bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal Complexes with Macrocyclic Ligands. XV. The Complexation Kinetics of Open Chain and Cyclic Tetraazaligands with Ni2+ in DMSO and DMF
Authors: Hertli Liselotte , Kaden Thomas A.
Published: December 2004

The complexation kinetics of 2,6,9, 13‐tetraazatetradecane (1), 1,4,8, 11‐tetraazacyclotetradecane (2) and N,N′,N″,N'‐tetramethyl‐1,4,8, 11‐tetraazacyclotetradecane (3) with Ni2+ were studied by the stopped‐flow technique in DMSO and DMF. The biomecular rate constants kLNi (Table 2) follow in both solvents the order 1≳2>3. The similar complexation rates of 1 and 2 in their unprotonated form indicate that for both the open chain and the cyclic ligand the same mechanism holds. By comparison with the solvent exchange the rate determining step of the complexation is the dissociation of the first solvent molecule in the outer‐sphere complex. The lower reactivity of 3 is probably due to steric effects.

In the case of 2 a second step in the complexation process was observed and explained by a rearrangement of the ligand already coordinated to the metal ion.
The Configuration of Tricyclo [7.1.1.02,7]undecanes and the Stereochemistry of the Reduction of Tricyclone
Authors: Thomas Alan F. , Thommen Walter , Becker Josef
Published: December 2004

A full discussion of the configuration of tricyclo [7.1.1.02,7]undecanes related to cis‐10, 10‐dimethyltricyclo [7.1.1.02,7]undec‐2‐en‐4‐one (2), the Robinson annelation product from norpinone 1 and 3‐buten‐2‐one is given, based on 360‐MHz‐NMR. spectra. Nuclear Overhauser effects confirm the cis configuration of 2, and show that the saturated ketone 10, obtained by catalytic hydrogenation, is also all‐cis with the cyclohexanone ring in the boat conformation. The parent hydrocarbon, cis‐10, 10‐dimethyltricyclo[7.1.1.02,7]undecane is compared with one of the corresponding trans isomers prepared from pinocarvone (14). The stereochemistry of metal hydride reduction and Grignard reaction of 2 is examined.
Reduction of 2‐Bromo‐4, 4‐dimethyl‐2‐cyclohexenone at Mercury. A study on inverted peaks in cyclic voltammetry
Authors: Tissot Paul , Margaretha Paul
Published: December 2004

The parameters which influence the inverted wave appearing in the reverse (oxidation) sweep in the cyclic voltammogramme of the title compound 1 are discussed in detail. The inverted wave is due to the interaction of the reduction products of 1 with the electrode and the electrolyte (TBAFB). The key condition for the presence of the inverted peak is a slow scan rate on the reverse sweep, at least for the last 50 mV before the inversion of the current‐potential curve.
Photochemische Reaktionen. 117. Mitteilung [1] Zur Photochemie von 5,6‐Epoxydienen und konjugierten 5,6‐Epoxytrienen
Authors: Alder Alex Peter , Wolf Hans Richard , Jeger Oskar
Published: December 2004

Photochemistry of 5,6‐Epoxydienes and of Conjugated 5,6‐Epoxytrienes

On singulet excitation (δ = 254 nm) the 5,6‐epoxydiene 6 and the conjugated 5,6‐epoxytrienes 7 and 8 exclusively give products arising from cleavage of the C, C‐bond of the oxirane (cf. 6→9, 10, 11; 7→ (E)‐15, 16, 17; 8→ 18 (A+B), 19 (A+B), 20, 21). The dihydrofuran compounds 11 and (E/Z)‐15 are formed by cyclization of a ketonium‐ylide a and d, respectively. Photolysis of a gives the carbene b which yields the cyclopropene 9, whereas d forms photochemically the carbenes f and g which yield the methano compounds 16 and 17. The isomeric cyclopropene derivatives 20 and 21 are products of the intermediates h and i, respectively, which are formed by photolysis of the ylide e. The cyclopropene 21 isomerizes by intramolecular cycloadditions to 18 (A+B) and 19 (A+B). ‐ On triplet excitation (λ⩾LD nm; 280 nm; acetone) 6 undergoes cleavage of the C(5), O‐bond and isomerizes to 12 and 14. However, 7 is converted by cleavage of the C, C‐bond of the oxirane to yield 15. On treatment with BF3O(C2H5)2 6 gives 14, whereas 7 yields 22, and 8 forms 23 and 24.
Photochemische Reaktionen. 118. Mitteilung [1] Zur vinylogen β‐Spaltung von Enonen. UV.‐Bestrahlung von 4‐(3',7',7'‐Trimethyl‐2'‐oxabicyclo [3.2.0]hept‐3'‐en‐1'‐yl)but‐3‐en‐2‐on
Authors: Murato Kazuo , Wolf Hans Richard , Jeger Oskar
Published: December 2004

Vinylogous β‐Cleavage of Enones: UV.‐irradiation of 4‐(3′,7′,7′‐trimethyl‐2′‐oxabicyclo[3.2.0]hept‐3′‐ene‐1′‐yl)but‐3‐ene‐2‐on

On 1π,π*‐excitation (λ = 254 nm) in acetonitrile (E/Z)‐2 is converted into the isomers 4–9 and undergoes fragmentation yielding 10; in methanol (E/Z)‐2 gives 7–10 and is transformed into 11 by incorporation of the solvent.

On 1π,π*‐excitation (λ λ⩾347 nm; benzene‐d6) (E)‐2 is isomerized into (Z)‐2, which is converted into the isomers 3 and 4 by further irradiation.

1π,π*‐Excitation (λ = 254 nm; acetonitrile) of 4 gives 6 and (E)‐9, whereas UV.‐irradiation (λ = 254 nm; acetonitrile‐d3) of 5 yields (E)‐7 and 8.

On 1π,π*‐excitation (λ = 254 nm; acetonitrile) of (E/Z)‐12 the compounds (E)‐14 and (E)‐15 are obtained.
Crystal Structures of rac‐Methyl‐ (3R*, 3aS*, 4R*, 7R*, 7aR*)‐7‐Acetoxymethyl)‐3‐benzyl‐4,5‐dimethyl‐1‐oxo‐3a,4,7,7a‐tetrahydroisoindoline‐7a‐carboxylate
Authors: Zehnder Margareta
Published: December 2004

The X‐ray structures of the compounds 4 and 2 have been determined by direct methods and refined by least squares techniques. Crystals of C22H27NO5 and C27H27NO5 are triclinic, space groups PĪ with lattice parameters a = 13.652 (5) Å, b = 10.926 (3) Å, c = 7.755 (2) Å, a = 111.554 (4) Å, β = 85.541 (3) Å, γ = 104.813 (4) Å, and a = 15.394 (4) Å, b = 9.674 (3) Å, c = 8.522 (3) Å, a = 111.04 (4) Å, ß = 93.65 (4) Å, γ = 95.01 (4) Å, respectively.
ESR. Study of an X‐Irradiated Single Crystal of Methylene Diarsonic Acid
Authors: Geoffroy Michel , Llinares Antoine
Published: December 2004

X‐Irradiation of single crystals of methylene diarsonic acid gives rise to a variety of radicals which have been identified by ESR. spectroscopy; (OH)2As(O)CHAs(O) (OH)2, −OÅs(OH)2CH2As(O)(OH)2, AsO3– and (OH)Ås(O)CH2As(O)(OH)2. The spin densities have been obtained from the 75As‐hyperfine tensors. An additional species ‐ probably a radical anion localized on a pentacoordinated arsenic ‐ is also detected after annealing at room temperature. The radiation damage process is discussed.
Absorption Spectra and Termination Kinetics of Transient Free Radicals in Solution Observed by UV./VIS. Spectroscopy with modulated excitation
Authors: Huggenberger Christian , Fischer Hanns
Published: December 2004

Free radicals are generated in liquid solutions by harmonically modulated photolysis of suitable substrates. Harmonic analysis of the absorbance as functions of wavelength and modulation frequency yields the optical spectra and the decay kinetics of the transient species. The experimental technique and the analysis are described in detail. Results on t‐butyl, 2‐propyl and benzyl radicals generated by photolysis of the corresponding dialkyl resp. dibenzyl ketones are reported. They confirm previous spectral assignments and show that the termination reactions are diffusion controlled.
1,1‐Dihalogenoanthra [b]cyclopropenes. Preliminary communication
Authors: Müuller Paul , Rey Michel
Published: December 2004

1,1‐Dichloro‐ and 1,1‐difluoroanthra [b]cyclopropene (1 and 2) are synthesized in 8 steps from the Diels‐Alder adduct of benzocyclobutene and maleic anhydride.
Studies on the Conversions of Diols and Cyclic Ethers. Part 48. Dehydration of alcohols and diols on the action of dimethylsulfoxide
Authors: Molnár Árpád , Bartók Mihály
Published: December 2004

The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied. Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism. The ether formation observed with certain alcohols proceeds via a carbenium cation. The reaction conditions applied were found suitable for inducing water elimination from the ditertiary 1,2‐ and 1,3‐diols (pinacol rearrangement, 1,2‐elimination). From the 1,4‐ and 1,5‐diols the corresponding oxacycloalkanes can be obtained in good yield. Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism. The effect of DMSO is exerted directly, and protoncatalysis occurs simultaneously.
Stoffwechselprodukte von Mikroorganismen. 202. Mitteilung. Strukturaufklärung von Elaiophylin: Spektroskopische Untersuchungen und Abbau
Authors: Kaiser Hanspeter , Keller‐Schierlein Walter
Published: December 2004

Structure Elucidation of Elaiophylin: Spectroscopy and Chemical Degradation

The structure of the antibiotic elaiophylin (azalomycin B) was elucidated by extended spectroscopic investigations and chemical degradation. Elaiophylin (26) is a macrodiolide with a 16membered dilactone ring. The synthesis of 7‐acetoxy‐6‐ethyl‐3‐octanone (14), the acetyl derivative of an important degradation product, is described.
‘Through Space’ and ‘Through Bond’ Interactions in [2.2]Cyclopanes; the Assignment of their Photoelectron Spectra
Authors: Kovač Branka , Allan Michael , Heilbronner Edgar
Published: December 2004

The photoelectron spectra (PE.) of ten cyclophanes (7 to 14, 16, 18) have been assigned on the basis of a simple molecular orbital model proposed recently for the cyclophanes 2 (1,4) to 6. It is shown that the agreement between calculated and observed band positions provides strong evidence for the validity of the model.
Dediazoniation of Arenediazonium Ions in Homogeneous Solutions. Part XVI. Kinetics and mechanisms of dediazoniation of p‐chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutions under nitrogen gas
Authors: Schwarz Wolfgang , Zollinger Heinrich
Published: December 2004

The kinetics of reactions of p‐chlorobenzenediazonium ions in aqueous buffer solutions (pH 9.0–10.6) under N2 (< 5 ppb of O2) have been measured between 20 and 50°C. The formation of trans‐diazotate is first‐order with respect to the concentration of hydroxyl ions and to the equilibrium concentration of diazonium ions, if the diazonium ion⇄cis‐diazotate equilibrium is considered as a fast prior equilibrium. This indicates that the p‐chlorobenzenediazonium ion, in contrast to all previous investigations with the p‐nitrobenzenediazonium ion and benzenediazonium ions carrying similar substituents with a −M effect, rearranges from the cis‐ to the trans‐configuration as diazohydroxide and not as diazotate. The formation of trans‐diazotate is catalyzed by carbonate and inhibited by hydrogen carbonate ions; mechanisms of these catalyses are discussed, and the solvent isotope effect KH2O/KD2O measured by an 1H‐NMR. technique reported. The kinetics of the dediazoniations can be analyzed as a mixture of two reactions, a relatively fast first reaction, reaction A, which is responsible for about 5% of the total reaction, and a second reaction F. Both are first‐order with respect to diazonium ion; reaction A is also first‐order in hydroxyl ions. There are some indications that reaction A corresponds to the hydrolysis of the diazonium ion to give eventually amine and nitrite ions. Reaction F shows a complex dependence on hydroxyl ions; it is related to the homolytic dediazoniation.
Dediazoniation of Arenediazonium Ions in Homogeneous Solutions. Part XVII. Kinetics and mechanisms of dediazoniation of p‐chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutions in the presence of oxygen
Authors: Besse Jacques , Zollinger Heinrich
Published: December 2004

The kinetics of dediazoniation of p‐chlorobenzenediazonium tetrafluoroborate have been studied in buffer solutions in the pH‐range 9.0–10.0, ionic strength I = 0.10, at 20.0° in glass and polytetrafluoroethylene vessels. The presence of oxygen (<5 ppb of O2, 60 to 100 ppb of O2, air, > 99% of O2) has a decisive influence on the rate and kinetic order of the dediazoniation. Iodoacetic acid inhibits the reaction, whereas p‐chlorophenol has a catalytic effect, and in air and >99% of O2 it acts as an autocatalyst. The reaction is subject to general‐base catalysis by water, hydroxyl ions, hydrogen carbonate and carbonate ions. The kinetic results are interpreted in conjunction with data concerning the reaction products [2] and a 15N‐CIDNP. investigation of a related system [3]. Specific radical chain mechanisms are consistent with the results.
Notizen zur Synthese sulfonierter Derivate von 5,6,7,8‐Tetrahydro‐1‐naphthylamin und 5,6,7,8‐Tetrahydro‐2‐naphthylamin
Authors: Courtin Alfred
Published: December 2004

Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8‐Tetrahydro‐1‐naphthylamine and 5,6,7,8‐Tetrahydro‐2‐naphthylamine

Sulfonation of 5,6,7,8‐tetrahydro‐1‐naphthylamine (1) with sulfuric acid gave a mixture of 1‐amino‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (2), 4‐amino‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (13) and 4‐amino‐5,6,7,8‐tetrahydronaphthalene‐1‐sulfonic acid (3). The same reaction with 5,6,7,8‐tetrahydro‐2‐naphthylamine (20) yielded 3‐amino‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (21); formation of 2‐amino‐5,6,7,8‐tetrahydronaphthalene‐1‐sulfonic acid (16) or of 3‐amino‐5,6,7,8‐tetrahydronaphthalene‐1‐sulfonic acid (24) was not observed. Treatment of 4‐bromo‐5,6,7,8‐tetrahydro‐1‐naphthylamine (4) or of its 4‐chloro analogue 5 with amidosulfuric acid gave 1‐amino‐4‐bromo‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (9) and its 4‐chloro analogue 10, respectively, which were dehalogenated to 2. Preparations of 13 and 24 were achieved by sulfonation of 5‐nitro‐1,2,3,4‐tetrahydronaphthalene (14) and 6‐nitro‐1,2,3,4‐tetrahydronaphthalene (22) to 4‐nitro‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (15) and 3‐nitro‐5,6,7,8‐tetrahydronaphthalene‐1‐sulfonic acid (23), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4‐amino‐1‐bromo‐5,6,7,8‐tetrahydronaphthalene‐2‐sulfonic acid (11) or of its 1‐chloro analogue 12; compounds 11 and 12 were synthesized from N‐(4‐bromo‐5,6,7,8‐tetrahydro‐1‐naphthyl)acetamide (7) and from its 4‐chloro analogue 8, respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2‐nitro‐5,6,7,8‐tetrahydro‐1‐naphthylamine (17) giving 2‐nitro‐5,6,7,8‐tetrahydronaphthalene‐1‐sulfonyl chloride (18), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.
Benzo[9]annulenone. Synthesis and acid‐induced antiaromaticity. Preliminary communication
Authors: Anastassiou A. G. , Kasmai H. S. , Saadein M. R.
Published: December 2004

The synthesis and acid‐induced pericyclization of the title substance (3), the simplest known [9]annulenone, are described.
2‐Bis (dimethylamino)phosphinoyl‐1‐lithio‐1, 2, 3, 4‐tetrahydroisoquinoline. A highly nucleophilic d1‐reagent for the preparation of 1‐substituted tetrahydroisoquinolines
Authors: Seebach Dieter , Yoshifuji Masaaki
Published: December 2004

The title compound 4 is generated from the phosphoric amide 5 in tetrahydrofuran with butyllithium. The lithium reagent 4 is stable at room temperature; its reactions with electrophiles furnish the products 6–22, 26, 27, see Table 1 and the Scheme. A second alkylation is also possible, see 23–25. The cleavage to tetrahydroisoquinolines is accomplished in refluxing aqueous‐methanolic hydrochloric acid, see Table 2. Phosphinoylation, lithiation, reaction with electrophiles and cleavage constitute an efficient sequence for 1‐alkylation of the isoquinoline nucleus.
Chirale elektrophile Synthesebausteine mit vier verschiedenen funktionellen Gruppen aus Weinsäure, 2, 3‐ und 3, 4‐Epoxy‐butandiolderivate in allen vier stereoisomeren Formen
Authors: Hungerbühler Ernst , Seebach Dieter
Published: December 2004

Chiral Electrophilic Synthetic Building Blocks with Four Different Functional Groups from Tartaric Acid, 2, 3‐ and 3, 4‐Epoxy‐butanediol Derivatives in All Four Stereoisomeric Forms

Efficient and simple procedures have been developed for the preparation of the threo‐ and erythro‐3, 4‐epoxy‐1, 2‐butanediol derivatives 3 and 8 and of the cis‐ and trans‐2, 3‐epoxy‐1, 4‐butanediol derivatives 7 and 9 in both enantiomeric forms from tartaric acid (see Scheme 2). These epoxides should prove versatile as alkylating reagents in syntheses of enantiomerically pure natural products and of physiologically active compounds.
Unkatalysierte sigmatrope 1,5‐Wanderung von Acylgruppen bei der Thermolyse von 5‐Acyl‐5‐methyl‐1,3‐cyclohexadienen
Authors: Schiess Peter , Dinkel Rolf , Fünfschilling Peter
Published: December 2004

Uncatalyzed Sigmatropic 1,5‐Shift of Acyl Groups in the Thermolysis of 5‐Acyl‐5‐methyl‐1,3‐cyclohexadienes

Four different 5‐acyl‐5‐methyl‐1,3‐cyclohexadienes 1a–d (R = COOCH3, COCH3, COC6H5, CHO) have been shown to yield mixtures of 1,3‐disubstituted cyclohexadienes 2–7 and 1,3‐disubstituted aromatic product 8 upon thermolysis at 150–300° in solution and at 350–500° in the gas phase in a flow system. Two reaction pathways (A and B in Scheme 2) are considered for the rearrangement of the C‐Skeleton. For the ester 1a 13C‐isotopic substitution shows that products arise to 75–86% through a 1,5‐sigmatropic shift of the methoxycarbonyl group (A in Scheme 2) and to 14–25% through a sequence of reaction steps involving a 1,7‐H‐shift reaction in an acyclic intermediate (B in Scheme 2). For the more reactive compounds 1b–d isomerization is assumed to follow the 1,5‐sigmatropic pathway exclusively (A in Scheme 2). A kinetic study yields the following sequence for the migration tendency of acyl groups toward sigmatropic 1,5‐shift: COOCH3 < COCH3 < COC6H5 < CHO.
Synthese optisch aktiver Nickel‐Komplexe mit porphinoidem Ligandsystem
Authors: Vogel Ulrich , Meier Kurt , Löliger Jürg , Scheffold Rolf
Published: December 2004

Synthesis of Optically Active Porphine‐type Nickel Complexes

Both enantiomers of [1‐methyl‐8 H‐HDP]nickel‐perchlorate

For nomenclature see footnote 5 in this paper.

(
2a
and
2b
, respectively) have been synthesized by the following reaction sequence: (a) base induced addition of (−)‐(
R
)‐2‐octanol to
1
, (b) separation of the two diastereomeric monoadducts
4a
and
4b
, (c) reaction with methyl magnesium iodide containing an excess of methyl iodide, (d) acid induced elimination of 2‐octanol from the diadducts
6a
and
6b
. By a similar procedure both enantiomers of [1‐butyl‐8 H‐HDP] nickel‐perchlorate (
3a
and
3b
, respectively) have been prepared. The reaction of
3a
with butyl lithium yields in a kinetically controlled addition predominantly the optically active
cis
‐1, 11‐dibutyl adduct
8
and in minor quantity the
meso
‐
cis
‐1, 11‐dibutyl adduct
9
.
Nitrosoalkenes: Synthesis and Reactivity
Authors: Francotte Eric , Merényi Robert , Vandenbulcke‐Coyette Brigitte , Viehe Heinz‐Günther
Published: December 2004

Some α‐ and β‐halonitrosoalkenes1have been synthesized and characterized. The halogen atoms of the oxime precursors2can be substituted by alkoxy groups. Two kinds of cycloaddition reaction of1have been observed: (i) reaction of the NO group with dienes gives 3, 6‐dihydrooxazine derivatives6which isomerise to epoxyepimines7in most cases of β‐substituted nitrosoalkenes; (ii) if 4, 5‐dihydrooxazines22are obtained, the cycloaddition of the nitrosoalkenes as 4π‐component is presumed.
Azimine. V.. Untersuchungen zur stereoisomerie an der N(2), N(3)‐bindung von 2, 3‐dialkyl‐1‐phthalimido‐aziminen
Authors: Leuenberger Christian , Hoesch Lienhard , Dreiding André S.
Published: December 2004

Azimines. V. Investigation on the Stereoisomerism Around the N (2), N (3) Bond in 2, 3‐Dialkyl‐1‐phthalimido‐azimines

2, 3‐(cis‐1, 3‐Cyclopentylene)‐1‐phthalimido‐azimine (7) and isomerically pure (2 Z)‐ and (2 E)‐2, 3‐diisopropyl‐1‐phthalimido‐azimine (9a and 9b) were prepared by the addition of phthalimido‐nitrene (1) to 2, 3‐diazabicyclo [2.2.1]hept‐2‐ene (6) and to (E)‐ and (Z)‐1, 1′‐dimethylazoethane (8a and 8b), respectively. Comparison of their UV. spectra with those of two stereoisomeric azimines of known configuration, namely (1 E, 2 Z)‐ and (1 Z, 2 E)‐2, 3‐dimethyl‐1‐phthalimido‐azimine (5a and 5b), reveals that 2, 3‐dialkyl‐1‐phthalimido‐azimines with (2 Z)‐configuration are characterized by a shoulder at about 258 nm (ϵ ≈︂ 14,000) and those with (2 E)‐configuration by a maximum at 270–278 nm (ϵ ≈︂ 10,000). The (2 E)‐azimine 9b isomerizes under acid catalysis as well as thermally and photochemically into the more stable (2 Z)‐isomer 9a. Under the last two conditions the isomerization is accompanied by a slower fragmentation with loss of nitrogen into N, N′‐diisopropyl‐N, N′‐phthaloylhydrazine (4, R = iso‐C3H7). The same fragmentation was also observed on thermolysis and photolysis of the (2 Z)‐isomer 9a. The kinetic parameters for the thermal isomerization of 9b (they fit first‐order plots) and for the fragmentation of 9a and 9b were determined by 1H‐NMR. spectroscopy in benzene, trichloromethane and acetonitrile. In the photolysis of 9a or 9b the fragmentation is accompanied by dissociation into the azo compounds 8a or 8b and the nitrene 1, the latter being subject to trapping by cyclohexene. With the azimine 7, an analogous thermal fragmentation was observed to give N, N′‐(cis‐1, 3‐cyclo‐pentylene)‐N, N′‐phthaloylhydrazine (15), but more energetic conditions were required than with 9. Photolysis of 7 led exclusively to dissociation into the azo compound 6 and the nitrene 1, perhaps because the fragmentation of 7 is prevented by ring strain.
Multiple Wagner‐Meerwein Shift. Biogenesis‐like conversion of (±)‐Δ7,8‐Protoilludene to (±)‐Hirsutene and related reactions
Authors: Hayano Kiyoharu , Ohfune Yasufumi , Shirahama Haruhisa , Matsumoto Takeshi
Published: December 2004

Experimental details are given for the previous preliminary reports concerning conversion of protoilludane (28) to hirsutene (3) and related reactions. Treatment of each of the bicyclic analogs 9, 10, 12 and 13 of the former compound afforded a hirsutene analog 8, through multiple 1,2‐shift, together with other products. Treatment of a mixture of α‐ and β‐protoilludene ‐epoxides (29α and 29β) with BF3 · Et2O in hexane yielded hirsutane derivatives 30 and 32. Compound 30 in turn was converted to endo‐hirsutene 36, which had already been isomerized to hirsutene (3).
A Dynamic Study of the Stereoisomerization of Pentaphenylethane by Molecular Mechanics Methods
Authors: Bernardinelli Gerald , Gerdil Raymond
Published: December 2004

Two conformations, 1 and 2, of pentaphenylethane are compared. The ground state conformation 2 results from an earlier computational work by force fields procedures [1], whereas 1 has been more recently observed in the crystalline state by X‐ray diffraction methods. The strain energy of 1 minimizes very close to the value computed for 2. These conformations belong to two distinct minima of the potential energy surface and are at the most separated by a barrier of about 7 kcal/mol. The pathway converting 1 into its enantiomer is shown to run over a barrier of only 1.5 kcal/mol.
Homologues of p‐Menthane Derivatives in Roman Camomile
Authors: Thomas Alan F. , Schouwey Marina , Egger Jean‐Claude
Published: December 2004

5‐Isopropyl‐2‐propyl‐2‐cyclohexen‐1‐one (1) and 5‐isopropyl‐2‐(2‐methylpropyl)‐2‐cyclohexen‐1‐one (2), homologues of the p‐methene ketone carvotanacetone, have been identified in the oil of Anthemis nobilis. Their synthesis involved allylation of a cyclohexane‐1,3‐dione, and the acid‐catalyzed cyclization to dihydrofurans of the 2‐allylcyclohexane‐1,3‐diones is described. The stereochemistry of metal hydride reduction of 3‐ethoxy‐5‐isopropyl‐2‐propyl‐2‐cyclohexen‐1‐one (18) is mentioned in the course of the synthesis of the natural products. Some biogenetic considerations are discussed.
Kristallstruktur eines Tetrahydro‐1(1H)‐isoindolons
Authors: Prewo Roland , Bieri Jost H. , Widmer Ulrich , Heimgartner Heinz
Published: December 2004

Crystal Structure of a Tetrahydro‐1(1H)‐isoindolone

The structure of the tetrahydro‐1 (1H)‐isoindolone 4a, the product of an intramolecular Diels‐Alder addition, has been determined by X‐ray analysis. The revised relative configuration of 4a suggests a formation via the exo‐transition state of the [4 + 2]‐cycloaddition, followed by enolization to the more stable cis‐fused product.
Structural Modifications of Chaparrinone Using Benzeneseleninic Anhydride. Preliminary communication
Authors: Khôi Nguyên , Polonsky Judith
Published: December 2004

Treatment of chaparrinone triacetate with benzeneseleninic anhydride afforded in addition to the Δ14,15‐dehydro compound two products arising from angular hydroxylation at C(5). The mechanism of this reaction is discussed. The corresponding deacetylated compounds do not display significant antineoplastic activity.
Nucleotide. XV. Synthese und Eigenschaften von 2′‐O‐t‐Butyldimethylsilyl‐5′‐O‐monomethoxytritylribonucleosid‐3′‐phosphotriestern, Ausgangssubstanzen für Oligonucleotid‐Synthesen
Authors: Silber Gunter , Flockerzi Dieter , Varma Rajendra Singh , Charubala Ramamurthy , Uhlmann Eugen , Pfleiderer Wolfgang
Published: December 2004

Nucleotides. XV. Synthesis and Properties of 2′O‐t‐Butyldimethylsilyl‐5′‐O‐monomethoxytritylribonucleoside‐3′‐phosphotriesters, Starting Materials for Oligonucleotide Syntheses

The syntheses of two types of fully blocked ribonucleoside 3′‐phosphotriesters 6–14 have been achieved in excellent yields from 2′‐O‐t‐butyldimethylsilyl‐5′‐O‐monomethoxytrityl‐ribonucleosides 1–5 by phosphorylation with 2‐chloro‐ and 2,5‐dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6, 8, 10, 12 and 14 and by p‐nitrophenylethanol to 7, 9, 11 and 13. These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15–23 with free HOC(5′) could be obtained by detritylation and the 3′‐phosphodiester triethylammonium salts 24–32 by deblocking of the cyanoethyl and the 2,5‐dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.‐and NMR.‐spectra as well as C, H, N elementary analyses.
The Stability of Divalent 3d‐ and Trivalent 4f‐Metal Complexes with Diazapolyoxa Macrocyclic Ligands
Authors: Anderegg Giorgio
Published: December 2004

The complex formation of some divalent 3d‐ and trivalent 4f‐metal ions with four macrocyclic ligands has been investigated in methanol/water 95:5 by use of alkalimetric titrations. In contrast to alkali and alkaline‐earth cations the obtained stability constants are quite low. The reasons of this effect are discussed.
Alkaloid Production in Catharanthus roseus Cell Cultures. VII.. Effect of parameter changes and catabolism studies on cell line PRL No. 953
Authors: Kutney James P. , Choi Lewis S. L. , Kolodziejczyk Pawel , Sleigh Stephen K. , Stuart Kenneth L. , Worth Brian R. , Kurz Wolfgang G. W. , Chatson Kenneth B. , Constabel Friedrich
Published: December 2004

Catharanthus roseus cells suspended in production medium showed the presence of four Aspidosperma‐type alkaloids, however, no vindoline. Cells grown in media with the pH adjusted to 7.0 produced 3.3 mg total alkaloids/g dry weight. At pH 5.0, 1.7 mg of alkaloid/g dry weight was produced. (S)‐Adenosyl‐methionine did not stimulate the production of vindoline. When added to cell suspensions for 21 days, vindoline and catharanthine were degraded to non‐alkaloidal substances, not dimerized to bisindole alkaloids.
Mono et Diglycosylbutadiynes
Authors: Tronchet Jean M. J. , Bonenfant Alain‐P.
Published: December 2004

Mono and Diglycosylbutadiynes

Cadiot's dissymmetric coupling of bromoethynylsugar derivatives with therminal acetylenes led in good to excellent yields to the expected mono or diglycosylbutadiynes. In the same way, terminal acetylenic sugar derivatives could be coupled with bromoacetylenic compounds. Symmetric coupling of sugars bearing a bromoethynyl group has also been achieved. (UV., CD., IR., 1H‐NMR.) of these compounds are reported and discussed.
(25 S)‐1α, 25, 26‐Trihydroxycholecalciferol, a New Vitamin D3 Metabolite: Synthesis and Absolute Stereochemistry at C(25)
Authors: Partridge John J. , Shiuey Shian‐Jan , Chadha Naresh K. , Baggiolini Enrico G. , Hennessy Bernard M. , Uskoković Milan R. , Napoli Joseph L. , Reinhardt Timothy A. , Horst Ron L.
Published: December 2004

The 1α, 25, 26‐trihydroxy metabolite of vitamin D3, isolated from bovine serum, was shown to possess the (25 S)‐configuration by HPLC. comparison of the 1, 3, 26‐triacetate derivative with authentic (25 R)‐ and (25 S)‐samples. The convergent synthesis of (25 R)‐1α, 25, 26‐ and (25 S)‐1α, 25, 26‐trihydroxycholecalciferols (10a) and (10b) has been accomplished.
Characterization of the Excited State Properties of Some New Photosensitizers of the Ruthenium (Polypyridine) Family
Authors: Juris Alberto , Balzani Vincenzo , Belser Peter , von Zelewsky Alex
Published: December 2004

The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized. The complexes studied are Ru (bpy)3‐n (LL)2+n, where n varies from 0 to 3, and LL is 4, 4′‐di‐t‐butyl‐2,2′‐bipyridine (DTB‐bpy), 3, 3′‐dimethyl‐2, 2′‐bipyridine (DM‐bpy), or a 2, 2′‐diquinolyl derivative (DMCH). The results obtained show that the Ru (bpy)2(DMCH)2+ complex is expected to be a more efficient mediator than Ru (bpy)2+3 in the water‐splitting reaction by solar energy.
Beiträge zur Kenntnis des chromophoren Systems der Corrine: XII [1]. Chemische Eigenschaften des Reaktionsproduktes aus Dicyanocobyrinsäure‐heptamethylester mit hypochloriger Säure
Authors: Sauer Ernst Michael , Broschinski Klaus , Ernst Ludger , Inhoffen Hans Herloff
Published: December 2004

Contributions to the Knowledge of the Corrin Chromophore: XII [1]. Chemical Behaviour of the Reaction Product of Heptamethyl Dicyano‐cobyrinate with Hypochlorous Acid

Heptamethyl chloro‐cyano‐5α, 10, 15‐trichloro‐6α, 14‐dihydroxy‐5,6,14,15‐tetrahydrocobyrinate (2) in CH3OH/H2SO4 yields with RuO2 under 50 bar hydrogen and at 100° during 2 h a mixture of heptamethyl dicyanocobyrinate (1) with an epimeric ester. Using deuterium instead of hydrogen in this reaction, C(13) comes out as the probable epimerization center.
Improved Nitroaldol Reactions and Reductive Routes to Vicinal Aminoalcohols
Authors: Colvin Ernest W. , Beck Albert K. , Seebach Dieter
Published: December 2004

Regioselective and flexible procedures are described for the preparation of a variety of protected vicinal nitroalcohols 1, 3 and 5 (see Scheme 5), as is an efficient method for their reduction to the corresponding vicinal aminoalcohols 2, 4 and 6.
Novel Ketones from Roman Camomile Oil
Authors: Thomas Alan F. , Egger Jean‐Claude
Published: December 2004

β‐Damascenone (1) has been identified in the fraction of Roman camomile (Anthemis nobilis) oil that contains homologues of carvotanacetone. 5‐(3‐Furyl)‐2‐methyl‐1‐penten‐3‐one (2), (E)‐1‐(2,6‐dimethylphenyl)‐2‐buten‐1‐one (8), 4‐isopropenylbenzaldehyde (4), were also identified and synthesized.
A Short and Efficient Synthesis of (±)‐Modhephene by a Stereoelectronically‐Controlled Ene‐Reaction
Authors: Oppolzer Wolfgang , Bättig Kurt
Published: December 2004

(±)‐Modhephene (6) has been synthesized from the easily available trimethylpentalenone 1 in 6 steps in 26% overall yield (Scheme 2). The remarkably smooth 1,4‐addition/enolate trapping 1 → 2 and subsequent selenoxide elimination after oxidation furnished the key intermediate 3 which underwent an expedient and highly stereoselctive intramolecular ene‐reaction to give the propellane 4, readily convertible to (±)‐6.
Low Temperature Grignard Reactions with Pure Mg Slurries. Trapping of cyclopropylmethyl and benzocyclobutenylmethyl Grignard reagents with CO2
Authors: Künding Ernst Peter , Perret Celia
Published: December 2004

Cyclopropylmethyl bromide reacts readily at −75° with a Mg/THF slurry formed by evaporation of Mg in a rotating‐solution reactor to yield after carbonation cyclopropyl acetic acid and 4‐pentenoic acid in a ratio of 11:1. Addition of benzaldehyde to the Grignard solution again predominantly yields the addition product containing the cyclopropylmethyl unit. Using the same low temperature Grignard method, benzocyclobutenyl acetic acid is isolated upon carbonation of the Grignard reagent derived from the corresponding bromide, whereas under normal conditions o‐vinylphenylacetic acid, the product corresponding to ring cleaved Grignard is obtained.
Methylthiofurane: Herstellung und Reaktionen
Authors: Eugster Conrad Hans , Balmer Markus , Prewo Roland , Bieri Jost H.
Published: December 2004

Preparation and Reactions of Methylthiofurans

By lithiation of 3,4‐dimethoxyfuran, 2‐methylfuran and furan, followed by reaction with dimethyldisulfide, the methylthiofurans 2, 8, and 10 have been prepared. Reaction of 8 with maleic anhydride has yielded 6‐methyl‐3‐(methylthio)phthalic anhydride (9), a yellow substance with a strong greenish fluorescence, obviously formed by elimination of H2O from an unstable cycloadduct. An analgous reaction of 2 resulted in an unexpected mixture from which the following yellow compounds were isolated: 3‐hydroxy‐4,5‐dimethoxy‐6‐(methylthio)phthalic anhydride (3), 4‐hydroxy‐5‐methoxy‐3,6‐bis(methylthio)phthalic anhydride (4), and bis(S‐methyl) (2Z,4E,6Z)‐2,3,6,7‐tetramethoxy‐4,5‐bis(methylthio)‐2,4,6‐octatrienethioate (5). Compound 5 is also formed on standing of 2 at RT. Mild acid hydrolysis of 2 results in ring‐opening accompanied by an intramolecular oxido‐reduction to yield S‐methyl(3Z)‐3‐methoxy‐4‐(methylthio)‐2‐oxo‐3‐butenethioate (6a). The structures of compounds 5 and 6a have been determined by X‐ray analysis.
Action de nucléophiles simples sur un bromoénurononitrile, précurseur et équivalent synthétique partiel d'un ynurononitrile
Authors: Tronchet Jean M. J. , Martin Olivier R.
Published: December 2004

Reactions of Mononucleophiles with a Bromoenurononitrile, Precursor and Partial Synthetic Equivalent of an Ynurononitrile

Several mononucleophiles (bases) have been reacted with one or the other of the geometrical isomers of the bromoenurononitrile 1. Depending on the nucleophile and the conditions, many different mechanistic pathways were followed, f. ex.: with OH−, stereospecific elimination from (Z)‐1 leading to 2, with N−3 and F−, stereospecific E‐AN reactions leading from (Z)‐1 to (Z)‐8 and (Z)‐12 respectively, with PhCH2SH, conjugate nucleophilic addition to 7, with Me2NH, conjugate nucleophilic addition followed by a SN2 to 11, as well as several cases of nonstereoselective, probably AN‐E, reactions leading to 3,6,9 and 10. In spite of their diversified reactivity, bromoenurononitriles like 1, partial synthetic equivalent of 2, constitute useful synthetic intermediates.
High Asymmetric Induction in Conjugate Additions of RCu · BF3 to Chiral Enoates. Preliminary communication
Authors: Oppolzer Wolfgang , Löher Heinz J.
Published: December 2004

1,4‐Additions of PhCu · BF3, n‐Bu · BF3 and MeCu · BF3 to the trans‐8‐phenyl‐menthyl enoates 1 proceeded with high chiral induction. Saponification of the resulting esters 2 gave the corresponding enantiomerically pure β‐substituted alkanoic acids 3 and the recovered (−)‐8‐phenylmenthol in good overall yields. Analogous additions to the cis‐crotonate 1 led preferentially to the acids 3 enantiomeric to those obtained from the trans‐crotonate 1, although with lower selectivity. A stereochemical model is proposed consistent with the observed results (Scheme 2, Table).
Nucleophilic aromatic substitution. Part XV. Phase‐transfer catalysis of sulfodechlorination and identification of a primary product of sulfite ion with 1‐chloro‐2, 4‐dinitrobenzene
Authors: Bunnett Joseph F. , Gisler Markus , Zollinger Heinrich
Published: December 2004

With conventional phase‐transfer catalysis using quaternary ammonium salts, yields of 2, 4‐dinitrobenzenesulfonic acid (2) in the sulfodechlorination of 1‐chloro 2.4‐dinitrobenzene (1) with sulfite ions are no better than those obtained with the classical method in aqueous ethanol (80–82%). Yields up to 97% and a very pure product are obtained, however, by using protonated tertiary amines as catalysts. The optimum chain‐length of the amine is found with tributylamine. On mixing solutions of the reagents and catalysts a strong bluish‐red colour develops immediately, but disappears within ca. 1 h. Comparison of the NMR. spectrum of this primary product with model adducts of sulfite ions and di‐ and trinitrobenzene derivatives demonstrates that the primary addition of the nucleophile to 1‐chloro‐2, 4‐dinitrobenzene does not take place at C (1), but at C(5). It is shown that the increments calculated for a C‐SO group and for the 1, 3‐dinitro‐ and 1, 3, 5‐trinitropentadienyl ring moieties can be employed for the approximate calculation of 1H‐chemical shifts using Clerc & Pretsch's modification of the Shoolery rules [3].
Fulven‐Dimere: Synthese, Strukturbeweis and thermisches Verhalten
Authors: Uebersax Beat , Neuenschwander Markus , Kellerhals Hans‐Peter
Published: December 2004

Fulvene‐Dieters: Synthesis, Structure Elucidation and Thermal Behaviour

In contrast to earlier assumptions, thermal reaction of pure fulvene (1a), 6‐methylfulvene (lb) and 6, 6‐dimethylfuivene (1c) at 227deg; gives oligomeric mixtures consisting mainly of the endo‐[4 + 2]‐eycloaddition products 2a, 2b and 2c. Thermal reactivity of the fulvenes decreases strongly in the series 1a > 1b > 1c. While the dimers 2b and 2c equilibrate very easily in solution above room temperature with 1b and 1c, respectively, 2a equilibrates with the isomer 5a (1, 6‐Dimethyliden3a α, 3bβ, 6a α, 6bβ‐tetrahydro‐1‐H), 6 H‐bi (cyclopentadienylen). This surprising rearrangement envolves a formal 1,3‐shift of the 1, 2‐dihydrofulvene‐unit of 2a (s. Scheme 4).
Polyamines XIV. Protonation Equilibria of Linear Tetraamines Containing two Ethylenediamine Residues
Authors: Anderegg Giorgio , Bläuenstein Peter
Published: December 2004

The syntheses of the linear tetraamines H2N(CH2)2NH(CH2)2NH(CH2)2NH2(n = 4 and 5) are described. The protonation of the homologous tetraamines for n = 2, 3, 4, 5, 6 and 8, as well as ofN‐methylethylenediamine, was investigated using potentiometric and calorimetric measurements. The results obtained are discussed taking into consideration the substituent effect on the basicity of the aminic N‐atoms.
[2 + 2]‐Cycloadditions to Strained Bridgehead Olefins. I. 1, 1‐Dichloro‐2,2‐difluoroethene
Authors: Becker Konrad B. , Hohermuth Martin K.
Published: December 2004

The strained bridgehead olefins bicyclo [3.3.1]non‐1‐ene (1), bicyclo [4.2.1] non‐‐1‐(8) (2), and bicyclo [4.2.1]non‐1‐ene (3) react rapidly with 1,1‐dichloro‐2, 2‐‐difluoroethene (5) to yield mixtures of regioisomeric dichlorodifluorocyclobutanes 8/9, 10/11 and 12/13, respectively. On the contrary, the reaction of 5 with the model compound (E)‐l‐methylcyclooctene (4) is completely regioselective. The structure of the cycloadducts has been elucidated mainly by 19F‐NMR. and 13C‐NMR. spectroscopy.
[2 + 2]‐Cycloadditions to Strained Bridgehead Olefins. II. Diphenylketene
Authors: Becker Konrad B. , Hohermuth Martin K. , Rihs Grety
Published: December 2004

The strained bridgehead olefins bicyclo [3.3.1]non‐1‐ene (1), bicyclo [4.2.1 ]non‐1(8)‐ene (2), and bicyclo [4.2.1]non‐1‐ene (3), and the comparable monocyclic (E)‐1‐methylcyclooctene (4) react with diphenylketene (6) to give a single cycloadduct 7, 8, 9 and 10, respectively, in which the diphenyl‐substituted C‐atom is bound to the bridgehead. The structure of the cyclobutanone 8 has been determined by X‐ray analysis of a twin crystal obtained by crystallization with spontaneous enrichment of enantiomers.
Visible Light Induced Generation of Hydrogen from H2S in CdS‐Dispersions, Hole Transfer Catalysis by RuO2
Authors: Borgarello Enrico , Kalyanasundaram Kuppuswamy , Grätzel Michael , Pelizzetti Ezio
Published: December 2004

Illumination of US‐dispersions by visible light in solutions containing H2S or sulfide ions leads to efficient generation of hydrogen and sulfur. Very small quantities of RuO2 deposited on the CdS‐particles improve markedly the quantum yield of H2‐formation for which the optimum value obtained so far is ϕ = 0.35 ± 0.1. The effect of RuO2 is attributed to catalysis of hole transfer from the valence band of CdS to H2S or sulfide in solution.
Heterocyclische und carbocyclische 12‐π‐ and 14‐π‐Molekülsysteme, 47. Mitteilung. Herstellung von 7, 9‐Dimethyl‐4, 5‐dihydro‐3 H‐benz [cd]‐ azulen‐3‐on and 7,9‐Dimethyl‐3H‐benz [cd]azulen‐3‐on. Eine einfache Synthese eines Azulenopseudophenalenons
Authors: Neidlein Richard , Kramer Walter
Published: December 2004

Heterocyclic and Carbocyclic 12‐π‐and 14‐π‐Systems, 47th Commnunication1. Synthesis of 7,9‐Dimethyl‐4,5‐dihydro‐3H‐benz[cd]azualene‐3‐one and 7,9‐Dimethyl‐3H‐benz[cd]azulene‐3‐one. A Simple Synthesis of Azulenopseudophenalenons

4, 6, 8‐Trimethylazulene (3) reacts after metalation with lithiumdiisopropyl‐amide in ether with bromoacetic acid to the 6, 8‐dimethylaltulene‐4‐propionic acid (4), which undergoes cyclization to the 7, 9‐dimethyl‐4, 5‐dihydro‐3H‐benz [cd]‐azulene‐3‐one (5) in the presence of p‐toluenesulfonic acid; oxidation of 5 with 2, 3‐dichloro‐5, 6‐dicyanobenzoquinone yields 7, 9‐dimethyl‐3H‐benz [cd]azulene‐3‐‐one (1b). Alkylation of 1b with triethyloxonium tetrafluoroborate in CH2C12 gives the 3‐ethoxy [cd]benzazulenium tetrafluoroborate (6).
d5‐Reactions of Doubly Deprotonated γ,δ‐Unsaturated Carbonyl Derivatives with Electrophiles. A Novel Approach to the Synthesis of Tetrahydrofuran and Tetrahydropyran Derivatives
Authors: Seebach Dieter , Pohmakotr Manat , Schregenberger Christian , Weidmann Beat , Mali Raghao S. , Pohmakotr Srisuke
Published: December 2004

The dienone‐dianion derivatives 1 react with all types of electrophiles tested (alkyl halide, silyl chloride, ester, ketone, aldehyde, epoxide) to give β, γ‐unsaturated carbonyl compounds of type A (see Formulae 2–6, 13, 14 and Tables 1–5). The α‐ and β‐hydroxyalkylation products obtained from 1a–1d can be converted to tetra‐hydrofuran and tetrahydropyran derivatives 7 and 16, respectively (Tables 1 and 2), those from the sulfur analogues 1e and 1f to ketene thioacetals 9 and to dienone derivatives 10 and 12. The t‐butyl and α‐hydroxy‐ketones are cleaved to give nitriles, amides, carboxylic acids and esters (Formulae 16‐25). The reagents 1 allow to synthesize products with distant functional groups in one step (cf. 1,8‐diketones 14 and Formulae 26–30); they correspond to the d5‐synthons 31–33; in Table 6, they are compared with other d5‐reagents.
Über die Depolymerisierung von Poly‐(R)‐3‐hydroxy‐buttersäureester (PHB)
Authors: Seebach Dieter , Züger Max
Published: December 2004

On the Depolymerization of Poly‐(R)‐3‐hydroxy‐butanoate (PHB)

From cell‐free PHB or from dried cells of Alcaligenes eutrophus H 16, which had been grown in an aqueous fructose solution, enantiomerically pure methyl, ethyl, butyl or β‐methoxyethyl (R)‐3‐hydroxy‐butanoates are obtained in yields ranging from 75–90% (0.1 to 70 g scale). The depolymerization is achieved by heating the PHB‐containing materials to temperatures of 80–160° in the corresponding alcohol with or without the cosolvent dichloroethane in the presence of either sulfuric acid or tetraethoxytitanium catalyst. Since (S)‐3‐hydroxy‐butanoates are also readily obtained (by yeast reduction of aceto‐acetates), starting materials derived from 3‐hydroxy‐butyric acid now belong to the especially useful group of synthetic building blocks which are available in both enantiomeric forms.
Linear‐Reactor‐IR.‐Matrix and Microwave Spectroscopy of the System O3/NO2/(Z)‐2‐Butene
Authors: Dommen Joseph , Forster Martin , Ruprecht Heidi , Bauder Alfred , Günthard Hans‐Heinrich
Published: December 2004

Investigation of the formation of complex reaction products in the gas‐phase system O3/NO2/(Z)‐2‐butene by combination of linear reactors with IR. matrix and microwave Stark Spectroscopy is reported. Besides the polyatomic products observed earlier in the gas‐phase ozonolysis of (Z)‐2‐butene, the following products were identified; N2O5, HNO3, HNO4, CH3NO2, CH3ONO, CH3COONO2 and CH3COO2NO2 (peroxyacetyl nitrate, PAN). Matrix IR. spectra of N2O5, HNO3. CH3COONO, CH3COONO2 required for reference purposes are presented. It is shown that PAN‐formation occurs already in the absence of light. A reaction scheme is proposed for explanation of the observed complex NOx‐containing products, which assumes methyldioxirane as a central intermediate. Particular reaction steps of the scheme will be discussed, including thermochemical estimates of reaction enthalpies.
The ESR. Spectrum of the Radical Anion of 1,1,2,2,9,9,10,10‐Octafluoro [2.2]paracyclophane
Authors: Gerson Fabian , Ohya‐Nishiguchi Hiroaki , Plattner Georges
Published: December 2004

The radical anion of 1,1,2.2,9,9,10, 10‐octafluoro[2.2]paracyclophane (1) has been generated by electrolytic reduction of 1 in 1,2‐dimethoxyethane (tetrabutylammonium perchlorate as the supporting salt). The hyperfine coupling constants of the eight 19F‐nuclei and the eight protons, af = 3.35 and aH ≈ 0.10 mT, are qualitatively reproduced by INDO. calculations. According to these calculations, the singly occupied orbital of 1⊖ can be represented by an Ag‐combination of two ‘symmetric’ benzene LUMO's, with a substantial transfer of spin population into the 2s‐AO's of the F‐atoms. Line‐width alternation in the ESR. spectrum of 1⊖ indicates an ion pairing of the radical anion with its counter‐ion Bu4N⊖. The energy barrier to the migration of the cation between two equivalent sites at the radical anion is determined as 14±2 kJ/mol.
Transition metal complexes with bidentate ligands spanning trans‐positions. XII. The preparation and properties of complexes trans‐[MX2 (1)] and trans‐[PtHCl (1)] (M = Ni, Pd and Pt; X = Cl and NCS; 1 = ditertiary phosphine)
Authors: Kapoor Pramesh N. , Pregosin Paul S. , Venanzi Luigi M.
Published: December 2004

Complexes [MX2(1)] (M = Ni, Pd and Pt; X=Cl and NCS; 1 = 2,11‐bis(dialkyl‐[or diaryl]phosphinomethyl)benzo[c]phenanthrene; alkyl = cyclohexyl t‐butyl; aryl = m‐tolyl, p‐anisyl and m‐CF3 C6H4) have been synthesized.

An NMR. study of the t‐butyl complexes provides evidence for a “fan‐like” motion of the benzo[c]phenanthrene moiety over the plane of the complex.