculations for cis‐diimid where Δn becomes minimal for a NNH angle φ ≈ 100°, whereas Δn for the corresponding trans‐structure goes through a maximum in this region. The experimental finding as well as the calculated results confirm the predictions made by Gimarc [15] who attributes the behaviour of Δn for cis‐azo groups to a ‘through‐bond’ interaction of the n+‐orbital with a lowerlying NN σ‐orbital; this interaction becomes maximal for NNR angles of the size present in a fourmembered ring, e.g. in 12 or 13.
The Photolysis of Tricyclo[4.2.1.02,5]nonadiene: Support of a Doughert ‘type N’ mechanism from photoelectron spectroscopical studies
Authors: Haselbach Edwin , Eberbach Wolfgang
Published: December 2004

In earlier work on the photolysis of derivatives of tricyclo[4.2.1.02,5]nonadiene (I), the intermediacy of a biallyl‐like structure has been postulated which is formed by C1‐C2 bond cleavage of I in its first excited state. This mechanism is now supported by the results of photoelectron spectroscopical studies on I and its two dihydroderivatives. Further support is gained from the theoretically calculated Ehrenson C1‐C2‐bond indices for the ground and the first excited state of these molecules. While the results for I in principle can be rationalized on the (one‐electron) basis of ‘through bond’ interaction between the two π‐bonds, the absence of C1‐C2 photocleavage for a substituted tricyclo[4.2.2.02,5]decadiene also requires consideration of an (all‐electron) thermochemical driving force.
Heterotricyclodecane XVI. 2‐Oxa‐7‐aza‐isotwistane und 2‐Oxa‐7‐aza‐twistane
Authors: Portmann Robert Ernst , Ganter Camille
Published: December 2004

The synthesis of several derivatives of 2‐oxa‐7‐aza‐isotwistane (20–29 and 35) and 2‐oxa‐7‐twistane (30–34) is described starting from cis,cis‐cycloocta‐1, 5‐diene (1). The bicyclic acetoxy‐olefin 10 was used as a key intermediate.

The 10N(7)‐isotwistane 22 was treated under reaction conditions suitable for molecular rearrangements involving an oxonium ion g, by neighbouring group participation, leading to 2‐oxa‐7‐aza‐twistanes.
Applications Synthétiques de la Cyclisation d′Alcools Tertiaires γ‐Éthyléniques en α‐Bromotétrahydrofurannes sous l'action du N‐Bromosuccinimide. III. Synthèse du Triméthyl‐2,6,10‐hydroxy‐10‐dodécatriène‐2,6,11‐al (trans/trans et trans/cis), Hydroxy‐Aldéhyde apparenté aux Sinensals
Authors: Demole Edouard , Enggist Paul
Published: December 2004

The reaction of 1‐formyl‐ethylidene‐triphenylphosphorane with trans‐ and cis‐4,8‐dimethyl‐8‐hydroxy‐deca‐4,9‐dienal (7) obtained from (±)‐nerolidol through a novel bromination/oxidation/debromination sequence, afforded 2,6,10‐trimethyl‐10‐hydroxy‐dodeca‐2,6‐11‐trienal 6 (trans‐2/trans‐6) and 10 (trans‐2/cis‐6), respectively. These hydroxyaldehydes closely related to the natural α‐ and β‐sinensals display a powerful, flower‐like odour.
Couplages J des groupes méthyle dans les phényltriméthylsilanes p‐substitués: Effets de solvants
Authors: Brouant P. , Limouzin Y. , Maire J. C.
Published: December 2004

The J coupling constants of a series of p‐substituted phenyltrimethylsilanes were measured in CH2Cl2 and CCl4 solutions. The solvent effect is discussed; it is too large to allow any straightward conclusion on ring‐substituent interaction.
Zur Struktur des Scillicyanosids. 57. Mitteilung über Herzglykoside
Authors: Lichti Heinz , Niklaus Peter , von Wartburg Albert
Published: December 2004

Based on chemical and NMR. evidence structure 1 is assigned to the cardioactive scillicyanoside isolated from white squill.
Der A2+‐Mechanismus der säurekatalytischen Hydrolyse von Epoxiden und anderen cyklischen Oxa‐ Verbindungen
Authors: Willi Alfred V.
Published: December 2004

It is suggested that the acid catalyzed hydrolyses of isobutene oxide and propene oxide proceed via rate‐determining bimolecular reaction between a carbonium ion and solvent water (A2+ mechanism). The carbonium ion is formed by ring opening of the protonated epoxide, in a relatively fast preceding step. This mechanism is in agreement with all experimental facts known today. There is evidence for a similar mechanism in the acid catalyzed hydrolyses of cyclic acetals.
Bemerkung zur Gleichheit der Aufspaltungen ΔI (zwischen den ersten beiden π‐Ionisationspotentialen) und ΔE (zwischen den entsprechenden π* ← π Übergangsenergien) des Spiro[4,4]nonatetraens. Vorläufige Mitteilung
Authors: Batich Christopher , Heilbronner Edgar , Semmelhack Martin F.
Published: December 2004

For a given molecule M, the difference ΔI between the first two vertical ionization potentials Iv,2 and Iv,2 (from MOs ψ1 and ψ2) and ΔE between the corresponding singlet‐singlet excitation energies E1 and E2 (transitions ψ−1 ←1, ψ−1 ψ2) are related by ΔE = ΔI‐ (J2,−1−J1,−1) −2(K1,−1 − K2,−1), using Koopmans approximation. A simple MO model suggests that under certain conditions of symmetry and quasi‐alternancy (e. g. in spiro[4,4]nonatetraene 1) the bracketed differences between the Coulomb‐ and exchange‐integrals should vanish to first order, thus leading to the simple (almost) equality ΔE = ΔI. It is shown that the results from a photoelectron‐ and electron‐spectroscopic investigation of 1 support this conclusion i.e. ΔI = 1.23 eV, ΔE = 1.19 to 1.23 eV.
Isolierung und Konstitutionsermittlung von Chrysodin
Authors: Closse Annemarie , Hauser Daniel
Published: December 2004

The constitution of Chrysodin (2), a metabolite of Sepedonium chrysospermum, is proposed on the basis of chemical transformations and physical measurements.
Photochemische Reaktionen. 75. Mitteilung. Die UV.‐Bestrahlung von 3β‐Acetoxy‐18‐dimethoxy‐20‐oxo‐Δ16‐5α‐pregnen
Authors: Marti Franz , Wehrli Hansuli , Jeger Oskar
Published: December 2004

On UV.‐irradiation in i‐octane the α,β‐unsaturated ketone 14 is transformed into a mixture of 15 and 16.
Chemistry of Succinylsuccinic Acid Derivatives. Part III. The Crystal and Molecular Structure of anti‐Tricyclo[4.4.01,6.07,12]‐1,4,7,10‐tetraethoxycarbonyl‐3,6,9,12‐tetrahydroxy‐dodeca‐3,9‐diene, C24H32O12, a Photodimer of Diethyl Succinylsuccinate
Authors: Mez Hans‐Christian , Rihs Greti
Published: December 2004

X‐ray structure analysis of the title compound (II) is reported. Diffractometer data and the Faltmolekül method were used. Refinement converged at R 0.044. The molecule assumes the syn,syn‐conformation in the crystal.
The Stereoselectivity of Ketone Reduction with Sporotrichum Exile. Resolution of cis‐ and trans‐2‐benzoyloctahydro‐6(2H)‐isoquinolones
Authors: Uskoković M. R. , Pruess D. L. , Despreaux C. W. , Shiuey S. , Pizzolato G. , Gutzwiller J.
Published: December 2004

Das 4a(S), 8a(R)‐Enantiomere des cis‐2‐Benzoyloctahydro‐6(2H)‐isochinolons wird durch Sporotrichum exile QM‐1250 unter anaerobischen Bedingungen achtmal schneller reduziert als das 4a(R), 8a(S)‐Enantiomere. Bei der entsprechenden trans‐Verbindung wurde diese Stereospezifität nicht beobachtet.
Acetolysis of 4‐endo‐diazoacetyl‐bicyclo[3.1.0]hexene: a new synthesis of semibullvalene. Preliminary communication
Authors: Malherbe Roger
Published: December 2004

Acetolysis of diazoketone 1 gives in good yield 6‐acetoxy‐tricyclo[3.3.0.02,8]octan‐3‐one (2) which is converted into semibullvalene in a three‐step sequence. Compound 2 is potentially a good starting material for 3,6‐substituted semibullvalenes.
Absolute Konfiguration von β,ε‐Carotin‐2‐ol, β,β‐Carotin‐2‐ol und β,β‐Carotin‐2,2′‐diol
Authors: Buchecker Richard , Eugster Conrad Hans , Kjøsen Helge , Liaaen‐Jensen SynnøVe
Published: December 2004

By chemical degradation and application of the modified Horeau method the xanthophylls of Trentepohlia iolithus, namely 1a, 2a and 3a, have been shown to possess the (2 R, 6′ R)‐, (2R)‐, and (2R, 2′ R)‐configurations respectively.
Über Pterinchemie. 46., vorläufige Mitteilung. Identifizierung von substituierten Tetrahydropterinen durch Gas‐Chromatographie und Massenspektrometrie
Authors: Weber Rudolf , Frick Willi , Viscontini Max
Published: December 2004

Silylierte, substituierte Tetrahydropterine lassen sich mit Hilfe der Glaskapillarchromatographie voneinander trennen. Die Kombination Glaskapillarchromatographie‐Massenspektrometrie erlaubt, die getrennten Tetrahydropterine zu identifizieren.
Sur les dérivés de la fluorénone VII. Bifluorényles et bifluorénonyles
Authors: Chardonnens Louis , De Blasi Vito , Rotzetter Armand
Published: December 2004

Starting from 3‐bromo‐, 1‐iodo‐ and 4‐iodo‐9‐oxo‐fluorene three symmetrical bifluorenonyls and the corresponding hydrocarbons 3,3′‐, 1,1′‐ and 4,4′‐bifluorenyls are prepared. An attempt to obtain the non‐symmetrical 1,2′‐bifluorenyl is also described.
Kinetische Untersuchung der durch Imidazol katalysierten Acylübertragung von Thioestern auf Cyanessigester, einer Modellreaktion zur enzymatischen Knüpfung von C, C‐Bindungen
Authors: Wenck Helmut , Schallies Michael
Published: December 2004

‐ Die durch Imidazol katalysierte Acylübertragung von Thioestern auf Cyanessigsäureäthylester in wässerigem Medium als Modellreaktion zur enzymatischen Knüpfung von C, C‐Bindungen besteht aus zwei Teilreaktionen: Bildung von N‐Acetylimidazol und Übertragung des Acylrestes auf den Acceptor. Letztere Teilreaktion ist spektroskopisch einheitlich. Mit dieser konkurriert die durch das entstehende RSH katalysierte Hydrolyse des N‐Acetylimidazols als Nebenreaktion. Hierdurch erklärt sich die gegenuber den beiden Teilschritten beträchtlich verminderte Geschwindigkeit der Gesamtreaktion.

Bei konstantem pH nimmt. die Geschwindigkeitskonstante der Gesamtreaktion linear mit steigendem pKSHab.
Transition Metal Ions and Amides, VI. Complexation of the neutral and the anionic forms of 3, 7‐diazanonanedioic acid diamide and 3, 7‐diazanonanedioic acid diethylamide with Cu2+ and Ni2+
Authors: Kaden Thomas A. , Zuberbühler Andreas D.
Published: December 2004

Two tetradentate ligands, 3, 7‐diazanonanedioic acid diamide (DANA) and 3, 7‐diazanonanedioic acid diethylamide (DANEA) have been synthesized and their complexes with Cu2+ and Ni2+ studied potentiometrically and spectrophotometrically. Three monomeric species, ML, MH−1L, and MH−2L, are formed. In ML, the two carbonyl oxygens are bound to the metal ions. Whilst Cu2+ gives complexes CuH−1DANA+ and CuH−1DANEA+ with one deprotonated amide group, the corresponding Ni2+ chelates do not exist in detectable concentrations. CuH−2DANA and NiH−2DANA are formed below pH 9. In the case of the diethyl derivative DANEA, however, steric interaction strongly hinders coordination of two deprotonated amide groups.
Die Hysterese der Adsorptions‐ und Desorptionsisothermen an porösen Silicagelen und Aluminiumoxiden
Authors: Kohlschütter Hans Wolfgang , Lüscher Madeleine , Signer Rudolf
Published: December 2004

In selected groups of amorphous silica gels and finely crystalline aluminium oxides, hysteresis loops between the adsorption‐ and desorption isotherms of water were determined. The total volumes of the pore systems were analysed with the aid of the differential quotients of the hysteresis loops. In the group of silica gels relationships will be demonstrated between the precipitation of polysilicid acids and the distribution of the pore volume in the xerogels. In the group of aluminium oxides the influence of sintering at high temperatures on the distribution of the pore volume will be described.

The hysteresis loops and especially the differential quotients distinctly differentiate specific properties of the used materials with their variables pore systems.

An apparatus was used which recorded weights of water (= volumes and volume differences) with high sensitivity over the entire range p/po = 0 to 0,95. The appearance of hysteresis according to the fundamental theory was a sign that in this range adsorption and desorption of the liquid phase water took place in mesopores.
Reaktionskinetische Untersuchungen der Hydratisierung von Acetylen zu Acetaldehyd an Molekularsieben, die mit katalytisch wirksamen Metall‐Ionen beladen sind
Authors: Gut Günther , Aufdereggen Klaus
Published: December 2004

The kinetics of the catalytic hydration of acetylene to acetaldehyde in the gas‐phase by incorporation of catalytic metal ions on molecular sieves has been studied in a differential reactor. The main product was acetaldehyde besides of small amounts of crotonaldehyde and acetic acid. The catalysts [cadmium(II)‐, zinc(II)‐, copper(II)‐ and silver(I)‐13 X‐molecular sieves] were deactivated at a rate proportional to the square of the hydration rate. The initial hydration rate calculated on the basis of this relation was first order in the acetylene concentration. Starting rate of hydration and rate of deactivation increase with increasing concentration of metal ions on the sieve. The temperature dependence of the rate follows the law of Arrhenius The activation energies of hydration and deactivation, respectively, were calculated. Pore diffusion is a limiting factor. The poison is homogeneously deposited on the catalyst and weakly adsorbed, as it is shown by the criterion of Wheeler. The rate of deactivation decreases with increasing water/acetylene ratio. The deactivation rate which is due to deposition of polymerised acetylene and/or acetaldehyde, is slow with zinc and cadmium catalysts, and more rapid with copper and silver catalysts.
Quadricyclanes. Part II: Electronic structure and chemical reactivity
Authors: Haselbach Edwin , Martin Hans‐Dieter
Published: December 2004

The electronic structure of quadricyclane and 3‐methylidenequadricyclane obtained by photoelectron spectroscopy, is used as a basis for the discussion of cycloadditions to these systems. The electronic structure of 3‐heteroquadricyclanes, arrived at by theoretical calculations, agrees well with that expected from the above measured systems. A surprising outcome is that the orbital most responsible for the observed 2,4‐cycloadditions to these heterosystems in not the HOMO but the third highest orbital which lies well below the former. This strongly suggests that these 2,4‐cycloadditions proceed not in a concerted fashion but presumably involve as rate‐determining step the formation of a resonance‐stabilized zwitterionic intermediate. The nature of this intermeiate is discussed and the feasability of its formation investigated on the basis of thermochemical considerations.
The Crystal and Molecular Structure of 1‐Methyl‐1‐Thionia‐Cyclohexane Iodide
Authors: Gerdil Raymond
Published: December 2004

Crystals of 1‐methyl‐1‐thionia‐cyclohexane iodide are orthorhombic with space group Pna21, a = 18.036, b = 6.611, c = 7.420 Å, Z = 4. The crystal structure was solved by the heavy‐atom method. Very strong parameter interactions prevented least‐squares refinement of atoms other than S and I. The molecule adopts the chair conformation with the methyl group in equatorial position.
Stereochemistry from X‐Ray Diffraction Studies of Three Palladium(II) Complexes with Terdentate Chelating Amines
Authors: Manohar Hattikudur , Schwarzenbach Dieter
Published: December 2004

X‐ray crystal structure analysis of three Pd(II) complexes with cis‐3,5‐diaminopiperidine (DAPI) shows that the metal ion has a square planar coordination. The DAPI groups are trans in the protonated and mixed complexes. Most surprisingly, the unprotonated complex has a basket‐like structure with the DAPI groups cis.
Isolierung und Strukturaufklärung von Chlamydocin
Authors: Closse Annemarie , Huguenin René
Published: December 2004

The constitution of Chlamydocin – a metabolite of Diheterospora chlamydosporia with pronounced cytostatic activity – is proposed on the basis of chemical reactions and physical data. The synthesis of a derivative of a new amino acid is described. The biological activities of this compound and of derivatives of Chlamydocin are discussed.
Fluorénacènes et fluorénaphènes synthèses dans la série des indéno‐fluorènes, XVII. Dérivés méthylés du cis‐fluorénacène, du trans‐fluorénacène et du trans‐fluorénaphène
Authors: Chardonnens Louis , Laroche Bernard , Sieber Willy
Published: December 2004

By condensation of the chlorides of the three 9‐oxo‐fluorene‐2‐, ‐3‐, and ‐4‐carboxylic acids with 4‐bromo‐1,2‐xylene on one side, and of the chlorides of o‐bromobenzoic acid, 2‐bromo‐4‐methyl‐benzoic acid and 2‐bromo‐4,5‐dimethyl‐benzoic acid with fluorene, 2‐methylfluorene and 3‐methylfluorene on the other side, followed by direct or indirect cyclisation and by final reduction, several new methyl derivatives of the indenofluorenes I, II and IV are synthesized.