bluuebunny/crossref_metadata_2025_split huggingface dataset:
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 SolutionIt 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‐Benzisothiazoles2, 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‐azabenzvalene4‐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

AbstractThirteen 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)fluorenoneUnsuccessful 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

AbstractThe 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 NonaheptafulvaleneThe 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‐ImidazolesIn 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 IsoxazolesSchiff'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 solutionsIn 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

AbstractAminoisoxazoles C‐nucleosidesUpon 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 anionsN‐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

AbstractCob(I)alamin as Catalyst. 4. Communication. Reduction of α,β‐Unsaturated NitrilesUsing 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 acetalsAcetals 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 ReagentsThe 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

AbstractUV.‐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

AbstractSodiumthiophenoxide 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 DThe 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 D3‐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

AbstractThe 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‐lactonesThis 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 arsonateL'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) furanonesWe 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.