bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cardenolides of Asclepias syriacaL., Probable Structure of Syrioside and Syriobioside. Glycosides and aglycones, 334th communication
Authors: Brown Peter , von Euw Josef , Reichstein Tadeus , Stöckel Klaus , Watson Thomas Robert 
Published: December 2004

AbstractAus den oberirdischen Teilen der Seidenpflanze, Asclepias syriaca L. (Asclepiadaceae) isolierten Masler et al. [2] [3] fünf krist. Cardenolide, u. a. Syriobiosid und Syriosid, denen sie die Formeln 5 und 6 zuschrieben. A. syriaca ist eine der Futterpflanzen, auf denen die Larven von Schmetterlingen leben, welche die Cardenolide der Nahrung zu speichern vermögen und dadurch von der Vertilgung durch insektenfressende Tiere (bes. Vögel) teilweise geschützt sind. Die Inhaltsstoffe der Pflanze variieren stark. Bei dem uns zur Verfügung stehenden Material enthielten Blätter und Stengel nur Spuren von Cardenoliden, relativ viel enthielten die Wurzeln. Aus solchen konnte krist. Syriosid sowie eine Spur krist. Syriobiosid direkt durch Chromatographie gewonnen werden, die Hauptmenge des letzteren wurde erst nach fermentativem Abbau mit β‐Glucosidasen erhalten. Chemische und physikalische Methoden zeigten, dass die vorgeschlagenen Formeln 5 und 6 unrichtig sind. Syriobiosid besitzt vermutlich Formel 7 und Syriosid Formel 10. Letzteres liefert bei fermentativem Abbau mit β‐Glucosidasen nicht Syriobiosid, wie die tschechischen Autoren glaubten, sondern einen um zwei H‐Atome ärmeren Stoff, den wir Desglucosyriosid (12) nennen. Die Formeln sind gut begründet, aber nicht eindeutig bewiesen. Syriosid und Syriobiosid enthalten somit als Zuckerbaustein eine 4,6‐Didesoxy‐hexosulose (33), wie sie im Gomphosid (20) und den Calotropis‐Cardenoliden (22, 24 etc.) vorkommt, die ebenfalls von den Larven der genannten Schmetterlinge mit der Nahrung aufgenommen werden und als Abwehrstoffe wirksam sind.
Veronicosid, ein neues Iridoidglucosid aus Veronica officinalisL.(Scrophulariaceae)
Authors: Sticher Otto , Afifi‐Yazar Fatma Ü. 
Published: December 2004

Veronicoside, a new iridoid glucoside from Veronica officinalis L. (Scrophulariaceae)A new iridoid glucoside, Veronicoside (1) has been isolated from Veronica officinalis L. The structure of 1 has been determined by chromatographic and spectroscopic analysis as 6‐benzoylcatalpol.
Photochemische Reaktionen. 103. Mitteilung [1]. Zur Photochemie konjugierter Epoxy‐en‐carbonylverbindungen der Jonon‐Reihe: UV.‐Bestrahlung α,β‐ungesättigter ε‐Oxo‐γ, δ‐epoxy‐carbonylverbindungen und Untersuchung des Mechanismus der Epoxy‐enon/Furan‐Isomerisierung
Authors: Frei Bruno , de Weck Guy , Müllen Klaus , Wolf Hans Richard , Jeger Oskar 
Published: December 2004

The Photochemistry of Conjugated γ,δ‐Epoxy‐ene‐carbonyl Compounds of the Ionone Series: UV.‐Irradiation of α,β‐Unsaturated ε‐Oxo‐γ,δ‐epoxy Compounds and Investigation of the Mechanism of the Isomerization of Epoxy‐enones to FuranesOn 1n, π*‐excitation (λ ≥ 347 nm; pentane) of the enonechromophore of 3, three different reactions are induced: (E/Z)‐isomerization to give 13 (7%), isomerization by cleavage of the C(γ)–C(δ) bond to yield the bicyclic ether 14 (36%) and isomerization by cleavage of the C(γ)O bond to give the cyclopentanones 15 (13%) and 16 (11%; s. Scheme 2). On 1π, π*‐excitation (λ = 254 nm; acetonitrile) 13 (14%), 15 (6%), and 16 (6%) are formed, but no 14 is detected. In contrast, isomerization by cleavage of the C(δ)O bond to give the cyclopentanone 17 (23%) is observed. The reaction 3→17 appears to be the consequence of an energy transfer from the excited enone chromophore to the cyclohexanone chromophore, which then undergoes β‐cleavage. Irradiation of 4 with light of λ = 254 nm (pentane) yields the analogous products 20 (18%), 21 (9%), 22 (7%), and 24 (7%; s. Scheme 2). Selective 1n, π*‐excitation (λ ≥ 280 nm) of the cyclohexanone chromophore of 4 induces isomerization by cleavage of the C(δ)O bond to give the cyclopentanones 23 (9%) and 24 (44%). Triplet‐sensitization of 4 by excited acetophenone induces (E/Z)‐isomerization to provide 20 (12%) and isomerization by cleavage of the C(δ)O bond to yield 21 (26%) and 22 (20%), but no isomerization via cleavage of the C(δ)O bond.It has been shown, that the presence of the ε;‐keto group facilitates C(γ)C(δ) bond cleavage to give a bicyclic ether 14, but hinders the epoxy‐en‐carbonyl compounds 3 and 4 from undergoing cycloeliminations.The activation parameters of the valence isomerization 13 → 18, a thermal process, have been determined in polar and non‐polar solvents by analysing the 1H‐NMR. signal intensities. The rearrangement proceeds faster in polar solvents, where the entropy of activation is about −20 e.u. Opening of the epoxide ring and formation fo the furan ring are probably concerted.
Hydroxid‐bewirkte Halogenwasserstoff‐Abspaltungen aus vic‐Dihalogeniden unter heterogenen Bedingungen: Reaktionssteuerung dank überraschender Solvens‐ und Metall‐Einflüsse
Authors: Tarchini Claudio , An Tran Dinh , Jan Gérald , Schlosser Manfred 
Published: December 2004

Hydroxide‐Promoted Dehydrohalogenation of vic‐Dihalides under Heterogeneous Conditions: Control Over the Reaction Outcome Due to Surprising Solvent and Metal EffectsSelective elimination of either one or two molecules of hydrogen halide from vic‐dihalides can be conveniently achieved by employing solid sodium or potassium hydroxide in the presence of solvents such as glycol dimethylether or tetraethyleneglycol dimethylether.
Thermische Umlagerung von 2‐Oxa‐bicyclo [3.3.1]‐non‐7‐en‐3‐on; eine neuartige Lactonumlagerung. Vorläufige Mitteilung
Authors: Fráter György 
Published: December 2004

Thermal Rearrangement of 2‐Oxa‐bicyclo [3.3.1]‐non‐7‐en‐3‐ones; a Novel Lactone RearrangementLactone (+)‐2 was prepared by iodolactonisation and subsequent elimination in 51% yield from the known acid (+)‐1 (Scheme 1). Alkylation of (+)‐2 furnished (+)‐3a, (+)‐3b and (+)‐3c, respectively (Scheme 2). Heating of (+)‐3a in boiling DMF racemized the compound ((+)‐3a ⇆ (−)‐4a). Heating of (+)‐3b and (+)‐3c, respectively, equilibrated them with (−)‐4b and (−)‐4c, respectively. This results are interpreted as a [3.3]‐sigmatropic rearrangement with a transition state as depicted in a.
Metal Complexes of Macrocyclic Ligands. XII. A Complexone‐like Tetraazamacrocycle
Authors: Häfliger Hans , Kaden Thomas A. 
Published: December 2004

AbstractThe complexone‐like tetraazamacrocycle 1 (LH4) forms a series of metal complexes with Co2+, Ni2+, Cu2+ and Zn2+ (M2+) of the type MLH2, ML2− and M2L, which have been isolated and characterized by VIS., IR. and NMR. spectroscopy. Based on these results tentative structures for the different species are proposed.
Triterpènes de la «mousse de chêne» (Evernia Prunastri (L.) ACH.). 5e Communication
Authors: Nicollier Gilles , Tabacchi Raffaele , Gavin José , Breton José Luis , Gonzalez Antonio G. 
Published: December 2004

Triterpenoids from ‘Oakmoss’ (Evernia Prunastri (L.) ACH.)Seven triterpenoids have been isolated from ‘oakmoss’ (Evernia Prunastri (L.) ACH.) extracts by column chromatography and identified as friedelin (1), taraxerol (2), 29‐nor‐21 α‐hopan‐3,22‐dione (3), moretenone (4), ursolic acid (5), lupeol (6) and lanosterol (7).
Synthese eines 33gliedrigen Polyaminolactams durch Anwendung der «zip»‐Reaktion. 6. Mitteilung über Umamidierungsreaktionen
Authors: Kramer† Urs , Schmid† Hans , Guggisberg Armin , Hesse Manfred 
Published: December 2004

Synthesis of a 33‐membered Polyaminolactam by Use of the Zip‐reactionThe pentaamino lactam derivative 11 was synthesized from the 13‐membered tosylaminolactam 2. The prolongation of the side chain was achieved using the phthalimido derivative 3. After removal of the protecting groups the resulting base 11 was treated with KAPA reagent (1,3‐propanediamine/potassium‐3‐aminopropyl‐amid). By zip‐reaction the 33‐membered 13, 17, 21, 25, 29‐pentaaza‐32‐dotriacontanelactam (1) was formed in 85% yield.
The Photorearrangements of a Naphthobarrelene‐like System. Dependence on excited‐state spin multiplicity and electronic configuration, and evidence for biradical intermediates. Preliminary communication
Authors: Demuth Martin , Bender Christopher O. , Braslavsky Slivia E. , Görner Helmut , Burger Ulrich , Amrein Walter , Schaffner Kurt 
Published: December 2004

Abstract8‐Benzoyl‐9‐deuterio‐naphtho [de‐2.3.4]bicyclo [3.2.2]nona‐2,6,8‐triene (1) rearranged quantitatively in a photochemical di‐π‐methane‐type process to 2‐, 6‐, and 9‐deuteriated 1‐benzoyl‐naphtho [de‐2.3.4]tricyclo [4.3.0.02,9]nona‐2, 6‐diene (8a–c). The phenylhydroxymethyl analogue 2 underwent a similar regioselective rearrangement to 9a–c. The rearrangement 1 → 8a–c is proposed to proceed along three reaction paths evolving from two primary photochemical processes of naphthylvinyl and vinyl‐vinyl bonding (1 → 3 + 6). Evidence for a competition between several paths and involvement of biradical intermediates derives from changes in the isotopomeric composition with temperature, and from laser flash detection (λexc 353 nm) of a transient. The dependence of the quantum yield for product formation from 1 on excitation wavelength and sensitizer triplet energy leads to the conclusion that reaction to the primary biradicals occurs directly from the S1 (n, π*) and T2 (n, π* ) states, and that reaction from T1 (π, π*) and from S2 (π, π*) proceed either directly or via T2.
Cyanohalogénométhylidènetriphénylphosphoranes. Note de Laboratoire
Authors: Tronchet Jean M. J. , Martin Oliver R. 
Published: December 2004

CyanohalogenomethylidenetriphenylphosphoranesIodo‐, bromo and chlorocyanomethylidenetriphenylphosphoranes are described as well as a procedure for the in situ generation of cyanofluoromethylidenetriphenylphosphorane. These ylides are reactive towards aldehydosugars.
Phenylselenoacetaldehyde, a Useful Reagent for the Homologative Conversion of Halides to Phenylselenomethyl Ketones
Authors: Baudat Roger , Petrzilka Martin 
Published: December 2004

AbstractThe conversion of primary, secondary and vinylic halides to the two C‐atoms homologated phenylselenomethyl ketones 8 is described. The method involves addition of the readily available phenylselenoacetaldehyde 5 to the Grignard reagents 9 and oxidation of the resulting β‐hydroxy‐selenides 10 (Scheme 3).
Anil‐Synthese. 20. Mitteilung. Über die Herstellung von Stilbenyl‐Derivaten des 1,2,4,‐Oxadiazols
Authors: Berger Hanny , Siegrist Adolf Emil 
Published: December 2004

Preparation of Stilbenyl Derivatives of 1,2,4‐OxadiazolesSchiffs bases derived from 3‐ and 5‐(p‐formylphenyl)‐phenyl‐1,2,4‐oxadiazoles and chloroanilines are reacted with various p‐tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). The reactivity of 5‐[4‐(chlorophenylimino‐methyl)phenyl]‐3‐phenyl‐1,2,4‐oxadiazoles is very low and side reactions will predominate.
Homonuclear Overhauser1H‐NMR. Experiments on the Carotenoid Pigments Lycopene and Prolycopene
Authors: Englert Gerhard 
Published: December 2004

AbstractThe recently proposed structure of the carotenoid pigment prolycopene as the 7,9,7′,9′‐tetra‐cis isomer of lycopene has been unambiguously confirmed by a series of homonuclear Overhauser 1H‐NMR. experiments at 270 MHz. Comparative measurements are reported for lycopene.
Complexation dans le méthanol anhydre de Cu (II) et Zn (II) par des ligands diaza‐polyoxamacrocycliques
Authors: Spiess Bernard , Arnaud‐Neu Françoise , Schwing‐Weill Marie‐José 
Published: December 2004

Complexation in anhydrous methanol of Cu (II) and Zn (II) with diaza‐polyoxamacrocyclic ligandsProtonation of five diaza‐polyoxamacrocyclic ligands, (L = [2.1], [2.2], [2.1.1.], [2.2.1], [2.2.2]), and their complexing properties towards Cu2+ and Zn2+ cations have been studied in anhydrous methanolic solutions.Potentiometric measurements have been carried out at 25°, using 5 · 10−2MEt4N+ClO as support‐electrolyte, in order to determine the nature of the species formed upon complexation and their stability constants. The results were confirmed by spectrophotometry, for the cupric complexes of [2.1] and [2.2.2], and the electronic spectra of the different complexes were calculated.Comparison between complexation in aqueous and methanolic solutions have been made: as in water, ML2+ species and sometimes protonated MHL3+ species, with higher stability constants, are present in methanol; but the main difference is the formation of dinuclear complexes M2L4+, between Cu2+ and all ligands except [2.1]. In these complexes the Cu2+ cations cannot be both ‘encaged’ in the ligand cavity because of its small size. The different possible structures are discussed in terms of the stability constants values. The protonation constants values and the existence of the binuclear complexes may indicate a possible conformational change in the complexing ligand on changing the solvent from water to methanol.
Synthesis and Properties of Some Spin Labeled Uridine and 2′‐Deoxyuridine Analogues
Authors: Ozinskas Alvydas J. , Bobst Albert M. 
Published: December 2004

AbstractThe synthesis of the spin‐labeled uridine and 2′‐deoxyridine analogues RUGT 2, DUGT 3, l‐RUGT 4, and l‐DUGT 5 is described. DUGT 3 showed some activity against the leukemia P388 cell line.
Enantioselektive 1,2‐Additionen von Li‐, Mg‐, Zn‐ und Cu‐organischen Verbindungen und von Li‐Enolaten an Carbonylverbindungen im chiralen Medium DDB
Authors: Seebach Dieter , Langer Werner 
Published: December 2004

Enantioselective 1,2‐addition of Li‐, Mg‐, Zn‐, and Cu‐organic compounds and of Li‐enolates to carbonyl derivatives in the chiral medium DDBDDB = 1,4‐Dimethylamino‐2,3‐dimethoxybutan (= 2,3‐Dimethoxy‐N,N,N′,N′‐tetramethyl‐1,4‐butandiamin).
The (+)‐enantiomer of the methoxyamine DDB is used as a chiral cosolvent in the title reactions. As evident from the results listed in the table, enantiotopic faces are generally differentiated with preferences ranging from 55:45 to 60:40.
Indor and 1H‐NMR. Studies of the Ansa Conformation of Hexahydrorifamycin S
Authors: Cassidei L. , Sciacovelli O. , Martinelli E. , Ripamonti A. , Gallo G. G. 
Published: December 2004

AbstractThe study of 16, 17, 18, 19, 28, 29‐hexahydrorifamycin S by 1H‐NMR. spectroscopy using INDOR at 100 MHz and homodecoupling at 270 MHz has shown that the conformation of the ansa fragment C(20)‐C(27) and the position of this fragment relative to the naphthoquinone chromophore are practically the same as those of rifamycin S. This finding rules out the hypothesis that the lower activity of the hydrogenated rifamycins could be due to a different conformation.
Strukturelle Abwandlungen am Vitamin D3. 3. Mitteilung [1]. Synthese und eigenschaften von SO2‐addukten des (5Z)‐ und (5E)‐vitamins D3
Authors: Reischl Wolfgang , Zbiral Erich 
Published: December 2004

Structural Modifications of Vitamin D3. Synthesis and Properties of the SO2‐Adducts with (5Z)‐ and (5E)‐Vitamin D3Treatment of (5Z)‐ and (5E)‐vitamin D3 (4) with sulfur dioxide yields each quantitatively the cyclic sulfones 1a and 1b. Thermally induced elimination of sulfur dioxide leads to either isotachysterol3 (3) alone or mixtures of isotachysterol3 (3) and isovitamin D3 (2). On the other hand the extrusion of SO2 can be brought about by means of KOH/CH3OH or on an alumina surface affording (5E)‐vitamin D3 (4). On treatment with CD3UD/tBuOK/D2O 1a and 1b are transformed (5E)‐6, 19, 19′‐trideuteriovitamin D3 (4a).
Chemistry of Superoxide Ion as Revealed by the Differential Oxidation of Arylpyruvates
Authors: Jefford Charles W. , Cadby Peter A. 
Published: December 2004

AbstractSuperoxide ion apparently reacts with acidic substrates via species such as O2, HO2, O, HO and H2O2. Arylpyruvates give arylacetates and arylaldehydes indicating competing nucleophilic and free radical oxidation. Benzaldehyde is further oxidized by free radical and nucleophilic dioxygen species giving benzoic acid. p‐Hydroxybenzaldehyde gives the corresponding benzoic acid which is best accounted for by HO2, since O and O2 are without effect. Hydroquinone is also produced presumably by nucleophilic attack of HO. Replacement of the acidic hydrogen atoms by sodium changes the product distribution in accord with these findings.
Inhaltsstoffe des Osmanthus‐Absolues. 5. Mitteilung. (8E)‐4, 7‐Epoxymegastigma‐5(11),8‐dien
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

Constituents of Osmanthus absolute, 5th communication. (8E)‐4,7‐Epoxymegastigma‐5(11),8‐dieneThe title compound 1 has been identified as trace constituent in Osmanthus absolute. The synthesis of 1 was performed by reaction of α‐ionone‐epoxide (4) with aluminum tri (isopropylate) in 2‐propanol at 130°. Besides 1 we found another bicyclic ether 5 in the lower boiling part of the reaction mixture, and ten further substances with interesting structural features from the less volatile part. Formation mechanism as well as some spectral particularities are discussed in more detail.
Conformation and Optical Activity of all‐trans, mono‐cis, and di‐cis Carotenoids: Temperature Dependent Circular Dichroism
Authors: Noack Klaus , Thomson Andrew J. 
Published: December 2004

AbstractThe CD. spectra of carotenoids with an asymmetric centre at C(3) have the following unusual features: (1) All‐trans and di‐cis compounds with two end‐rings, at least one of which possesses an asymmetric C‐atom, have very similar CD. spectra, whereas the corresponding mono‐cis compounds give mirror‐image CD. spectra; (2) In carotenoids or apocarotenoids with only one end‐ring all‐trans and mono‐cis compounds have the same CD. spectra; (3) The CD. spectra of such carotenoids are strongly temperature dependent either increasing in magnitude or completely changing in sign upon cooling.These properties have been rationalized with the aid of a model with takes the total chromophore of the carotenoid as being intrinsically chiral with symmetry C2. It seems that the chirality arises not only from the presence of the hydroxyl group of an asymmetric carbon atom, C(3), which occupies an equatorial position thereby locking the conformation of the end‐ring, but also from the steric hindrance across the formal single bond C(6), C(7), linking the end‐ring to the chain and thus creating a chiral π‐system. (The twist about the C(6), C(7)‐bond acquires a handedness because of the predominance of one conformational form of the end‐ring. In this way, the double bonds of the end‐ring become twisted out of the plane of the chain with one hand predominating. Thus the whole conjugated system becomes chiral). The reversal of sign between the trans (and di‐cis) and mono‐cis compounds is due to a tilt of the 2‐fold symmetry axis and thereby a change of chirality. The temperature dependence stems from the varying population of forms of different twist of the end‐group relative to the chain.Compounds with 7, 8‐triple bonds also show distinct CD. spectra and a sign change between all‐trans and mono‐cis isomers in addition to temperature dependence. The latter property demonstrates that some steric hindrance between the end‐ring and the main chain is present in these compounds.Some suggestions for the origins of the sign patterns and band intensities of the CD. and absorption spectra are included.
Carotinoid‐Glycosylester. 3. Mitteilung. Die synthese von crocetin‐di‐(β‐D‐glucosyl)‐ester. Eine neue methode zur selektiven veresterung von ungeschützter β‐D‐glucose
Authors: Pfander Hanspeter , Wittwer Fritz 
Published: December 2004

Carotenoid Glycosyl Esters. The Synthesis of Crocetin‐di‐(β‐D‐glucosyl) Ester. A New Method for the Selective Esterification of Unprotected β‐D‐GlucoseThe naturally occurring crocetin‐di‐(β‐D‐glucosyl) ester is easily synthesized by the reaction of crocetin‐di‐imidazolide or crocetin‐di‐(1,2,4‐triazolide) and unprotected β‐D‐glucose in pyridine in presence of a base (Scheme 4). Under the described experimental conditions the esterification takes place exclusively at the anomeric C‐atom and furthermore produces only the β‐anomer. It is the first time that an unprotected carbohydrate has been used for the selective synthesis of glucosyl esters at the anomeric C‐atom. This represents the major advantage of this new method.
Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S1vs. T2 Reactivities of Cyclopent‐2‐enyl Methyl Ketones
Authors: Henne Andreas , Siew Nancy P. Y. , Schaffner Kurt 
Published: December 2004

AbstractOn ultraviolet irradiation of the cyclopent‐2‐enyl methyl ketones 1a–c at −54° ⩽ t ⩽ 139°, photo‐CIDNP. effects of the starting ketones, the 1,3‐acetyl shifted isomers (2), and radical disproportionation and combination products (4–7) were observed. These effects show a unique dependence of the polarization phase on temperature which is a novel feature in photo‐CIDNP. studies. The results of the investigation, which also included experiments using triplet quenchers, triplet sensitizers and radical scavengers, are rationalized in terms of Schemes 2 and 3.α‐Cleavage is a major excited‐state reaction of 1a–c on direct irradiation. Temperature‐activated α‐cleavage (k(t)) to the radical pair R · · R′1 and intersystem crossing (kisc) to the T2 state are among the competing S1 deactivation processes. The T2 state in turn cleaves (k) to R · · R′3 A ‘low‐temperature range’ with kisc ≫ k(t) and a ‘high‐temperature range’ with k(t) ≫ kisc exhibiting preferential reactivity from the T2 and S1 states, respectively, can be defined for all three β,γ‐unsaturated ketones 1a–c.
High Syn Selectivity of a SE′ Reaction: Acylation of an Optically Active 1,1‐Disilyl‐2‐alkene. Preliminary communication
Authors: Wetter Hansjürg , Scherer Paul , Schweizer W. Bernd 
Published: December 2004

AbstractThe disilane/disilylmethane rearrangement of an optically active disilanyl sulfide 9B was used to prepare an optically active disilylalkene 10 whose absolute configuration was established by X‐ray analysis of the bromo derivative 13 (P21, a = 7.847 (3) Å, b = 9.487 (3) Å, c = 20.010 (8) Å, β = 82.28° (3), Z = 2). Acylation of 10 furnished an optically active ketone 14, which was degraded to 16, a compound of known absolute configuration. The enantiomeric excess of 10 was determined by alkylation with an optically active lithium compound and that of 14 by an optically active NMR.‐shift reagent. The SE′ reaction 10 → 14 was thus shown to proceed with 94% (97% syn/3% anti) stereoselectivity.
1‐Substituted 1,3‐Dihydroisothianaphthen‐2,2‐dioxides: Preparation and Use as ortho‐Quinodimethane Precursors in Intramolecular Cycloadditions. Preliminary communication
Authors: Oppolzer Wofgang , Roberts David A. , Bird T. Geoffrey C. 
Published: December 2004

Abstract1,3‐Dihydroisothianaphthen‐2,2‐dioxide (1) was readily converted to the 1‐substituted sulfones 3 by deprotonation and subsequent electrophilic attack (Scheme 3 and Table). The appropriate 1‐alkenyl‐ and 1‐alkenoyl‐sulfones 3 on heating at 213° to 240° underwent SO2‐extrusion to give, via the non‐isolated (E)‐quinodimethanes II (Scheme 1), polycyclic products such as 4, 6 and 7 in good yields (Schemes 4 and 5). On the other hand, thermolysis of the 1‐alkenoyl‐1‐thioether sulfones 9 furnished mainly the isochromenes 10 (Scheme 6).
Synthetische Verwendung von Epoxynitronen. III. Der anomere Effekt als bestimmender Faktor für die Konformation der 3‐Cyano‐perhydro‐1,2‐benzoxazine
Authors: Riediker Martin , Graf Walter 
Published: December 2004

The anomeric effect as a conformation determining factor for 3‐cyano‐perhydro‐1,2‐benzoxazinesAn unusual population of conformer II is found by 1H‐NMR. spectroscopy in the conformation equilibrium I⇄ II of 1b (Fig. 3) in which the non‐bonding nitrogen electronpair is anti‐periplanar to the CCN bond. This finding is interpreted in terms of a generalized anomeric effect operating in the α‐cyano‐hydroxylamin‐ether structural unit.