bluuebunny/crossref_metadata_2025 huggingface dataset:
On the stereochemistry of allylmetal‐aldehyde condensations. Preliminary communication
Authors: Denmark Scott E. , Weber Eric J.
Published: December 2004

The stereochemical course of the intramolecular allylsilane‐aldehyde condensation of 1a has been investigated. A modest preference for the product arising from a synclinal orientation of double bonds was observed with Lewis‐acid catalysts. Cyclization induced by fluoride ion resulted in stereochemical reversal.
Deoxy‐nitrosugars. 5th Communication. The anomeric effect of the nitro group
Authors: Aebischer Bernard , Hollenstein Roger , Vasella Andrea
Published: December 2004

The 1‐deoxy‐1‐nitro‐D‐manno‐pyranose 4 was transformed into the nitroolefin 5 and hence into the anomeric 1,2‐dideoxy‐1‐nitro‐3, 4, 6‐tri‐O‐benzyl‐D‐arabino‐hexopyranoses (3a and 3b; cf. the Scheme). Conformational analysis of 1‐benzyloxy‐2‐nitroethane (6) by 1H‐NMR spectroscopy (Fig. 2) showed the synclinal conformation to be more stable than the antiperiplanar one by about 1.4 kcal/mol (attractive gauche‐effect). This gauche‐effect favours the 1‐deoxy‐1‐nitro‐2, 3, 4, 6‐tetra‐O‐benzyl‐β‐D‐manno‐hexopyranose (1b) possessing an equatorial nitro group, which is, however, qualitatively the less stable anomer. The relative concentrations of the anomers of 1 and 3, respectively, were determined by 1H‐NMR spectroscopy after base catalyzed equilibration at 37° in CHCl3‐solution (Table). Anomeric effects for the nitro group of approximately 2.4 kcal/mol in 3 and of approximately 3.4 kcal/mol in 1 were calculated.
Stable Liquid Crystals with Large Negative Dielectric Anisotropy. Part IV
Authors: Osman Maged A. , Huynh‐Ba T.
Published: December 2004

Stable liquid crystals with negative dielectric anisotropy containing the bicyclo [2.2.2]octyl group were synthesized. The incorporation of this moiety in the molecules increased the thermodynamic stability of the mesophase and lowered the smectic tendency. These new compounds can be useful in liquid crystal mixtures for homeotropic nematic displays.
The chemistry of thujone. VIII. Thujone as a chiral synthon for the synthesis of optically active steroid analogues. The enol lactone route
Authors: Kutney James P. , Grice Peter , Pascoe Keith O. , Piotrowska Krystyna , Rettig Steven J. , Szykula Jerzy , Trotter James
Published: December 2004

The thujone‐derived enone 1 is converted via enol lactone intermediates 4 and 5 to the optically active steroidal analogue 13 and the corresponding 19‐norsteroid analogue 14. The structure of 13 was determined by X‐ray diffraction analysis. The acid‐catalyzed cyclopropane‐ring opening of 13 and ozonolysis of the resulting olefin provided the 16‐keto‐steroid analogue 18.
The chemistry of thujone. IX. Thujone as a chiral synthon for the synthesis of optically active steroid analogues. The vinylpicoline route
Authors: Kutney James P. , Grice Peter , Piotrowska Krystyna , Rettig Steven J. , Szykula Jerzy , Trotter James , Van Chu Loc
Published: December 2004

The thujone‐derived enone 1, upon base‐catalyzed reaction with 2‐methyl‐6‐vinylpyridine is converted to the pyridine analogue 5 (Scheme 1). Catalytic reduction of the latter to 6 generates two new centers of chirality which eventually become C(8) and C(14) in the ultimate synthetic steroid analogue 12. An X‐ray analysis of 6 establishes the structure and absolute configuration so as to determine its suitability in subsequent synthetic studies. The acetal derivative 7, via Birch reduction, hydrolysis, and internal aldol cyclization, is converted into the cyclohexenone analogue 10 (Scheme 2). This ‘one‐pot’ process affords an efficient conversion of the pyridine ring into a cyclohexenone system required for A‐ring construction of the steroid skeleton. Finally, conversion of 10, via the unsaturated diketone 11, provides the chiral steroid analogue 12.
Umwandlung von Bicyclo [3.2.0]hept‐2‐en‐6‐on in Cyclopentadienessigsäure‐Derivate
Authors: Wallquist Olof , Rey Max , Dreiding André S.
Published: December 2004

Conversion of Bicyclo [3.2.0]hept‐2‐en‐6‐one into Cyclopentadienylacetic Acid Derivatives

The reaction of a mixture of 4exo‐bromobicyclo [3.2.0]hept‐2‐en‐6‐one (2) and ‐7‐one (3) with O‐ or N‐nucleophiles yielded cyclopentadien‐5′‐yl‐acetates 4a–f or‐acetamides 4g–h. Due to their rapid isomerization, the products 4 were not isolated, but some of them were demonstrated spectroscopically or captured in situ with maleimide as 10′‐substituted norbornene derivatives 7. The formation of 4 from 2/3 involves a fragmentation of the bond between the carbonyl and the bridge‐head C‐atom, induced by the attacking nucleophile and the leaving Br‐ion and aided by the relief of the four‐membered ring strain. Some of the isomerization products of 4, i.e. the cyclopentadiene‐1′‐yl‐ and 2′‐yl‐acetyl derivatives were captured with maleimide as the 1′‐ and 8′‐substituted norbornene‐derivatives 8 and 9. Two C‐nucleophiles did not induce the fragmentation: sodium acetylacetonate substituted the Br‐atom and sodium (diethoxyphosphoryl)ethoxycarbonylmethide condensed with the carbonyl group of 2/3, yielding 11/12 and 13/14, respectively.
Correction for Inner Filter Effects in Fluorescence Spectroscopy
Authors: Lutz Hans‐Peter , Luisi Pier Luigi
Published: December 2004

A method is proposed for correcting experimental fluorescence readings for inner filter effects, i.e. the absorption of the exciting light and/or the absorption of the emitted radiation, which cause the non‐linearity between fluorescence intensity and fluorophor concentration. Basically the method consists of measuring the fluorescence intensity at two different points along the diagonal in the cell. Unlike similar methods proposed in the literature, the two points are corrected simultaneously for both absorption of excitation and of emission radiation without the necessity of reading the optical density of the solution, and with a very simple data elaboration.
Carbon Participation in the Solvolysis of 6‐ and 7‐Substituted 2‐Norbornyl p‐Toluenesulfonates. Norbornanes, Part 11
Authors: Flury Peter , Grob Cyril A.
Published: December 2004

The solvolysis rates and products of several 7‐anti‐substituted 2‐endo‐norbornyl p‐toluenesulfonates 11 have been determined and compared with those of the previously reported 6‐exo‐substituted 2‐exo‐norbornyl p‐toluenesulfonates 1. Although the number of bonds between the substituent and the reaction site is the same in the two series, the inductive effect of the substitutents is transmitted far more strongly in the 6‐exo‐2‐exo‐series 1 than in the 7‐anti‐2‐endo‐series 11; i.e. their inductivities differ widely. It is concluded that through space induction involves graded bridging of the substituent‐bearing C‐atom to the incipient cationic center at C(2) and that this involves differential bridging strain. The different reactivities of unsubstituted 2‐exo‐ and 2‐endo‐norbornyl derivatives can then be ascribed to a stereoelectronic effect.
Die Hydrolyse von 7‐anti‐substituierten p‐Toluolsulfonsäure‐[2‐endo‐und 2‐exo‐norbornyl]estern. Norbornanreihe. 12. Mitteilung
Authors: Flury Peter , Grob Cyril A.
Published: December 2004

The Hydrolysis of 7‐anti‐Substituted 2‐endo‐ and 2‐exo‐Norbornyl p‐Toluenesulfonates

The hydrolysis products of the title compounds have been determined. The preparation of the hitherto unknown solvolysis products is described.
Nucleotide, XVII. Synthese von homogenen Adenosyl‐3′,5′‐Oligomeren nach dem Phosphotriester‐Verfahren
Authors: Flockerzi Dieter , Uhlmann Eugen , Pfleiderer Wolfgang
Published: December 2004

Nucleotides, XVII. Synthesis of Homogeneous Adenosyl‐3′,5′‐oligomers by the Phosphotriester Method

The chemical synthesis of the fully protected trimer 12, the tetramers 11 and 23 as well as the pentamer 14 was achieved in preparative scales starting from the fully blocked adenosine‐3′‐phosphotriesters 1, 2, and N6‐benzoyl‐2′,3′‐bis‐O‐(tert‐butyldimethylsilyl)adenosine (6). All intermediates and end products have been isolated, purified and characterized by elemental analyses, UV, and CD spectra. Deprotection of the various blocking groups proceeds without difficulties to afford the free trimeric, tetrameric, and pentameric oligoadenylates 15, 16, and 24 in high yields.
The Radical Ions of Indolizino [6,5,4,3‐aij]quinoline and Some of its Derivatives
Authors: Gerson Fabian , Metzger André
Published: December 2004

Indolizino [6,5,4,3‐aij]quinoline (1) and its 3,9‐dimethyl‐ (2), di‐tert‐butyl‐ (3) and diphenyl‐(4) derivatives yield persistent radical cations which have been studied by ESR and ENDOR spectroscopy. The corresponding radical anions have also been prepared, but only that of 3 was amenable to a complete characterization by hyperfine data. The π‐spin populations in the radical anions are essentially localized on the 13‐membered C‐perimeter, and thus both the HOMO and LUMO of 1 exhibit an ‘annulenyl character’. The radical anions of 1 and 2 have gradually been converted into those of the corresponding 3,4‐dihydro derivatives (1‐H2 and 2‐H2) which have been unambiguously identified by a combination of preparative and spectroscopic methods.
Synthese von β‐D‐Glucopyranosiden einiger hydroxylierter Vitamin‐D‐Verbindungen
Authors: Fürst Andor , Labler Ludvik , Meier Werner
Published: December 2004

Synthesis of β‐D‐Glucopyranosides of some Hydroxylated Vitamin‐D Compounds

Cholesta‐5, 7‐diene‐1α, 3β‐diol (1a) was glycosylated with ‘α‐acetobromoglucose’ (2) as well as with ‘α‐acetobromocellobiose’ (4) to yield the 3‐(glycosides) 1b and 1c, respectively. Irradiation of these products with UV light followed by thermal isomerization led to the corresponding vitamin‐D derivatives 3a and 3c. Direct glucosylation of vitamin D3 (3f) and vitamin D2 (5a) with 2 gave the derivatives 3g and 5b, respectively. With 25‐hydroxycholecalciferol ( = calcidiol; 6a) as substrate, besides the 3‐(glucoside) 6b small amounts of the C(25)‐analog 6c were formed. The reaction of 1α, 25‐dihydroxycholecalciferol ( = calcitriol; 6e) with 2 furnished the 3‐ and the 1‐(glucoside) (6f and 6g, respectively) as the major components and the C(25)‐analog 6h in minor quantity. From the acetylated 3‐(glucosides) 3a, 3g, 5b, 6b, and 6f, the free glucopyranosides 3b, 3h, 5c, 6d, and 6i, respectively, were prepared as well as the free glucopy‐ranosyl‐glucopyranoside 3d from the acetylated disaccharide 3c.
Discrimination between an Antiparallel and a Parallel β5.6‐Helix Using 1Hα‐NMR Spin‐Lattice Relaxation
Authors: Lorenzi Gian Paolo , Tomasic Lera , Bangerter Felix , Neuenschwander Peter , Di Blasio Benedetto
Published: December 2004

The 1H‐NMR spectrum of Boc‐(L‐Val‐D‐Val)4‐OH in CDCl3 can be attributed either to an antiparallel or to a parallel double‐stranded β5.6‐helical structure. To resolve this ambiguity, T1‐measurements have been carried out for the α‐protons of Boc‐(L‐Val‐D‐Val)4‐OH and its monodeuterated analogue Boc‐(L‐Val‐D‐Val)2 ‐α‐2H‐L‐Val‐D‐Val‐L‐Val‐D ‐Val‐L‐Val‐D‐Val‐OH. The results show that the Hα of the fifth residue in one strand is close to the Hα of the seventh residue in the other strand, as expected for an antiparallel arrangement, a conclusive demonstration that the correct structure of Boc‐(L‐Val‐D‐Val)4‐OH is antiparallel.
Studies related to biological detoxification of kraft pulp mill effluent. VII. The biotransformation of 12‐chlorodehydroabietic acid with mortierella isabellina
Authors: Kutney James P. , Hewitt Gary M. , Salisbury Philip J. , Singh Mahatam , Servizi James A. , Martens Dennis W. , Gordon Robert W.
Published: December 2004

A detailed study of the biodegradation of one of the fish‐toxic chlorinated resin acids, 12‐chlorodehydroabietic acid (3), is discussed. When 3 is exposed to the fungus Mortierella isabellina, it is converted into the monohydroxylated metabolites 2α‐hydroxy‐12‐chlorodehydroabietic acid (5) and 16‐hydroxy‐12‐chlorodehydroabietic acid (8) after short‐term (26 h) incubation, and into the 2α, 16‐dihydroxy derivatives 11 and 14 after 96 h incubation. These metabolites show low levels of toxicity to fish.
New Sesquiterpenoids from Clary Sage Oil (Salvia sclarea L.)
Authors: Maurer Bruno , Hauser Arnold
Published: December 2004

Six sesquiterpenoids, (R, 5E)‐2, 12‐epoxycaryophyll‐5‐ene (1), (2 R, 5E)‐caryophyll‐5‐en‐12‐al (2), (2S, 5E)‐caryophyll‐5‐en‐12‐al (3), isospathulenol (4), (1R, 5R)‐ 1,5‐epoxysalvial‐4(14)‐ene (5), and salvial‐4(14)‐en‐l‐one (6) have been identified for the first time in clary sage oil (Salvia sclarea L.). The structures and absolute configurations of 1–6 are corroborated by partial syntheses and their organoleptic properties are discussed.

The compounds 5, 6 and mintsulfide (14) possess the rare C‐skeleton C, for which the semisystematic name ‘salvialane’ is proposed. The sesquiterpenoids 1–5 are new.
Photochemische Reaktionen 130. Mitteilung. Zur Photochemie von 5,6‐Epoxy‐1,3‐dienen: Der Einfluss eines 7‐Hydroxysubstituenten auf die Carbenbildung
Authors: De Weck Guy , Nakamura Norio , Tsutsumi Kentaro , Wolf Hans Richard , Frei Bruno , Jeger Oskar
Published: December 2004

Photochemistry of 5,6‐Epoxy‐1,3‐dienes: Influence of a 7‐Hydroxy Substituent on the Carbene Formation

On singlet excitation (λ=254 nm) in MeCN the hydroxy‐epoxydiene (E)‐4 undergoes photocleavage to the carbene intermediates d and e as main processes. The carbene d, showing behaviour typical of vinyl carbenes, undergoes addition to the adjacent double bond furnishing the cyclopropenes 5A + B. The carbene e, however, undergoes an insertion reaction into the neighbouring carbinol C,H‐bond leading to the enol intermediate 21, which gives rise to the compounds 6A + B and 7A + B. To a lesser extent the products 8A + B are formed via another enol intermediate (32). On photolysis of (E)‐4 in MeOH instead of MeCN the enol intermediates 21 and 32 undergo rapid tautomerisation to the ketones 9A + B (main products) and 11.
Bestimmung der Struktur von Phenyläthinyllithium in Lösung mittels Tieftemperatur‐NMR‐Spektroskopie
Authors: Hässig Robert , Seebach Dieter
Published: December 2004

The dimeric and tetrametic structures of complexes of phenylethinyllithium, as recently discovered by X‐ray analysis in the solid state, were also found to be present in solution. Tetrahydrofuran solutions of 1‐(6Li)‐[1‐13C]‐2‐phenylethyne in the presence or absence of N,N,N′,N′‐tetramethylpolymethylenediamines show a pentuplett 13C‐NMR signal [δ=140 ppm, J(C,Li)=8.2 Hz] from the labelled C‐atom at low temperatures (−95 to −110°). This proves the dimeric structure. When (6Li)BuLi is added, a mixed dimer [(C6H5CCLi)(C4H9Li)] is formed [δ=142 ppm, J(C,Li) = 7.8 Hz]. This is converted to a mixed tetramer [(C6H5CCLi)(C4H9Li)3] upon addition of larger amounts of (6Li)BuLi, as concluded from a signal at δ = 133.5 ppm, J(C,Li) = 5.6 Hz. The multiplicity of this signal suggests that a static tetramer is present, in which the C‐atoms couple only with three next Li‐neighbors.
Über die Enantiomerentrennung durch Verteilung zwischen flüssigen Phasen. 3. Mitteilung. Selektivität der lipophilen Weinsäureester für chirale Ammonium‐Salze verschiedener Konstitution und Konfiguration
Authors: Prelog Vladimir , Mutak Stjepan , Kovačević Krunoslav
Published: December 2004

Separation of Enantiomers by Partition between Liquid Phases. 3. Communication. Selectivity of Lipophilic Tartaric Acid Esters for Chiral Ammonium Salts of Different Constitution and Configuration

Several methods are described which allow determination on a small scale of the enantiomer distribution constant Q, and the affinity coefficient P, which characterize the enantioselectivity and the affinity of a lipophilic phase for ammonium salts of different constitution and configuration.

The influence of concentration of the tartaric acid ester, temperature, concentration and type of the lipophilic anion on Q and P was investigated to find out favourable experimental conditions for resolutions of racemates by iterative process, e.g. partition chromatography.

The relationship between Q and the configuration of aminoalcohols 1–12 was explored and the observed regularities are pointed out.

In addition it was found that lipophilic tartaric acid esters are enantioselective to salts of threo‐1,2‐diphenyl‐1,2‐ethanediamine 13, and to phenylglycine and its derivatives 14–16.
Butatrien durch Thermolyse von Propiolsäure‐(2‐propinyl)ester
Authors: Bilinski Vanda , Dreiding André S. , Hollenstein Hans
Published: December 2004

Flow thermolysis of 2‐propynyl propiolate (5) at 580° afforded butatriene (6) (ca. 50%) and, as by‐products, 4‐methylene‐2‐cyclobuten‐1‐one (7), 2‐ethynylpropenal (8), 1‐penten‐4‐yn‐3‐one (9), 4‐penten‐2‐ynal (10) (total ca. 10%), along with some propynal, acetylene, CO2 and CO. In the same way, propiolic acid (1,1‐D2)‐2‐propynyl propiolate (11) led to (1,1‐D2)‐butatriene (12) and a little 4‐((D2)methylene)‐2‐cyclobuten‐1‐one (13). A mechanism is proposed for the transformation of 5 into 6 and of 11 into 12, which also accounts for the formation of 7,8,9 and 10, as well as 13. The position of one of the published 13C‐NMR signals of butatriene (6) must be revised. Thermolysis of methyl‐(1) and ethyl propiolate (2) resulted in small yields of 2‐buten‐4‐olide (3) and 2‐penten‐4‐olide (4).
2‐Vinylcyclobutanones by Cycloaddition of Vinylketenes to Simple Olefins
Authors: Jackson David A. , Rey Max , Dreiding André S.
Published: December 2004

Selected [2+2]‐cycloadditions of three alkylvinylketenes 2 to one mono‐ and seven dialkyl‐olefins 3 yielded eleven 2‐alkyl‐2‐vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl‐elimination from α,β‐unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]‐cycloadditions were fully regio‐ and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that ‐ where possible ‐ two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their 1H‐NMR, spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.
The Tricyclooctanone Approach to the Total Synthesis of Steroids. The Cyclization of the A‐CD Unit
Authors: Mikhail Gamal , Demuth Martin
Published: December 2004

The first steps of a novel approach to the total synthesis of 9, 11‐dehydroestrone via tricyclo[3.3.0.02,8]octan‐3‐one (2) are described. One route involves a tandem‐type transformation of the key intermediate 3 (A‐CD unit) consisting of cyclopropane cleavage and ring B closure to afford C, 18‐bisnor‐13 α, 17 α‐estradiol derivatives. E.g. the 3‐methoxy‐9 ζ‐hydroxy‐17 α‐methanesulfonyloxy derivative (‐)‐6 has been synthesized in 8 steps and 10% overall yield from 1,3‐cyclohexadiene. As an alternative, the A‐CD type intermediate 4b has been prepared and could be used for a ring C enlargement prior to cyclization.
Synthesen und chemisches Reaktionsverhalten neuer überbrückter Chinonderivate. Kupplungsreaktionen von Diazoniumsalzen mit 2‐Methoxy‐1,6‐methano [10]annulen
Authors: Neidlein Richard , Radke Christoph Martin
Published: December 2004

Syntheses and Chemical Properties of New Bridged Quinone Derivatives. Coupling Reactions of Aryldiazonium Salts with 2‐Methoxy‐1,6‐methano[10]annulene

Coupling of 2‐methoxy‐1,6‐methano[10]annulene (3) with the aryldiazonium salts 4a‐4i yields the quinone hydrazones 5a‐5i. The spectroscopic properties of these products are described. The reaction of 3 with 4‐nitrophenyldiazonium tetrafluoroborate buffered with sodium acetate in dry methanol yielded after chromatographic separation the azo derivative 7 on the one hand and a mixture of the valence tautomers 8a and 8b on the other.
Isolement et identification de la C‐galactosyl‐8 apigénine dans les tiges feuillées de Carlina acanthifolia
Authors: Proliac Arlette , Raynaud Jean
Published: December 2004

Isolation and Identification of 8‐C‐Galactosylapigenin from Leaves of Carlina acanthifolia

8‐C‐galactosylapigenin was isolated from the leaves of Carlina acanthifolia (Compositae). This identification represents only the third report of a mono C‐galactosylapigenin in plants and the first report in the Compositae.
Réarrangements en milieu acide trifluoroacétique de deux alcaloïdes indoliques: la desformocorymine et la dihydrocorymine
Authors: Massiot Georges , Lavaud Catherine , Vercauteren Joseph , Le Men‐Olivier Louisette , Lévy Jean , Guilhem Jean , Pascard Claudine
Published: December 2004

The rearrangement in trifluoroacetic acid of two indole alkaloids of the echitamine series, desformocorymine (14) and dihydrocorymine (9), has been investigated. Desformocorymine (14) was tranformed into a mixture of carbinolamines 17a,b, with the akuammiline skeleton, which were reduced (Et3SiH, CF3CO2H) into an isomer 12 of cathafoline (6). This sequence constitutes the first example of an interconversion of the corymine skeleton into the akuammiline skeleton (Scheme 2). In the case of dihydrocorymine (9), the rearrangement followed a different pathway owing to the formation of a hemiacetal between the primary alcohol CH2(17)‐OH and a carbonyl formed at C(3). Treatment of this hemiacetal 26 with aqueous base led to its opening with concomitant formation of a lactam. 13C‐NMR seems to indicate that this lactam exists under a hydrated form 27. This highly unstable intermediate was cleanly transformed (MeONa‐MeOH) into a 2‐acyl indole 30 (Scheme 4), the structure of which was determined by X‐ray crystallography. The formation of this acylindole involves the rupture of the C(7)C(16) bond; it is the reverse of the reaction generally postulated as occurring in the biogenesis of the pentacyclic alkaloids. The structure of a by‐product 34 was established as 17‐hydroxymethylvincoridine by X‐ray crystallography.

The acid‐catalyzed rearrangements involve the rupture of the Ph‐NCN chromophore, with formation of a carbonyl at C(3). The reversibility of these steps is used in an easy correlation of dihydrocorymine and of 3‐epidihydrocorymine via their trifluoroacetates.
Efficient Molecular Catalysis of ATP‐Hydrolysis by Protonated Macrocyclic Polyamines
Authors: Hosseini Mir Wais , Lehn Jean‐Marie , Mertes Mathias P.
Published: December 2004

Molecular catalysis of ATP‐hydrolysis by a number of protonated macrocyclic polyamines 1–9 has been investigated by 31P‐NMR spectroscopy, and marked rate enhancements have been obtained. The largest acceleration is produced by the [24]‐N6O2 macrocycle 1, and the process displays the following properties: 1. protonated 1 forms very stable complexes with ATP, as well as with ADP and AMP; 2. it enhances the rate of ATP‐hydrolysis by a factor of 103 at pH = 8.5; the rate of hydrolysis is constant over a wide pH‐range, from pH = 2.5 to 8.5; 3. 1 is more efficient than acyclic analogues; 4. the products of the reaction are orthophosphate (OP) and ADP, which is subsequently hydrolyzed to OP and AMP at a slower rate; 5. at pH > 6.5, a transient species is detected, which is tentatively identified as a phosphoramidate intermediate, resulting from phosphorylation of the macrocycle 1; 6. the reaction presents first‐order kinetics and is catalytic. The mechanism of the process is discussed in terms of initial formation of a complex between ATP and protonated 1, followed by an intracomplex reaction which may involve a combination of nucleophilic or acid catalysis with electrostatic catalysis.
Competitive Formation of Ylide and Carbene Intermediates from 1π,π*‐Excited α,β‐Unsaturated γ,δ‐Epoxyketones
Authors: Bischofberger Norbert , Frei Bruno , Wirz Jakob
Published: December 2004

Laser flash photolyses (λ = 265mm) of the γ,λ‐epoxyenones 1–3, 7 and 8, the α,β‐unsaturated γ,δ‐epoxy ester 6, and the epoxytriene 9 at ambient temperature produced short‐lived transients with broad absorption maxima in the visible region, which are identified as carbonyl ylides. Comparison of the rather long‐wavelength absorption maxima with the results of standard PPP SCF SCI calculations suggests that some degree of twisting is present in all the ylides studied. The lifetimes of the order of hundreds of ns of these intermediates and Stern‐Volmer analysis of the trapping of the carbonyl ylide derived from 2 with CH3COOH provide conclusive evidence that the carbene products are not formed via the carbonyl‐ylide intermediate (Scheme 3).
A Novel Pentannulation Sequence. Facile Access to Key Intermediates for the Synthesis of Exaltone® and Muscone
Authors: Fehr Charles
Published: December 2004

Treatment of the sulfonyl ketones 1a and 1b with potassium t‐butoxide in toluene or with potassium hydroxide in toluene/dimethyl sulfoxide affords in high yield the bicyclic dienes 3a and 3b, important precursors for Exaltone® and (±)‐muscone. An application of this novel pentannulation sequence is demonstrated for the sulfonyl ketones 6, 10, and 14. An intermolecular variant is exemplified by the synthesis of diene 22.
Photoreduction of Cyclic α‐Fluoroketones
Authors: Reinholdt Karin , Margaretha Paul
Published: December 2004

Irradiation of the α‐fluoroketones 1a and 6a in i‐PrOH selectively affords the parent ketone 1b and 6b, respectively. It is concluded that in this solvent heterolytic C‐F bond cleavage of the anion radical‐formed by electron transfer to the excited fluoroketone‐is a faster process than the subsequent protonation by the cation radical of the solvent. In cyclohexane 1b and 6b are only formed in minor amounts, the fluorinated RH‐reduction product 4 now being the major product from 1a. In non‐reducing solvents as t‐BuOH or benzene 2‐fluorocyclohexanone (1a) exhibits a similar behavior as cyclohexanone (1b) on excitation. The quantum yields for α‐cleavage are alike for both compounds, but oxetane formation with 2‐methylpropene as olefinic component occurs much more readily with 1a than with 1b.
Synthesis of Cycloprop[b]anthracenes via Trapping of o‐Naphthoquinodimethane
Authors: Müller Paul , Rodriguez Domingo
Published: December 2004

Cycloprop[b]anthracenes 1, 1a, 1b are prepared in a 3‐step synthesis starting from o‐di(iodomethyl)benzene. The key step consists of trapping of o‐naphthoquinodimethane (9) with 1,2‐di‐ and tetrahalogenocyclopropenes (3, 3a, 4b).
Radikaltrianionen von Isopyrenen
Authors: Huber Walter
Published: December 2004

Radical Trianions of Isopyrenes

The radical trianions derived from acepleiadylene (1), dicyclopenta [ef,kl]heptalene (2) and dicyclohepta [cd, gh]‐pentalene (3) are described. Whereas the hyperfine data of \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} are consistent with the predictions of an HMO‐McLachlan‐procedure, the corresponding data of \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} substantially differ from the calculated values. The spin distribution in \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} is polarized by the counterions in such a way, that the hyperfine data of this radical trianion no longer reflect the D2h‐symmetry of the neutral compound 3 and the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}. In addition, the interaction of the charged organic ion \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} with the counterions influences the energy of the low‐lying antibonding molecular orbitals LUMO (lowest unoccupied molecular orbital) and NLUMO (next lowest unoccupied molecular orbital). The passage from a looser ion pair (\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}/3Li+) to a tighter ion pair (\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}/3Na+, \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}/3K+) causes a change in the orbital sequence of LUMO and NLUMO.
Construction of Large Carbocyclic Rings by Ireland‐Claisen Rearrangement of O‐Silylated Lactone Enolates: Synthesis of (±)‐muscone
Authors: Brunner Rudolf K. , Borschberg Hans‐Jürg
Published: December 2004

(±)‐Muscone (5) has been synthesized from methyl 13‐(chloroformyl)tridecanoate (6) in nine steps in an overall yield of 24%. The key steps involve an efficient transformation of the readily accessible 14‐hydroxy‐15‐methyl‐15‐hexadecenoic acid (9) into the tetradecanolide 1 and a subsequent Ireland‐Claisen rearrangement of its triethylsilyl enolate 2 to a 8:1‐mixture of the stereoisomeric 15‐membered carbocycles 4 and 10 (Scheme 4).
On cardioactive steroids. XII. The synthesis of (natural) bufalin and α′‐isobufalin
Authors: Wiesner Karel , Tsai Thomas Y. R. , Sen Alina , Kumar Ravindra , Tsubuki Masayoshi
Published: December 2004

An efficient and simple synthesis of bufalin (1) via furan‐containing intermediates is described. The same method was also used for the synthesis of α‐isobufalin (2) which was prepared with equal simplicity, but in lower yield.
Propellanes. Part LXIX. Preparation of lactones from the three isomeric [4.3.3]propellane‐8,11‐diols
Authors: Bhanumati Soundararajan , Ashkenazi Pnina , Migdal Shmuel , Ginsburg David
Published: December 2004

Each of the three isomeric[4.3.3]propellane‐8,11‐diols was lactonized by using 1, ω‐diacids of different chain lengths. The minimal chain length required to bridge the syn‐syn diol is –CO(CH2)11CO–.
Propellanes. Part LXXII. The structure of the 4‐methyl‐1,2,4‐triazoline‐3,5‐dione adduct of the propellane lactone obtained by oxidation of biphenylene
Authors: Ashkenazi Pnina , Kaftory Menachem , Ginsburg David
Published: December 2004

The title compound reacts with the dienophile by attacking the face of a cyclo‐hexadiene ring which is syn‐ to the lactone ring.
Zum Mechanismus der α‐Alkinon‐Cyclisierung: Synthese und Thermolyse von 1‐(1‐Methylcyclopentyl)[3‐13C]prop‐2‐inon
Authors: Koller Manuel , Karpf Martin , Dreiding André S.
Published: December 2004

On the Mechanism of the α‐Alkynone Cyclization: Synthesis and Thermolysis of 1‐(1‐Methylcyclopentyl)[3‐13C]prop‐2‐ynone

The relative migratory aptitude of two acetylenic substituents in the α‐alkynone cyclization, a thermal conversion of α‐acetylenic ketones A to 2‐cyclopentenones C, was investigated by isotope‐labeling experiments. The α‐alkynone [β‐13C]‐1, specifically labeled with 13C at the β‐acetylenic C‐atom C(3), was synthesized by an intramolecular Witting reaction (230–300°) of the diacylmethylidenephosphorane [13C]‐7. The latter resulted from acylation of methylidenetriphenylphosphorane with the acid chloride 4 to yield the acylmethylidenephosphorane 5, which in turn was formylated with acetic [13C]formic anhydride ([13C]‐6.) Upon thermolysis of [β‐13C]‐1, its label at C(β) was transferred almost exclusively to C(β) of the 2‐cyclopentenone moiety in the resulting cyclization product [13C]‐2. We conclude that there is a distinct preference for hydrogen migration in the acetylene → alkylidene carbene isomerization (A → B) which precedes the cyclization step (B → C). No evidence was found for a fast reversibility of this isomerization (A ⇄ B) involving both acetylenic substituents.
The He(Iα) Photoelectron Spectra of the Perfluoroderivatives of Trisannelated Benzenes and Tetrakisannelated Cyclooctatetraenes
Authors: Heilbronner Edgar , Wirz Jakob , Soulen Robert L.
Published: December 2004

The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4(F)

3,3,4,4,7,7,8,8,11,11,12,12‐Dodecafluorotetracyclo[8.2.0.02,5.06,9]dodeca‐1,5,9‐triene

, tris(perfluorocyclopenta)benzene 5(F)

1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9‐Octadecafluoro‐2,3,4,5,6,7,8,9‐octahydro‐1H‐trindene.

, tetrakis(perfluorocyclobuta)cyclooctatetraene 6(F)

3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16‐Hexadecafluoropentacyclo[12.2.0.02,5.06,9.010,13]hexadeca‐1,5,9,13‐tetraene.

, and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7(F)

1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12‐Tetracosafluoro‐1,2,3,4,5,6,7,8,9,10,11,12‐dodeca‐hydrotetracyclopenta[a,c,e,g]cyclooctene.

are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6(F) retains the D4h‐conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.
Photochemical reactions. 132nd communication. Photochemistry of 5,6‐epoxy‐5,6‐dihydro‐7‐methyl‐β‐ionine: Influence of a methyl group at the enone side chain on the oxirane cleavage
Authors: Siewnski Antoni , Henggeler Barbara , Wolf Hans Richard , Frei Bruno , Jeger Oskar
Published: December 2004

1n, π*‐Excitation of the γ,δ‐epoxy‐enone (E)‐3 leads exclusively to the conformers (Z)‐3A + B. On 1π, π*‐excitation of (E)‐3, in addition to (Z)‐3A + B, products 6–9 arising from a carbene intermediate e are formed. However, products of an isomerization via C(γ), O‐bond cleavage of the oxirane were not formed on either mode of excitation. On thermolysis, at 80° the conformer (Z)‐3A is transformed into (Z)‐3B, which on photolysis returns to (Z)‐3A and (E)‐3. At 160°, however, (Z)‐3B rearranges to the isomers 6, 10 and 11.
Stereochemistry of an Ene Reaction Involving 1,7‐Dienes; Bicyclo[3.3.1]nonanes from (3‐Cyclohexenyl)diallylcarbinols
Authors: Thomas Alan F. , Lander‐Schouwey Marina
Published: December 2004

(3‐Cyclohexenyl)diallylcarbinols undergo a thermal retro‐ene reaction to give crotonylcyclohexenes at ca. 200°. A side‐reaction is an ene reaction to give bicyclo[3.3.1]nonanes. These become the main products above 300°. The stereochemistry of 2‐allyl‐1,4,6‐trimethylbicyclo[3.3.1]‐6‐none‐2‐ols and related compounds is discussed, and a case is described in which the allyl group is not freely rotating.
Molecular Structure of the Bis[tris(2‐aminoethyl)aminecyano]dicobalt(III) Ion and its UV/VIS Spectrum
Authors: Fallab Silvio , Zehnder Margareta
Published: December 2004

Formation of μ‐peroxodicobalt(III) complexes has been studied in solutions containing tris(2‐aminoethyl)aminecobalt(II) and additional monodentate ligands X. Depending n the nature and the concentration of X and on pH, singly bridged [(tren)XCoOOCoX(tren)]4+ and/or doubly bridged [(tren)Co(C2OH)Co(tren)]3+ are formed. The UV/VIS spectra of these complexes are discussed on the basis of a theoretical model which stresses the importance of the dihedral angle of the CoOOCo‐group. [(tren)(CN)CoOOCo(CN)(tren)](ClO4)2 has been synthesized and its structure determined by single crystal X‐ray diffraction. The CoOOCo‐group of the cation is planar. Solutions of the complex as well as the solid show two CT bands in the 300–400 nm region.
Complexation de l'argent(I) par des teramines cycliques
Authors: Suet Elisabeth , Laouenan André , Handel Henri , Guglielmetti Robert
Published: December 2004

Complexation of Silver(I) by Cyclic Tetramines

The nature of Ag(I)‐complexes with 1,4,8,11‐tetraazacyclotetradecane (1), 1,5,9,13‐tetraazacyclohexadecane (2) 1,5,10,14‐tetraazacyclooctadencane (3) and 1,6,11,16‐tetraazacycloeicosane (4) is studied. The effect of ring size on disproportionation of the Ag() cation in the presence of ligand is reported. The stability of Ag(I)‐complexes with 3 and 4 in aqueous solution is determined by means of potentiometric titration.
The structure of melinonine‐E, a quaternary indole alkaloid from Strychnos melinoniana baillon. Part 190: Studies on organic natural products
Authors: Borris Robert P. , Guggisberg Armin , Hesse Manfred
Published: December 2004

The structure of melinonine‐E (2) with relative configuration was established on the basis of spectral data for 2 and its acetate 3.
1, 1‐Difluoro‐1H‐cyclopropa[a]naphthalene
Authors: Müller Paul , Nguyen‐Thi Huong‐Can
Published: December 2004

1, 1‐Difluorocyclopropa[a]naphthalene (1b) is prepared in three steps from 4‐bromo‐1,2‐dihydronaphthalene (7) via carbene addition, benzylic bromination and bidehydrohalogenation. Structural evidence for formation of 1b is based on 1H‐ and 19F‐NMR spectroscopy. Compound 1b is stable in solution at −30°. Upon reaction with MeOH/H+ it is converted to a 1:2 mixture of 1‐ and 2‐methylnaphthoate (10 and 11, respectively).
Synthetic routes to trace constituents of algal pheromone bouqets and other information‐imitating substances
Authors: Boland Willhelm , Mertes Karin
Published: December 2004

Structural modifications of multifidene (1), viridiene (2) and ectocarpene (5) led to the synthesis of eleven new pheromone components or imitatin substances mostly by Grignard alkylation of cyclopentene and cycloheptadiene synthons. A new lactone α,ω dienol conversion is reported.
Radikalionen von überbrückten [14] Annulenen. Untersuchungen zum Frontorbitaleinfluss auf Reaktivität und Bindungszustand
Authors: Huber Walter
Published: December 2004

Radical Ions of Bridged [14] Annulenes. Investigations on the Influence of Frontier Orbitals on Reactivity and Bonding

The radical anions and the radical cations derived from trans‐15, 16‐dimethyl‐1, 4:8,11‐ethandiyliden[14]annulene (6), trans‐15‐methyl‐1,4:8,11‐ethandiyliden[14]annulene (7) and cis‐15, 16‐propano‐1,4:8,11‐ethandiyliden[14]annulene (8) are described. The hyperfine data of the radical anions 6, 7 and 8 resemble those of the structurally related radical anions of trans‐10b, 10c‐dimethyldihydropyrene (4) and trans‐10b, 10c‐dihydropyrene (5). This finding leads to the conclusion, that the change in the relative arragement of the saturated bridge within the fourteen‐membered π‐perimeter by passing from 4 (5) to 6 (7, 8) does not in fluence the energetic sequence of the lowest unoccupied molecular orbitals. The behavior of 6 and 7 towards oxidation parallels the photochemical reactivity of 4. The hyperfine coupling constants of the radical cations derived from 6 and 7 indicate that the removal of an electron is accompanied by an isomerization of the molecular framework. The investigation of the electron transfer process gby cyclic voltammetry supports these findings. The radical cations prefer the cyclophane‐like structures 6a and 7a, in which the central σ‐bond (C(15)–C(16) bond) is broken.
Differential Bridging in the Solvolysis of Epimeric Bicyclic Sulfonates, Norbornanes, Part 17
Authors: Grob Cyril A. , Waldner Adrian , Zutter Ulrich
Published: December 2004

The solvolysis rates and products of the 2‐exo‐ norbornyl, bicyclo[3.2.1]oct‐8‐yl, bicyclo[3.3.1]non‐2‐yl, bicyclo[3.2.1]oct‐6‐yl, bicyclo[3.2.1]oct‐2‐yl and bicyclo[3.2.2]non‐6‐yl p‐toluenesulfonates 10–15, respectively, are reported. The exo/endo rate ratios for these epimeric secondary tosylates in 80% EtOH varied from 1125 for 11 to 1.6 for 15. The relative rates varied between 2278 for exo‐10 and 4 ·10−3 for endo‐11. The hydrolysis products were mainly rearranged alcohols and olefins. The unrearranged alcohols from the exo‐tosylates were formed with complete or predominant retention of configuration, whereas those derived from the endo‐tosylates were mostly inverted. These results confirm the hypothesis that relative rates, as well as products, are largely determined by the degree of bridging between the cationic center and a dorsal C‐atom in the transition state and in the resulting ion pairs. Since bridging is a directed bonding interaction, it is subject to the same angle and conformational strains as ordinary covalent bonds. But bridging requires less geometrical change than the formation of normal bonds and of nonclassical ions.
Über die Bildung von Dihydro‐1,2‐oxazin‐N‐oxiden durch intramolekulare Addition eines Nitronat‐Anions an eine Carbonylgruppe
Authors: Kienzle Frank , Fellmann Jean‐Yves , Stadlwieser Josef
Published: December 2004

The Formation of Dihydro‐1,2‐oxazine N‐Oxides through an Intramolecular Addition of a Nitronate Anion to a Carbonyl Group

Highly substituted 4‐keto‐1‐nitroalkanes cyclize under basic conditions to dihydro‐1,2‐oxazine N‐oxides. These N‐oxides are thermally unstable and decompose to 1,4‐diketones, BF3 catalyzes a similar decomposition, but probably via a different mechanism.
Stereoselectivity in reactions of metal complexes IX Stereoselective formation of cobalt(III) complexes with new linear pentadentate ligands
Authors: Bernauer Klaus , Pousaz Philippe
Published: December 2004

The synthesis of cobalt(III) complexes with the new linear pentadentate ligands meso‐ and racemic 2,6‐bis(3S)‐3‐carboxy‐4‐methyl‐2‐azapentylpyridine (2) are described. Only one of the different possible isomers is obtained from each ligand. The structure of the complexes has been assigned on the basis of their 1H‐NMR and CD spectra. The structure of the aqua‐cobalt(III)‐1a and the aqua‐cobalt(III)‐1b has been confirmed by X‐ray analysis. Partial resolution of optical antipodes of the aquacobalt(III)‐1b was achieved by column chromatography and a tentative assignment of their absolute configuration is made.
Photochemical reactions, 136th communication. Photochemistry of conjugated epoxyenones and dienes of the ionone series: Influence of a neighboring spiro‐oxirane function
Authors: O'Sullivan Anthony , Frei Bruno , Jeger Oskar
Published: December 2004

The preparation and photolyses of the diepoxyenones (E)‐8 and (E)‐9 as well as the diepoxydiene (E)‐10 are described. On 1π,π*‐excitation (λ = 254 nm), the diastereoisomeric diepoxyenones (E)‐8 and (E)‐9 undergo isomerization via the ylide intermediate f and the carbene intermediate g leading to the primary photoproducts 17A and 18–21 (Scheme 8). On 1n, π*‐excitation (λ > 347 nm), (E)‐8 shows behaviour typical of epoxyenones undergoing C(γ), O‐bond cleavage of the oxirane and isomerization to compounds 22, (E/Z)‐23 and (E)‐24 (Scheme 10). On singlet excitation, the diepoxydiene (E)‐10, is cleaved to the carbonyl ylide j and the carbenes 1 and m (Scheme 11). The carbonyl ylide j fragments via the dipolar intermediate k to the acetylenic dienone (E)‐31. The carbene 1, showing behaviour typical of vinyl carbenes, furnishes the cyclopropene 30. The alternative carbene m, however, undergoes an insertion reaction into the neighboring oxirane C,C‐bond leading to the proposed but not isolated oxetene 43, which is further transformed to the products 33A _ B by an intramolecular cycloaddition.
Asymmetric induction bny enantiotopically differentiating retro‐claisen reaction of P{rochiral bicyclic β‐diketones
Authors: Duthaler Rudolf O. , Maienfisch Peter
Published: December 2004

The possibility of preparing cycloalkanones with an asymmetric β‐C‐atom by enantiotopically differentiating retro‐Claisen reactions of bicyclic diketones a (Scheme l) is tested with the decalin‐1,8‐diones 1 and 7, as well as with the bicyclo[3.3.0]octane‐2,8‐diones 10 and 11. Treatment of the reactive dione 1 with chiral tetra‐alkyl titanate catalysts results in a low optical induction (13%, Scheme 2). Cleavage with the Nasalts of a‐amino‐alcohols and hydrolysis of the resulting amides or esters gives much better optical yields, reaching 86% ee with dione 1 and (−)‐ephedrine (Scheme 3). Almost as efficient is N‐methylephedrine with 75% optical induction (Scheme 5). Lower enantiotopical differentiation is, however, observed with (−)‐ephedrine and diones 7 (44% ee), 10 (8% ee), and 11 (48% ee) (Schemes 3 and 4, Table l), or with dione 1 and L‐prolinol (37% ee) or (−)‐2‐amino‐1‐butanol (11% ee) (Scheme 5, Table 2). The moderate chemical yields of these transformations (500–70%) can be ascribed to side‐reactions of the ketones under the strongly basic conditions.
Synthesis of a S‐(Carboxymethyl)cysteine Analog of (L‐2‐Amino‐6‐adipyl)‐L‐cysteinyl‐D‐valine and its Cell Free Biosynthetic Conversion into 6‐[2‐(D‐2‐Amino‐2‐carboxyethyl)thio) acetamido]penicillanic Acid
Authors: Shields James E. , Campbell Charles S. , Duckworth Dale C. , Neuss Norbert , Queener Steven W.
Published: December 2004

A new tripeptide (dimer), bis[(L‐cysteine‐S‐acetyl)‐L‐hemicystinyl(S2 → S2)‐D‐valine] (6) was synthesized by coupling N‐(tert‐butoxycarbonyl)‐S‐carboxymethyl‐L‐cysteine benzyl ester (1) with S‐trityl‐L‐cysteinyl‐D‐valine benzyl ester and subsequent removal of the protecting groups. After reduction of the disulfide, the free tripeptide Cys (CH2CO‐Cys‐D‐Val) (Ib) was used as a substrate of isopenicillin‐N synthetase in a cell‐free conversion to 6‐[2‐((D‐2‐amino‐2‐carboxyethyl)thio)acetamido]penicillanic acid (IIa).
HNO, an Intermediate in (Light‐induced) Rearrangement Reactions of Nitrosooxy Compounds and Nitrosamines
Authors: Müller René‐Pierre , Murata Shigeo , Nonella Marco , Huber J. Robert
Published: December 2004

IR‐spectroscopic investigations of light‐induced rearrangement reactions of nitrosooxymethane (CH3ONO3), nitrosooxyethane (CH3CH2ONO) and N,N‐dimethylnitrosamine ((CH3)2NNO) in low‐temperature rare‐gas matrices have established that these molecules are transformed in two photolysis steps to the previously unknown C‐nitroso compounds nitrosomethanol (CH2(OH)(NO)), 1‐nitrosoethanol (CH3CH(OH)(NO)), and methyl(nitrosomethyl)amine CH2(NO)(NH)(CH3). Evidence for a similar rearrangement reaction has been advanced for N‐Nitrosopyrrolidine magnified image which is converted to C‐nitrosopyrrolidine magnified image. The matrix‐isolation technique in combination with wavelength‐selective irradiation allowed to trap and characterize an intermediate of rearrangement which revealed to be nitroxyl (HNO) complex (CH2…HNO, CH3CHO…HNO, CH3N = CH2…HNO, and magnified image). Since these findings have a close resemblance with rearrangement reactions of more complex nitrosooxy compounds, nitrosamines, or nitrosohydrazines used in organic synthesis, it is suggested that also in these reactions nitroxyl is present as an intermediate species.
Aliphatic Liquid Crystals with Positive Dielectric Anisotropy
Authors: Osman Maged A. , Huynh‐Ba T.
Published: December 2004

Cyanothyl‐subsituted cylohexyl cyclohexanoates, bi(cyclohexanes) and phenyl cyclohexanes were synthisized. Their mesmorphic behaviour is compared to that of the corresponding cyano derivatives. (Cyanoethyl)cyclohexyl cyclohenxanoates show mesmorphic properties in contrast to the corresponding cyano derivative. Separation of the cyano substituent from the rigid core of an anisotropic aliphatic compound by methylene groups enhances the thermodynamic stability of the mesophase. In aromatic compound, the cyanoethyl group leads to lower clearing points. These phenomena are attributed to teh influence of steric effects on the packing density and to the dependence of the clearing point on molecular association.