bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthese des (±)‐Oncinotins
Authors: Schneider Fernand , Bernauer Karl , Guggisberg Armin , Van DenBroek Peter , Hesse Manfred , Schmid Hans 
Published: December 2004

Abstract(±)‐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

AbstractThe 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

AbstractAnalysis 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

AbstractIt 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

AbstractDie 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

AbstractUsing 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

AbstractThe 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

AbstractThe 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.
Thermische Umlagerung von (trans‐2,3‐Diphenylcyclopropyl)‐dipyrrolidino‐methan. vorläufige Mitteilung
Authors: Huber Martin K. , Dreiding André S. 
Published: December 2004

AbstractThermal 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

Abstract25‐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

AbstractDie 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

AbstractAus 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

AbstractAlkalische 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

Abstract6‐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

AbstractStarting 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractIn 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

AbstractSynthetic 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

AbstractThe 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

AbstractFour 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

AbstractSimilarly 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 12While 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.
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

AbstractPhysical 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

AbstractHeptalene – 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

AbstractThe 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.
Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26
Authors: Grob Cyril A. , Ide Junya 
Published: December 2004

AbstractIn 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.
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

Abstract2, 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.
Die durch Lewis‐Säuren katalysierte Cyclisierung von Geranylaceton
Authors: Schulte‐Elte Karl H. , Ohloff Günther 
Published: December 2004

AbstractGeranylacetone (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

AbstractSeveral 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.