bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition‐Metal Complexes with Bidentate Ligands Spanning trans‐Positions. III. Preparation and solution studies of complexes [MX(1)] (M = Cu, Ag and Au; X = anionic ligand; 1 = 2, 11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene)
Authors: Johnson D. K. , Pregosin P. S. , Venanzi L. M. 
Published: December 2004

AbstractThe preparation of monomeric complexes [MX(1)] is reported where M = Cu, Ag, Au; X = I, Cl, NO3, BF4 and 1 = 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene. The solution structure of the complexes is discussed on the basis of molecular weight, conductivity and NMR. measurements. In acetonitrile and nitromethane, the nitrate and fluoroborate complexes exist as ionic species [M(1)]+X− whereas the halo‐complexes are present as equilibrium mixtures of ‘covalent’ and ‘ionic’ forms. All the complexes are associated in CH2Cl2‐solutions. The values of 1J show that this association in [Ag(NO3) (1)] and [Ag(BF4) (1)] is best described in terms of ion‐pairing while that for species [AgX(1)] (X = Cl, Br and I) is mainly ‘covalent’ in nature. Evidence is presented for the formation of the complex ion [Ag(CH3CN)n(1)]+ in acetonitrile solution.
Synthese von bromosubstituierten Butenoliden II
Authors: Martin Roger , Chapleo Christopher B. , Svanholt Karen L. , Dreiding André S. 
Published: December 2004

Synthesis of Bromosubstituted Butenolides II.Methyl 4,4′‐dibromosenecioate (2) was prepared by double N‐bromosuccinimide bromination of methyl senecioate (1) and converted to methyl 4,4′‐diiodo‐senecioate (3) with sodium iodide and to 3‐bromomethyl‐2‐buten‐4‐olide (4) with aqueous hydrobromic acid. A mixture of methyl (Z)‐ and (E)‐4‐bromosenecioate (8 and 9) yielded 3‐methyl‐2‐butenolide (5) with aqueous hydrobromic acid and a mixture of (Z)‐and (E)‐4‐methoxy‐senecioic acid (10 and 11) with methanolic potassium hydroxide. N‐Bromosuccinimide treatment of the butenolide 5 afforded 4‐bromo‐3‐methyl‐2‐buten‐4‐olide (6) and 4,4‐dibromo‐3‐methyl‐2‐buten‐4‐olide (7).
L'acide hydroxylamine‐O‐sulfonique, réactif de choix pour la conversion d'aldéhydes en nitriles
Authors: Streith Jacques , Fizet Christian , Fritz Hans 
Published: December 2004

Hydroxylamine‐O‐sulfonic acid: a convenient reagent for the conversion of aldehydes into nitriles.Hydroxylamine‐O‐sulfonic acid (HAS) proved to be an excellent reagent for the conversion of aliphatic, aromatic and heteroatomic aldehydes into nitriles. There, aldehydes in the form of suspension in HAS water solution, react rapidely to give the corresponding nitriles in high yield. Only with formylpyridines could the intermediate oxime‐O‐sulfonic acids be isolated.
Nouveaux types de sucres triazotés: triazènes et phénylimino‐2‐oxadiazoles‐1,3,4. Communication préliminaire
Authors: Tronchet Jean M. J. , Rachidzadeh Faranak 
Published: December 2004

Novel types of sugars bearing three nitrogen atoms: triazenes and 2‐phenylimino‐1, 3, 4‐oxadiazoles.A series of aminodeoxysugars treated with p‐nitrobenzenediazonium tetrafluoroborate led to the corresponding triazenes, each of which in chloroform solution existing as an equilibrium between its two tautomeric forms. The free energy of activation of the exchange of the proton between the two nitrogen atoms has been estimated by variable temperature 1H‐NMR. measurements. Each triazenylsugar gave on acetylation an unique positional isomer bearing its acyl group on the nitrogen atom directly attached to the glycosyl group. Phenylsemicarbazones of two keto‐sugars were oxidized with El Khadem's reagent (I2, HgO, MgO) to give the corresponding spiro‐2‐phenylimino‐1, 3, 4‐oxadiazoles.
Photochemistry of Tricyclo[3.3.1.02,7]nonan‐6‐ones. Preliminary communication
Authors: Margaretha Paul 
Published: December 2004

AbstractSensitized irradiation (λ = 254 nm) of the title compounds 2 a and 2 b in benzene affords the tetracyclic oxetanes 3 a and 3 b. The irradiation of 2 c under similar conditions yields equal amounts of 3 c and the cyclopentadiene derivative 5. The formation of the photoproducts is discussed.
Heterotricyclodecane XXII 2‐Aza‐7‐thia‐isotwistane
Authors: Szczepanski Henry , Ganter Camille 
Published: December 2004

2‐Aza‐7‐thia‐isotwistanes.2‐Aza‐7‐thia‐isotwistanes were synthesized either starting from suitable 9‐thiabicyclo[3.3.1]nonenes by olefin‐amination (1 → 4, 2 → 5, 3 → 6, 8 → 10 and 9 → 11) as well as by intramolecular substitution (25 → 26) or by molecular rearrangement starting from twistanes (21 → 19 and 22 → 10). From the isotwistanes thus obtained several other compounds (7, 12–18, 20, 23 and 24) were prepared, too.
Isolement et identification de l'évernine dans la «mousse de chêne» (Evernia prunastri (L.) Ach.). 2e Communication
Authors: Nicollier Gilles , Tabacchi Raffaele 
Published: December 2004

Isolation and identification of evernine in ‘Oakmosse’ (Evernia prunastri (L.) Ach.).A new depside, evernin (1), has been found in the lichen Evernia Prunastri (L.) Ach. The determination of the structure and the spectral parameters of 1, especially the 13C‐NMR. spectrum, are described.
Extended Hückel Molecular Orbital Calculations for the Bridged Annulenes
Authors: Gavezzotti Angelo , Simonetta Massimo 
Published: December 2004

AbstractExtended Hückel molecular orbital calculations have been performed for bridged [10], [12] and [14]annulenes. Orbital energies and wave functions were used to investigate the relative stabilities of different geometries. The theoretical results were also used to reinforce and complement available experimental information about aromaticity and reactivity of this series of molecules. Some spectroscopic properties are also discussed.
The Synthesis of Strained Methylene‐bridged Bicyclic Olefins by the Intramolecular Wittig Reaction
Authors: Becker Konrad B. 
Published: December 2004

AbstractA convenient synthesis of the strained methylene‐bridged trans‐cyclooctenes bicyclo[3.3.1]‐1 (2)‐nonene (1), bicyclo[4.2.1]‐1(8)‐nonene (2), and bicyclo[4.2.1]‐1(2)‐nonene (3) by the intramolecular Wittig reaction is described (see Schemes 1–4). The (3‐oxocycloalkyl)alkyl‐phosphonium bromides 20, 27 and 38 undergoing cyclization to the bridgehead olefins are formed by simple reaction sequences. The spectral properties (IR., 1H‐NMR., 13C‐NMR., and UV.) of the olefins are discussed with regard to their strain.
Der massenspektrometrische Verlust von Vinylalkohol aus 1‐Amino‐3‐aryloxy‐2‐propanolen. 24. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Longoni Rita , Berntsson Peder , Bild Norbert , Hesse Manfred 
Published: December 2004

Loss of vinyl alcohol from 1‐amino‐3‐aryloxy‐2‐propanols under electron impactUnder electron impact compounds of type 1 (see Scheme 1) split off 44 mass units from the molecular ion. This unusual reaction was studied using derivatives and deuterium labelled compounds. It could be demonstrated that for this fragmentation reaction 16 is the important structural feature from which H2(C3)C(2)HOH (44 mass units) is lost. The preferred reaction mechanism involves a transition state in which four members of the side chain are involved (Scheme 2, mechanism 2).
The Thermal Benzoxazinone‐Benzoxazole Conversion, a Reexecution of a Mass Spectrometric Decay by Thermolysis
Authors: Reichen Werner 
Published: December 2004

AbstractThe base peak in the mass spectrum of several 1,4,2‐benzoxazinone derivatives 1a–f (cf. Scheme 1 and the Table) suggests a clean carbon monoxide elimination leading to benzoxazole radical cations 2a–f. This benzoxazinone‐benzoxazole conversion can be reproduced quantitatively by flash vacuum thermolysis.The isomeric 2,4,1‐benzoxazinone 4 (cf. Scheme 2) eliminates carbon dioxide – the resulting biradical species 5 does not recombine to benzazete 10 but fragments into nitrile and benzyne (7).
Zur Bildung polycyclischer Ketone bei der Umsetzung von 5, 6‐Dimethyliden‐bicyclo[2.2.1]hept‐2‐en mit Dieisen‐enneacarbonyl
Authors: Steiner Ulrich , Hansen Hans‐Jürgen 
Published: December 2004

On the Formation of Polycyclic Ketones in the Reaction of 5, 6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene with Diiron‐enneacarbonyl5,6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene (4), in the presence of diiron‐ennea‐carbonyl in boiling hexane, produces the endo‐and exo‐tricarbonyl‐iron complex of 4 (endo‐ and exo‐5). A mixture of numerous tricarbonyl‐iron complexes with ligands derived from coupling and carbonylation reactions of 4 are also formed. The endo‐ and exo‐5 compounds as well as two tricarbonyl‐iron complexes (7 and 8) of penta‐cyclic ketones could be isolated and characterized. After oxidative removal of the tricarbonyl‐iron groups in the reaction mixture the three pentacyclic ketones 9, 10 and 11 were separated. Structure and configuration of these ketones were deduced from spectroscopic analyses, especially from their 1H‐ and 13C‐NMR. spectra (see tables 1–4). Whereas the symmetric pentacyclic ketone 11 is of a known type (cf. [1]) the two spiroketone 9 and 10 represent compounds of a new type. Their structure and configuration shows that in ironcarbonyl induced thermal cyclopentanone formations, an exocyclic double bond can also take part.
Intramolekulare Cycloaddition von [1,1′‐Binaphthyl]‐2,2′‐bis(allylamin)
Authors: Nakamura Yushin , Zsindely Janos , Schmid Hans 
Published: December 2004

Intramolecular cycloaddition of [1,1′‐binaphthyl]‐2,2′‐bis(allylamine)Unlike the 1,1′‐binaphthyl‐2,2′‐bis(allylether) the corresponding [1,1′‐binaphthyl]‐2,2′‐bis(allylamine) (1) upon heating to 230° in mesitylene undergoes thermal decomposition only. However, when 1 is heated in a mixture of 2‐methylaminoethanol and water, besides 3 the policyclic ketones 4 and 5 are formed in isolated yields of 28 and 10%, respectively (Scheme 1). Intermediates are the imines corresponding to 4 and 5 which are hydrolysed under the reaction conditions rather than decomposed. The imines are formed by a intramolecular Diels‐Alder reaction, in which the double bond of one N‐allylgroup reacts with the naphthalene ring of the second half of the molecule.The policyclic ketones 4 and 5 are characterized as acetates 6 and 7, respectively, and as the acetylated reduced products 11, and 12 and 13, respectively. The constitutions of all compounds are derived from spectroscopic data, chiefly from the 1H‐NMR. spectra.
Complex Formation between Sugars and the Sodium Cation in Non‐Aqueous Solvents
Authors: Grandjean Jean , Laszlo Pierre 
Published: December 2004

AbstractIn low dielectric solvents such as pyridine or isopropylamine, sodium perchlorate interacts strongly with a variety of sugars. The interaction is best described as non‐specific, with close proximity of the ionic partners maintained, as in a sugar‐shared ion pair.
A New Xanthone Diglucoside from Swertia perennisL.
Authors: Hostettmann Kurt , Miura Iwao 
Published: December 2004

AbstractA new xanthone diglucoside (1) has been isolated from the aerial parts of Swertia perennis L. (Gentianaceae) by means of column chromatography on polyamide, followed by preparative TLC. on silica gel. From UV. and NMR. data, its structure has been established as 1,3‐di‐β‐D‐glucopyranosyl‐7,8‐dihydroxyxanthone or norswertianine‐1,3‐diglucoside.
Isolation and structure analysis of a photoproduct of the new photoaffinity label p‐nitrophenylalanine. Preliminary communication
Authors: Escher Emanuel 
Published: December 2004

AbstractThe isolation and structural analysis of a photoproduct of Ac · p‐nitrophenyl‐alanine ethyl ester is described and discussed. Nitrophenylalanine is proposed as a hydrogen fluoride stable photoaffinity label.
13C‐NMR. Study on Isoalloxazine and Alloxazine Derivatives
Authors: Grande Hans J. , Gast Robert , Van Schagen Cees G. , Van Berkel Willem J. H. , Müller Franz 
Published: December 2004

AbstractA series of isoalloxazine and alloxazine derivatives have been investigated by 13C‐NMR. The synthesis of selectively 13C‐enriched derivatives made it possible to assign unambiguously the signals due to the quaternary carbon atoms at position 4, 4a and 10a of the isoalloxazine ring system. The assignment of the other resonances was ensured by the use of selectively deuteriated and chemically modified compounds as well as by decoupling techniques. The assignments differ in part from those published by Breitmaier & Voelter [2] on FMN and FAD. The solvent dependence of the resonances has been studied in dioxan/water mixtures. The experimental data are compared with published MO calculations and discussed.
Acetale von 1,2,3,4‐Tetraoxobutan: Herstellung und Struktur von rac‐ und meso‐2,3,3,4,4,5‐Hexamethoxy‐tetrahydrofuran
Authors: Iten Peter Xaver , Weber Hans Peter , Eugster Conrad Hans 
Published: December 2004

Acetals of 1,2,3,4‐tetraoxobutane: preparation and structure determination of rac‐ and meso‐2,3,3,4,4,5‐hexamethoxy‐tetrahydrofuranOxidation of 3,4‐dimethoxyfuran with 2 equiv. of bromine at −75° in the presence of triethylamine and methanol leads to a mixture of rac‐ and meso‐2,3,3,4,4,5‐hexamethoxy‐tetrahydrofuran (cf. Scheme 1, 4 and 5). The structure of the crystalline rac‐compound has been determined by X‐ray analysis.
Über Pterinchemie. 61. Mitteilung. Die Kristallstruktur von 5‐Formyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterin
Authors: Bieri Jost H. , Viscontini Max 
Published: December 2004

The crystal structure of 5‐formyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterineThe crystal structure of the title compound, a tetrahydropterine, has been determined by X‐ray analysis (direct method) and refined with 1579 structure amplitudes to R = 0.054. The crystal system is triclinic, space group P1, with unit cell dimensions a = 7.171, b = 7.255, c = 12.369 Å, α = 100.64, β = 93.32, γ = 98.27°. The tetrahydropyrazine ring exists in a distinctly flattened conformation. The C(13)‐ and C(14)‐CH3‐groups possess a cis‐configuration with axial position for C(13)‐CH3 and equatorial for C(14)‐CH3. The carbonyl‐group of the N‐formyl function has an (E)‐configuration.
Comportement an 1H‐RMN. des diaryl‐1,3‐triazènes dans les solvants neutres et acides. III
Authors: Vernin Gaston , Siv Chhan , Metzger Jacques , Elguero José , Archavlis André 
Published: December 2004

1H‐NMR. behaviour of 1,3‐diaryltriazenes in neutral and acidic solventsFormation and decomposition of 1,3‐di‐aryltriazenes can be studied by 1H‐NMR. Triazenes decompose in acidic medium or by addition of isoamylnitrite: in the last case, the spectrum shows emission lines characteristic of the CINDP effect. At −80° the prototropic rate is slow enough to permit the observation of two aromatic systems.
Thermolysis of Carbamoyl Azides. II. A. Novel Reduction of Azides with Elemental Copper
Authors: Reichen Werner 
Published: December 2004

AbstractCopper(0) does not catalyze the decomposition of dialkylcarbamoyl azides 5a–e but instead it is oxidized to copper(II) while the azides 5 are reduced by uptaking one electron per molecule and eliminating nitrogen. A probable explanation for the formation of the resulting copper(II) diisocyanate diamine complexes 8a, b (see Scheme 2) as well as the other reaction products is given. A mechanism involving a carbamoyl nitrene as well as a Curtius rearrangement can be excluded.
Synthese von 5,6‐Dimethyl‐4‐oxo‐1,3,4,5‐tetrahydro‐imidazo‐[4,5‐c] [1,2,6]thiadiazin‐2,2‐dioxid und 7‐Methyl‐4‐oxo‐1H‐3,4‐dihydro‐pyrimido[4,5‐c][1,2,6]thiadiazin‐2,2‐dioxid
Authors: Edenhofer Albrecht , Meister Walter 
Published: December 2004

Synthesis of 5,6‐Dimethyl‐4‐oxo‐1,3,4,5‐tetrahydro‐imidazo[4,5‐c][1,2,6]thiadiazin 2,2‐dioxide and 7‐Methyl‐4‐oxo‐1H‐3,4‐dihydropyrimido[4,5‐c][1,2,6]thiadiazin 2,2‐dioxideThe derivatives of the above heterocyclic ring systems were prepared by reaction of the corresponding o‐amino esters with sulfamoylchloride.
Synthèse et réactions de didésoxy‐5,6‐halogéno‐6‐α‐D‐xylo‐hepténo‐5‐furannurononitriles. Communication préliminaire
Authors: Tronchet Jean M. J. , Martin Olivier R. 
Published: December 2004

Synthesis and reactions of 5,6‐dideoxy‐6‐halogeno‐α‐D‐xylo‐hept‐5‐eno‐furanurononitrilesThe 5,6‐dideoxy‐6‐chloro‐, 6‐iodo‐ and 6‐fluoro‐3‐O‐methyl‐α‐D‐xylo‐hept‐5‐eno‐furanurononitriles have been prepared, their properties described as well as the methods used for the assignment of the configuration of the geometrical isomers. Some new reactions of the 6‐bromo analog (1) of these compounds are reported. For example, when reacted with 2‐mercaptoethanol or N,N′‐dimethyl‐ethylenediamine in the presence of NaOH, 1 gave the corresponding six‐membered ring, stereo‐isomers of an oxathiane or of a perhydrodiazine respectively. When the base used was Et3N and the binucleophile the N‐methyl‐ethanolamine or the N,N′‐dimethyl‐ethylene‐diamine the major product was a cyano‐enamine which could be hydrolysed to a β‐cyanoketone or cyclized to a five‐membered ring, an oxazolidine or an imidazolidine respectively.
Chlorine Hyperfine Splittings and Spin Density Distributions of Phenoxy Radicals. An ESR. and Quantum Chemical Study
Authors: Graf Federico , Loth Klaus , Günthard Hans‐Heinrich 
Published: December 2004

AbstractESR. spectra of the chlorine substituted phenoxy radicals listed in Table 1, which were produced by photo‐oxidation of the parent phenols in aprotic solvents, are reported. In most cases the chlorine splittings could be resolved and analysed in detail. Experimental data as well as quantum chemical calculations were used for assignment of all measured chlorine couplings and determination of their relative signs.Spin density distributions and polarization parameters for chlorine are discussed and compared with the results from current semiempirical molecular orbital theories.Chlorine couplings, associated with the larger splittings are found positive in sign, whereas signs of small couplings appear difficult to establish. Limitations in the applicability of McConnell or Karplus‐Fraenkel type relations to chlorine substituted aromatic radicals will be discussed and related to peculiar properties of the spin density matrix of such systems.
The Structure of the Antibiotic Hedamycin. I. Chemical, Physical and Spectral Properties
Authors: Séquin Urs , Bedford Colin T. , Chung Sung K. , Scott A. Ian 
Published: December 2004

AbstractInterpretation of the chemical and spectral (IR., UV., 1H‐ and 13C‐NMR.) properties of the antitumor antibiotic hedamycin (C41H50N2O11) suggests that the molecule contains a methyl substituted 1‐hydroxyanthraquinone nucleus, an α, β‐unsaturated ketone, two sugar‐like tetrahydropyran rings (4 and 8) and an aliphatic chain 2, presumably with an epoxy group (see the Scheme).
Isolierung von (−)‐Dunnion aus Calceolaria integrifolia MURR. (Scrophulariaceae)
Authors: Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Isolation of (−)‐dunnione from the leaves of Calceolaria integrifolia, MURR. (fam. Scrophulariaceae)From the leaves of Calceolaria integrifolia, a plant often used in horticulture. partially racemic (−)‐dunnione (1) has been isolated. This seems to be the first record of its occurrence outside the family Gesneriaceae, where it previously has been found in two species as the (+)‐enantiomer.
13C‐NMR. Spectra, Structure and Reactivity of Cyclic Oxocarbons
Authors: Städeli Werner , Hollenstein Roger , Von Philipsborn Wolfgang 
Published: December 2004

AbstractThe structures of cyclic polyketones, their hydrates and reduction products were studied in different solvents by 13C‐NMR. spectroscopy. In dimethylsulfoxide solution rhodizonic acid (1), croconic acid (2) and squaric acid (3) exhibit signal averaging. In anhydrous tetrahydrofuran 1 and 2 could be observed as non‐dynamic species. The spontaneous reactions of dodecahydroxycyclohexane (5) and decahydroxycyclopentane (‘leuconic acid’) (6) and the sequence of formation of ring‐contracted products were investigated. Key intermediates could be clearly identified which support the mechanism proposed earlier involving a benzylic acid type rearrangement followed by decarboxylation and subsequent redox reactions.
Aktivierte Chinone: Substitution von Azulenen, Benzofuran und Indolen durch 2‐Methoxycarbonyl‐1,4‐benzochinon. Regiospezifische Synthesen von Polymethoxy‐fluorenonen und eine neue Synthese des 2,6‐Dihydro‐naphtho[1,2,3‐cd]indol‐6‐on‐Systems
Authors: Tsaklidis Joannis N. , Hofer Arnold , Eugster Conrad Hans 
Published: December 2004

Activated quinones: substitution reactions by methoxy‐carbonyl‐1,4‐benzoquinone of azulenes, benzofuran and indoles; regiospecific syntheses of polymethoxy‐fluorenones; a new synthesis of the 2,6‐dihydro‐naphtho[1,2,3‐cd]indol‐6‐one system.We present new electrophilic substitution reactions of azulenes and 5‐membered heterocyclics by methoxy‐carbonyl‐1,4‐benzoquinone. Hydroquinones 3a and 5 are prepared from azulene, and 3b from guaiazulene (see Scheme 1). Benzofuran undergoes α‐ and β‐substitution (hydroquinones 9 10) (see Scheme 2). Only β‐substitution is observed with indole (hydroquinone 20) (see Scheme 4). After methylation, saponification and intramolecular acylation of the substituted indoles 22c, 22d, derivatives of 2,6‐dihydro‐naphtho[1,2,3‐cd]indol‐6‐one have been obtained. Spectral data prove the presence of the methylidenequinone tautomer. By protonation or alkylation at the carbonyl group of 23, the violet, highly delocalized 16π‐electron systems 25 are generated. Analogously, polymethoxy‐fluorenones have been prepared from methoxylated diphenylquinones 15 (see Scheme 3). They also are transformed by protonation and alkylation to the highly coloured and delocalized 12 π‐electron systems 18. By contrast, anthracene is not substituted by methoxycarbonyl‐1,4‐benzoquinone, but undergoes cycloaddition to the triptycene derivative 1 (see Scheme 1). A summary is presented of previously described reactions of activated quinones.
Synthese von Fulvenen über 1‐Chloralkyl‐acetate
Authors: Neuenschwander Markus , Iseli Rudolf 
Published: December 2004

Synthesis of fulvenes via 1‐chloroaklyl‐acetatesThe synthesis of fulvenes (5) via l‐chloroalkyl acetates (3) is extended to 6‐alkyl‐fulvenes with branched side‐chains, to 6‐phenylfulvene (5f) and 6‐(2‐furyl)fulvene (5g), as well as to 6‐vinylfulvenes (5h and 5i) containing chlorine and acetoxy‐substituents in ω‐position. The reaction is carried out at low temperature under water‐free conditions. The purification of the reaction products is simple. ‐ An improved procedure for the preparation of pure fulvene (5a, R=R′=H) is reported.
Neues über den Mechanismus der retentiven Substitution am Dreiring von Propellanen. Vorläufige Mitteilung
Authors: Lindner Hans Jörg , Kitschke Brigitte , Liesner Michael , Seebach Dieter 
Published: December 2004

New results concerning the mechanism of retentive substitution at the three membered ring of propellanesThe reaction of the endo‐ and exo‐bromide 1a and 1b with acetate ion in aprotic polar solvents carried out at high concentrations of 1 furnishes the dimeric dehydro‐halogenation products 3a and 3b, the structures of which are determined by x‐ray crystallography (Fig. 1). The formation of 3a and 3b as well as of the products 2 of a retentive substitution process can be explained by assuming that the strained benzo‐tropones 4 are intermediates. Their high barrier to inversion is confirmed by π‐SCF‐molecular mechanics calculations.
(Z)‐5‐Tetradecen‐14‐olide, a New Macrocyclic Lactone, and Two Unsaturated Straight Chain Acetates from Ambrette Seed Absolute
Authors: Maurer Bruno , Grieder Alfred 
Published: December 2004

Abstract(Z)‐5‐Tetradecen‐14‐olide (1), (Z)‐5‐dodecenyl acetate (2), and (Z)‐5‐tetradecenyl acetate (3) have been isolated from the absolute oil of Hibiscus abelmoschus L. The lactone 1 is a new macrocyclic musk compound, and the occurrence of the two acetates 2 and 3 in a plant is reported for the first time. Syntheses of the three compounds are described.