bluuebunny/crossref_metadata_2025 huggingface dataset:
Photolyse des 3‐Phenyl‐2, 1‐benzisoxazols und einiger seiner Derivate in Salzsäure bzw. Schwefelsäure
Authors: Giovannini Edgardo , De Sousa Bernardo F. S. E.
Published: December 2004

Photolysis of 3‐phenyl‐2,1‐benzisoxazole and some derivates in hydrochloric and sulfuric acid

The photolysis of 3‐phenylanthranils (3‐phenyl‐2, 1‐benzisoxazoles) in conc. hydrochloric or sulfuric acid leads to the formation of 5‐substituted 2‐amino‐benzophenones wherein the 5‐substituent is the anion of the acid employed. 5‐Halo‐substituted 3‐phenylanthranils, however, show a differing reaction pattern in the two acids. Whereas 2‐amino‐3, 5‐dihalo‐benzophenones are obtained when photolysis is effected in conc. hydrochloric acid, irradiation in sulfuric acid causes the hydroxy group to substitute the halogen which migrates to the 4‐position of the 2, 1‐benzisoxazole to yield 2‐amino‐5‐hydroxy‐6‐halo‐benzophenones. A similar behaviour in sulfuric acid is also observed with 5, 7‐dichloro‐3‐phenylanthranil. When the 5‐position of the anthranil is blocked by a phenyl group, irradiation in conc. hydrochloric acid leads to entry of the halogen mainly in this 5‐phenyl substituent, as can be expected from mesomeric structures.

The reaction mechanisms for the photolytic behaviour of 3‐phenylanthranils in both conc. hydrochloric and sulfuric acid is discussed.
Pyrrole Ligands. III. The Stability of Dipyrromethenato Complexes of Cu (II) and Ni (II) in Aqueous Solutions
Authors: Stünzi Hans , Anderegg Giorgio
Published: December 2004

The protonation and complex formation of the new ligand 3,3′, 5,5′‐tetramethyl‐dipyrromethene‐4,4′‐dicarboxylate in aqueous solutions was investigated by alkalimetric titrations and spectrophotometric measurements (25°, I = 1 (KNO3)). The pK values for the NH groups are 8.03 and 16.1 and logβ2 of the complexes with Cu (II) and Ni (II) are 31.0 and 24.4, respectively. Comparison with other ligands shows that the dipyrromethenato group acts as a normal rigid aromatic dinitrogen ligand, despite the charge on one nitrogen atom.
Zur Photochemie von 1H‐ und 2H‐Indazolen in saurer Lösung
Authors: Georgarakis Emanouil , Schmid Hans , Hansen Hans‐Jürgen
Published: December 2004

On the Photochemistry of 1H‐ and 2H‐Indazoles in Acidic Solution

It is shown that 1H‐ and 2H‐indazoles (cf. Scheme 2) on protonation (0, 1N H2SO4 in water or alcoholic solution) give analogous indazolium ions (see Fig. 1 and 2) which on irradiation undergo heterolytic cleavage of the N (1), N (2) bond whereby aromatic nitrenium ions in the singlet ground state are formed (cf. Scheme 13). If the para position of these nitrenium ions is not occupied by a substituent (e.g. a methyl group) they are readily trapped by nucleophiles present (e.g. water, alcohols, chloride ions) to yield the corresponding 5‐substituted 2‐amino‐benzaldehydes or acetophenones (cf. Schemes 4–10). Photolysis of indazole (4) and 3‐methyl‐indazole (5) in 0,75N H2SO4 in alcoholic solutions gives in addition minor amounts of the corresponding 3‐substituted 2‐amino‐benzaldehydes and acetophenones, respectively (cf. Schemes 6 and 8 and Table 2). Phenylnitrenium ions carrying a methyl group in the para position give in aqueous sulfuric acid mainly the reduction products, i.e. 2‐amino‐5‐methyl‐benzaldehydes (cf. Schemes 11 and 12 and Table 3). In methanolic sulfuric acid, in addition to the reduction products, 6‐methoxy substituted benzaldehydes are found (cf. Schemes 11 and 12 and Table 3) which are presumably formed by an addition‐elimination mechanism (cf. Scheme 18). It is assumed that precursors of the reduction products are the corresponding nitrenium ions in the triplet ground state. Singlet‐triplet conversion of the nitrenium ions may become efficient when addition of nucleophiles to the singlet nitrenium ions is reversible (cf. Scheme 22) thus, enhancing the probability of conversion or when conjugation in the singlet nitrenium ions is disturbed by steric effects (cf. Scheme 20) thus, destabilizing the singlet state relative to the triplet state.
Einige bestrahlungsexperimente mit 2, 1‐Benzisothiazolen
Authors: Jackson Barry , Schmidt Hans , Hansen Hans‐Jürgen
Published: December 2004

Some Irradiation Experiments with 2, 1‐Benzisothiazoles

2, 1‐Benzisothiazole (1) on irradiation with a mercury high‐pressure lamp in benzene/diethylamine yields, after acetylation, 2‐acetylamino‐benzaldehyde (3; Scheme 1). Similarly, irradiation of 3‐chloro‐2, 1‐benzisothiazole (2) in benzene/diethylamine leads to a mixture of 3‐dimethylamino‐2, 1‐benzisothiazole (6a) and N, N‐diethyl‐thioanthranilamide (7a; Scheme 2). Benzisothiazole 6a, on irradiation, is not transformed into 7a. On the other hand, when 2 is irradiated in methanol a mixture of 3‐methoxy‐2, 1‐benzisothiazole (4a) and methyl anthranilate (5a; Scheme 2) is obtained. In this case, 4a on irradiation in methanol or ethanol also yields 5a. No exchange of the methoxy group in 4a is observed when the irradiation is performed in ethanolic solution. Thus, 2, 1‐benzisothiazoles 1, 2 and 4a react photochemically by N,S‐bond cleavage and hydrogen‐atom abstraction from the solvent (Scheme 3). 3‐Chloro‐2, 1‐benzisothiazole (2) shows a second photoreaction, i.e. nucleophilic exchange of the chloro substituent by methanol or diethyl amine. The latter reaction can also be observed thermally, e.g. in boiling methanol in the presence of methoxide ions.
Valenzisomere aromatischer systeme. Die Synthese des Pyrrolo‐3‐azabenzvalens
Authors: Burger Ulrich , Dreier Francine
Published: December 2004

Valence Isomers of Aromatic Systems. The Synthesis of Pyrrolo‐3‐azabenzvalene

4‐Azapentalenyl anion (4) is shown to react with dichloromethane/butyl lithium in two fundamentally different ways depending on whether diethyl ether or tetrahydrofuran is chosen as solvent. In the first case a tetracyclic valence isomer of indolizine, i.e. pyrrolo‐3‐azabenzvalene (6) is formed together with indolizine (8) itself. In THF however, a pyrrylbutenyne (9), isomeric with the products mentioned above is obtained in a stereospecific reaction. Once again the appearance of indolizine (8) accompanies the reaction. Mechanistic implications, based on the finding that the heterovalene 6 is not a precursor of the pyrrylbutenyne 9, are discussed.
Synthesis of angiotensins, bradykinins and substance P octapeptides in which the residues Phe and Tyr have been replaced with car and of [Car1, Leu5]‐enkephalin
Authors: Leukart Othmar , Escher Emanuel , Regoli Domenico , Schwyzer Robert
Published: December 2004

Thirteen peptides, analogues of bradykinin (BK), enkephalin, Substance P (SP) and [Sar1]‐angiotensin II ([Sar1]‐ATII) have been synthesized by the solid‐phase method. In all these peptides the residue Phe and Tyr were substituted with the boron‐containing amino‐acid L‐o‐carboranylalanine (Car). The purity and identity of the peptides were established by TLC., cellulose‐electrophoresis and amino acid analysis.
Sur les dérivés de la fluorénone. IX. La (pyridyl‐2)‐3‐fluorénone, la méthyl‐2‐(pyridyl‐2)‐3‐fluorénone et la méthyl‐3‐(pyridyl‐2)‐3‐fluorénone
Authors: Chardonnens Louis , Sunder‐Plassmann Paul , Stauner Thomas
Published: December 2004

Fluorenone Derivatives. IX. 3‐(Pyrid‐2‐yl)‐fluorenone, 2‐methyl‐3‐(pyrid‐2‐yl)‐fluorenone, and 2‐(3‐methyl‐pyrid‐2‐yl)fluorenone

Unsuccessful attempts to synthesize an aza‐cis‐fluorenacene system starting from 2‐aza‐chalcone or 6‐methyl‐2‐aza‐chalcone led to the title compounds.
Photoenolisation. X.. An ab initio SCF‐CI study
Authors: Sevin A. , Bigot B. , Pfau M.
Published: December 2004

The processes involved in photoenolisations are theoretically simulated by an ab initio SCF‐CI method, using cis‐2‐butenal as a prototype structure. The prominent role of the hydroxyl group conformation in the resulting transient (2a) is emphasized; its rotation ‘out of the reaction site’ allows the next reaction paths to proceed exothermally. The equilibration of the different types of twisted biradicals in the triplet manifold, which only involves a low energy barrier, is thus possible, populating in quite equal weights the precursors of both E‐ and Z‐dienols. In the singlet state, the formation of the Z‐isomer is expected to be kinetically dominant. An examination of the role of the substituents suggests that, in related systems, the steric crowding induces important structural relaxation of the dienol geometries.
Versuche zur Synthese von Nonafulvenen und von Nonaheptafulvalen
Authors: Rutsch Werner , Frey Alfred , Neuenschawander Markus , Engel Peter
Published: December 2004

Attempted Synthesis of Nonafulvenes and of Nonaheptafulvalene

The reaction of cyclononatetraenide with α‐bromobenzyl acetate (6) as well as with 1,1‐dihalodimethylether gives at −50°, instead of the expected cyclononatetraenes, bicyclo[6.1.0]nona‐2,4,6‐triene derivatives 10d and 16 (Scheme 3 and 5, respectively). It seems that in some cases the well known thermally disrotative valence isomerization of cyclononatetraenes 7 to 3a, 7a‐dihydroindenes 8 is much slower than the formation of bicyclo[6.1.0]nona‐2,4,6‐trienes of the type 10 and 16. This type of reaction hurts the Woodward‐Hoffmann rules.

Possible precursors of the attractive nonaheptafulvalene are prepared by reaction of acetoxy‐tropylium fluoborate (19a) as well as of bromo‐tropylium bromide (19b) with lithium‐cyclononatetraenide (Scheme 8). So far, the attempted gas‐phase pyrolysis of the precursors 21a and 21b failed to give nonaheptafulvalene (5).
Reaktionen von 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin mit. NH‐aciden Heterocyclen; Synthese von 4H‐imidazolen
Authors: Mukherjee‐Müller Gabriele , Chaloupka Stanislav , Heimgartner Heinz , Schmid† Hans , Link Helmut , Bernauer Karl , Schönholzer Peter , Daly John J.
Published: December 2004

Reactions of 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine with NH‐Acidic Heterocycles; Synthesis of 4H‐Imidazoles

In this paper, reactions of 3‐dimethylamino‐2,2‐dimethyl‐2H‐azirine (1) with heterocyclic compounds containing the structure unit CONHCONH are described. 5,5‐Diethylbarbituric acid (5) reacts with 1 in refluxing 2‐propanol to give the 4H‐imidazole derivative 6 (Scheme 2) in 80% yield. The structure of 6 has been established by X‐ray crystallography. Under similar conditions 1 and isopropyl uracil‐6‐carboxylate (7) yield the 4H‐imidazole 8 (Scheme 3), the structure of which is deduced from spectral data and the degradation reactions shown in Scheme 3. Hydrolysis of 8 with 3N HCl at room temperature leads to the α‐ketoester derivative 9, which in refluxing methanol gives dimethyl oxalate and 5‐dimethyl‐amino‐2,4,4‐trimethyl‐4H‐imidazole (10). On hydrolysis the latter is converted to the known 2,4,4‐trimethyl‐2‐imidazolin‐5‐one (11) [6]. Quinazolin‐2,4 (1H, 3H)‐dione (12) and imidazolidinetrione (parabanic acid, 14) undergo with 1 a similar reaction to give the 4H‐imidazoles 13 and 15, respectively (Schemes 4 and 5).

In Scheme 6 two possible mechanisms for the formation of 4H‐imidazoles from 1 and heterocycles of type 16 are formulated. The zwitterionic intermediate f corresponds to b in Scheme 1. Instead of dehydration as in the case of the reaction of 1 with phthalohydrazide [3], or ring expansion as with saccharin and cyclic imides [1] [2], f, undergoes ring opening (way A or B). Decarboxylation then leads to the 4H‐imidazoles 17.
Anil‐Synthese. 19. Mitteilung. Über die Herstellung von Stilbenyl‐Derivaten des Isoxazols
Authors: Berger Hanny , Siegrist Adolf Emil
Published: December 2004

Preparation of Stilbenyl Derivatives of Isoxazoles

Schiff's bases derived from 3‐ and 5‐(p‐formylphenyl)‐phenylisoxazoles and o‐ or p‐chloroaniline are reacted with various p‐tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t‐but‐oxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). 5‐[4‐(Chlorphenylimino‐methyl)phenyl]‐phenylisoxazoles react less readily than the corresponding 3‐isomers.
Influence de l'imidazole, de quelques sels métalliques et de mélanges imidazole/sel métallique sur des réactions de condensation «prébiotiques» induites par les polyphosphates en milieu aqueux
Authors: Rabinowitz Joseph , Hampai Aioub
Published: December 2004

Influence of imidazole, metal salts and mixtures of imidazole/metal salt on ‘prebiotic’ condensation reactions induced by polyphosphates in aqueous solutions

In the presence of imidazole, aqueous solutions 0.1 M in glycine and 0.1 M in sodium trimetaphosphate, at pH 8.0–8.6 and room temperature, yield after 14 days up to 3% of triglycine. Addition of Cd2+ or Zn2+ decreases the yields, while Mg2+ increases them slightly.

The significance of the systems trimetaphosphate/imidazole and trimetaphosphate/imidazole/magnesium salt in the promotion of ‘prebiotic’ condensation reactions in aqueous solutions, especially the condensation of amino acids, is discussed.
C‐nucleosides aminoisoxazoliques. Communication préliminaire
Authors: Tronchet Jean M. J. , Martin Oliver R. , Grouiller Annie , Sarda Nicole
Published: December 2004

Aminoisoxazoles C‐nucleosides

Upon treatment with bromocyanomethylenetriphenylphosphorane, a series of aldehydosugar derivatives gave in good to excellent yields the corresponding terminal gem‐bromocyanoenoses 3, 7–10 and 16. Reacted with hydroxylamine, these unsaturated sugars led to the expected [3] 5‐amino‐3‐glycosylisoxazoles 4, 11, 12 and 17, whereas using hydroxyurea as a binucleophile they gave the corresponding 3‐amino‐5‐glycosylisoxazoles 13 and 14 as previously described in other series [3]. The major interest of these compounds rests in their being close analogs (or enantiomers of analogs) of important biological compounds as f.e. AICAR.
Bildung von 4‐, 5‐ und 6gliedrigen Heterocyclen durch ambidoselektive Ringschlüsse von Enolat‐Ionen
Authors: Kunz Walter , Kristinsson Haukur
Published: December 2004

Formation of 4‐, 5‐ and 6‐membered heterocycles by ambidoselective cyclization of enolate anions

N‐Acylmethyl‐N‐chloracetyl‐2,6‐dimethylanilines 4 were cyclized with base to 4‐, 5‐ or 6‐membered ring compounds, depending on the substituent R2 (Scheme 2). All products can be rationalized as derived from the intermediate enolate anions a and b. The enolate anion a reacts by intramolecular alkylation to yield either 1, 4‐oxazines 5 or azetidines 6 (Schemes 1, 3 and 7). The regioselectivity observed is expected on the basis of the allopolarization principle. The enolate anion b reacts only with formation of a new CC bond (Scheme 5). Comparison with the behaviour of the 2, 6‐unsubstituted anilines 9, 1a and 12, shows a strong dependence not only on electronic but also on steric factors (Scheme 4 and 6).
Cob (I)alamin als Katalysator 4. Mitteilung. Reduktion von α,β‐ungesättigten Nitrilen
Authors: Fischli Albert
Published: December 2004

Cob(I)alamin as Catalyst. 4. Communication. Reduction of α,β‐Unsaturated Nitriles

Using catalytic amounts of cob (I)alamin and an excess of metallic zinc as source of electrons 1‐naphthonitril (5) has been reduced to (1‐naphthyl)methylamin (6) and in small amounts to (1‐naphthyl)methanol (7) and (1,2,3,4‐tetrahydro‐1‐naphthyl)methanol (8) (5 ½ h, CH3COOH/H2O; s. Scheme 3). Starting from cyclododecylideneacetonitrile (15) similar conditions (68 h, CH3COOH/H2O) produced the amines 16–19 as well as the nitrogen free saturated aldehyde 20, the corresponding allylic alcohol 21 and the saturated derivative 22 (s. Scheme 6). It is deduced that the first attack of cob (I)alamin on an α,β‐unsaturated nitrile might occur on both the nitrile dipole as well as on the carbon atom in β‐position. Cob (I)alamin in aqueous acetic acid saturates the isolated double bonds in allylic alcohols and amines. In a slow reaction the two different aromatic rings of (1‐naphthyl)methanol (7) have been reduced giving the corresponding tetrahydronaphthalene derivatives 8 and 12, and in one case the production of the octahydroderivative 14 has been observed in a low yield (s. Scheme 5).
Bakteriochlorophyll aGg und Bakteriophäophytin aP in den photosynthetischen Reaktionszentren von rhodospirillum rubrum G‐9+
Authors: Walter Erhard , Schreiber Jakob , Zass Engelbert , Eschenmoser Albert
Published: December 2004

Bacteriochlorophyll aGg and Bacteriopheophytin ap in Photosynthetic Reaction Centers from Rhodospirillum rubrum G‐9+

In photosynthetically active reaction centers from Rhodospirillum rubrum G‐9+, the magnesium complex bacteriochlorophyll a contains geranylgeraniol as the alcohol component, while the metal‐free bacteriopheophytin a contains phytol instead. These pigments bacteriochlorophyll aGg (4) and bacteriopheophytin aP (1) were isolated from reaction center preparations in a ratio of 2:1 and (after demetallation of 4) identified as bacteriopheophytin aGg (2), and aP (1) by comparison with authentic samples (UV./VIS., CD. and mass spectra as well as mixed HPLC.).
Nouvelle méthode de préparation d'éthers vinyliques à partir d'acétals
Authors: Barbot Francis , Miginiac Philippe
Published: December 2004

A new way to vinylic ethers from acetals

Acetals react at low temperatures in presence of a Lewis acid (aluminium chloride or magnesium bromide) with tertiary amine to give in good yields the vinylic ethers corresponding to the elimination of one molecule of alcohol.
1H‐NMR.‐spektroskopische Analyse von prochiralen Allencarbonsäureestern mit optisch aktiven Europium‐Verschiebungsreagenzien
Authors: Lang Robert W. , Hansen Hans‐Jügen
Published: December 2004

1H‐NMR. Spectroscopic Analysis of Prochiral Allenic Esters Using Optically Active Europium Shift Reagents

The prochiral allenic methyl esters 1–4 (cf. Scheme) show in the presence of 1 mol‐equiv. tris[3‐(heptafluorobutyryl)‐(+)‐camphorato]europium (III) (Eu (hfc)3) in 1,1,2‐trichloro‐1,2,2‐trifluoroethane (TCFE) induced unlike 1H‐NMR. shift differences (ΔΔδ) for the enantiotopic protons and methyl groups on C(4), respectively (cf. Fig. 2 and 3). This effect allows to determine directly the 2JH,H coupling constants of the geminal protons on C(4) of the allenic esters 1 (15.5 Hz) and 2 (14.5 Hz) (cf. Table 2).
Norrish Type I Cleavage of Aliphatic Carboxylic Acids and Esters in Solution. A CIDNP.‐study
Authors: Kaiser Tony , Fischer Hanns
Published: December 2004

UV.‐irradiation of pivalic and isobutyric acid and their methyl esters as well as of α‐hydroxy isobutyric and malonic acid in solution lead to chemically induced dynamic nuclear polarization (CIDNP.) of parent compounds and of various reaction products. CIDNP.‐effects and product distributions confirm α‐cleavage of the C(α), CO bond to be the major mode of photodecomposition. Scavenger experiments indicate that decomposition of the molecules from a triplet excited state is roughly equally or more probable than from a singlet excited state. Quantum yields of educt disappearance are also given for the methyl esters of pivalic and isobutyric acid.
Displacement of Activated Amino Groups. C,N‐ vs. N,S‐Bond Cleavage in the Reaction of N‐Alkyl‐disulfonamides with Nucleophiles
Authors: Müller Paul , Thi Minh Phuong Nguyen
Published: December 2004

Sodiumthiophenoxide and sodiumphenylselenide react with N‐benzyl‐ and N‐hexyl‐di‐p‐toluenesulfonamides (1 and 2) via displacement at the C‐atom to afford the corresponding organosulfides and selenides in yields of 68–96%. In contrast, sodium cyanide converts disulfonamides to monosulfonamides by attack on the S‐atom. The different selectivities of phenylsulfide and selenide as compared to cyanide anions with respect to attack on the C‐ and S‐atoms are rationalized on the grounds of the HSAB (hard and soft acids and bases) principle of Pearson.
Stoffwechselprodukte von Mikroorganismen. 186. Mitteilung. Über die Aspochalasine A, B, C und D
Authors: Keller‐Schierlein Walter , Kupfer Ernst
Published: December 2004

Metabolites of Microorganisms. The Aspochalasins A, B, C, and D

The structures of the antibiotic aspochalasin B (asposterol) and its inactive co‐metabolites aspochalasin A, C, and D from Aspergillus microcysticus (Tü 502) were elucidated by extended spectroscopic studies and chemical degradation. The structures are: aspochalasin A = 10‐isopropyl‐14‐methyl[11]cytochalasa‐6, 13‐dien‐1, 17, 18, 21‐tetrone (32), aspochalasin B = 17‐hydroxy‐10‐isopropyl‐14‐methyl‐[11]cytochalasa‐6, 13, 19‐trien‐1, 18, 21‐trione (11), and aspochalasin C = 17, 18‐dihydroxy‐10‐isopropyl‐14‐methyl[11]cytochalasa‐6, 13, 19‐trien‐1, 21‐dione (29). Aspochalasin D (1) is a diastereomer of aspochalasin C (different configuration at C (17) or C (18)).
Stoffwechselprodukte von Mikroorganismen. 187. Mitteilung. Synthese des 3‐Isobutyl‐4,5‐dimethylisoindolin‐1‐ons, eines Abbauproduktes von Aspochalasin D
Authors: Kupfer Ernst , Keller‐Schierlein Walter
Published: December 2004

Metabolites of Microorganisms. Synthesis of 3‐Isobutyl‐4,5‐dimethylisoindolin‐1‐one, a Degradation Product of Aspochalasin D

3‐Isobutyl‐4,5‐dimethylisoindolin‐1‐one (1) and 3‐isobutyl‐6, 7‐dimethyl‐isoindolin‐1‐one (6) were synthesized in a non‐regioselective way. The structures could be assigned unequivocally by spectroscopic means. Compound 1 was identical with a degradation product of Aspochalasin D.
Influence of Amino Acids, Ammonium and Potassium Cations on the Self‐Assembly of 5′‐GMP
Authors: Detellier Christian , Laszlo Pierre
Published: December 2004

The self‐ordered supramolecular structures formed by 5′‐guanosine monophosphate (disodium salt) in aqueous solution at pH 7.8 show pronounced interaction with ammonium ions. Rather than competing with potassium ions for the central cavity in hydrogen‐bonded guanine tetramers, ammonium ions bring about ‐ in synergism with potassium ions ‐ further aggregation. Glycine appears to destroy the aggregates, by competing with potassium ions for the core positions within the tetramers. Conversely, alanine does not interact significantly with the system. These conclusions follow from analysis, at various concentrations, of the microdynamics and of the mole fractions of sodium ions bound to self‐assembled 5′‐GMP−−, obtained from relaxation rate measurements for the 23Na nucleus, as the 5′‐GMP−− counter‐ion.
Triazènes. Etude XPS. et 1H‐RMN. des complexes mercuriques des diaryl‐1,3‐triazènes
Authors: Maire Jean‐Claude , Baldy André , Boyer Daniel , Llopiz Pierre , Vernin Gaston , Bachlas Beni Prashad
Published: December 2004

XPS. and 1H‐NMR. spectra of 1,3‐diaryltriazenes complexes of Hg(II)

The core binding energies C 1s, N 1s, Hg 4f7/2, Hg 4f5/2 in 7 symmetrical p‐substituted 1,3‐diphenyltriazenes complexes of Hg(II) have been measured by XPS. Within the limits of experimental error (± 0.2 eV) only one N 1s signal could be detected. This indicates the equivalence of the 3 N‐atoms. Invariance of C 1s, N 1s, Hg 4f7/2, Hg 4d5/2 signals with the para substituents on the phenyl ring is explained on the basis of ionic character in the Hg, N bond. These results are corroborated by the 1H‐NMR. spectra.
Synthetische Verwendung von Epoxynitronen. II. Synthese von Steroid‐α‐methyliden‐γ‐lactonen
Authors: Riediker Martin , Graf Walter
Published: December 2004

Synthetic application of epoxynitrones. II. Syntheses of steroidal α‐methylidene‐γ‐lactones

This communication describes the application of the epoxynitrone/CF3SO3SiR3 → 1,2‐oxazine annelation‐reaction [1] to the syntheses of steroidal α‐methylidene‐γ‐lactones from olefines, e.g. 12 → 14a/b → 16a/b → 18a/b → 20 → 22 (Scheme 2).
Etude par résonance paramagnétique électronique des radicaux piégés dans un monocristal de diméthylarsinate de sodium irradié aux rayons X
Authors: Geoffroy Michel , Llinares Antoine
Published: December 2004

E.S.R. study of radiation damage in a single crystal of sodium dimethyl arsonate

L'irradiation aux rayons X, à 77 K, d'un monocristal de diméthylarsinate de sodium provoque le piégeage de \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} \left({\rm O} \right){\rm As}\left({{\rm O}^ -} \right)\mathop {\rm C}\limits^ \cdot {\rm H}_{\rm 2} $\end{document} et de (CH3)2AsO−. En fonction de la température ces radicaux se réorientent ou donnent naissance à de nouvelles espèces radicalaires. Les tenseurs g et de couplage hyperfin avec 75As ont été déterminés à 105 K, 165 K, 215 K et 295 K et permettent de proposer une identification de plusieurs espèces radicalaires localisées sur l'atome d'arsenic. Le rǒle de la température d'irradiation et l'influence de l'oxygène sur la réactivité des radicaux piégés dans le cristal sont également étudiés.
Réactions de Friedel et Crafts de dérivés aromatiques sur les composés dioxo‐1,4,2,3‐non saturés. IV. Réactions des hydroxy‐5‐ouchloro‐5‐diméthyl‐3,5‐ ou diméthyl‐4,5‐dihydro‐2,5‐furannones‐2
Authors: Canévet Jean‐Claude , Graff Yves
Published: December 2004

Friedel‐Crafts reactions of aromatic derivatives with 1,4‐dicarbonyls 2,3‐éthylenic compounds. Part IV. Reactions of 5‐hydroxy or 5‐chloro 3,5‐dimethyl or 4,5‐dimethyl 2 (5 H) furanones

We studied the Friedel‐Crafts reactions of 2‐(5H)‐furanones. In the presence of sulfuric acid and of an aromatic derivative, 5‐hydroxy‐ or 5‐chloro‐5‐methyl‐2‐(5H)‐furanones with one methyl group either in the 3 position, or in the 4 position generally give the corresponding 5‐aryl‐2‐(5H)‐furanones, while with aluminium chloride, it is possible to obtain, when a reaction takes place, isomeric 1H‐indenecarboxylic acids. However, in a particular case, an addition to the substrate's double bond is observed. The 3‐aryl‐5‐hydroxy‐tetrahydrofuran‐2‐one obtained is methylated in two ways and gives either a cyclic product, or a linear one. In two cases tautomerism between 1H‐1‐indenecarboxylic acid and 1H‐3‐indenecarboxylic has been shown by 1H‐NMR.
1H‐ und 13C‐NMR.‐Spektren von 6‐(p‐X‐Phenyl)fulvenen. Kurzmitteilung
Authors: Otter Albin , Mühle Hansueli , Neuenschwander Markus , Kellerhals Hans Peter
Published: December 2004

1H‐ and 13C‐NMR.‐spectra of 6‐(p‐X‐phenyl)fulvenes

The 1H‐ and 13C‐NMR.‐spectra of a series of 6‐(p‐X‐phenyl)fulvenes 3, measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5‐membered ring. Small changes in bond length are observed by comparison of the vicinal 1H, 1H‐coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).
Analogues de la lincomycine. I. Allongement de la chaîne du di‐O‐isopropylidène‐1,2:3,4‐α‐D‐galacto‐hexodialdopyrannose‐1,5
Authors: Tronchet Jean M. J. , Massoud Mohammed A. M.
Published: December 2004

Lincomycin analogues. I. Chain‐extensions of [1,2:3,4]‐di‐O‐isopropylidene‐α‐D‐galacto‐hexodialdo‐1,5‐pyranose

The title aldehydosugar 1 treated with Wittig reagents led in good to excellent yields to the unsaturated sugar derivatives 3–7 and 10–15, 8 having been prepared by condensation of 1 with malonic acid. The configuration (Z or E) of each compound obtained has been established by 1H‐NMR. These chain‐extensions constitute the first synthetic step towards the preparation of lincomycin analogues.
Photochemische Reaktionen. 104. Mitteilung [1]. Zur Photospaltung der C,C‐Oxiranbindung konjugierter γ, δ‐Epoxy‐enone: Photolyse von 4‐Methyliden‐5,6‐epoxy‐5,6‐dihydro‐β‐jonon
Authors: Frei Bruno , Wolf Hans Richard , Jeger Oskar
Published: December 2004

The photoinduced cleavage of the C,C‐oxirane bond of γ, δ‐epoxy‐enones: UV.‐irradiation of 4‐methylidene‐5,6‐epoxy‐5,6‐dihydro‐β‐ionone

On 1n, π*‐excitation (λ ≥ 347 nm, pentane) 5 gives the isomeric bicyclic ether 10 in 75% yield (s. Scheme 2). In methanol the photoconversion of 5 to 10 is strongly reduced (12%) in favour of the formation of the methanol adduct 11 (43%). On photolysis in aqueous acetonitrile 5 is converted to the bicyclic ether 10 (9%), the dihydrofurane 12 (18%) as well as to the triketones 13A and 13B (7%), and 14 (23%).

On 1π, π*‐excitation (λ = 254 nm) in pentane no 10 is formed, but 5 isomerizes to the tricyclic cyclopropyl compound 16 (59%), the allenic product 17 (10%), and the cyclopropene compound 18 (12%; s. Scheme 3). Photolysis in methanol furnishes 11 (63%), and 18 (4%), but no tricyclic cyclopropyl compound 16. In a secondary photoreaction (λ = 254 nm) the dihydrofurane 12 is isomerized to the bicyclic cyclopropyl compound 20.

Evidence is given that the products 11 and 13 are formed by solvent addition to an intermediate ketonium ylide b (s. Scheme 12). The presence of b is further proven by the formation of 12, a product of an electrocyclization of b. On photofragmentation of b carbenoids d and e are presumably formed (s. Scheme 14). 1,2‐Hydrogen shift in d yields the allene derivative 17, and cyclization of d gives the cyclopropene compound 18. On the other hand, e cyclizes to the non isolated cyclopropene compound 69 which is transformed to 16 by an intramolecular [4 + 2]‐cycloaddition.

The present investigation shows that the photochemistry of 5 is determined by photoinduced C,C‐bond cleavage of the oxirane ring. This is in sharp contrast to the photochemistry of conjugated γ, δ‐epoxy‐enones without the additional double bond in ε, ζ‐position, where selective photocleavage of the C(λ), O‐bond is observed.
Chemistry of Succinyl Succinic Acid Derivatives. Part V. On the transesterification of succinyl succinates
Authors: Sinnreich Joel , Batzer Hans
Published: December 2004

The unique stabilization of the ester link in dialkyl succinyl succinates is explained and a facile route to known as well as to hitherto inaccessible succinyl succinates is suggested. New representatives of this series are described.
Enantioselektive 1,4‐Additionen von metallorganischen Verbindungen an konjugierte Systeme im chiralen Medium DDB
Authors: Langer Werner , Seebach Dieter
Published: December 2004

Enantioselective 1,4‐additions of organometallic compounds to conjugated systems in the chiral medium DDB

DDB = 1,4‐Dimethylamino‐2,3‐dimethoxybutan (= 2,3‐Dimethoxy‐N,N,N′,N′‐tetramethyl‐1,4‐butandiamin).

The chiral methoxyamine DDB is used as a cosolvent to add achiral Li‐, Cu‐, and Zn‐organic compounds enantioselectively to prochiral β‐carbon atoms of α, β‐unsaturated aldehydes, ketones, nitro compounds and ketene‐thioacetals (Tables 1 and 2). The selectivity generally ranges from 55:45 to 63:27, in one case (9b) an enantiomeric excess of 43% was obtained.
On the Position of the Intramolecular Equilibrium between Opened and Aromatic‐Ring Stacked Forms in Ternary Complexes Composed of Adenosine 5′‐triphosphate, Mg2+ or Zn2+, and L‐Tryptophanate, and in Related Ternary Systems
Authors: Mitchell Paul R. , Prijs Bernard , Sigel Helmut
Published: December 2004

The intramolecular and dimensionless equilibrium constant, K′, for the equilibrium between open and aromatic‐ring stacked isomers of ternary complexes formed between adenosine 5′‐triphosphate, inosine 5′‐triphosphate, or uridine 5′‐triphosphate, Mg2+ or Zn2+, and L‐tryptophanate, 2,2′‐bipyridyl (bipy), or 1,10‐phenanthroline (phen) have been estimated by 1H‐NMR. shift measurements in D2O (I = 0.1M, NaNO3; 27°). The approximate equilibrium constants K′ are ≥ 20, ≥ 20, 1.2, 0.9, 0.7, 0.5, and 0.3 for the ternary complexes Zn (phen) (ATP)2−, Mg (phen) (ATP)2−, Zn (bipy) (ATP)2−, Zn (bipy) (ITP)2−, Zn (bipy) (UTP)2−, Zn (trp) (ATO) 3−, and Mg (trp) (ATP)3−, respectively. The percentages of the stacked isomers decrease in the order Zn (phen) (ATP)2− (≥ 95%) ≫ Zn (bipy) (ATP)2− (55%) > Zn (bipy) (ITP)2− (48%) > Zn (bipy) (UTP)2− (∼ 40%), which coincides with the order of stability of the binary metal‐free adducts (phen) (ATP)4− > (bipy) (ATP)4− ≃ (bipy) (ITP)4− > (bipy) (UTP)4−; the corresponding stability constants are K = 28.2 ± 4.7, 8.1 ± 2.6, 8.8 ± 1.8, and ∼ 1 (M−1), respectively (D2O; I = 0.1 M, NaNO3; 27°): these series reflect the decreasing size of the aromatic‐ring systems forming the stacks. The indole moiety of tryptophan resembles 2,2′‐bipyridyl rather than 1,10‐phenanthroline and K = 6.2 ± 1.8 M−1 for (trp) (ATP)4−. Implications with respect to the stability of ternary complexes, and to biological systems are indicated briefly.
Pyrazolo [1,5‐a]indole. 10. Mitteilung über metallogranische reaktionen und folgeprodukte
Authors: Marxer Adrian , Siegrist Max
Published: December 2004

Pyrazolo[1,5‐a]indoles

Treatment of 1‐(2‐heteroaroyl or aroyl‐phenyl)‐pyrazoles (3) with potassium hydroxide in 95% ethanol or with sodium ethanolate in ethanol produces a novel ring closure to new 4‐hydroxy‐4‐(4‐heteroaryl or aryl)‐4H‐pyrazolo [1,5‐a]indoles 5 and 6 (Table 1). A 2, 3, or 4‐pyridyl at position 4 is easily reduced yielding the 4‐(2, 3, or 4‐piperidyl)‐derivatives 7 and 8 (Table 2). Water is split off from these piperidyl‐derivatives 7 or 8 to give the piperidylidene derivatives 9 or 10 (Table 3) which may be considered as heterocyclic analogues to known tricyclic psychopharmaceuticals with antidepressant or neuroleptic activities.
Über Reaktionen Oxygenierter Kobalt (II)‐Komplexe. X. 1,4,7,10‐Tetraazadecan‐kobalt (II) und 4, 7‐dimethyl‐1,4,7,10‐tetraazadecan‐kobalt (II) als sauerstoffträger
Authors: Mäcke H. , Zehnder M. , Thewalt U. , Fallab S.
Published: December 2004

Reactions of oxygenated cobalt (II) complexes. X. 1,4,7,10‐tetraazadecanecobalt (II) and 4,7‐dimethyl‐1,4,7,10‐tetraazadecanecobalt (II) as dioxygen carriers

IX: siehe [1].

Oxygenation of cobalt (II) chelates with fourdentate amines such as 1,4,7,10‐tetraazadecane (= tad) in aqueous solution yields μ‐peroxo‐μ‐hydroxo‐dicobalt (III) complexes. Due to facultative ligand disposition of the amine, 8 different diastereoisomers are possible. Introducing methyl groups in positions 4 and 7 of tad destabilizes the isomers with β‐configuration. A crystallized perchlorate, obtained by oxygenation of 4, 7‐dimethyl‐1,4,7,10‐tetraazadecanecobalt (II) (= dmtad) in alcaline solution, proved to be of the expected μ‐peroxo‐μ‐hydroxo type. The ligand configuration is and lattice constants a (ΔΔ/ΛΛ). The X‐ray structure was solved by Patterson's method and refined to R = 0.093. The crystals are orthorhombic with space group Pna21 and lattice constants a = 14.632 (4), b = 17.525 (5), c = 12.888 (5) Å. In its UV./VIS. absorption spectrum and its solution reactivity the binuclear cation is closely related to oxygenation products obtained with the chelate of unsubstituted tad. The kinetic parameters of the decomposition reaction of the μ‐peroxo complexes in acidic solution are compared. The binuclear cations with 4, 7‐dimethyl‐1,4,7,10‐tetraazadecane as ligand are generally more reactive. In slightly alcaline solution isomerization of the μ‐peroxo‐μ‐hydroxo complexes has been observed.
Anil‐Synthese. 21. Mitteilung. Über die Herstellung von stilbenyl‐derivaten des pyrazols
Authors: Palmberg Roger B. , Siegrist Adolf Emil
Published: December 2004

Preparation of Stilbenyl Derivatives of Pyrazoles

Schiffs bases derived from 1‐, 3‐ and 5‐(p‐formylphenyl)phenylpyrazoles and p‐chloroaniline are reacted with various p‐tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t‐butoxide to yield the corresponding heterocyclic substituted stilbenes (anil synthesis). Introduction of a chloro substituent in the 4‐ and 4,5‐positions of the pyrazole system causes a decrease in yield and a hypsochromic shift in the absorption and fluorescence maxima of the title compounds.
Carbocyclische Verbindungen aus Monosacchariden. I. Umsetzungen in der glucosereihe
Authors: Bernet Bruno , Vasella Andrea
Published: December 2004

Carbocyclic Compounds from Monosaccharides. 1. Transformations in the Glucose Series

A method for the preparation of pentasubstituted cyclopentanes from monosaccharides is presented, involving two crucial steps, viz. the reductive fragmentation of 5‐bromo‐5‐deoxyglucosides (such as 10, 17 and 23, see Scheme 3) with Zn or butyl lithium yielding 5,6‐dideoxy‐hex‐5‐enoses (such as 11 and 24, see Schemes 3 and 4), and the subsequent cyclization of these hexenoses with N‐methyl‐ or N‐(alkoxyalkyl)hydroxylamines (via the corresponding nitrones) to form cyclopentano‐isoxazolidines (see Scheme 2). Thus, the glucosides 17 and 23 were converted diastereoselectively and in good yields into the cyclopentano‐isoxazolidines 27 and 45 (Schemes 5 and 7), which were characterized by their transformation into various derivatives. 27 and 45 were correlated through the common derivative 62. The configuration of the cyclization products were established by pyrolysis of the N‐oxide 65 to the enol ether 67 (Scheme 10).
Préparation de phosphonates de sucres ramifiés par addition nucléophile conjuguée. Communication préliminaire
Authors: Tronchet Jean M. J. , Neeser Jean‐Richard , Gonzalez Luis , Charollais Etienne J.
Published: December 2004

Preparation of unsaturated sugars phosphonates using nucleophilic conjugate addition

Different types of phosphorus nucleophiles underwent conjugate addition reaction with one of the branched‐chain sugars 4, 5 or 11 the addition taking place either on the endo or the exo face of the furanose ring (or on both faces in the case of 11). The configuration at C(3) of these new phosphorus‐bearing types of sugars as well as the configuration at the phosphorus atom of the cyclic phosphinates 9 and 10 was established by NMR. (3JP,H–C(2), 3JP,C(1)). Small amounts (7%) of the spiro enol phosphonate 16 were formed when 11 reacted with trimethyl phosphite.
Ergosta‐5,7,9(11), 22‐tetraen‐3β‐ol and its 24ξ‐Ethyl Homolog, Two New Marine Sterols from the Red Sea Sponge Biemna fortis
Authors: Delseth Claude , Kashman Yoel , Djerassi Carl
Published: December 2004

The steroidal components of a Red Sea sponge, Biemna fortis, were fractionated through reversed phase HPLC. and analyzed by a combination of physical methods, including high resolution GC./MS. and 360 MHz 1H‐NMR. The sponge contains five conventional Δ5‐sterols, 1a–c, 1e, 1g, which comprise about 25% of the mixture and 2,5% of gorgosterol (1h), a sterol never found before in Porifera. Three Δ5,7,22‐sterols were also present as major components in the mixture (∼70%): cholesta‐5,7,22‐trien‐3β‐ol (2a), ergosta‐5,7,22‐trien‐3β‐ol (2c) and (24R)‐ethylcholesta‐5,7,22‐trien‐3β‐ol (2e) whereas two new tetra‐unsaturated sterols were identified in minor amounts (2%): ergosta‐5,7,9(11),22‐tetraen‐3β‐ol (3c) and 24ξ‐ethylcholesta‐5,7,9 (11), 22‐tetraen‐3β‐ol (3e or 3f). NMR. spectroscopy made possible the assignment of a 24R configuration for all the C(24) substituted sterols isolated in sufficient amount from the mixture. The possible symbiotic, dietary or biosynthetic origins of these sterols are discussed.
Preparative Scale Separation of Xanthones and Iridoid Glycosides by Droplet Counter‐Current Chromatography
Authors: Hostettmann Kurt , Hostettmann‐Kaldas Maryse , Sticher Otto
Published: December 2004

Droplet counter‐current chromatography (DCCC.) has been used for the preparative scale separation of pure constituents from crude medicinal plant extracts. Xanthones and the bitter principles have been isolated from North‐American Gentiana species. From a crude extract of Ajuga pyramidalis L. (Labiatae), several hundred mg of iridoid glycosides were obtained within eight hours. The total volume of mobile phase employed for the elution was less than 150 ml. All the separations were achieved far more readily than by conventional chromatography. In addition, some general rules for solvent system selection are proposed.
Reaktion oxygenierter Kobalt (II)‐Komplexe. XII. Über einen binuclearen μ‐Peroxodikobalt (III)‐Komplex mit makrocyclischem Brückenring
Authors: Zehnder Margareta , Thewalt Ulf , Fallab Silvio
Published: December 2004

Reactions of oxygenated cobalt(II) complexes. XII. A binuclear μ‐peroxodicobalt(III) complex with a macrocyclic bridging ring

XI: siehe [1].

Singly bridged [(tren) (NH3) CoO2(NH3) (tren)]4+ reacts with excess tren by replacement of NH3 in cis‐position to the peroxo group and formation of a new type of doubly bridged μ‐peroxo complex. An X‐ray structure determination of [(tren)‐Co(O2, tren)Co(tren)] (ClO4)4 · 2 H2O showed that the additional tren forms a macrocyclic bridging ring. The conformation of the CoOOCo group is transoid with a dihedral angle of 20°. The crystals are monoclinic with space group P21/c. The lattice constants are a = 9,798, b = 26,385, c = 16,385 Å, β = 110,2° with four formula units in the cell. The final R value is 0,124. ClO anions are disordered.

The reactions of [(tren)Co(O2, tren)Co(tren)]4+ in aqueous solution are compared with those of [(tren) (NH3) CoO2Co (NH3tren)]4+. In acidic solution the new complex mainly decomposes to CoII and O2. In alcaline medium the bridging tren is replaced by an OH bridge, forming the well characterized doubly bridged [(tren)‐Co(O2, OH)Co(tren)]3+. Differing from the singly bridged bis (ammino) complex, the reactions of which show no pH dependency at all, the decomposition of the tren bridged complex is H+‐catalyzed. The kinetic data have been interpreted as (i) preceding fast protonation step which is followed by a conformational change of the bridging ring, (ii) acid hydrolysis of a Co‐μ‐tren bond and (iii) fast cleavage of the Co‐OO bond which is labilized by coordinated H2O.
Fragmentation of Energy Selected Butadiyne‐ and 1,3‐Pentadiyne Radical Cations
Authors: Dannacher Josef , Heilbronner Edgar , Stadelmann Jean‐Pierre , Vogt Jürgen
Published: December 2004

Monomolecular fragmentations of butadiyne‐ and 1,3‐pentadiyne radical cations in their electronically excited states have been investigated by use of the photoelectron‐photoion coincidence technique. Breakdown curves for the molecular and various fragment ions have been recorded over the ionization energy range of 9 to 17 eV. These breakdown curves reveal the extent of the competition between the radiative relaxation (ion fluorescence) and the non‐radiative internal conversion followed by fragmentation for the decay of the first excited electronic states. Extensive hydrogen scrambling and/or ionic‐carbon‐skeleton isomerization takes place prior to fragmentation, as revealed by the breakdown curves obtained for the site specifically deuteriated 1,3‐pentadiynes.
Cycloadditionen von 3,4‐Dimethoxyfuran an Dienophile
Authors: Iten Peter Xaver , Hofmann Alfred André , Eugster Conrad Hans
Published: December 2004

On cycloaddition reactions with 3,4‐dimethoxyfuran

We describe new cycloadditions of 3,4‐dimethoxyfuran (3,4‐DF, 1) with various dienophiles. In contrast to furan, the reaction of 3,4‐DF with maleic anhydride gives exo‐ and endo‐adducts at approximately the same rate. The thermodynamically more stable product is again the exo‐product. Less active dienophiles lead also to mixtures of exo‐ and endo‐adducts, except for citraconic anhydride (methylmaleic anhydride) which forms only the adduct with an endo‐methyl group. Dimethylmaleic anhydride could not be reacted with 3,4‐DF.

All adducts with 3,4‐DF contain a hidden 1,2‐dicarbonyl group in the form of an endiolether. Its pronounced nucleophilic character allows a series of further additions. Noteworthy are the stereospecific cis‐additions of halogens and the preparation of several acetals. Ozonolysis of the enolether in 4 allows the preparation of the hitherto unknown 2r, 3trans, 4trans, 5cis‐tetrahydrofuran tetracarboxylic acid and derivatives thereof (5 and 6).
Cycloadditionen von 3,4‐Dimethoxyfuran an Benzochinone
Authors: Hofmann Alfred André , Wyrsch‐Walraf Ingeborg , Iten Peter Xaver , Eugster Conrad Hans
Published: December 2004

Cycloadditions of 3,4‐dimethoxyfuran with benzoquinones

Cycloaddition of 3,4‐dimethoxyfuran (3,4‐DF, 1) with 1,4‐benzoquinones furnishes isolable (2 + 4)‐adducts in high yield. The crystalline products with benzoquinone, 2‐methyl‐benzoquinone, 2,3‐dimethoxy‐benzoquinone have endo‐configuration, whereas 2,3‐dimethyl‐benzoquinone gives the exo‐adduct 4c exclusively. Halogens (Cl2, Br2) add rapidly across the highly nucleophilic double bond of 3 or 4 in stereospecific cis‐manner, and exclusively from the exo‐side. The product 5c shows no sign of enolization to the hydroquinone; but with 3a and 3d the hydroquinones 6 were found. Methanolysis of 5 leads to the stable acetals 7 and 8. On oxidation of the hydroquinones 7 the thermolabile quinones 10 were obtained. Preparative pyrolysis of 10a under relatively mild conditions (N2, 200°, 0.1 Torr) gives tetramethoxy ethene (11) and isobenzofuran‐4,7‐quinone 12, a yellowish, crystalline and stable compound.
Lithium‐ und Kupfer‐Derivate von α,α‐doppeldeprotonierten Nitroalkanen. – Erzeugung, Eigenschaften und Umsetzungen mit Alkyl‐ und Allylhalogeniden
Authors: Seebach Dieter , Lehr Friedrich
Published: December 2004

Lithium‐ and copper‐derivatives of α,α‐doubly deprotonated nitroalkanes. Generation, properties and reactions with alkyl‐ and allylhalides

Aus der Dissertation von F.L., ETH Zürich, 1979; Nr. 6356. Die Arbeiten wurden teilweise am Institut für Organische Chemie der Justus‐Liebig‐Universität Giessen durchgeführt.

Vorläufige Mitteilungen siehe [1] und [2].

Primary nitroalkanes are deprotonated twice in the α‐position when treated with two mol‐equiv. of butyllithium at −78° to −100° in THF containing HMPT to give dilithium derivatives 15 (the compound with R = C2H5 is stable up to −30°). The acidity of the nitronate proton of 13 is estimated to be in the same range as that of diisopropylamine. The C‐nucleophilicity of the novel reagents 15 is dramatically increased as compared with that of simple nitronates 5: C,C‐bond‐forming reactions readily take place with alkylhalides (→22c–e,g,h,j–m) and benzylbromide (→22b,f,i); allylations are possible via nitroalkycopper‐lithium‐derivatives (→27–29).
Stereospezifische Synthese von 6β,7β‐Methylen‐20‐spirox‐4‐en‐3,21‐dion (Prorenon). Über Steroide. 235. Mitteilung
Authors: Wieland Peter
Published: December 2004

Stereospecific synthesis of 6β,7β‐methylene‐20‐spirox‐4‐ene‐3,21‐dione

A stereospecific synthesis of the highly active 6β,7β‐methylene‐20‐spirolactone 4 (Prorenone) is described.
The Four Diastereomeric Thio‐Analogues of (±)‐Muscarine
Authors: Giannella Mario , Pigini Maria , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Die vier diastereomeren Thioanalogen des (±)‐Muscarins

Im Zusammenhang mit pharmakologischen Arbeiten über die chemische Natur des cholinergischen Rezeptors haben wir die reinen (±)‐Thiomuscarinjodide 4a–d hergestellt und ihre relativen Konfigurationen an C(2), C(3) und C(5) an den nor‐Basen 3a–d in 1H‐NMR.‐Spektren mit Lanthanidverschiebung aufgeklärt. Auf der Stufe der 3‐Hydroxymide 2 wurden die vier Diastereomere chromatographisch voneinander getrennt.
Aktivierte Chinone: O‐ versus C‐Addition von Phenolen; eine neue, regiospezifische Synthese von Xanthonen, Thioxanthonen und N‐Methyl‐9‐acridonen
Authors: Müller Peter , Venakis Thomas , Eugster Conrad Hans
Published: December 2004

Activated quinones: O‐ versus C‐addition of phenols. New regiospecific syntheses of xanthones, thioxanthones and N‐methyl‐9‐acridones

The acid catalyzed reaction of phenols with activated quinones, e.g. 2‐methoxycarbonyl‐1, 4‐benzoquinone or 2‐acetyl‐1, 4‐benzoquinone, leads to substituted biphenylderivatives (C, C‐addition) as has been previously described [1]. O, C‐Addition of phenols has now been achieved by using 2‐methoxypyridin or 4‐dimethyl‐aminopyridin [4] as basic catalysts. The resulting substituted diphenylethers can serve as convenient starting materials for regiospecific syntheses of substituted xanthones, especially for 1, 4‐dimethoxyxanthones.

Arylthiols and N‐methyl‐N‐arylamines also react readily with activated quinones to give substituted di‐aryl‐thioethers and N‐methyl‐N, N‐diarylamines respectively; both types of compounds are convenient materials for regiospecific syntheses of substituted thioxanthones and N‐methyl‐9‐acridones.