bluuebunny/crossref_metadata_2025 huggingface dataset:
Participation of Non‐Conjugated Double Bonds in Diels‐Alder Reactions. A kinetic study of the addition of tropone to norbornens
Authors: Pfaendler H. R. , Tanida Hiroshi , Haselbach Edwin
Published: December 2004

A kinetic study of Diels‐Alder additions between norbornene derivatives acting as dienophiles and the dienes tropone, perchlorocyclopentadiene and 9,10‐dimethylanthracene is presented. The results suggest that tropone thereby acts as an electron acceptor, classifying these reactions then as Diels‐Alder additions with ‘inverse electron demand’.

The role of non‐reacting double bonds was investigated using 7‐alkylidenorbornene derivatives as dienophiles. These show comparable reactivity in ‘normal’ but enhanced reactivity in ‘inverse electron demand’ Diels‐Alder additions. This outcome is interpreted in terms of frontier orbital interactions between the reactants using photoelectron spectroscopical results as a basis for the qualitative perturbation treatment. It is suggested that the enhanced reactivity in the case of the 7‐alkylidene derivatives does not necessitate the consideration of a direct (‘through‐space’) participation of the non‐reacting double bond.
Synthese des (±)‐Oncinotins
Authors: Schneider Fernand , Bernauer Karl , Guggisberg Armin , Van DenBroek Peter , Hesse Manfred , Schmid Hans
Published: December 2004

(±)‐Oncinotin (19) is synthesized through the crucial intermediates 11 and 15. By comparison of the synthetic product with natural (−)‐oncinotin, it is found that the latter contains an isomeric substance, represented by structure 20.
Nachbargruppeneffekte bei der massenspektrometrischen Fragmentierung: N‐Acetyl‐ω‐Phenylalkylamine. 20. Mitteilung über das massenspektrometrische verhalten von stickstoffverbindung
Authors: Wild René , Hesse Manfred
Published: December 2004

The mass spectral behaviour of the difunctional alkane N‐acetyl‐4‐phenyl‐butylamine (3) was investigated. The main fragmentation of compound 3 is caused by the interaction on the two functional groups, which could be shown by comparison of the corresponding monofunctional compounds n‐butylbenzene (4) and N‐acetyl‐n‐butylamine (5). On the bases of high resolution data, the analyses of metastable transitions and the comparison of the spectra of some homologs and deuterated analogs of 3 the structures and their genesis of the main fragment ions were deducted.
Stereoelectronic Properties of Tetrahedral Species derived from Carbonyl Groups. Ab initio study of the hydroxymethanes
Authors: Lehn Jean‐Marie , Wipff Georges , Bürgi Hans‐Beat
Published: December 2004

Analysis of the electronic structure of the hydroxymethanes provides a consistent picture of stereoelectronic effects in such molecules: The average CO bond length decreases in the series methanol, methanediol, methanetriol. An oxygen (O′) lone pair, which is trans‐anti‐periplanar (app) to another oxygen (O″), shortens and strengthens the CO′ bond and simultaneously lengthens and weakens the CO′ bond. This is consistent with solid state structural evidence and with the reactivity patterns of tetrahedral species resulting from nucleophilic addition to a carbonyl group.
Thermodynamique des mélanges liquides binaires. Volume de mélange et nombre moyen de configurations gauches des alcanes
Authors: Steiger M. , Boissonnas C. H. G. , Fernández‐García J. G. , Stoeckli H. F.
Published: December 2004

It is shown that there exists a fair correlation between the average number of ‘gauche’ conformations of normal and branched alkanes, and their volumes of mixing.
The structure of Arteannuin B and its Acid Hydrolysis Product
Authors: Leppard David G. , Rey Max , Dreiding André S. , Grieb Rita
Published: December 2004

Die Struktur des Sesquiterpen‐γ‐Laktons Arteannuin B (1) wurde röntgenographisch und diejenige seines Hydrolyseproduktes (2) durch eine vollständige Analyse des NMR.‐Spektrums ermittelt.
Polimeri vinilici otticamente attivi XXI. Determinazione del tipo e del grado di stereoregolarità in alcuni polivinilchetoni
Authors: Allio A. , Pino P.
Published: December 2004

Using NMR. spectroscopy it has been shown that the stereoregularity in the polyvinylketones prepared with Zn(i‐C4H9)2 or LiAlH4 as initiator is of the isotactic type. A surprisingly high stereoregularity (% isotactic diads > 95) has been observed not only in polymethylvinylketone but also in poly[(S)‐1‐methyl‐propyl]vinylketone.
Die Kristallstruktur eines Sulfatkomplexes mit Cyanguanidin und Lupetidin
Authors: Weber H. P.
Published: December 2004

The crystal structure of a complex prepared from sulfuric acid, cyanoguanidin and lupetidin has been determined by X‐ray analysis and refined to R = 0.053. It consists of a sulfate ion, multiply hydrogen bonded to two protonated molecules of lupetidin and a neutral molecule of cyanoguanidin.
The Crystal Structure of the NaNCS Complex of Nonactin
Authors: Dobler Max , Phizackerley Richard Paul
Published: December 2004

The NaNCS complex of the macrotetrolide antibiotic nonactin, which acts as an ionophore with biological and artificial membranes crystallizes in the space group C2/c, a = 15.55, b = 19.59, c = 15.31 Å, β = 90°. The X‐ray crystal structure investigation shows that Na+ is coordinated by four carbonyl oxygen atoms (Na+ … O, 2.42 Å) and four ether oxygen atoms (Na+ … O, 2.77 Å). The cubic coordination by eight equidistant oxygen atoms observed in the K+ complex (K+ … O, 2.81 Å) is thus deformed. This, however, requires only very small changes in the ligand conformation.
Synthesis of Somatostatin. Preliminary communication
Authors: Immer Hans U. , Sestanj Kazimir , Nelson Verner R. , Götz Manfred
Published: December 2004

A tetradecapeptide with the proposed structure of growth hormone release inhibiting factor was synthesized by a classical fragment approach.
Thermische Umlagerung von (trans‐2,3‐Diphenylcyclopropyl)‐dipyrrolidino‐methan. vorläufige Mitteilung
Authors: Huber Martin K. , Dreiding André S.
Published: December 2004

Thermal rearrangement of (trans‐2,3‐diphenylcyclopropyl)‐dipyrrolidino‐methane under different conditions leads to mixtures which, after mildly acid work up, yield 2‐benzylidene‐1‐pyrrolidino‐indane (3) and 2‐benzyl‐indan‐1‐one (4) in strongly varying proportions. Under one of these conditions 4 is obtained from 3.
Vitamin D3 Metabolites I. Synthesis of 25‐hydroxycholesterol
Authors: Partridge John J. , Faber Stephanie , Uskoković Milan R.
Published: December 2004

25‐Hydroxycholesterin (4) ist in 30proz. Ausbeute in sieben Schritten aus Stigmasterin (6) hergestellt worden. Der wichtigste Schritt ist die Umsetzung des Tosylats 11 mit dem Acetylenderivat 13 zu 14 unter Bildung des vollständigen Cholesteringerüsts.
Vitamin D3 Metabolites III. Synthesis and X‐ray analysis of 1α, 25‐dihydroxycholesterol
Authors: Narwid Thomas A. , Blount John F. , Iacobelli Jerome A. , Uskoković Milan R.
Published: December 2004

Die Synthese von 1α, 25‐Dihydroxycholesterin (1) aus 3‐O‐Acetyl‐25‐hydroxy‐cholesterin (2) in 18proz. Gesamtausbeute wird beschrieben. Die Struktur von 1 wurde durch Röntgen‐Strahlendiffraktion bewiesen.
Welkstoffe und Antibiotika. 41. Mitteilung [1]. 2,4‐Dimethoxy‐8‐hydroxy‐, 2,4‐dimethoxy‐7‐hydroxy‐ und 1,3,4‐Trimethoxy‐6‐hydroxy‐9‐methyl‐phenanthren
Authors: Egli Christian , Seres Josef , Steiner Kurt , Helali Salah E. , Hardegger Emil
Published: December 2004

Aus den Tetralonen I und XIII wurden auf zwei verschiedenen Wegen die Phenanthrene VIII bzw. VIIIb und XVI hergestellt. Versuche zur Synthese von Orchinol (2,4‐Dimethoxy‐7‐hydroxy‐9,10‐dihydrophenanthren) scheiterten in der partiellen Dehydrierung der tricyclischen Ketone X und XI und führten unter vollständiger Aromatisierung zum Dehydroorchinol (XII).
The double bamford‐stevens Reaction with Tricyclo [5.1.0.03,5] octane‐2,6‐dione (Bis‐homo‐p‐quinone). Synthesis and Reactions of 4,5‐Dihydro‐4,5‐methano‐1,7‐diaza‐7aH‐indene (4,5‐Homo‐1,7a‐diaza‐indene)
Authors: Chapleo Christopher B. , Dreiding André S.
Published: December 2004

Alkalische Zersetzung der bis‐p‐Toluol‐sulfonylhydrazone 3 und 4 von sowohl anti‐ (1) wie auch syn‐Bis‐homo‐p‐chinon (2) ergab 4,5‐Homo‐1,7‐diaza‐inden (5). Das Produkt hat Eigenschaften eines Pyrazols und eines Olefins. Durch katalytische Reduktion entstand 6,7‐Dihydro‐4,5‐homo‐1,7‐diaza‐inden (12) und bei der Bromierung in Äthanol 3,6α‐Dibrom‐7β‐äthoxy‐4,5‐homo‐1,7a‐diaza‐inden (11). Spektroskopische Daten gaben Aufschluss über die Konstitutionen von 5, 11 und 12, über die bevorzugte Konformation von 11 und 12, und über die Konfiguration von 11.

Die Umwandlung von 3 oder 4 zu 5 beinhaltet eine weitgehende Umlagerung des Ringskeletts, welche möglicherweise über das Diazo‐carben 15 mit nachfolgender Fragmentierung des Cyclopropanringes zu einem Acetylen‐olefin, anschliessender Cyclisierung zu einem Pyrazolring und schliesslich intramolekularer Anlagerung eines Pyrazolstickstoffatoms an die Dreifachbindung verläuft.
Antibiotic X‐5108. VII. Absolute stereochemistry of 8‐amino‐3‐methoxy‐2,4‐dimethyl‐4,6‐octadienal, a compound derived from antibiotic X‐5108 and mocimycin [1]
Authors: Maehr Hubert , Blount John F. , Leach Michael , Stempel Arthur
Published: December 2004

6‐Bromo‐4‐fluoro‐1,3‐dinitrobenzol ist ein wertvolles Reagens zur Herstellung kristalliner Derivate von Aminen, Phenolen und Alkoholen. Die resultierenden 5‐Bromo‐2,4‐dinitrophenylverbindungen können zur Charakterisierung und Kristallstrukturanalyse durch Röntgendiffraktion dienen.

Aus den Antibiotika X‐5108 und Mocimycin haben wir kürzlich ein neuartiges Octadienal isoliert, das mit 6‐Bromo‐4‐fluoro‐l,3‐dinitrobenzol reagiert und in das Dimethylacetal umgesetzt wurde. Das resultierende Derivat wurde auf kristallanalytischem Wege als 8‐(5‐Bromo‐2,4‐dinitroanilino)‐3(S)‐methoxy‐2(R),4‐dimethyl‐4(trans),6(trans)‐octadienal‐dimethylacetal identifiziert.
Synthesis of [1, 6‐α, α′‐Diaminosuberic acid]oxytocin (‘Dicarba‐oxytocin’)
Authors: Keller Oskar , Rudinger Josef
Published: December 2004

Starting from a selectively protected derivative of α,α′‐diaminosuberic acid (3) the linear protected peptide 11 has been obtained. Cyclisation to 12 followed by removal of the protecting groups by hydrogenolysis afforded the ‘dicarba’ analogue of oxytocin, 1 c, which showed about 5 IU/μmol of uterotonic activity in vitro.
Primary Photophysical and Photochemical Processes in the Photoreduction of a Naphthoquinone methide: 2‐phenylnaphtho[1, 8‐bc]furan‐5‐one
Authors: Wirz Jakob
Published: December 2004

The photochemical reactivity of the title compound 3 was studied in the context of a novel acid catalysed photocyclisation reaction recently discovered by Barton et al. [1b]. The following results were obtained by flash photolysis methods and steady state irradiations in the presence and absence of quenchers and sensitisers combined with luminescence measurements: The fluorescence of 3 in benzene is very weak and short‐lived (ϕF1 ≤ 10−4, τF1 ≤ 10−9 s) due to efficient intersystem crossing (ϕT = 0.8 ± 0.15). On the other hand, the conjugate acid 4 exhibits an intense green fluorescence (ϕF1 = 0.97 ± 0.1) with a lifetime of (4. ± 1.) · 10−9 s. Acidity constants of 4 in the ground and first excited triplet state were estimated in acetic/trifluoroacetic acid mixtures by comparison with Hammett indicators: pK(S0) = −0.3, pK(T1) = +1.

The Förster cycle yields pK(S1) = +6, however, adiabatic protonation of S1 (3) to produce fluorescent 4 is not efficient. The lowest ππ* triplet state of 3 (ET = 45 ± 1 kcal/mol, 3τ = 8 · 10−4 s in dilute, degassed benzene solution) is an intermediate in the photoreduction of 3 by oxidisable substrates. Hydrogen abstraction from 2‐propanol by T1 (3) yields the semiquinone methide radical 5 which dimerises to 6. On readmission of air after irradiation, 6 is reoxidised to the starting material 3. Predictions derived from PPP SCF CI calculations are in accord with the observed spectroscopic and photochemical properties of 3.
Chelate Complexes with Methylmercury and Phenylmercury Cations
Authors: Anderegg Giorgio
Published: December 2004

The complex formation of Hg2+, CH3Hg+ and C6H5Hg+ with eight substituted quinolines, α,α′‐bipyridyl and 1, 10‐phenanthroline has been investigated in water and 75(v)% dioxane by pH and pHg methods. Hg2+ forms mercurated products with 8‐hydroxyquinolines, if the 5‐ or 7‐positions are unsubstituted. The formation of chelates by CH3Hg+ and C6H5Hg+ is postulated.
Formation and Dissociation Mechanism of Amide Complexes, IV. Protonation and deprotonation of the Cu2+ and Ni2+ complexes of 3,7‐diazanonanediamide and 3,7‐diazanonane‐N,N′‐diethylamide
Authors: Zuberbühler Andreas D. , Kaden Thomas A.
Published: December 2004

The protonation and deprotonation rates of the coordinated amide groups in the Ni2+ and Cu2+ complexes of 3,7‐diazanonanediamide (DANA) and in the Cu2+ complex of 3,7‐diazanonane‐N,N′‐diethylamide (DANEA) have been studied by stopped‐flow techniques. For the interconversion M(H−2L) ⇌ ML, two consecutive reactions are observed in the case of Cu2+ with DANA or DANEA, whereas there is only one reaction for Ni2+ with DANA. Cu(H−2DANEA) is unusually labile, indicating a strong interaction between the N‐ethyl groups. The conversion of the O‐ into the N‐coordinated amide groups in NiDANA2+ is 25 times slower than in CuDANA2+. In the case of Ni2+ this excludes a step with water substitution, which is involved in one of the reaction paths observed for the Cu2+ complexes, since the rates of water exchange differ by a factor of 105 for the two metal ions.
Über die Umsetzung von 1‐Phenylpyrazol mit Äthylmagnesiumbromid. 8. Mitteilung über Grignard‐Reaktionen [1]
Authors: Marxer Adrian , Siegrist Max
Published: December 2004

In contrast to butyllithium, ethylmagnesium‐bromide reacts with 1‐phenyl‐pyrazole exclusively by deprotonation, at the ortho position of the phenyl‐ring. With nitriles the intermediate 2‐(1‐pyrazolyl)‐phenylmagnesiumbromide gave good to excellent yields of 1‐(2‐aroyl or 2‐hetaroyl‐phenyl)‐pyrazoles (Table 1, compounds 5a–5i); with ketones the corresponding methanol derivatives (Table 2, compounds 6a–6c) were found, whilst CO2 yielded the corresponding 1‐(2‐carboxyphenyl)‐pyrazole (3). Surprisingly enough, 1‐(o‐bromo‐phenyl)‐pyrazole and magnesium did not yield a single product, but a mixture of 3 compounds, which on reaction with 4‐benzoylpyridine gave the three alcohols 19, 20 and 21.
Darstellung und Bildungsmechanismus von π‐Cyclopentadienyl‐nickel‐(tert.‐phosphit)‐dialkylphosphonat‐Komplexen – eine metallorganische Variante der Michaelis‐Arbuzov‐Reaktion
Authors: Clemens John , Neukomm Heinrich , Werner Helmut
Published: December 2004

Synthetic routes for complexes of the type π‐C5H5Ni[P(OR)3]X have been developed. Nickelocene reacts with tertiary phosphites P(OR)3 in the presence of CX4 to give the complexes for which R = Me, Ph; X = Cl, and R = Ph; X = Br. π‐C5H5Ni(CO)I reacts with P(OR)3 to give the complexes for which R = Me, Et, Ph. [π‐C5H5Ni(P(OMe)3)2]Cl is also formed in the preparation of π‐C5H5Ni[P(OMe)3]Cl from nickelocene; the corresponding [π‐C5H5Ni(P(OEt)3)2]I is obtained from π‐C5H5Ni[P(OEt)3]I and P(OEt)3. π‐C5H5Ni[P(OMe)3]X (X = Cl, I) react with P(OMe)3 to give π‐C3H5Ni[P(OMe)3] [P(O)(OMe)2] in quantitative yields, but with P(OEt)3 and P(OPh)3 π‐C5H5Ni[P(OEt)3] [P(O)(OMe)2] respectively π‐C5H5Ni[P(OPh)3] [P(O)‐(OMe)2] are obtained as the main products. The complex (t‐C4H9C5H4)Ni[P(OMe)3] [P(O) (OMe)2] can be synthesized by the same route.

The course of the reactions of π‐C5H5Ni[P(OR)3]X and P(OR′)3 has been investigated in some detail. Intermediate compounds {C5H5Ni[P(OR)3] [P(OR′)3]X} with a π‐bonded cyclo‐ pentadienyl ligand have been detected at low temperatures by 1H‐ and 13C‐NMR.‐spectroscopy. They are stable up to about −10° and react at higher temperatures smoothly to π‐C5H5Ni[P(OR)3] [P(O) (OR′)3] and R′X. The structure proposed for the intermediates suggests that the mechanism of formation of the nickel phosphonate complexes is quite similar to that of the Michaelis‐Arbuzov reaction.
Terpenoids Derived from Linalyl Oxide. Part 2. The isolation and synthesis of nordavanone, A C11‐terpenoid from Artemisia pallens
Authors: Thomas Alan F. , Ozainne Michel
Published: December 2004

The isolation, absolute stereochemistry, and synthesis of a new C11‐terpenoid, 3S,4S,7R‐3,7‐dimethyl‐4,7‐oxido‐non‐8‐en‐2‐one, related to davanone, are described.
Synthesis of Some Structural Analogues of LH‐RH Modified in Position 5, their in vivo and in vitro Gonadotropin‐releasing Activity and Immunoreactivity
Authors: Künzi Hans , Gillessen Dieter , Trzeciak Arnold , Studer Rolf O. , Kerdelhué Bernard , Jutisz Marian , Lotz Wolfgang
Published: December 2004

Four analogues of LH‐RH modified in position 5 have been synthesized using either classical procedures or the solid phase method. The gonadotropin‐releasing activities were determined by radioimmunological measurements of LH and FSH in vivo and in vitro and the immunoreactivities by a specific LH‐RH radioimmunoassay (RIA). The following relative potencies and immunoractivities were found:

in vivo
in vitro
Immuno‐reactivity

LH‐RH:
100 %
100 %
100 %

[Tyr(Me)5]
‐LH‐RH:
8.6%
6.0%
40.0%

[Phe5]
‐LH‐RH:
42.5%
27.5%
17.0%

[Cha5]

Abbreviations were used according to [37]; Cha = cyclohexyl‐L‐alanine.

‐LH‐RH:
22.4%
27.8%
10.0%

[Gly5]
‐LH‐RH:
0.1%
0.5%
0.7%
Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit Ketonen, Acylcyaniden und Ketoestern. 33. Mitteilung über Photoreaktionen
Authors: Claus Peter , Gilgen Paul , Hansen Hans‐Jürgen , Heimgartner Heinz , Jackson Barry , Schmid Hans
Published: December 2004

Similarly to aldehydes [6] ketones form 3‐oxazolines via cyclo‐addition to the benzonitrile‐methylides 2 that arise photochemically from the 3‐phenyl‐2H‐azirines 1. With various ketones benzonitrile‐isopropylide (2a) gives cyclo‐addition products in very good preparative yields (scheme 1). Benzonitrile‐ethylide (2c) and benzonitrile‐benzylide (2b) [8] react, however, sluggishly with ketones, smooth cyclo‐addition being observed in their case only with «activated» ketones (2,2,2‐trifluoro‐acetophenone, 1,1,1‐trifluoro‐2‐propanone). With 1a acetonyl‐acetone forms the bis‐adduct 12

While the azirine 1a reacts with cyclohexanone to yield essentially only the spiro‐(3‐oxazoline) 13, it gives with cyclopentanone, depending on the reaction conditions, either the spiro‐(3‐oxazoline) 14 or the butenyl‐3‐oxazoline 15 (scheme 3). The formation of 15 has to be preceded by the photochemical formation of 4‐pentenal from the ketone. Norcamphor and camphor react in a similar way (schemes 4 and 5).

The azirines 1a–c react smoothly with the keto groups in acylcyanides and α‐keto‐esters, giving with the former 5‐cyano‐3‐oxazolines and with the latter 5‐ethoxycarbonyl‐3‐oxazolines (schemes 6 and 7).

β‐Keto‐esters (acetoacetic ester) form with the dipole arising from 1a the expected addition product 31 and, via the protonated dipole d (scheme 8), finally the benzylidene‐acetoacetic ester. Analogous results are obtained with malonodinitrile, trifluoro‐acetamide and other weak acids such as alcohols [29] [30] (scheme 9).

The light‐induced rearrangement of the bicyclic isoxazoline 37 into the oxazoline 38 is visualized as an intramolecular cyclo‐addition reaction (scheme 10). The cyclo‐addition in this case proceeds with the aldehyde group inversed as compared to the related intermolecular benzonitrile–methylide addition to aldehydes.
Configuration of Pilocarpus Alkaloids
Authors: Link Helmut , Bernauer Karl , Oberhänsli Willi E.
Published: December 2004

The validity of stereoformula 1, 2 and 3 for (+)‐pilosine and related alkaloids is discussed.
Umlagerung und Spaltung von α, β‐Dioxopropionsäureestern in alkalischem Milieu. 28. Mitt. über Reduktone und Tricarbonylverbindungen [1]
Authors: Rodé‐Gowal Heike , Dao Huu Lé , Dahn Hans
Published: December 2004

The behaviour of α,β‐dioxopropionic acid derivatives of the type RCOCOCOX (R = phenyl, p‐substituted phenyls, CF3, mesityl; X = OC2H5, NH2) was investigated under benzilic acid rearrangement conditions. Nearly all compounds were cleaved by alkali to give the corresponding acids RCOOH and glyoxylic acid. Only the sterically hindered ethyl β‐mesityl‐α,β‐dioxopropionate underwent rearrangement (after hydrolysis of the ester group); it was shown by 14C‐labelling that the carboxylate group migrates to the β‐carbonyl group.
Selektive Synthesen mit Organometallen II: Metallierung und Abwandlung funktionell substituierter Alkene
Authors: Hartmann Jürgen , Muthukrishnan Ramamurthi , Schlosser Manfred
Published: December 2004

1,4‐Dienes, vinyl ethers, allyl ethers, allyl thioethers and propene‐thiolates are efficiently metalated by butyllithium in the presence of an activator such as potassium t‐butoxide. Since the solvent, the counter‐ion or the temperature may be varied before subsequent treatment with an electrophilic reagent, the critical ratio of direct vs. vinylogous attack (substitution at the α‐ or γ‐position, respectively) can usually be adjusted within large limits. In many cases stereo‐selectivity is achieved as well.
The Gas‐Solid Interface the adsorption of nitrogen, argon, neopentane, sulfur dioxide, carbon dioxide and sulfur hexafluoride on rhombic sulfur
Authors: Sollberger Frédéric , Stoeckli Fritz
Published: December 2004

Physical adsorption of the title compounds on rhombic sulfur of 0.4 to 0.5 m2/g is reported. The isotherms are of type II for N2, Ar and C5H12, of type III for SO2 and CO2, and linear for SF6. There is no hysteresis. The method of Ross & Olivier shows that the surface is relatively heterogenous (γ 17). Isosteric heats of adsorption and c values of the B.E.T. equation are also reported.
The Dianion of Heptalene
Authors: Oth Jean F. M. , Müllen Klaus , Königshofen Heinrich , Wassen Jürgen , Vogel Emanuel
Published: December 2004

Heptalene – a very unstable compound – can be reduced by lithium at −80° into its dianion. 1H‐ and 13C‐NMR. studies indicate that this dianion, contrary to the neutral molecule, has its π‐bonds delocalized. The magnetic field induces in this species a large diamagnetic ring current. The dianion of heptalene is thermally very stable, much more so than the neutral compound. All these observations point to an appreciable stabilization energy associated with the 14°‐electron system; this stabilization energy is probably large enough to impose a planar geometry to this dianion.
Selective Population of the n, π* and π, π* Triplet States of 1‐Indanones
Authors: Amrein Walter , Larsson Inga‐Mai , Schaffner Kurt
Published: December 2004

The two components of the dual phosphorescence of 1‐indanone (1) and six related ketones (2–7) possess different excitation spectra exhibiting the vibrational progression characteristic of the S0 → S1 (n, π*) transition (shorter‐lived emission) and two bands of the S0 → S2 and 3 (π,π*) 0–0 transitions, respectively. The most favorable intersystem crossing routes are S1 (n, π*) → T (n, π*) and S2,3 (π*) → T (π, π*). Internal conversion to S1 competes more effectively with S (π, π*) → T (π, π*) intersystem crossing only from higher vibrational levels of the S2 and S3 states.
Synthèse de sucres aminès ramifiés II. Synthèse et réactions de spiro‐aziridines. Communication préliminaire
Authors: Bourgeois Jean‐Marc
Published: December 2004

Treatment of 3‐C‐cyano‐1,2:5,6‐di‐O‐isopropylidene‐3‐O‐(toluene‐p‐sulfonyl)‐α‐D‐allofurannose with AlLiH4 or RMgX yields spiro‐aziridines with two identical substituents on C(3′) (H, CH3, C2H5). Reactions of these products and their derivatives are briefly described. If the C(3′) substituents are protons, the aziridine ring is easily opened. In acidic media (HCl), an amino‐sugar containing the branched chain CH2Cl is produced; with hydrogenation, a CH3 branched chain results. If the C(3′) substituents are methyl groups, the aziridine ring cannot be opened neither with HCl nor with hydrogen. The acetylated derivative of this latter compound rearranges to the corresponding allylamide with HCl. For both types of spiro‐aziridine, the nitrous deamination leads to the corresponding alkene.
Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26
Authors: Grob Cyril A. , Ide Junya
Published: December 2004

In 70% aqueous dioxane thian‐3‐one anti‐oxime p‐toluenesulfonate (tosylate) (8b) undergoes concerted fragmentation to the methylidenesulfonium ion 14, part of which recyclizes to 1,3‐thiazepin‐4‐one (11). With the syn‐isomer 8b rearrangement to 1,4‐thiazepin‐3‐one (10) and fragmentation to 14 occur in the ratio 4:1. Analysis of the rate data in 80% ethanol shows that anti fragmentation is 142 times as fast as syn fragmentation, but only 26 times as fast as rearrangement of the ‘homomorphous’ thian‐4‐one oxime tosylate (18b). A comparison of the rates of cyclohexanone oxime tosylate 20, thian‐3‐ and ‐4‐one oxime tosylates reveals the rate retarding influence of sulfur. – The configurations assigned to the stereoisomeric thian‐3‐one oximes (8a) in the literature have to be reversed in the light of present results.
Allenic and Acetylenic Spiropiperidine Alkaloids from the Neotropical Forg, Dendrobates histrionicus
Authors: Tokuyama T. , Uenoyama K. , Brown G. , Daly J. W. , Witkop B.
Published: December 2004

Four analogs of the acetylenic alkaloid, histrionicotoxin (C19H25NO) and the allenic alkaloid, isodihydrohistrionicotoxin have been isolated from extracts of skins of the arrow poison frog, Dendrobates histrionicus and characterized as neodihydrohistrionicotoxin, tetrahydrohistrionicotoxin, isotetrahydrohistrionicotoxin and octahydrohistrionicotoxin. These spiropiperidine (8‐hydroxy‐1‐azaspiro[5.5]undecane) alkaloids differ only in the degree of unsaturation in the five carbon atoms (position 2) and four carbon atoms (position 7) side chains. A fifth compound, HTX‐D, corresponds in empirical formula to a tetrahydrohistrionicotoxin with a 7‐(cis‐1‐butenyl‐3‐ynyl) side chain, but the major mass spectral fragmentation with loss of C2H5O is not characteristic of the histrionicotoxins. Reduction of histrionicotoxin with hydrogen and Lindlar catalyst affords an isomeric dihydrohistrionicotoxin with the terminal acetylene of the five carbon atoms side chain reduced, tetrahydrohistrionicotoxin and hexahydrohistrionicotoxins, while reduction with hydrogen and palladium on charcoal affords dodecahydrohistrionicotoxin which is readily methylated to the tertiary amine by methyl iodide.
Synthese von 2H‐Isoindol‐4,7 ‐dionen durch photochemische Cycloaddition von 2,3‐Diphenyl‐2H‐azirin an 1,4‐Chinone. 38. Mitteilung über Photoreaktionen
Authors: Gilgen Paul , Jackson Barry , Hansen Hans‐Jürgen , Heimgartner Heinz , Schmid Hans
Published: December 2004

2, 3‐Diphenyl‐2H‐azirine (1) reacts on irradiation with light of wavelength 290–350 nm with 1,4‐benzoquinones 3–6 or with 1,4‐naphthoquinones 7–9 forming the yellow to red coloured 1,3‐diphenyl‐2H‐isoindole‐4, 7‐diones 10–13 (33–43% yield) resp. 1, 3‐diphenyl‐2H‐benzo[f]isoindole‐4,9‐diones 14–16 (33–36% yield) (Scheme 1). The structures of these hitherto unknown products follow from the analytical and spectral data.

The probable formation of the isoindole‐diones is depicted in Scheme 2. The intermediate benzonitrile‐benzylide (2), which most certainly arises, adds onto the unsubstituted C, C‐double bond of the quinones and not onto the C,O‐double bonds. On exclusion of atmospheric oxygen there results from 1 and 2‐methyl‐1, 4‐benzoquinone (4) a product (probably b) which hardly absorbs in the region 350–450 nm. The latter, with the agency of atmospheric oxygen (but not 4), is converted into 5‐methyl‐1, 3‐diphenyl‐2H‐isoindole‐4, 7‐dione (11). The relative slowness of this oxidation (see Fig. 2) enables an almost complete photochemical transformation of the azirine 1, which only weakly absorbs above 290 nm. Otherwise 11, which strongly absorbs above 290 nm, would hinder the photolysis of 1.
Zur Kenntnis der Indolreaktion nach Fischer, I. Thermische und Säurekatalysierte Reaktionen von N, N′‐Dimethyl‐N‐phenyl‐N′‐alkenylhydrazinen
Authors: Schiess Peter , Grieder Alfred
Published: December 2004

N,N′‐dimethyl‐N‐phenyl‐N′‐alkenylhydrazines 9a–9f (Scheme 2) have been prepared by three different routes. These compounds yield N‐methyl‐indols 14a–14f (Scheme 3) upon thermolysis at 110° or upon treatment with dilute acid in anhydrous solvents at room temperature. The rate of the acid catalysed reaction varies by several orders of magnitude within the range of the examples studied. The observed structure‐reactivity relationship can be rationalized as reflecting the different tendency of the alkenylhydrazines 9a–9f for protonation on carbon vs. protonation on nitrogen (Scheme 4), the nitrogen protonated tautomer undergoing a rapid charge induced [3,3]‐sigmatropic rearrangement leading ultimately to indol.
Zur Photochemie des Iso‐methyl‐α, (E)‐jonons
Authors: Becker Josef , Ehrenfreund Josef , Jeger Oskar , Ohloff Günther , Wolf Hans Richard
Published: December 2004

UV.‐irradiation of iso‐methyl‐α, (E)‐ionone (4) in neutral solvents yields iso‐methyl‐α, (Z)‐ionone (5), the bicyclic ether 6 and the epoxide 7 by a sequence of successive photoisomerizations. The steps leading to des‐methyl homologues of 6 and 7 do not occur on irradiation of α, (E)‐ionone (1) [10]. The reversible isomerization 4 ⇄ 5 is followed by the irreversible photoprocess 5 → 6 and the final transformation 6 → 7. Irradiation of iso‐methyl‐α, (E)‐ionone (4) in acidic or basic solvents leads to a deep change in the type of products and gives the isomeric ketones 9 and 10 in high yields. A tentative mechanism for the photoisomerization steps 5 → 6, 6 → 7 and 5 → 9 + 10 is proposed.
Die durch Lewis‐Säuren katalysierte Cyclisierung von Geranylaceton
Authors: Schulte‐Elte Karl H. , Ohloff Günther
Published: December 2004

Geranylacetone (1a, 1b) in the presence of a Lewis acid, undergoes a novel cyclization reaction to yield the two diastereomers 9‐oxabicyclo[3·3·1]nonene 2 and 3 as main products. The formation of 2 and 3 is not stereospecific, i.e. both isomers 1a and 1b produce the same product mixture (2/3 ∼ 2:1 ratio).

This is in contrast to the known Brønsted‐acid catalyzed cyclization of 1, leading exclusively to the chromenes 4 and 5 in a stereospecific reaction.

The reaction mechanisms and the structural assignments are discussed.
Zur Verwendung des Tosylaminocarbonyl‐Restes als Amino‐Schutzgruppe in der Peptidchemie
Authors: Künzi Hans , Studer Rolf O.
Published: December 2004

Several N‐tosylaminocarbonyl amino acids and corresponding di‐ and tripeptides were prepared in order to investigate the suitability of the tosylaminocarbonyl group as an amino protecting group in peptide chemistry. The group is shown to be selectively cleavable under neutral conditions.
1,5‐Cyclooctadiyne. Preparation and Reactivity
Authors: Kloster‐Jensen Else , Wirz Jakob
Published: December 2004

1,5‐Cyclooctadiyne 1 was isolated in 2 percent yield from polymerized butatriene 5. Other oligomers of 5 were detected in the reaction mixture by combined GLC./MS. analysis but have not been identified. Diels‐Alder adducts of 1 with two equivalents of 1,3‐butadiene and of 2,3‐dimethyl‐1,3‐butadiene have been prepared. In the presence of strong base 1 isomerized to cyclooctatetraene. 5 was reformed by photolysis of 1. Attempts to prepare transition metal complexes of 1 failed. Effects of ring strain and of transannular interaction on the reactivity of 1 are discussed. The dimerization of 5 to 1 is predicted to be strongly exothermic.
The Nitration of Pentamethylbenzene with Nitronium Hexafluorophosphate and water in nitromethane
Authors: Hunziker Erich , Myhre Philip C. , Penton John R. , Zollinger Heinrich
Published: December 2004

The nitration of pentamethylbenzene in nitromethane has been studied under conditions that allow two mechanisms of nitration to be distinguished. One has been identified as nitration via the nitronium ion; the other nitration involves an oxidation of the molecular complex ArH‐NO⊕PF6⊖ by nitrogen dioxide followed by reaction of the aromatic substrate with the incipient nitronium ion and loss of nitric oxide. Either reaction can be made predominant by an appropriate change in the proportions of the reactants in the system.

A consideration of the σ‐complexes formed by attack of the electrophile at aromatic carbon bearing a methyl substituent can provide a satisfactory explanation for the features observed in this and in other nitrations of pentamethylbenzene.
Steric Effects in Nucleophilic Aromatic Substitution reactions with aromatic amines 12th communication on nucleophilic aromatic substitution reactions
Authors: Eggimann Walter , Schmid Peter , Zollinger Heinrich
Published: December 2004

The kinetics of the SNAr reactions of aniline and N‐methylaniline with a variety of substituted nitrochlorobenzenes in acetonitrile demonstrate that the formation of the intermediate σ‐complex is rate determining. The ratio of the rate constants of the aniline and the N‐methylaniline reactions (kA/kM) increases with increasing size of the 6‐substituent; with picryl chloride kA/kM reaches a value of over 20 000. The reaction of aniline with 4‐X‐2,6‐dinitrochlorobenzenes is subject to considerably larger para‐substituent effects than the corresponding reactions with N‐methylaniline. These results are interpreted in terms of two effects: (i) A primary steric effect, which renders the approach of N‐methylaniline to the substrate difficult. (ii) A shift towards earlier, more reactant‐like transition state structures caused by the primary steric effect. In early transition states the activating power of the electron‐withdrawing substituents in the substrate is expected to be relatively small. An early transition state for the slow N‐methylaniline reaction and a late transition state for the fast aniline reaction is in apparent contradiction to what would be expected on the basis of the Hammond postulate.
Synthetische Juvenilhormone 4. Mitteilung. p‐Substituierte 5‐Phenyl‐penten(1)‐carbonsäurederivate
Authors: Franke Albrecht , Mattern Günter , Traber Walter
Published: December 2004

The synthesis of p‐substituted 2‐methyl‐5‐phenyl‐penten(1)‐carboxylic acid derivatives is described: the formed Grignard compounds react with ethylene‐oxide to the corresponding alcohols which are transformed by following reactions to the above mentioned compounds.
Synthese einiger Glucuronid‐Metaboliten von Phenacetin und Phenetidin, Teil II
Authors: Kiss Joseph , Noack Klaus , D'Souza Richard
Published: December 2004

The anomeric configuration of the main metabolite of phenacetin, p‐acetamido‐phenyl β‐D‐glucopyranosido‐uronic acid, was established by configurative correlation with a cyclohexyl β‐D‐glucopyranosido‐uronic acid derivative. Furthermore, some anomeric D‐gluco‐pyranoside conjugates of 2‐ethoxy‐5‐acetamido‐phenol were synthesized and characterized using NMR.‐spectroscopy and ORD./CD.
Neue spiro‐Cyclopropyl‐cyclohexendion‐Diterpene: Coleone M, N, P, Q, R sowie Barbatusin aus Plectranthus caninus ROTH und Coleon O aus Coleus somaliensis S. MOORE
Authors: Arihara Shigenobu , Räedi Peter , Eugster Conrad Hans
Published: December 2004

The yellow glands on the leaves and racemes of Plectranthus caninus ROTH (Labiatae) are a rich source of spiro‐abietanes. Five new coleons have now been isolated, together with barbatusin, and their structures have been determined. Coleon O occurs in similar glands of Coleus somaliensis S. MOORE. From the biogenetic point of view the simultaneous occurrence of both structures with normal gem. C(4)‐dimethyl group, and rearranged δ3,4‐19 (or 18) (4 → 3)abeo‐abietan‐structures appears most remarkable.

We discuss the origin of the unusual spiro‐cyclopropane structure with respect to the various oxygen functions present in these molecules. The application of the excitonchirality rule of Nakanishi et al. allows the determination of the chirality at C(7).
Sur les dérivés de la fluorénone VIII. Difluorénonyl‐cétones, difluorényl‐cétones et difluorényl‐méthanes
Authors: Chardonnens Louis , De Blasi Vito , Barras Jean‐Luc
Published: December 2004

By condensation of the chlorides of the four isomeric fluorenecarboxylic acids, respectively of the three 1‐, 3‐ and 4‐fluorenonecarboxylic acids with fluorene, followed by reduction of the obtained mono‐respectively diketones, the four difluorenylmethanes I, II, III and IV are synthesized. The oxydation of the diketones gives the corresponding triketones. Starting from the chloride of 4‐fluorenecarboxylic acid and 1‐methylfluorene, a methyl derivative of IV is analogically obtained.
Zur Frage der Existenz isomerer, äquatorial koordinierter 1:2‐Co(III)‐Komplexe aus symmetrischen o, o'‐Dihydroxyazofarbstoffen
Authors: Schetty Guido
Published: December 2004

2,2′‐Dihydroxy‐3,3′‐dimethyl‐5,5′‐di‐t‐butyl‐1,1′‐azobenzene has been metallized to the 1 : 2‐Co‐(III)‐complex. In addition to the main product a further complex was isolated by chromatography in a yield of about 2% and proved to be an isomer of the main complex. The cause of the isomerism could not be elucidated.
1H‐ and 13C‐NMR. Studies of the molecular conformations of cyclo‐tetraglycyl [1]
Authors: Grathwohl Christoph , Tun‐Kyi Aung , Bundi Arno , Schwyzer Robert , Wüthrich Kurt
Published: December 2004

The 1H‐ and 13C‐NMR. spectra of cyclo‐tetraglycyl show that the four peptide groups are magnetically equivalent, and different from either a standard trans or a standard cis peptide group. It is suggested that the observed NMR. features correspond to a non‐planar form of the peptide groups. On the one hand these data confirm the earlier conclusions from theoretical investigations of the molecular geometry, that cyclic tetrapeptides could not contain four standard trans peptide groups. On the other hand they are not consistent with a previously suggested alternative molecular conformation according to which cyclo‐tetraglycyl would adopt a conformation similar to cyclo‐tetrasarcosyl, with two cis and two trans peptide bonds. The different behaviour of glycine and sarcosine under the steric strains of tetrapeptide ring closure would appear to suggest that with the exception of the X‐Pro bonds, transoid peptide groups in polypeptide chains of the common amino acids should be more likely to occur than the cis form, which has as yet apparently not been observed for N‐unsubstituted peptide groups in natural peptides or proteins.
A carbon‐13 study of bis‐phosphine platinum complexes
Authors: Pregosin P. S. , Kunz R.
Published: December 2004

The 13C‐NMR. spectra of a series of complexes of type [PtCl2(PR3)2] and [PtCl4(PR3)2] have been measured. The values 2J(Pt, C) are shown to reflect changes in the metal hydridization while the values [3J(PA, C) + 5J(PB, C)] are found to vary only slightly. It is suggested that the phosphorus hybridization in these complexes varies only slightly.
Synthese yon 2,6‐Diencarbonsäuren Vorläufige Mitteilung
Authors: Fráter György
Published: December 2004

Through sequential Claisen‐ and Cope rearrangements the chainlengthening of allylic alcohols by one isoprene unit was achieved. Treatment of (E)‐1a first with lithium N‐cyclohexyl‐N‐isopropylamide at −70°, followed by trimethylsilylchloride and warming up to room temperature yielded after work‐up 3a (R = H), which rearranged at 156° in high yield to (E/Z)‐4a. An analogous reaction sequence transformed 6 to 8. Choosing lithium N‐methylanilide as a base (E/Z)‐9 was selectively rearranged to 12, which was converted to the Cecropia juvenile hormone precursor (E/Z)‐4b.
Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno‐fluorènes, XIX Dérivés tétraméthylés du trans‐fluorénaphène et du trans‐fluorénacène
Authors: Chardonnens Louis , Bitsch Serge , Häger Josef
Published: December 2004

By condensation of isophthaloyldichloride resp. of terephthaloyldichloride with 4‐bromo‐1,2‐xylene according Friedel‐Crafts, followed in each case by a double cyclisation and a final reduction, the 2,3,9,10‐tetramethyl‐7,12‐dihydro‐indeno[1,2‐a]fluorene resp. the 2,3,8,9‐tetramethyl‐6, 12‐dihydro‐indeno[1,2‐b]fluorene are synthesized.
Neue Umlagerungsreaktionen des Trichothecangerüsts Verrucarine und Roridine, 31. Mitteilung [1]
Authors: Müller Beat , Tamm Christoph
Published: December 2004

Treatment of the apotrichothecane derivative 4 with H2SO4 in dioxan gave the acetal 6 and with H2SO4 in acetone the ketal 9. Whereas the oxidation of 4 with Ag2CO3 yielded the hydroxy aldehyde 7, the reaction with CrO3 or MnO2 led to the α,β‐unsaturated ketone 8. Upon treatment of 8 with base the cyclic keto ether 11 was obtained due to 1,4‐addition. Acetylation of the latter compound gave a mixture consisting of the enolacetate 13 and the acetylketone 14. The oxim 15 of ketone 14 was transformed to the nitrile 16 and not the Beckmann fragmentation product 18. For the identification of the C(11) hydrogen atom in biosynthetic studies the triol 22 was oxidized to the keto aldehyde 26 which, upon treatment with methanolic K2CO3, gave the spirolactol 30 and the cyclic acetal 29 as second product when the reaction was carried out in dilute solution. The spirolactol 30 was oxidized to the spirolactone 31. The corresponding 19 possessing the intact 12,13‐epoxy group underwent rearrangement to the apotrichothecane derivatives 20 and 21 under the same conditions. Oxidation of the triol 22 with MnO2 or CrO3 gave a mixture of the acetal 23 and the keto acid 24. – The mechanisms of the rearrangements observed are discussed.
Enäther als Reaktionspartner von Organometallen II Hydroxyäthyl‐allene und andere Folgeprodukte aus Dihydrofuran‐Derivaten
Authors: Schaub Bruno , Schlosser Manfred
Published: December 2004

Upon treatment with organolithium compounds, 2‐alkyl‐4,5‐dihydrofurans undergo ring opening through β‐elimination leading to the corresponding 3,4‐dien‐1‐ol. If 3‐chloro‐2‐methyl‐4,5‐dihydrofuran serves as a substrate, however, no 3‐chloro‐3,4‐dien‐1‐ol can be isolated though it acts as a reaction intermediate. Its formation is slow compared to subsequent replacement of halogen by the organic moiety of the alkyllithium reagent. Thus penta‐3,4‐dien‐1‐ols are formed, which may isomerize, however, under certain reaction conditions affording terminal acetylenes. These as well as their allene precursors can be converted with sodium in ammonia into pent‐4‐en‐1‐ol or, respectively, pent‐3‐en‐1‐ol derivates.
Structural and Dynamic Study of SnCl4 · 2 Me2O and SnCl4 · 2 Me2Se Preliminary communication
Authors: Ruzicka Steve J. , Merbach André E.
Published: December 2004

The solid cis‐SnCl4 · 2Me2O and trans‐SnCl4 · 2Me2Se adducts have been synthesised and characterised by IR. and Raman spectroscopy. NMR. and vibrational spectroscopy show a fast cis‐trans equilibrium for both complexes in solution in an inert solvent.
Azidiniumsalze 14. Mitteilung [1] Die Reaktion des 2‐Azido‐3‐äthyl‐benzthiazolium‐tetrafluoroborats mit Sulfit‐Ionen: Kinetik der Bildungs‐, Isomerisierungs‐ und Zersetzungsreaktionen des Additionsproduktes
Authors: Hellrung Bruno , Balli Heinz
Published: December 2004

Die Reaktion des 2‐Azido‐3‐äthyl‐benzthiazolium‐tetrafluoroborats mit Sulfit‐Ionen, die Isomerisierung und der Zerfall des Additionsproduktes 3‐(3‐Äthyl‐benzthiazolin‐2‐yliden)‐triazen‐1‐sulfonsäure wurden untersucht. – UV.‐Spektren, Säure‐Base‐Gleichgewichtskonstanten bzw. Geschwindigkeitskonstanten der Reaktionsprodukte bzw. ‐schritte in wässeriger, gepufferter Lösung bei 25° wurden gemessen.
Dynamische Jahn‐Teller Verzerrungen und chemische Bindungsverhältnisse in orbitalentarteten Sandwichkomplexen
Authors: Ammeter J. H. , Oswald N. , Bucher R.
Published: December 2004

In order to derive information on the Jahn‐Teller effect and on chemical bonding in orbitally degenerate sandwich molecules, the low‐spin d5(2E2g) metallocenes Mn(cp)2 and Fe(cp) as well as the d7(2E1g) metallocenes Co(cp)2 and Ni(cp) have been diluted in a variety of diamagnetic host systems and studied by ESR. at liquid helium temperature and slightly higher temperatures. Analysis of the measured anisotropic Zeeman and hyperfine data leads to the conclusions that the Jahn‐Teller distortions remain entirely dynamic in all four cases (EJT ≲ hv), and that the covalent delocalization of the singly occupied degenerate metal 3d orbital over the ligand rings correlates well with the observed Jahn‐Teller distortion increasing strongly along the series Fe(cp) < Mn(cp)<2 < Co(cp)2 < Ni(cp). This finding agrees with the expectation that the ligand components of the singly occupied e2g(e1g*) orbitals are mainly responsible for the dynamic e1g(e2g) distortions in the cyclopentadienyl rings.
Über vinyloge English‐Zimmerman‐Spaltungen in der Jononreihe
Authors: Skorianetz Werner , Ohloff Günther
Published: December 2004

Two pent‐2‐en‐1, 5‐diols are shown to undergo facile vinylogous English‐Zimmerman fragmentation.
Helicenes: Thermally induced intramolecular 4 + 2 cycloadditions involving the [6]helicene skeleton
Authors: Martin Richard H. , Jespers Jacques , Defay Nicole
Published: December 2004

Treatment of dl‐1‐formyl[6]helicene (1) with the ylid of (EtO)2P(O)CH2CO2Et in boiling C6H6 gave a mixture of two dl epimeric cycloaddition products: trans‐2a (80%) and cis‐2b (12%) An X‐ray diffraction study (Van Meerssche et al. [2]) fully confirmed the structure and the stereochemistry assigned to the most abundant stereoisomer 2a by UV., 1H‐INDOR, NOE and catalytic hydrogenation of the non‐benzenoid double bonds.
Infrared Spectroscopic Studies on Metal Carbonyl Compounds. Part XIX. Analysis of the terminal CO stretching region of the infrared spectra of tetracobalt and tetrarhodium dodecacarbonyl by 13C isotopic enrichment and of hydridoirontricobalt dodecacarbonyl. Calculation of CO stretching force and interaction constants
Authors: Bor György , Sbrignadello Gino , Noack Klaus
Published: December 2004

Based on 13C‐enriched spectra the assignment of the terminal CO stretching bands of Co4(CO)12, Rh4(CO)12, and HFeCo3(CO)12 is presented. This corresponds in all three cases to the scheme A1 > A1 > E > E > A1 > E. For the calculation of the ‘non‐rigorous’ CO stretching force and interaction constants a parametric method is described. On the basis of the extremely low CO stretching force constant of the ligands bonded to the iron atom in HFeCo3(CO)12 a considerable polarization of the Fe‐H bond in the sense Fe(δ−)––H(δ+) is suggested, and the position of the H‐ligand is supposed ‘in the cage’ near, or on the Co3 plane.
Eine Cyanogruppe als Dienophil in einer intramolekularen π4 + π2‐Cycloaddition
Authors: Pfoertner Karl‐Heinz , Oberhänsli Will E.
Published: December 2004

At elevated temperatures the 11, 14‐cycloadducts of tetracyanoethylene with esters of retinoic acid or with retinol acetate are transformed into 5,9‐methano‐2H‐cyclohepta[b]‐pyridines by intermolecular π4 + π2‐cycloaddition of a cyano group followed by a double bond shift. The resulting structure was determined by x‐ray analysis.
Interaction entre chromophores non‐conjugués: Diméthylidène‐2,3‐époxy‐5,6(exo)‐norbornane et diméthylidène‐2,3‐époxy‐5,6(exo)‐oxa‐7‐norbornane
Authors: Gergely Véra , Akhavin Zohreh , Vogel Pierre
Published: December 2004

Preparation of the title compounds 7 and 17 is described. A hypsochromic shift of the V ← N transition of the s‐cis‐butadiene chromophore in the UV. spectra of the epoxydienes 7 and 17 is observed relative to 2,3‐dimethylidene‐norbornanes (20, 29), and to 2,3‐dimethylidene‐7‐oxa‐norbornanes (22, 23). This effect is discussed in terms of geometry changes of the s‐cis‐butadiene and in terms of variation of the hyperconjugation of this chromophore with the σ‐skeleton of the bicyclic system.
Fukiinsäure und 3′‐O‐Methyl‐fukiinsäure, zwei phenolische Hydroxycarbonsäuren aus Piscidia Erythrina
Authors: Heller Werner , Tamm Christoph
Published: December 2004

Purification of crude piscidic acid from ‘Cortex Piscidiae Erythrinae’, the root bark of Piscidia Erythrina L. (Papilionaceae), led to the isolation of fukiic acid (5) and 3′‐O‐methyl‐fukiic acid (8). Since partition chromatography with alcoholic solvents produced the corresponding half‐esters as artefacts, the acids were transformed to their methyl esters before separation. Spectroscopic methods and comparison with authentic samples from Petasites japonicus F. SCHMIDT (Compositae) confirmed the structures 5 and 8.