bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tieftemperaturbestrahlungen von 3‐Phenyl‐2H‐azirinen
Authors: Sieber Willi , Gilgen Paul , Chaloupka Stanislav , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

Abstract2, 2, 3‐Triphenyl‐2H‐azirine (4a) in a matrix of 2, 2‐dimethylbutane/pentane 8:3 (DMBP) at −185° gave rise on irradiation with light of 250–350 nm to a new UV.‐maximum at 350 nm (Fig. 1). We assign the dipole benzonitrildiphenylmethylide (1a) to this new maximum. Irradiation with monochromatic light of 366 nm destroyed this maximum and the initial absorption curve reappeared (Fig. 2). When the azirine 4a was photolysed in DMBP at −185° in the presence of methyl trifluoracetate (TFEM), the maximum at 350 nm was obtained again. This maximum vanished upon increasing the temperature to −160°. Through gas chromatography we were able to show that 5‐methoxy‐5‐trifluormethyl‐2, 2, 4‐triphenyl‐3‐oxazoline (6a) was produced. 6a was also obtained upon irradiation of 4a at room temperature in the presence of TFEM (scheme 1 and table 1). Modification of the previously described experiment, in which the maximum at 350 nm was extinguished in the matrix due to irradiation at 366 nm gave, after warm up, almost no dipole adduct 6a (table 1). From these experiments, an extinction coefficient of 17, 000 for the 350 nm maximum of 1a, was calculated. These experiments have shown that irradiation of triphenylazirine 4a leads to the dipole 1a, which can be reversed photochemically – but not tharmally – into azirine 4a. 1a reacts at less than −160° with TFEM to give adduct 6a. The results which were obtained with triphenylazirine 4a could be correspondingly obtained with 2, 3‐diphenyl‐2H‐azirine 4b (Fig. 3, scheme 2 and table 2). The dipole 1b showed two UV.‐maxima at 330 nm (ε = 17, 500) and 343 nm (ε = 21, 000). Later experiments established, that the two maxima belonged to a single dipole species.The dipole 1c obtained upon irradiation of 2, 2‐dimethyl‐3‐phenyl‐2H‐azirine (4c) in DMBP at −190°, appears to absorb in the same region as the azirine 4c. The presence of the dipole 1c was univocally established by low temperature trapping experiments with TFEM. The dipole 1a showed no ESR.‐spectrum characteristic for a triplet state. We assume therefore, that 1a is in a singlet state. Photolysis of oxazolinone 7 at −190° in DMBP led to the dipole 1a with loss of CO2. 1a recombines apparently in considerable amount with the CO2 trapped in the matrix to give starting oxazolinone 7 because the 350 nm‐maximum of 1a appeared with low extinction. Irradiation with light of 366 nm into this matrix produccd triphenylazirine 4a. Low temperature trapping experiments with TFEM led to small amounts of 5‐methoxy‐5‐trifluormethyl‐triphenyl‐3‐oxazolinc (6a).
Über Pterinchemie. 42. Mitteilung [1]. Synthese von 6‐Hydroxymethyl‐mono‐, di‐ und triphosphat sowie deren 7, 8‐Dihydroderivate
Authors: Viscontini Max , Furuta Yoshiteru 
Published: December 2004

AbstractDie Behandlung des 6‐Hydroxymethylpterins mit Polyphosphorsäure führt zur Bildung der Mono‐, Di‐ und Triphosphorsäureester. Durch Chromatographie mittels Ionenaustauscher wurden die einzelnen Ester rein erhalten und konnten charakterisiert werden. Die Reduktion des Mono‐ und des Diphosphates mit Natriumdithionit ergibt die entsprechenden 7, 8‐Dihydroderivate.
Nuclear Quadrupole Resonance and Stereochemistry II. Vicinal cis‐ and trans‐dichloro derivatives of carbocyclic systems
Authors: Ardalan Ziba , Lucken Edwin A. C. , Masson S. 
Published: December 2004

AbstractThe 35Cl quadrupole resonance frequencies of sets of isomeric vicinal dichloro derivatives of carbocyclic molecules are presented. In all cases except one – cis‐ and trans‐1, 2‐dichloro‐acenaphthene – the configuration has only a small effect on the resonance frequency. This implies that the frequency‐differences in cyclic α‐chloroethers reported in Part I of this series [1] are indeed due to a specific interaction with the oxygen atom. The difference between the acenaphthenes may be due to hyperconjugation between the CCl bond and the aromatic system.
Repetitive Excess Mixed Anhydride (REMA) Synthesis of Peptides. The protected C‐terminal hexadecapeptide of secretin
Authors: van Zon A. , Beyerman H. C. 
Published: December 2004

AbstractThe usefulness of the repetitive excess mixed anhydride (REMA) method of peptide synthesis was demonstrated by the prompt synthesis of the protected C‐terminal hexa‐decapeptide of the gastrointestinal hormone secretin, Boc‐Arg(NO2)‐Leu‐Arg(NO2)‐Asp(Bzl)‐Ser(Bzl)‐Ala‐Arg(NO2)‐Leu‐Gln‐Arg(NO2)‐Leu‐Leu‐Gln‐Gly‐Leu‐Val‐NH2,(secretin 12–27). The overall yield was 31%, with an average coupling yield of 93%.Comparison of the physical constants of all intermediate sequcnces with those published, by Bodanszky et al. and by Wünsch et al. in their syntheses of secrctin, indicated identity. No significant raccmization could be detected in acid hydrolysates on digcstion with L‐amino acid oxidase.
Über den Einfluss nichtpolarer Lösungsmittel auf Lage und Intensität von Absorptionsbanden in den Elektronenspektren apolarer Molekeln: II. Polyacetylene
Authors: Christen Heinz , Kloster‐Jensen Else 
Published: December 2004

AbstractThe dispersive interaction of nonpolar solutes with nonpolar solvents is investigated in model systems consisting of solutions of dimethyl‐tetraacetylene, di‐t‐butyl‐tetraacetylene, dimethyl‐pentaacetylene or di‐t‐butyl‐pentaacetylene in binary mixtures of cyclohexane/carbondisulfide or n‐pentan/carbondisulfide. For this purpose the 1Σ → 1Σ transition in the electronic spectrum of the solutions has been recorded. With increasing concentration of the more strongly interacting solvent component (i.e. carbondisulfide) bathochromic shifts δν of the transition frequency accompanied by a decrease in oscillator strength fM are observed, which are consistent with calculated values based on a previously proposed exciton model [1].
Versuche zur Synthese der 4‐Thio‐D‐glucose
Authors: Vegh L. , Hardegger E. 
Published: December 2004

AbstractDie saure Hydrolyse des oxydationsempfindlichen Methyl‐(4‐thio‐α‐D‐glucopyranosids) (2) gab nur in geringer Ausbeute das Disulfid 11 der 4‐Thio‐D‐glucose. Versuche, die 4‐Thio‐D‐glucose (31) aus der leicht zugänglichen 1, 6; 3, 4‐Dianhydro‐2‐O‐tosyl‐β‐D‐galaktopyranose (14) über die Anhydroderivate 22 und 30 zu gewinnen, führten zu 4‐Thio‐D‐altrose‐Derivaten (32–35), zu ungesättigten 1, 6‐Anhydrozuckern (23–26), zu 2, 4‐Dithioglucosan‐ und 3, 4‐Dithioaltrosan‐Derivaten (18–21 bzw. 27, 28).
1, 4‐Dimethylcyclohex‐3‐enyl Methyl Ketone, a monoterpenoid with a novel skeleton
Authors: Thomas Alan F. 
Published: December 2004

Abstract1, 4‐Dimethylcyclohex‐3‐enyl methyl ketone (1) has been isolated from the oil of Juniperus communis L. (fruit). This is the first reported occurrence of this skeleton in nature. A curious effect on the NMR.‐spectrum of the compound (1) by the shift agent, Eu(fod)3, is described.
Utilisation d'ylides du phosphore en chimie des sucres. XVIII Synthèse de furannoses à insaturation conjuguée. Communication préliminaire
Authors: Tronchet Jean M. J. , Cottet Christian , Gentile Bernard , Mihaly Eva , Zumwald Jean‐Bernard 
Published: December 2004

AbstractSeveral sugars with conjugated unsaturation (dienes or α, β‐unsaturated carbonyl compounds) have been synthesised by use of Wittig reactions. Keto‐sugars bearing a carbonyl group α to a furanose ring are prone to undergo an elimination leading to conjugated unsaturated systems. This constitutes a novel kind of side‐reaction in the application of Wittig reactions to carbonyl sugars. The synthesis of a new kind of acetylenic sugar is also described.
Bildung von 2‐(1‐Methyl‐1, 4, 5, 6‐tetrahydropyridyl‐3)‐2‐oxazolin‐4‐on aus 1‐Methyl‐1, 4, 5, 6‐tetrahydronicotinsäureamid und Bromessigsäureäthylester und seine Überführung in O‐(1‐Methylnipecotinoyl)glykolsäureamid via das dazu tautomere Cyclol
Authors: Troxler Franz 
Published: December 2004

AbstractThe main product of the reaction between 1‐methyl‐1, 4, 5, 6‐tetrahydronicotin‐amide and ethyl bromoacetate is shown to be the 2‐(1‐methyl‐1, 4, 5, 6‐tetrahydropyridyl‐3)‐2‐oxazoline‐4‐one which on partial hydrogenation followed by reaction with alkali affords O‐(1‐methylnipecotinoyl)glycolic amide, presumably via the tautomeric cyclol.
Heterotricyclodecane XIV. 2‐Oxa‐6‐aza‐adamantan und Derivate
Authors: Portmann Robert Ernst , Ganter Camille 
Published: December 2004

AbstractThe synthesis of 2‐oxa‐6‐aza‐adamantane (21) and several of its derivatives (13–20, 22, 23, 25–34, 37, and 38) was achieved starting from the 9‐azabicyclo[3.3.1]nona‐2,6‐ dienes 2, and 3, and 9‐oxabicyclo[3.3.1]nona‐2,6‐diene (1).
Heterotricyclodecane XV. Synthese von 2,6‐Diaza‐adamantanen
Authors: Portmann Robert Ernst , Ganter Camille 
Published: December 2004

AbstractThe synthesis of several derivatives of 2,6‐diaza‐adamantane (2, 3, 5–9) is described using the diepoxides 1 and 4 as starting materials.
Oxydative Umsetzungen in der Damascon‐Reihe. 1ΔgO2‐ und SeO2‐Oxydation von β‐Damascenon
Authors: Schulte‐Elte Karl H. , Gadola Marcel , Ohloff Günther 
Published: December 2004

AbstractPhotooxygenation of β‐damascenone (1) leads to the 3,6‐endo‐peroxide (2) which has been converted to various oxygenated derivatives in the damascene series. Introduction of oxygen specifically into the 2‐position of β‐damascenone (1) occurs by selenium dioxide oxidation. A series of reduction products of 2‐oxo‐β‐damascone (9) is described.
Amino‐nucléosides IV (Amino‐3‐désoxy‐3‐érythrofurannosyl)‐9‐adénine
Authors: Tronchet Jean M. J. , Graf René 
Published: December 2004

AbstractThe synthesis of 9‐(3‐amino‐3‐deoxy‐β‐L‐(and D)‐erythrofuranosyl)‐adenine is described. This compound is a close analog of the aminonucleoside of puromycin.
Nucleophilic Reactions at Tertiary Carbon. Part 1. The 1,2‐dimethyl‐1‐cyclohexyl cation
Authors: Becker Konrad B. , Grob Cyril A. 
Published: December 2004

AbstractStereoisomeric ion pairs are implicated as intermediates in the solvolysis of cis and trans‐1‐chloro‐1,2‐dimethylcyclohexane, cis‐4 and trans‐4, respectively. This follows from the rates and products of these stereoisomeric tertiary chlorides in 80% ethanol and 50% acetone.The composition of elimination and substitution products from cis‐4 and trans‐4 differs markedly and the differences are accentuated by silver ion. Furthermore, substitution products are formed with predominant inversion of configuration.The equilibrium constant for isomerization of cis‐4 and trans‐4 shows the latter to be more stable by 0.7 kcal/mol. Since the solvolysis rates of the chlorides are equal, the transition state for trans‐4 is also more stable by 0.7 kcal. By inference the intermediates differ by a similar amount of energy which is ascribed to more efficient solvation of the trans ion pair 13.
Chemistry of Succinylsuccinic Acid Derivatives. Part II. The crystal and molecular structure of diethyl succinylsuccinate
Authors: Mez Hans‐Christian , Rihs Gret 
Published: December 2004

AbstractX‐ray structure analysis of the title compound (I) is reported. The results are interpreted to predict formation of anti‐tricyclo[4.4.01,6.07,12]‐1,4,7,10‐tetraethoxycarbonyl‐3,6,9,12‐tetrahydroxy‐dodeca‐3,9‐diene on UV.‐irradiation of solid (I).
Partialsynthese von Bufarenogin und Argentinogenin. Über Bufadienolide, 42. Mitteilung
Authors: Spengel Sigrid , Linde Horst H. A. , Meyer Kuno 
Published: December 2004

AbstractEs wird über die Struktur des Di‐O‐acetylbufarenogins (9) und die des Argentinogenins (14) abschliessend berichtet.
Radiolyse des hydrocarbures. 21e communication. Mécanismes radicalaires et non‐radicalaires dans les n‐alcanes en phase liquide
Authors: Rappoport Serge , Gäumann Tino 
Published: December 2004

AbstractContributions of radical and non‐radical processes have been determined in the formation of radiolysis products of n‐heptane, n‐octane, n‐nonane and n‐decane in a large range of temperature. Calculations are based on the combination and the dismutation of radicals, both reactions having nearly the same importance. Hydrogen abstraction reactions become important above – 25°. Intermediate molecular weight products and dimers are formed by statistical combination of the various radicals resulting from CC and CH scission. At low temperature, low molecular weight products are formed by both radical and non‐radical processes, the second one being more important (3/4 for alcanes and 2/3 for olefins). The yield of radicals increases with the chain length of the irradiated n‐alkane and amounts to 4.5 for n‐heptane and 6.8 for n‐decane at – 25°. This increase is due only to radicals from CH scission, while the yield of radicals from CC scission remains constant. Scission of CH2CH2 bonds is favored for bonds inside the molecule, but this affect diminishes with chain length and CH2CH2 rupture is equally probable at all positions for n‐alcanes heavier than decane. Methyl CH scission is 2.7 times less probable than methylene CH scission. The radiolysis of mixtures of protonated and deuterated n‐alcanes is shown to be able to give information concerning basic processes in radiation chemistry.
Zur Photochemie von Δ1,9‐10‐Methyl‐2‐octalon
Authors: Margaretha Paul , Schaffner Kurt 
Published: December 2004

AbstractSome aspects of the photochemistry of Δ1,9‐10‐methyl‐2‐octalone (1) were reinvestigated. In view of the hitherto neglected substantial thermal reversibility of the photolytic double bond shift under previous conditions of analysis (1) the solvent‐dependent selectivity in product formation in C6H6 and t‐BuOH was confirmed, (2) the essentially exclusive double bond shift and its intermolecular nature in C6F6 were established, (3) the quantum yields of the major products in these three solvents were measured, and (4) the dependence of triplet quenching data on temperature, enone concentration and conversion was shown in C6F6 for the double bond shift. In conclusion, the previously published experimental basis for the postulate of two differentially reactive triplet states of 1 is insufficient, although the postulate itself is not necessarily disproved.
On the Correlation between Ionization Potentials and Excitation Energies, part III: Pyrazine
Authors: Haselbach Edwin , Lanyiova Zuzanna , Rossi Michel 
Published: December 2004

AbstractA recently suggested scheme for relating ionisation potentials (IP) to excitation energies (E) has been applied to pyrazine and 2,6‐dimethylpyrazine. The results indicate that in these systems the energy gap (ΔE) between the two lowest lying 1n,π*‐states is significantly smaller than that (ΔIP) between the corresponding 2n‐states of the parent radical cations. The values estimated for ΔE on the basis of ΔIP, measurable by photoelectron spectroscopy, disagree with those calculated theoretically but seem to be supported by the experimental evidence available.Since ΔE = ΔIP would normally be expected, the relationship ΔE < ΔIP actually present in these systems is discussed and related to the different shape of the n‐MO's involved in the ionization and excitation processes.
Über Pterinchemie. 44. Mitteilung. Eine eindeutige Synthese isomerenfreier Folsäure
Authors: Bieri Jost H. , Viscontini Max 
Published: December 2004

AbstractA new, simplified and unequivocal synthesis of folic acid free of isomers is described. A melt of N(2′)‐acetyl‐6‐formylpterine and dimethyl‐N‐(p‐aminobenzoyl)‐L‐glutamate was quantitatively converted to 6‐azomethin‐pterine‐ester IV. NaBH4‐reduction followed by basic hydrolysis of acetyl and ester groups gives pure folic acid in good yield.
De la chimie des ptérines. 47e communication. Une confirmation de l'existence de dihydroptérines quinoïdiques: formation d'amino‐2‐alloxane pendant l'oxydation de tétrahydroptérines
Authors: Argentini Mario , Viscontini Max 
Published: December 2004

AbstractL'oxydation, dans des conditions physiologiques, de l'aminomethyl‐6‐diméthyl‐6,7‐tétrahydroptérine conduit à la formation d'amino‐2‐alloxane et d'aldéhyde acétique. Ces résultats étayent deux hypothèses déjà formulées par nous‐mêmes, à savoir: (a) qu'une dihydroptérine quinoidique apparaît comme produit intermédiaire d'oxydation, et (b) que le cycle pyrazine des tétrahydroptérines n'est pas stable et se laisse facilement ouvrir pendant l'oxydation avec possibilité de perte de la structure du noyau ptérinique.
The Mode of Incorporation of Farnesyl Pyrophosphate into Verrucarol. Preliminary communication
Authors: Arigoni Duilio , Cane David E. , Müller Beat , Tamm Christoph 
Published: December 2004

AbstractIn the course of the biosynthesis of verrucarol (3) from farnesyl pyrophosphate in Myrothecium roridum, strain S 1135, a hydride shift occurs from the central double bond of the precursor to C(2) of the product.
Die durch Silberionen katalysierte Umlagerung von Propargyl‐phenyläther
Authors: Koch‐Pomeranz Ursula , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

AbstractIt is known that propargyl‐phenylethers rearrange at about 200° to 2 H‐chromenes [1–4]. It is shown that this rearrangement occurs in benzene or chloroform at lower temperatures (20–80°) in the presence of silver‐tetrafluoroborate (or‐trifluoracetate). The ethers examined are presented in Scheme 1. Thus in chloroform at 61° in the presence of AgBF4, phenyl‐propargylether (3) yields 2 H‐chromene (13). With 0.78 molar equivalents AgBF4 in benzene at 80° the same ether 3 yields a 3:1 mixture of 2‐methyl‐cumaron (14) and 2 H‐chromene (13). From 1′‐methylpropargyl‐phenylether (4) and 2′‐butinyl‐3,5‐dimethylphenylether (5) under similar conditions the corresponding chromenes 16 and 17 resp. are obtained. Rearrangement of propargyl‐ and 2′‐butinyl‐1‐methyl‐2‐naphthylether (6 and 7 resp.) in benzene at 80° in the presence of AgBF4 gives the corresponding allenyl‐naphthalenones 18 and 19 resp. Treatment of propargyl‐ and 2′‐butinyl‐mesityl‐ether (8 and 9 resp.), and propargyl‐ and l′‐methylpropargyl‐2,6‐dimethyl‐phenylether (10 and 11 resp.) in benzene at 80° with AgRF, yields as the only product the corresponding 3‐allenyl‐phenols 21, 22,24 and 25 (Scheme 3). It is shown that in the presence of μ‐dichlor‐dirhodiuni (1)‐tetracarbonyl in benzene a t 80° the ether 4 rearranges to 2‐methyl‐2H‐chromene (16). However with this catalyst the predominant reaction is a cleavage to phenol. No reaction was observed when ethers 3 and 12, (Scheme 7 ) were treated with the tris‐(trimethylsily1)‐ester of vanadic acid in benzene a t 80° (see also [8]).By analogy with the known mechanism for thc silver catalysis of the reversible propargylesterl/allenylester rearrangement [S], the silver (1)ion is assumed to form a pre‐equilibrium π‐complex with the C, C‐triplebond of the substrate. This complex then undergoes a [3s, 3s]‐sigmatropic rearrangement (Scheme 2). In the case of the others 6, 7 and 12 the resulting allenyldienones were isolated. The 2,G‐dimethyl substituted ethers 8, 9, 10 and 11 resp. first give the usual allenyl‐ dienones (Scheme 3). These then undergo a novel silver catalysed dienon‐phenol‐rearrangement (Sclzenzu4) to give the 3‐allenylphenols 21, 22, 24 and 25. Thc others 3, 4 and 5 with free ortho positions presumably rearrange first to the non‐isolated 2‐allenyl‐phenols 15, 42 and 43 resp.(Scheme 7). These then rearrange, either thermally or by silver (1)ion catalysis to the 2H‐chromenes 13,16 and 17 resp. The rate of the rearrangement of 2‐allenylphenol (15) to 13 at room temperature in benzene or chloroform is approximately doubled when silver ions are present as catalyst.
Sur les dérivés de la fluorénone VI Les acides bromo‐3‐fluorénonecarboxylique‐2 et bromo‐2‐fluorénonecarboxylique‐3 et la bromo‐3‐méthyl‐4‐fluorénone
Authors: Chardonnens Louis , Horváth Ernö 
Published: December 2004

AbstractStarting from 2‐amino‐3‐bromo‐9‐oxofluorene and from 3‐methylfluorene respectively the preparation of 3‐bromo‐9‐oxofluorene‐2‐carboxylic acid and of 2‐bromo‐9‐oxofluorene‐3‐carboxylic acid is described. A synthesis of 3‐bromo‐4‐methyl‐9‐oxofluorene is also given.
Intramolekulare Additionen α‐lithiierter Amide; eine neue Synthese von 2‐Aryl‐ und 2‐Vinylindolen
Authors: Greuter Hans , Schmid Hans 
Published: December 2004

AbstractThe N‐alkylated 2‐benzoylamino‐benzophenones 2a–e on treatment with lithium diisopropylamide in tetrahydrofuran at − 78° gave the cyclic alchols 3a–e which were dehydrated with phosphorous oxychloride/pyridine to give the indoles 4a–e in 30–72% yield (Scheme 1).
Umlagerung von Prolinol‐Derivaten. 2. Mitteilung. N‐Alkoxycarbonyl‐prolinylester
Authors: Wiegrebe Wolfgang , Herrmann Ernst‐georg , Schlunegger Urs Peter , Budzikiewicz Herbert 
Published: December 2004

AbstractWhen heated, esters of N‐alkoxycarbonyl‐prolinol with arylsulfonic acids rearrange to alkylarylsulfonates and perhydro‐pyrrolo[1,2‐c]oxazol‐3‐one by an intermolecular process. The syntheses of pertinent prolinol derivatives are described and their mass‐spectrometric fragmentation processes investigated, using DADI‐analysis.
Steroide und Sexualhormone. 249. Mitteilung [1]. Zur Umwandlung von Dehydroabietinsäure in 14α‐Methylsteroide I Die Partialsynthese von 5‐Methoxy‐17‐oxo‐14α‐methyl‐Δ5, 7, 9‐des‐A‐östratrien
Authors: Wirthlin Toni , Wehrli Hansuli , Jeger Oskar 
Published: December 2004

AbstractA 18‐step transformation of dehydroabietic acid (1) into ketone 40, convenient starting material for the prparation of 14α‐methylsteroids, is described.
The Crystal and Molecular Structure of 3‐Oxo‐17β‐acetoxy‐Δ4‐14α‐methyl‐8α, 9β, 10α, 13α‐estrene
Authors: Koyama Gunji 
Published: December 2004

AbstractThe crystal and molecular structure of 3‐oxo‐17β‐acetoxy‐Δ4‐14α‐methyl‐8α, 9β, 10α, 13α‐estrene, C21H30O3, has been determined by X‐ray diffraction analysis. The crystals belong to the orthorhombic space group P212121, with the cell dimensions a = 12.093 Å, b = 19.667 Å, c = 7.746 Å; Z = 4. Intensity data were collected at room temperature with an automatic four‐circle diffractometer. The structure was solved by direct methods and the parameters were refined by least‐squares analysis. All the hydrogen atoms were included in the refinement. The final R value was 0.038 for 1413 observed reflections. The conformation of ring A is intermediate between a half‐chair and a 1, 2‐diplanar form. The hydrogens at C(9) and C(10) are anti, the B/C ring junction is trans, and rings B and C adopt chair conformations. Ring D is cis fused and is halfway between C2 and Cs forms.
Photochemie von Benzisoxazolen. (vorläufige Mitteilung)
Authors: Heinzelmann W. , Märky M. 
Published: December 2004

AbstractThe photochemical behaviour of benzisoxazoles 1 is remarkably solvent‐dependent: Irradiation in H2O or CH3O or CH3OH leads to benzoxazoles 2 in a virtually quantitative yield. However, at low concentrations of H2O or CH3OH in acetonitrile or hexane, photolysis of 3‐alkyl‐benzisoxazoles 1b–1e yields salicylamides 4 and salicylesters 5, while under these conditions o‐cyanophenol (3a) is the only photoproduct of benzisoxazole (1a). The course of these photochemical reactions is discussed from the standpoint of solvent‐dependence, multiplicity and the behaviour at low temperatures.
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

AbstractA 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.