bluuebunny/crossref_metadata_2025_split huggingface dataset:
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 FormsEfficient 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‐cyclohexadienesFour 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 ComplexesBoth enantiomers of [1‐methyl‐8 H‐HDP]nickel‐perchlorateFor 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

AbstractSome 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‐azimines2, 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

AbstractExperimental 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

AbstractTwo 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

Abstract5‐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)‐isoindoloneThe 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

AbstractTreatment 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 SynthesesThe 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

AbstractThe 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

AbstractCatharanthus 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 DiglycosylbutadiynesCadiot'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

AbstractThe 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

AbstractThe 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 AcidHeptamethyl 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

AbstractRegioselective 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

Abstractβ‐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

Abstract(±)‐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

AbstractCyclopropylmethyl 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 MethylthiofuransBy 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 YnurononitrileSeveral 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

Abstract1,4‐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

AbstractWith 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 BehaviourIn 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

AbstractThe 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

AbstractThe 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.