bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über Pterinchemie 52. Mittelung [1] Eine eindeutige Synthese isomerenfreier Pteroyl‐γ‐L‐glutamyl‐γ‐L‐glutamyl‐L‐glutaminsäure
Authors: Sengupta Pradip K. , Bieri Jost H. , Viscontini Max 
Published: December 2004

AbstractA new and unequivocal synthesis of pteroyl‐γ‐L‐glutamyl‐γ‐L‐glutamyl‐L‐glutamic acid free of isomers is described. A melt of N(2′)‐acetyl‐6‐formylpterine and tetramethyl‐N‐(p‐amino‐benzoyl)‐γ‐L‐glutamyl‐γ‐L‐glutamyl‐L‐glutamatewas quantitatively converted to the corresponding azomethin IX. NaBH4‐reduction followed by basic hydrolysis of acetyl and methylester groups gives pure pteroyl‐γ‐L‐glutamyl‐γ‐L‐glutamyl‐L‐glutamic acid in good yield.
Wurtzitan (Tetracyclo[5.3.1.12,6.04,9]dodecan)
Authors: Tobler Hans , Klaus Rolf Otto , Ganter Camille 
Published: December 2004

AbstractA new synthesis of wurtzitane (13) is described starting from 2‐oxo‐protoadamant‐4‐ene (2). The key intermediate ketone 7 was obtained by regiospecific ring expansion of the β‐amino alcohol 6. Entry to the wurtzitane system involved solvolysis of the tricyclic unsaturated mesylate 10 (→11).
A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.) VII. Identification and synthesis of twelve irregular terpenoids, related to solanone, including 7,8‐dioxabicyclo[3.2.1]octane and 4,9‐dioxabicyclo[3.3.1]nonane derivatives
Authors: Demole Edouard , Demole Cécile 
Published: December 2004

AbstractTwelve novel constituents isolated from Burley tobacco condensate by semi‐preparative GLC. have been identified as (E)‐3,4‐epoxy‐5‐isopropyl‐nonane‐2,8‐dione (A), exo‐(1‐methyl‐4‐isopropyl‐7,8‐dioxabicyclo[3.2.1]oct‐6‐yl)methyl ketone (B), exo‐1‐(1‐methyl‐4‐isopropyl‐7,8‐dioxabicyclo[3.2.1]oct‐6‐yl)‐ethanol (C), (E)‐5‐isopropyl‐8‐hydroxy‐8‐methyl‐non‐6‐en‐2‐one (D), (E)‐5‐isopropyl‐6,7‐epoxy‐8‐hydroxy‐8‐methyl‐nonan‐2‐one (E), endo‐2‐(1‐methyl‐4‐isopropyl‐7,8‐dioxabicyclo[3.2.1]oct‐6‐yl)‐propan‐2‐ol (F), 3,3,5‐trimethyl‐8‐isopropyl‐4,9‐dioxabicyclo[3.3.1]nonan‐2‐ol (G), (E)‐5‐isopropyl‐non‐3‐ene‐2,8‐diol (H), 5‐isopropyl‐nonane‐2,8‐diol (I), (E)‐5‐isopropyl‐8‐hydroxy‐non‐6‐en‐2‐one (J), 5‐isopropyl‐8‐hydroxy‐nonan‐2‐one (K), and (E)‐3‐isopropyl‐6‐methyl‐hepta‐4,6‐dien‐1‐ol (L). Compounds A–K were synthesized from norsolanadione (2), and compound L from 2‐isopropyl‐5‐oxo‐hexanal (15). The relative configuration of the bicyclic internal acetals B, C, F, G and their δ‐keto‐epoxide precursors A and E is discussed. All these Burley tobacco flavour components belong to a growing family of metabolites structurally related to solanone (1). They are believed to arise from the breakdown of cembrene‐type precursors.
A 13C‐NMR. Study of Some Arsenic Complexes of Platinum(II) and Palladium(II)
Authors: Balimann G. , Pregosin P. S. 
Published: December 2004

AbstractThe 13C‐NMR. spectra of a series of tri‐n‐alkyl arsenic complexes of platinum and palladium have been measured. In these complexes it is suggested that the carbon chemical shift of the atom bound directly to the arsenic is a useful structural probe. The chemical shift of the second carbon atom in the chain is interpreted in terms of interactions within the chains of anyone ligand. The values 2J(Pt, C) and 3J(Pt, C) are presented.
Pyrimidine Derivatives and Related Compounds II: Synthesis of some derivatives of pyrimido[1,2:2′,3′]pyrazolo[1,5‐a]pyrimidines, a new ring system
Authors: Elnagdi Mohamed Helmi , Sallam Mohamed Mohamed Mohamed , Ilias Mohamed Ajmal Mohamed 
Published: December 2004

Abstract3,5‐Diamino‐4‐phenylazo‐pyrazoles (1a–1c) react with acetylacetone and with ethyl acetoacetate to yield the corresponding pyrazolo[1,5‐a]pyrimidine derivatives 2a–2c and 3a–3c, respectively.Whereas 1a–1c add readily to methyl acrylate yielding the 4,5,6,7‐tetrahydropyrazolo[1,5‐a]‐pyrimidine derivatives 5a–5c, 1a–1c add to methylacrylonitrile or methyl methacrylate only under drastic conditions to yield 5d–5f. The pyrimido[1,2:2′,3′]pyrazolo[1,5‐a]pyrimidine derivatives 10a–10c are prepared by the action of acrylonitrile on 2a–2c. Compounds 10a–10c are readily converted into the corresponding oxo derivatives 12a–12c on treatment with acetic acid‐hydrochloric acid mixture.
Intramolekulare Cycloadditionen in der Reihe der Binaphthyle
Authors: Nakamura Yushin , Hollenstein Roger , Zsindely Janos , Schmid Hans , Oberhänsli Willi E. 
Published: December 2004

Intramolecular cyloadditions of binaphtyl compoundsThree new bridged ketones, 7,8 and 9, have been isolated in 44%, 3% and 19% yields respectively (Scheme 2) by heating 2,2′‐bis‐allyloxy‐1,1′‐binaphthyl (5) at 215° for 16 hours. These compounds could be epimerized about C(16) by bases, and in particular 9 yielded the new epimer 10. The structures of the alcohols obtained by reduction of the keto group are also given (Scheme 2). The constitution of all compounds was derived from spectroscopic data, chiefly from their 1H‐NMR, spectra (tab. 2, 3 and fig. 1). The assignments were based on the observed long‐range coupling constant between H(endo)‐C(16) and H(endo)‐C(5) in 7 and 10 and on the analysis of chemical shifts and coupling constants in both the ketones and their derivatives. Moreover, the structures of the compounds investigated have been proved by x‐ray analysis of ketone 8 (chap. 3, fig. 2). The thermal conversion of binaphthylether 5 to the bridged ketones proceeds via an intramolecular Diels‐Alder reaction, followed by Claisen rearrangement (Scheme 8). On heating, the bis‐beta‐methylallyl ether 20 yielded the ketone 21 and a small amount of the ether 23 (Schemes 5 and 7). Ether 23 and binaphthyl monoallyl ether 26 were converted thermally to the bridged ketones 31 (Scheme 7) and 27 (Scheme 6) respectively. In addition, 26 underwent an intramolecular ene‐reaction to give the spiroketone 28 (Schemes 6 and 9). The structures of these compounds were also established, mainly by analysis of their 1H‐NMR. spectra.
Preparation of Mikanecic Ester and its precursor, 1,3‐butadiene‐2‐carboxylic ester
Authors: Sydnes L. K. , Skattebøl L. , Chapleo Christopher B. , Leppard David G. , Svanholt Karen L. , Dreiding André S. 
Published: December 2004

AbstractEine thermische (a) und eine reduktive (b) Methode zur Herstellung von Mikanez‐Estern wird beschrieben. Bei der ersten gelang der Nachweis des monomeren Vorläufers, 1,3‐Butadien‐2‐carboxylester.

trans/cis‐Gemische von Methyl resp. Äthyl 2‐Brom‐1‐methylcyclopropancarboxylat (14/15 resp. 16/17), mit Tri‐n‐butylzinnhydrid aus den entsprechenden 2,2‐Dibrom‐1‐methylcyclopropancarboxylaten 12 resp. 13 hergestellt, wurden bei 480°/1,7 Torr pyrolysiert. Die bei −78° daraus abgefangenen Kondensate bestanden aus den 1,3‐Butadien‐2‐carboxylaten 5 und 6, im Falle des Äthylesters 6 durch seine 1H‐NMR.‐Signale charakterisiert und als Addukt (19) mit 4‐Phenyl‐1,2,4‐triazolin‐3,5‐dion (18) abgefangen (55%). Beim Erwärmen der Kondensate dimerisierten die Dienester 5 resp. 6, so dass sich Dimethyl resp. Diäthyl Mikanezat (9 resp. 10) isolieren liess (67 resp. 100%).
Behandlung von Methyl 2(E)‐2‐Methyl‐2‐butenoat (20) mit 2 Äquivalenten N‐Bromsuccinimid gab (25%) Methyl 2(Z)‐4‐Brom‐2‐brommethyl‐2‐butenoat (21). (Mit 3 Äquivalenten entstand ein Stereomerengemisch 2(Z)‐ und 2(E)‐4,4‐Dibrom‐2‐brommethyl‐2‐butenoat (22 und 23)). Reduktion des Dibromesters 21 mit Zink in Tetrahydrofuran, Methanol oder Eisessig ergab (50%) Dimethyl Mikanezat (9). Von einer Iodolaktonisierung der aus 9 durch Verseifung hergestellten Mikanezsäure (8) erhielt man 4‐Iodo‐7‐oxo‐1‐vinyl‐6‐oxabicyclo[3.2.1]octan‐4endo‐carbonsäure (24), dessen Bildungsleichtigkeit und IR.‐Bande bei 1780 cm eine unabhängige Bestätigung dafür liefert, dass Mikanezsäure (8) durch Kopf‐zu‐Kopf‐Diels‐Alder‐Dimerisierung von 1,3‐Butadien‐2‐carbonsäure (4) entsteht.Aus Methyl (E)‐2‐Methyl‐2‐pentenoat (25) wurde auf gleiche Weise, d.h. über Dibromierung zu 27 und Reduktion mit Zink in Äther, Dimethyl 3,2′‐Dimethylmikanezat (29) gewonnen. Die Multiplizität des 1H‐NMR.‐Signals von HC(3) in 29 bestätigt, wiederum unabhängig, dass die Dimerisierung des Dienesters (in diesem Fall 28) in Kopf‐zu‐Kopf‐Diels‐Alder‐Weise stattfindet.
Chemical Selectivities Disguised by Mass Diffusion. II. Mixing‐disguised nitrations of aromatic compounds with nitronium salts, . 2nd communication on the selectivity of chemical processes
Authors: Pfister Friedrich , Rys Paul , Zollinger Heinrich 
Published: December 2004

AbstractThe results of this study show that three parameters are sufficient to describe the selectivity behaviour of nitrations influenced by mixing as long as a fast combination of the reactant solutions takes place and fast agitation is employed. This is in full agreement with the prediction of the mixing‐reaction model developed previously [1]. Furthermore, the results show clearly that in nitromethane the formation rate of nitronium ions from nitric acid is slower than the mixing rate and the rate of the electrophilic substitution proper. From the mixing‐disguised selectivity curves for the nitrations of durene and prehnitene with nitronium hexafluorophosphate in nitromethane the ratio of the rate constants k2 for the second nitrations can be estimated to be 1:2. For the two aromatic compounds the k1/k2 ratios are ≥ 104. Finally it could also be shown that small impurities in the solvent (e.g. water) can influence strongly the selectivity curves, depending on the method used for mixing.
Orbital Correspondence Analysis in Maximum Symmetry
Authors: Halevi Emil Amitai 
Published: December 2004

AbstractA method is described in which the ‘allowed’ course of a reaction is determined by means of an analysis – within the symmetry point group common to reactants and products – of their molecular orbitals and of the distortions that occur along the reaction path connecting them. The procedure, and its relation to and advantages over conventional correlation methods, is illustrated with a few very well known reactions: Cyclization of hexatriene, the ‘photochemical Diels‐Alder reaction’ and the stepwise and concerted [2+2]‐cycloadditions.
Photochemische Reaktionen. 82. Mitteilung. Zur Photochemie der α,β‐Epoxylketone: γ‐Wasserstoffabstraktion versus Epoxyketon‐Umlagerung
Authors: Müller Ernst Peter , Jeger Oskar 
Published: December 2004

AbstractPhotochemistry of α,β‐epoxyketones: γ‐H‐abstraction versus epoxyketone‐rearrangement.The photochemical behaviour of conformationally mobile α,β‐epoxyketones that could undergo competing reactions has been studied. The UV.‐irradiation of 5 yields the stereoisomeric cyclobutanols 9 and 10 as well as the fragmentation product 11. Irradiation of 6 gives only the cyclobutanols 12 and 13, whereas 4 and 8 in inert solvents yielded only intractable gums. The non‐occurrence of the typical isomerization of α,β‐epoxylketones to the corresponding β‐diketones is attributed to steric factors.
Zur Reaktivität von π‐(η5‐)‐Cyclopentadienyl‐palladium‐σ‐(η1‐)‐allyl‐ und π‐(η5‐)‐Cyclopentadienyl‐palladium‐halogenid‐Komplexen; neue ortho‐Metallierungsreaktionen von Tri‐o‐tolylphosphit,
Authors: Tune David John , Werner Helmut 
Published: December 2004

One the Reactivity of π‐(η5‐)‐Cyclopentadienylpalladium‐δ‐(η1‐)‐allyl‐ and π‐(η5‐)‐Cyclopentadienylpalladiumhalide Complexes; New ortho‐Metallation Reactions of Trio‐o‐tolylphosphitTeil des Hauptvortrages von H. W. an der Jahrestagung der Chemical Society, York (U.K.), 7.‐11.4.1975.

20.Mitt. der Reihe «Untersuchungen zur Reaktivität von Metall‐π‐Komplexen»; 19.Mitteilung siehe [1].
(η5‐C5H5)Pd(η3‐2‐ClC3H4) reacts with Lewis bases L[PPh3, P(OPh)3, P(O‐p‐Tol)3, P(O‐o‐Tol)3, CO] in a 1:1 molar ratio to give the η1‐2‐chloroallyl complexes 2a–2e. (η5‐C5H5)‐Pd(η1‐2‐ClC3H4)P(O‐o‐Tol)3 (2d) which is stable at room temperature has been isolated as a red oil. It represents the first well‐characterized η1‐allylpalladium derivative.2a–2d eliminate allene to form (η5‐C5H5)PdClL (5a–5d). The tri‐o‐tolylphosphite complex 5d reacts with NaI to give (η5‐C5H5)PdIP(O‐o‐Tol)3 (6) and on Al2O3 to give (η5‐C5H5)Pd[P(OC6H3‐o‐Me)(OC6H4‐o‐Me)2] (7). Elimination of HCl leading to ortho‐metallation of one of the six‐membered rings of tri‐o‐tolylphosphite also occurs in the reaction of PdCl42− and P(O‐o‐Tol)3 to form Pd2Cl2[P(OC6H3‐o‐Me)(OC6 H4‐o‐Me)2]2 (9). This reacts with TlC5H5 to give 7. The preparation of Pd2Cl4[P(O‐o‐Tol)3]2 (8) and Pd2I2[P(OC6H3‐o‐Me)(OC6H4‐o‐Me)2]2 (10) is also reported.
Über die Hydrierung α‐cyanoäthylierter Aldimine
Authors: Zondler Helmut , Pfleiderer Wolfgang 
Published: December 2004

The catalytic hydrogenation of α‐mono‐ and bis‐cyanoethylated aldiminesThe catalytic hydrogenation of α‐mono‐ and ‐bis‐cyanoethylated aldimines using nickel catalysts was studied. Piperidine derivatives are formed in intramolecular cyclization reactions. The hydrogenation products of α‐bis‐cyanoethylated ketones, the decahydro‐1, 8‐naphthyridines, are observed here only as by‐products.
Electron Transfer Spectra of Some Adducts of Niobium (V), Tantalum (V), Titanium (IV) and Zirconium (IV) Halides with Lewis Bases
Authors: Valloton Mario , Merbach André E. 
Published: December 2004

AbstractThe electron transfer spectra of adducts of the title metal halides with a series of ligands (nitriles, dialkylchalcogenides, phosphoryl and thiophosphoryl ligands and phosphines) have been studied. The effect of halogen substitution on the halogen metal transitions is discussed by comparing the spectra of the adducts with those of the hexahalometalates. The origin of the two ligand‐metal transitions observed in most adducts is discussed, and the splitting of the metal d levels in these almost octahedral adducts is estimated. For each metal halide, the series of adducts with dialkyl chalcogenides show a linear relationship of slope one between the ligand ionisation potential and the ligand‐metal charge transfer energy. The ligand optical electronegativities have been estimated.
Über Enolderivate der Chlorophyllreihe. Darstellung von 132,173‐Cyclophäophorbid‐enolen. Vorläufige Mitteilung
Authors: Falk Heinz , Hoornaert Georges , Isenring Hans‐Peter , Eschenmoser Albert 
Published: December 2004

Enol derivatives in the chlorophyll series. Preparation of 132,173‐cyclopheophorbide enols132,173‐Cyclopheophorbide enols have been prepared as model systems for studying the effect of ring E enolization upon the properties of chlorophyll derivatives.
Über enolisierte Derivate der Chlorophyllreihe. 132‐Desmethoxycarbonyl‐173‐desoxy‐132,173‐cyclochlorophyllid a‐enol und eine Methode zur Einführung von Magnesium in porphinoide Ligandsysteme unter milden Bedingungen. (Vorläufige Mitteilung)
Authors: Isenring Hans‐Peter , Zass Engelbert , Smith Keith , Falk Heinz , Luisier Jean‐Luc , Eschenmoser Albert 
Published: December 2004

Enol derivatives in the chlorophyll series. 132‐Desmethoxycarbonyl‐173‐desoxy‐132,173‐cyclochlorophyllide a‐enol and a method for the introduction of magnesium into porphinoid ligands under mild conditionsMagnesium transfer from the iodo‐magnesium salt of 3,5‐di‐t‐butyl‐4‐hydroxy‐toluene (BHT) into methyl pheophorbide a is a fast process in methylenechloride/ether solution at ambient temperature. This procedure for the introduction of magnesium into labile chlorin ligands has made possible the preparation of a crystalline 132, 173‐cyclochlorophyllide a‐enol. Concomitant use of the lithium salt of BHT facilitates the more critical insertion of magnesium into methyl bacteriopheophorbide a. The preparative success of these magnesium transfers depends crucially upon the solvent system used. Under conditions where the complexation of methyl pheophorbide a with iodo‐magnesium‐BHT is essentially complete within 2 minutes at 12° in methylenechloride/ether solution, strong inhibition of the magnesium transfer is observed by cosolvents such as pyridine, dimethylacetamide, dioxan or tetrahydrofuran.
Neue β‐Lactam‐Antibiotika. Cephem‐Derivate mit elektronenanziehenden Substituenten in 3‐Stellung. Modifikationen von Antibiotika. 14. Mitteilung
Authors: Peter Heinrich , Müller Beat , Bickel Hans 
Published: December 2004

New β‐lactam antibiotics. Cephem derivatives with electron withdrawing substituents at position 3Oxidation of the 3‐formyl‐2‐cephem compound 1 according to Corey [6] gave 2‐cephem‐3‐carboxylic esters 4a, b, c (Scheme 1), which proved to be useful intermediates for the synthesis of cephalosporins bearing in position 3 a methoxycarbonyl group (10a, b, c, d / Scheme 2) or a carboxy group (20, 25, 30/Schemes 3, 4). The 3‐formyl‐3‐cephem compounds 31a, b could be transformed into cyano‐ (33a) or methoxyiminomethyl‐ (36a, c, d) cephems (Scheme 5), which represent further examples of cephalosporins with electron withdrawing groups in position 3.
Zur Rolle des Paliclavins in der Biosynthese der Ergot‐Alkaloide. 81. Mitteilung über Mutterkornalkaloide
Authors: Acklin Werner , Fehr Theo , Stadler Paul Albert 
Published: December 2004

The Rǒle of Paliclavine in the Biosynthesis of Ergot AlkaloidsFeeding of [N‐14CH3]‐paliclavine to submersed cultures of Claviceps paspali Stevens et Hall and to surface cultures of the ergot fungus from Pennisetum typhoideum Rich. has shown that paliclavine is not involved in the biosynthesis of either the ergolene carboxylic acids or the tri‐ and tetra‐cyclic clavines.
Ringschlüsse an Chinonylmethanfarbstoffen und analogen Merocyaninen. 3. Mitteilung. Chinoide Derivate des anellierten Tetrahydro‐isochinolino‐chinoxalins. Ringschluss nach 1,7‐Verschiebung von Wasserstoff?
Authors: Schelz Dieter , Priester Martin 
Published: December 2004

Cyclization Reactions of Quinonylmethane Dyes and Analogous Merocyanines. 3. Communication. Quinoid Derivatives of the Anellated Tetrahydro‐quinoxalino‐quinoxaline. Cyclization Following 1,7‐Hydrogene‐Shift?The title compounds were obtained by proton catalyzed cyclization of the corresponding 2‐(1‐alkyl‐3‐methyl‐1,2‐dihydroquinoxalin‐2‐ylidenmethyl)‐1,4‐naphtho‐ and 1,4‐anthraquinones. The visible and 1H‐NMR.‐ and some mass spectra of the dyes are given. Mechanistic aspects of the new‐type cyclization reaction are discussed.
Photochemical Reactions. IV. [1] Irradiation of 17 β‐acetoxy‐4‐aza‐androst‐5‐en‐3‐one with UV.‐light
Authors: Boix José , Gómez José , Bonet Juan‐Julio 
Published: December 2004

AbstractThe photochemical behaviour of the title compound (7) is described. The obtained results indicate the high reactivity of the enamidic Δ5 double bond.
Fluororganische Synthesen IV, 1‐Fluor‐1‐organyl‐cyclopropane und andere Cyclopropan‐Derivate durch Anlagerungsreaktion von «Nachfolge‐Carbenen»
Authors: Schlosser Manfred , Van Chau Le , Spahić Bojana 
Published: December 2004

Fluoroorganic Syntheses IV: 1‐Fluoro‐1‐organyl‐cyclopropanes and other Cyclopropane Derivatives by Addition of „Successor‐Carbenes”︁Treatment of chlorodifluormethane or dichlorodifluoromethane with methyllithium in the presence of an olefin affords 1‐fluoro‐1‐methylcyclopropanes in fair yields. Depending on the particular reaction conditions, 1,1‐difluorocyclopropanes, 1,1‐dimethylcyclopropanes and 1‐chloro‐1‐methylcyclopropanes may be obtained as well. Butyllithium and phenyllithium give rise to analogous products.
Réactions d'addition‐élimination à partir d'hétérocycles germaniés du type I. Cas des dioxolannes germaniés
Authors: Dousse Gabriel , Lavayssière Hélène , Satgé Jacques 
Published: December 2004

Addition‐elimination reactions from germanium heterocycles I. Germadioxolanes (XYO)The reactivity of 2‐germa‐1,3‐dioxolanes is studied with unsaturated compounds such as carbonyl compounds (aldehydes and ketones) or heterocumulenes (PhNCO, PhNCS). The formation of mono‐ and di‐insertion derivatives is observed. The structure of these adducts is established and their decomposition process, at atmospheric pressure or at high pressure, is precised.The mechanism of these addition‐elimination reactions is established from 4,5‐disubstitued germadioxolanes. The reaction takes place under steric control. The consecutive elimination reaction proceeds by a mechanism of intramolecular nucleophilic substitution.
The consequences of σ and π conjugative interactions in mono‐, di‐ and triacetylenes. A photoelectron spectroscopic investigation
Authors: Brogli Franz , Heilbronner Edgar , Wirz Jakob , Kloster‐Jensen Else , Bergman Robert G. , Vollhardt K. Peter C. , Ashe Arthur J. 
Published: December 2004

AbstractThe HeI photoelectron spectra of mono‐, di‐, and triacetylenes are presented. In these compounds the two‐centre π‐orbitals of the ethynyl groups conjugate with the π‐orbitals of double bonds or benzene moieties, or with the Walsh orbitals of three‐membered ring systems. Assuming the validity of Koopmans' approximation, the observed energies of the radical cation states reached by electron ejection from π‐orbitals can be rationalized in terms of a simple LCBO‐MO model in those cases, where the molecule is planar. The corresponding numerical results for the ionization energies are in excellent agreement with experiment, if the three parameters of the model are properly calibrated. In contrast, the bands assigned to ejection from in plane π‐orbitals are shifted to lower energies by ca. 0.5 eV with respect to the expectation values derived from the above model, due to ‘through‐bond’ interaction with lower lying σ‐orbitals.Extensive σ/π mixing occurs in the non planar compounds for all orbitals. The assignments of the spectra of diethynylmethane, 1,4‐hexadiyne, 1,2‐diethynylethane and of cis‐ and trans‐diethynylcyclopropane are backed by semiempirical SCF calculations. The spectra of the cis and trans isomers of diethynylethyleneoxide and diethynylethylenesulfide are discussed by comparison with the corresponding hydrocarbons and with oxirane and thiirane respectively.Finally, the following topics are considered in detail: (a) The effect of spin orbit coupling on the spectrum of 1‐iodo‐1‐butyne‐3‐ene; (b) the effect of the essentially free internal rotation in divinylacetylene on the band shapes of its photoelectron spectrum and (c) the relationship between the conjugative properties of ethylenic π‐orbitals and of the Walsh‐orbitals of cyclopropane.
Synthesis of Bromo‐substituted 2‐Buten‐ and 2‐Penten‐4‐olides
Authors: Chapleo Christopher B. , Svanholt Karen L. , Martin Roger , Dreiding André S. 
Published: December 2004

Durch Erhitzen mit Bromwasserstoffsäure lassen sich aus Methyl (2Z)‐4‐Brom‐2‐brommethyl‐2‐butenoat (1) bzw. ‐2‐pentenoat (3) die Lactone 2‐Brommethyl‐2‐buten‐4‐olid (2) bzw. ‐2‐penten‐4‐olid (4) gewinnen. Unter den gleichen Bedingungen werden Methyl (2Z)‐und (2E)‐4, 4‐Dibrom‐2‐brommethyl‐2‐butenoat (5 und 6) nur zu den entsprechenden Säuren 7 und 8 hydrolysiert. Die (2Z)‐ resp. (2E)‐Konfiguration von 7 und 8 werden durch die folgenden (trans/cis > 1) 13C zu 1H Kopplungen zwischen den an der Doppelbindung vicinal gelegenen Kohlenstoff‐ und Wasserstoffatomen im 13C‐NMR.‐Spektrum bestätigt: 13COO zu H—C(3) 5,7 Hz in 7 und 10,2 Hz in 8; 13CH2Br zu H—C(3) 8,7 Hz in 7 und 6,9 Hz in 8.Mittels N‐Bromsuccinimid werden 2‐Buten‐4‐olid (10) bzw. sein 2‐Methylderivat 12 in 4‐Brom‐2‐buten‐4‐olid (11) bzw. sein 2‐Methylderivat 13 übergeführt. Mit Methanol entsteht aus 13 4‐Methoxy‐2‐methyl‐2‐buten‐4‐olid (14). Die Bromierung von 2‐Penten‐4‐olid (15) oder von 3‐Penten‐4‐olid (16) unter denselben Bedingungen gibt hingegen 4,5‐Dibrom‐2‐penten‐4‐olid (17), während aus 2‐Brommethyl‐2‐penten‐4‐olid (4) ein Gemisch von 4‐Brom‐2‐brom‐methyl‐2‐penten‐4‐olid (20) und 4,5‐Dibrom‐2‐brommethyl‐2‐penten‐4‐olid (21) entsteht.
Halogenierte Pyridine III. Di‐ und trihalogenierte Pyridin‐3‐aldehyde
Authors: Horn Ulrich , Mutterer Francis , Weis Claus D. 
Published: December 2004

Halogenated pyridines III. Di‐ and trihalogenated pyridine‐3‐aldehydes.Three methods for the preparation of new ring chlorinated pyridine‐3‐aldehydes are investigated. Reactions of the new aldehydes are reported.