bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese und flüssigkristalline Eigenschaften 2,6‐disubstituierter Naphthaline
Authors: Lauk Urs H. , Skrabal Peter , Zollinger Heinrich
Published: December 2004

Synthesis and Liquid‐Crystal Properties of 2,6‐Disubstituted Naphthalene Derivatives

The syntheses and the mesomorphic properties of a series of novel 2,6‐disubstituted naphthalenes are described. 4‐[6‐(n‐Alkyl)‐2‐naphthyl]benzonitriles 5 and 4‐[6‐(n‐Alkoxy)‐2‐naphthyl]benzonitriles 8 exhibit widerange nematic mesophases. 6,6′‐Di(n‐alkyl)‐2,2′‐binaphthyls 6 have been isolated as by‐products from the reaction mixtures of 5. Some of these novel compounds have polymorphic properties. The esters 13 and 15 of 4‐(6‐hydroxy‐2‐naphthyl)benzonitrile show enhanced mesophase stabilities which reach maximum values in the series of α, β‐unsaturated esters 15. The 4‐(n‐pentyl)benzoate 14 of the same (hydroxynaphthyl)benzonitrile has a melting point of 125° and a clearing point of > 310°. This particular derivative belongs to those liquid‐crystalline compounds having the broadest purely nematic‐phase range. In addition, (RS)‐4‐(2‐pentyl‐6‐chromanyl)benzonitrile (20) and three compounds with two and four laterally arranged CN groups at the bicyclo[2.2.2]octene, bicyclo[2.2.2]octadiene, and the phenyl‐ring systems 31–33 were synthesized. Only 20 shows mesomorphic properties.
7‐Bromocavernicolenone, a New α‐Bromoenone from the Mediterranean Sponge Aplysina (= Verongia) cavernicola. Implied, Unprecedented Involvement of a Halogenated Dopa in the Biogenesis of a Natural Product
Authors: D'Ambrosio Michele , Mealli Carlo , Guerriero Antonio , Pietra Francesco
Published: December 2004

A novel, mildly antibacterial, α‐bromoenone (7‐bromocavernicolenone) has been isolated from the Mediterranean sponge Aplysina (= Verongia) cavernicola. Its structure, 7‐bromo‐1,5‐dihydroxy‐2‐azabicyclo[3.3.1]non‐6‐en‐3,8‐dione (3), is based on X‐ray and NMR analysis and on the observation that acetylation of 3 affords two monoacetates. An unprecedented phenol oxidative biogenetic pathway is suggested leading to 7‐bromocavernicolenone via 3‐bromotyrosine and 5‐bromodopa.
The Reaction of Dihalocarbenes with Quadricyclane
Authors: Jefford Charles William , Roussilhe Jacques , Papadopoulos Mihail
Published: December 2004

The reactions of difluoro‐, dichloro‐ and dibromocarbene with quadricyclane (2) were examined. In all cases, conversions were low (4–15%), but three distinct reaction courses were observed: cleavage, 1,2‐addition, and 1,4‐addition. Difluorocarbene gave mainly 6‐endo‐(2,2‐difluorovinyl)‐cis‐bicyclo[3.1.0]hex‐2‐ene (8; 52–89% relative yield), together with minor amounts of exo‐3,3‐difluorotricyclo[3.2.1.02,4]oct‐6‐ene (7; 13–17%), and 4,4‐difluorotetracyclo[3.3.0.02,8.03,6]octane (5; 2–4%). Dichlorocarbene gave analogous products, but in relative yields of 35 (17), 51 (11), and 12% (16). The product 11 of 1,2‐endo addition underwent further rearrangement to its allylic derivative 12. A small amount of 1,2‐endo addition also occurred (2% of 14/15). Dibromocarbene gave predominantly products derived from rearrangement of the 1,2‐exo (61% of 20/21) and 1,2‐endo adducts (10% of 23/24). In addition, a significant amount of 4,4‐dibromotetracyclo[3.3.0.02,8.03,6]octane (25; 21%) was formed. The cleavage product, 6‐endo‐(2,2‐dibromovinyl)‐cis‐bicyclo[3.1.0]hex‐2‐ene (26) was also observed (7%). The yields and product compositions were compared to those obtained from norbornadiene (1) and found to be entirely different (Table 1), for example no cleavage occurred with difluorocarbene.
A Mild, Facile Method for the Preparation of Amino‐esters
Authors: Stadler Paul Albert , Huegi Bruno Silvio
Published: December 2004

Lithium alcoholates prepared in situ react spontaneously with imidazolides derived from substituted aromatic carboxylic acids to provide the amino‐esters 4 in excellent yield.
Picosecond Time Resolved Studies of Photosensitized Electron Injection in Colloidal Semiconductors
Authors: Moser Jacques , Grätzel Michael , Sharma Devendra K. , Serpone Nick
Published: December 2004

Using a single picosecond pulse from a frequency‐doubled Nd:YAG‐mode‐locked laser for excitation, we measured directly the rate of electron injection from the excited singlet state of eosin in the conduction band of colloidal TiO2 particles. The rate constant for interfacial electron transfer is 9.5 × 108s−1 at 25°C and pH 3.
Nucleophilic Additions to N‐Glycosylnitrones. Asymmetric Synthesis of α‐Aminophosphonic Acids
Authors: Huber Rolf , Knierzinger Andreas , Obrecht Jean‐Pierre , Vasella Andrea
Published: December 2004

The hypothesis which explains the diastereoselectivity of the 1,3‐dipolar cycloaddition of the N‐glycosylnitrones 1–3 leading to the 5,5‐disubstituted isoxazolidines 4–6 on the basis of a kinetic anomeric effect predicts that nucleophiles should add to N‐glycosylnitrones with a high degree of diastereoselectivity. To test this prediction, the nucleophilic addition of lithium and potassium dialkylphosphites to the crystalline (Z)‐nitrone 11, prepared from oxime 9 and (benzyloxy)acetaldehyde has been examined. The addition of lithium phosphites gave the N‐glycosyl‐N‐hydroxyaminophosphonates 12–16 (d. e. 78–92%) in high yields (Scheme 4). The addition of potassium phosphites showed a much lower diastereoselectivity. Glycoside cleavage, hydrogenolysis, and dealkylation of 12–16 gave (+)‐(S)‐phosphoserine (+)‐19 (34–45% from 9). Its absolute configuration was confirmed by an X‐ray analysis of the N‐(3,3,3‐trifluoro‐2‐methoxy‐2‐phenylpropionyl) derivative 24. Similarly, the crystalline nitrone 25 gave the N‐glycosyl‐N‐hydroxyaminophosphonate 26, which was transformed into (+)‐(S)‐phosphovaline (+)‐31 (42% from 9). The diastereoselectivity of the nucleophilic addition and the enantiomeric purity of (+)‐31 were determined by the analysis of the derivative 30 (d.e. 92%) and 32 (d.e. 93%), respectively. The addition of lithium diethyl phosphite to the nitrone 33, prepared in situ, gave the N‐glycosyl‐N‐hydroxyaminophosphonate 34, (41%; d.e. 91%), which was transformed in (+)‐(S)‐phosphoalanine (+)‐37 (21% from 9).
Heterocyclic Rearrangement of 4,5,6,7‐Tetrahydro‐6,6‐dimethyl‐benzo[c][1,2,5]oxadiazol‐4‐one (Z)‐Arylhydrazones into Corresponding 2‐Aryl‐4,5,6,7‐tetrahydro‐2H‐benzo[d][1,2,3]triazol‐4‐one Oximes
Authors: Lefkopoulou Susan , Stephanidou‐Stephanatou Julia , Tsoleridis Constantine , Alexandrou Nicholas E.
Published: December 2004

The thermal base‐catalysed and photochemical transformation (Boulton‐Katritzky rearrangement) of the title tetrahydrobenzo[c][1,2,5]oxadiazoles to tetrahydro‐2H‐benzo[d][1,2,3]triazoles is studied. Attempts to induce analogous rearrangement in tetrahydro‐2H‐benzo[d][1,2,3]triazol‐4‐one arylhydrazones or oximes failed. Some CNDO/2 calculation are also carried out.
Structure and Reactivity of Xanthocorrinoids. Part III. The first example of a pinacol‐type rearrangement in the corrin series
Authors: Grüning Burghard , Holze Gerhard , Gossauer Albert , Ernst Ludger
Published: December 2004

The transformation of the c‐acetic‐acid chain of hexamethyl Coα, Coβ‐dicyanocobyrinate into an ethyl group (→2) as well as the synthesis of the pentadecaalkyl‐cobalticorrin 6d from commercial cyanocobalamin are described. On reaction of 2 or 6d with O2 in the presence of ascorbic acid, migration of the CH3 group at C(5) to the vicinal position C(6) takes place concomitantly with the introduction of a carbonyl group at C(5).
Neue Dimethinmerocyaninfarbstoffe mit J‐Aggregation in stark verdünnter Lösung
Authors: Langhals Elke , Balli Heinz
Published: December 2004

Novel Dimethinmerocyanine Dyes Performing J‐Aggregation in Highly Diluted Solution

A series of various novel long‐chain alkyl‐dimethinmerocyanine dyes containing sulfonate groups is obtained in high yield by modified condensation reactions of sulfoalkyl‐ or sulfophenylsubstituted methylene ketones. The dyes exhibit intense, red‐shifted absorption bands (ϵ up to 263 000) due to J‐aggregation in DMSO/H2O mixtures without addition of salt even at dye concentrations of 5 · 10−8M. The influence of dye structure and medium on the aggregation tendency is investigated. Besides it is found that exchange of the cationic counterions does not affect J‐aggregation.
The Characterization of Natural and Artificial Calcium Carbonates by Adsorption and Immersion Techniques
Authors: Morel Daniel , Stoeckli Fritz , Krähenbühl Francis , Misteli Laurent , Munyazikwiye Paulin
Published: December 2004

Nitrogen adsorption isotherms at 77K and enthalpies of immersion into water at 293K have been measured for a series of artificial and natural calcium carbonates. It appears that the external surface area and the micropore system can be fully characterized if a non‐porous sample, present in the series, is used as an internal reference. Data are given for the reference isotherm. Owing to high specific interactions, immersion into water only provides information on the total surface area of the samples.
Convenient Preparation and Spectroscopic Characterization of Methyl Hydrodisulfide and Methyl Deuterodisulfide
Authors: Grassi Guido , Tyblewski Marek , Bauder Alfred
Published: December 2004

Methyl hydrodisulfide and methyl deuterodisulfide have been prepared in a four‐step synthesis. These compounds have been characterized spectroscopically including microwave spectra.
Synthesen von optisch aktiven Carotinoiden mit einer (R)‐4‐Hydroxy‐β‐Endgruppe
Authors: Haag Andreas , Eugster Conrad Hans
Published: December 2004

Synthesis of Optically Active Carotenoids with (R)‐4‐Hydroxy β‐End Groups

We describe the synthesis of optically active iso‐β‐kryptoxanthin (12; (R)‐β,β‐caroten‐4‐ol), iso‐α‐kryptoxanthins 14 ((4R,6′RS)‐β,ε‐caroten‐4‐ol) and 16 ((4R,6′R)‐β,ε‐caroten‐4‐ol), 4′‐hydroxyechinenone (18; (R)‐4′‐hydroxy‐β,β‐caroten‐4‐one), and isorubixanthin (20; (R)‐β,ω,‐caroten‐4‐ol), their 400‐MHz‐1H‐NMR spectra, CD spectra and HPLC behaviour.
Synthesis of Oligodeoxynucleotides by the Phosphite‐Triester Method Using Dimer Units and Different Phosphorous‐Protecting Groups
Authors: Bannwarth Willi
Published: December 2004

A simple synthesis of phosphoamidite dinucleotides with two different phosphorous‐protecting groups and their use for the synthesis of 2′‐oligodeoxynucleotides on a polymer support is reported.
The Reductive Conversion of Some Cyclic and Acyclic vic‐Epoxides to Alcohols by Means of Lithium Aluminium Hydride/Aluminium Trichloride
Authors: Andrejević Vladimir , Bjelaković Mira , Mihailović Milan M. , Mihailović Mihailo Lj.
Published: December 2004

Unsubstituted medium‐ring 1,2‐epoxycycloalkanes and certain vic‐epoxyalkanes are reduced to the corresponding alcohols very slowly when LiAlH4 alone is used as reducing agent. However, the combination of LiAlH4 and AlCl3, in a 2:1 molar ratio (with respect to 1 mol‐equiv. of epoxide) used in refluxing Et2O, greatly enhances these reductions, rendering them of interest for practical purposes.
Propellanes. Part LXXXII. Preparation and Labelling of [20.3.3]Propellane‐24,27‐dione
Authors: Ashkenazi Pnina , Kettenring Jürgen , Migdal Shmuel , Gutman Arie L. , Ginsburg David
Published: December 2004

The title diketone has been prepared by a synthetic sequence beginning with decane‐1,10‐dicarboxylic acid.
Reactions of Cyclopalladated Benzylidene‐aniline Schiff's Base Complexes. Selective Synthesis of 2′‐Substituted Schiff's Base Derivatives and the X‐Ray Crystal Structure of the Dimer [Pd(μ‐OAc)(5′‐OCH3C6H3CHNC6H4‐4‐CH3)]2
Authors: Albinati Alberto , Pregosin Paul S. , Rüedi Regula
Published: December 2004

The 2′‐cyclopalladated imine complex , reacts with CO in MeOH to afford the 2′‐substituted aryl imine 2′‐CO2CH3‐5′‐OCH3C6H3CHNTol (Tol = C6H4‐4‐CH3). The product of this reaction can be altered by changing the bridging ligand from AcO to Cl, in which case only the 5‐membered ring heterocyclic compound is obtained. [Pd(μ‐OAc)(1a)]2 with 2 equiv. of Ph3P and CO (1 atm) gives the heterocyclic which arises from two CO insertion reactions, whereas [PdX(1a)]2 (X = AcO, Cl) with 4 equiv. of CNBut and 4 equiv. of Ph2PCH2CH2PPh2 affords the heterocyclic ketenimine [PdCl(1a)]2 reacts with CH2CHCO2CH2CH3 to afford 2′(CHCHCO2CH2CH3)‐5′‐OCH3C6H3CHO, and [Pd(μ‐OAc)(1a)]2 with I2 to give 2′‐I‐5′‐OCH3C6H3CHO. Excess CH3O2CCCCO2CH3 reacts with various substituted cyclopalladated Schiff's bases in MeOH to afford which we formulate as possessing two PdC bonds, and one coordinated ester O atom. The X‐ray crystal structure of [Pd(μ‐OAc)(1a)]2 has been determined; relevant bond lengths [Å] and bond angles [°] are: PdO(1), 2.139(6), PdO(2), 2.026(6), PdN, 2.039(6), PdC(2′), 1.951(8), PdPd, 3.113(1), NPdC(2′), 80.9(3), NPdO(1), 97.5(2), C(2′)PdO(2), 91.7(3), O(1)PdO(2), 89.2(2).
Synthesen überbrückter Bischinonmethide mit doppelter Acylketenaminal‐Struktur
Authors: Neidlein Richard , Hartz Georg
Published: December 2004

Syntheses of Bridged Bisquinonemethides with Double Acylketeneaminal Structure

Starting with 1, the synthesis of bis(tert‐butyl)ester 2 is described. Some reactions including methylation of 2 to give 3 and 4, (4 → 5) and deprotonation of 5 to 6 are reported. Possible structures of deprotonation products are discussed, based on NMR results.
Note on Attempts to Prepare Ring‐B Homomorphinan‐6‐ones by Grewe Cyclization from Octahydro‐1‐phenethylisoquinolines
Authors: Dumont Raymond , Pfander Hanspeter , Brossi Arnold
Published: December 2004

Grewe cyclization of the N‐formyl‐protected octahydroisoquinolin‐6‐one 1 prepared by conventional chemistry did not afford the expected homomorphinanone. The exclusive reaction product obtained in good yield was the α,β‐unsaturated N‐formyloctahydroisoquinolin‐6‐one 2, further converted by acid hydrolysis into the crystalline octahydroisoquinolin‐6‐one 8.
Ringerweiterung bei der Reaktion eines 1,3‐Cyclohexandions mit Diphenylcyclopropenon
Authors: Bilinski Vanda , Dreiding André S.
Published: December 2004

Ring Expansion during the Reaction of a 1,3‐Cyclohexanedione with Diphenylcyclopropenone

The reaction of 5,5‐dimethyl‐1,3‐cyclohexanedione (1) in form of its Na‐salt with diphenylcyclopropenone (2) in DMF yielded the bicyclic triketone 3 (58 %), the structure of which was deduced as an enolizeable bicyclo[5.2.0]nonane‐β‐diketone from spectral data and from the following reactions: hydrolysis or methanolysis of 3 cleaved the β‐dicarbonyl moiety, thereby opening the 4‐membered ring to yield the keto acid 9 or its methyl ester 10. Methylation of 3 afforded the two enol ethers 4 and 5. The ether 5 readily underwent a thermal electrocyclic ring opening to the monocyclic enol ether 8, whereas the ether 4 was thermally stable. The same electrocylic ring opening (in boiling benzene) converted 3 (probably via 3b) to the monocyclic triketone 7, which was also the hydrolysis product of the ring‐opened enol ether 8. By heating 3 in DMF/H2O, a partial (56 %) conversion to the lactone 6 took place. The tricyclic intermediate 11 was found useful to rationalize the ring expansion during the formation of 3 from 1 and 2 as well as the corresponding ring contraction during the conversion of 3 into 6.
Two New Syntheses of the Pyranojuglone Pigment α‐Caryopterone
Authors: Matsumoto Takeshi , Ichihara Akitami , Yanagiya Mitsutoshi , Yuzawa Tamio , Sannai Akiyoshi , Oikawa Hideaki , Sakamura Sadao , Eugster Conrad Hans
Published: December 2004

By a simple process, 3‐methoxyjuglone (= 8‐hydroxy‐2‐methoxy‐1,4‐naphthoquinone; 9) has been synthesized from 1,2,4‐trimethoxybenzene (5) and converted, after prenylation, to α‐caryopterone (1; Scheme 1), a pyranojuglone pigment from Caryopteris clandonensis. On the other hand, juglone (= 5‐hydroxy‐1,4‐naphthoquinone; 12) was regioselectively prenylated at C(2) via its 1‐methoxy‐cyclohexa‐1,3‐diene adduct 15 (Scheme 2). The 2‐prenyljuglone (4) thus formed led to 1 after oxidation and other reactions.
Template Synthesis, Crystal Structure, and Spectroscopic Characterization of [N,N′‐Bis(2‐pyridylmethylene)‐1,3‐diamino‐2‐methyl‐2‐nitropropane] copper(II) Perchlorate
Authors: Comba Peter , Hambley Trevor W. , Lawrance Geoffrey A.
Published: December 2004

In a facile carbon‐acid condensation reaction of bis(2‐aminomethylpyridine)copper(II) with nitroethane and formaldehyde in basic MeOH the N,N′‐bis(2‐pyridylmethylene)‐1,3‐(diamino‐2‐methyl‐2‐nitropropane)copper(II) cation is produced in essentially quantitative yield. The perchlorate salt crystallizes in space group P21en, a = 9.083(2), b = 15.198(3), c = 16.025(3). Cu(II) is essentially four‐coordinate, though there are weak axial interactions to the perchlorate O‐atoms. There is a large tetrahedral distortion from the least‐squares plane through the Cu and four N donors; with the Cu(II) in the plane, N‐atoms are up to 0.25 Å above or below. Solution spectroscopy confirms that the solution structure of the cation is qualitatively the same as in the solid. The complex and its precursor have been investigated by room‐temperature magnetic‐moment measurement, voltammetry, and by IR, electronic, and electron spin resonance spectroscopy.
Inhibition of Emulsin by D‐Gluconhydroximo‐1,5‐lactone and Related Compounds
Authors: Beer Dieter , Vasella Andrea
Published: December 2004

At pH 4.5 (citrate buffer), D‐gluconhydroximo‐lactone (2), the N‐methylurethane 3 and the N‐phenylurethane 4 inhibit competitively the hydrolysis of p‐nitrophenyl β‐D‐glucopyranoside by emulsin. The IC50 values of 2, 3, and 4 were 1.6 × 10−4, 1.0 × 10−4, and 5.8 × 10−6 M, respectively. The Ki values of 2 and 4 were 9.8 × 10−5 and 2.3 × 10−6 M, respectively, while D‐glucono‐1,5‐lactone (1) showed IC50 = 1.1 × 10−4 M and Ki = 3.7 × 10−5 M.
Circular Dichroism of Tricarbonyl(diene)iron Complexes. The Octant Rule Applied to Ketones Perturbed by Remote Fe(CO)3 Groups. Crystal Structure of (±)‐Tricarbonyl[(1RS,4RS,5RS,6SR)‐C5,6,C‐η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanone)]iron
Authors: Gabioud Raphy , Vogel Pierre , Pinkerton Alan A. , Schwarzenbach Dieter
Published: December 2004

The preparation and the CD spectra of optically pure (+)‐trans‐μ‐[(1R,4S,5S,6R,7R,8S)‐C,5,6,C ‐η : C,7,8,C‐η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo [2.2.2]octanone)]bis(tricarbonyliron) ((+)‐7) and (+)‐tricarbonyl[(1S,4S,5S,6R)‐C‐5,6,C‐η‐(5,6,7,8,‐tetramethylidene‐2‐bicyclo[2.2.2]octanone)]iron ((+)‐8), and of its 3‐deuterated derivatives (+)‐trans‐μ‐[(1R,3R,4S,5S,6R,7R,8S)‐C,5,6,C‐η : C,7,8,C‐η‐5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]‐(octanone)]bis(tricarbonyliron) ((+)‐11) and (+)‐tricarbonyl[(1S,3R,4S,5S,6R)‐C‐5,6,C‐ η‐(5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]octanone)]iron ((+)‐12) are reported. The chirality in (+)‐7 and (+)‐8 is due to the Fe(CO)3 moieties uniquely. The signs of the Cotton effects observed for (+)‐7 and (+)‐8 obey the octant rule (ketone n→π*CO transition). Optically pure (−)‐3R‐5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]octanone ((−)‐10) was prepared. Its CD spectrum showed an ‘anti‐octant’ behaviour for the ketone n→π*CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (−)‐trans‐μ‐[(1R,2R,4S, 5S,6R,7R,8S)‐C,5,6,C‐η : C,7,8,C‐ η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanol)]bis(tricarbonyliron) ((−)‐2) and (−)‐tricarbonyl‐ [(1S,2R,4S,5S,6R)‐ C,5,6,C‐ η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanol)]iron ((−)‐3) and of the 3‐denterated derivatives (−)‐5 and (−)‐6 are also reported. The CD spectra of the complexes (−)‐2, (−)‐3, (+)‐7, and (+)‐8 were solvent and temperature dependent. The ‘endo’‐configuration of the Fe(CO)3 moiety in (±)‐8 was established by single‐crystal X‐ray diffraction.
Preparation of Optically Active Secondary Amines by Thermal Decomposition of (Methylbenzyl)urea Analogs: Absolute Configuration of (+)‐ and (−)‐Mecamylamine. Preliminary Communication
Authors: Schönenberger Bernhard , Brossi Arnold , George Clifford , Flippen‐Anderson Judith L.
Published: December 2004

Thermolysis of the (α‐methylbenzyl)urea diastereoisomers 4 and 5 of (±)‐mecamylamine ((±)‐1) and 6 and 7 of (±)‐1‐noreseroline O‐methyl ether ((±)‐3) in refluxing alcohol afforded optically pure amines in high yield, besides optically pure carbamates of (α‐methylbenzyl)amine which can be recycled. The absolute configuration of (−)‐mecamylamine hydrochloride ((−)‐1 · HCl) was determined by X‐ray diffraction analysis.
Synthese von 4,4‐disubstituierten 1,3‐Thiazol‐5(4H)‐thionen
Authors: Jenny Christjohanes , Heimgartner Heinz
Published: December 2004

Synthesis of 4,4‐Disubstituted 1,3‐Thiazol‐5(4H)‐thiones

An easy synthesis for the 1,3‐thiazol‐5(4H)‐thiones 5, a class of heterocycles which have hitherto only been available with difficulty, is described. Reaction of 3‐amino‐2H‐azirines 25 with thiocarboxylic acids at 0° yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100°, undergo thiation and cyclization to give 5 in good yield.
Ditopic Ligands. The Synthesis of a Series of Phosphine‐Functionalised Macrocycles
Authors: Carroy Annick , Richard Langick C. , Lehn Jean‐Marie , Matthes Karen E. , Parker David
Published: December 2004

The synthesis of a series of phosphine‐functionalised macrocycles, 1–6, is described. The combination of N‐and O‐sites with P‐ and S‐sites provides ligands which may bind transition or non‐transition metal ions; as a consequence, they give access to dinuclear complexes containing both a Lewis acid and a redox metallic site. Compounds 1,2 and 6 are heterodinucleating ligands capable of binding two dissimilar metals in proximity. Macrocycles 3–5 are homotopic ligands which may form homodinuclear complexes of transition metals.
The mass spectra of organic compounds. 8th Communication. 1‐Buten‐3‐yn‐2‐ol. A new kinetically unstable C4H4O isomer
Authors: Tureček František , Havlas ZdenêK , Maquin Francis , Gäumann Tino
Published: December 2004

The unstable neutral enol, 1‐buten‐3‐yn‐2‐ol, and its deuterium‐labelled analogues were generated in the gas phase by high‐vacuum flash pyrolysis of the corresponding 2‐exo‐ethynylnorborn‐5‐en‐2‐ols, or alternatively from 1‐ethynylcyclobutanol. The ionization energy of the enol was measured as 8.92 ± 0.03 eV. The cation radical (HCC(OH)CH2)+· was prepared by electron‐impact ionization of the neutral enol, or by dissociative ionization of 1‐hexyn‐3‐ol and 1‐ethynylcyclobutanol, and its heat of formation was determined as 944 kJ·mol−1. The heat of formation of the neutral enol was assessed as 83 ± 7 kJ·mol−1 in good agreement with MNDO calculations. Cation radicals HCCC(OH)CH2+· undergo four main unimolecular fragmentations due to losses of the OH H‐atom, a CH3 group incorporating the C(1) methylene and the OH H‐atom, CO, and H2O. The structure of the neutral enol and the mechanisms of the ionic decompositions are discussed.
Pteridine. Teil LXXIX. Synthese, Reaktionen und Photochemie heterocyclischer N,‐Alkylthioamide
Authors: Heckel Armin , Pfleiderer Wolfgang
Published: December 2004

Synthesis, Reactions, and Photochemistry of Heterocyclic N‐Alkylthioamides

Various heterocyclic N‐alkylthioamides of the pteridine (2, 7) and pyridine series (13) have been synthesized and investigated regarding their photooxidation. The compounds are very photolabil under aerobic conditions and are converted into the corresponding amides (1, 6 and 12, resp.) on irradiation.
Ion‐Molecule reaction in the gas phase part VI Regioselective SN2 reaction from terpenoid diastereoisomeric diols using CI/NH
Authors: Tabet Jean‐Claude , Prevost Chantal , Bouillot Anne , Bastard Josette , Manh Due Do Khae , Tondeur Yves
Published: December 2004

A stereospecific and regioselective SN2 mechanism (Walden inversion) is observed during studies involving modified terpenoid epimeric diols in a high‐pressure ion source using ammonia as a reagent gas.
Poly{[μ‐(2,5‐dicarboxypyrazine‐ 3,6‐dicarboxylato)‐trans‐diaquairon(II) dihydrate]}, a Member of a New Class of Quasi‐Linear Chain Compounds. Preparation, Structure, and Magnetic Susceptibility
Authors: Marioni Pierre‐Alain , Steeckli‐Evans Helen , Marty Werner , Güdel Hans‐Ulrich , Williams Alan F.
Published: December 2004

The title compound 1, {[Fe(H2pztc)(H2O)2] · 2 H2O}∞, has been prepared from pyrazinetetracarboxylic acid (H4pztc) and Fe(II) salt in H2O. It crystallizes in the monoclinic space group P21/a with cell parameters a = 13.56(1) Å, b = 7.17(1) Å, c = 6.48(1) Å, β = 101.0(2)°, V = 618.4 Å3. The molecules form infinite parallel chains with bis(bidentate) coordination (through N and O) of the bridging pyrazine ligands. Two trans‐COOH groups of the ligand remain uncoordinated, and two trans‐H2O ligands complete a pseudo‐octahedral Fe(II) coordination which is distorted by the steric effect of the free COOH groups. The parallel polynuclear chains are linked through an extended network of H‐bonds involving the COO functions of the bridging ligand and the coordinated and lattice H2O molecules. Mössbauer and magnetic‐susceptibility data suggest normal paramagnetic behaviour of high‐spin Fe2+. An observed drop below 15 K in effective magnetic moment for 1 was attributed to temperature‐dependent population changes of the levels of the ground state 5Γ, and not to antiferromagnetic coupling (J < 1 cm−1). This result establishes that the obvious potential magnetic exchange pathway through the pyrazine bridges is inefficient, and this may be attributed, in part, to the high planarity of Fe(H2pztc) moieties.
1H‐and 13C‐NMR Investigation of Pentafulvenes
Authors: Bönzli Peter , Otter Albin , Neuenschwander Markus , Huber Hanspeter , Kellerhals Hans Peter
Published: December 2004

1H‐ and 13C‐NMR spectra of a series of 6‐(p‐X‐phenyl)pentafulvenes 1–9 as well as of 6‐R‐substituted and 6,6‐R1,R2‐disubstituted pentafulvenes 10–23 have been analysed. It turns out that the π‐system of pentafulvenes is an attractive probe for the investigation of electronic substituent effects. Changes of vicinal H,H‐coupling constants with increasing electron‐donating capacity of the substituents X and R are interpreted in terms of an increasing π delocalisation in the 5‐membered ring, and linear correlations of Hammett Substituent constants σ or MNDO‐calculated C–C bond lengths and 3J values are observed. On the other hand, a systematic high‐field shift of 13C chemical shifts of the ring C‐atoms is induced by electron‐releasing substituents R and X, which decreases in the series C(5) > C(2)/C(3) > C(1)/C(4), and which mainly reflects changes in π‐charge density.
Kupplung von Peptiden mit C‐terminalen α,α‐disubstituierten α ‐ Aminosäuren via Oxazol‐5(4H)‐one
Authors: Wipf Peter , Heimgartner Heinz
Published: December 2004

Peptide‐Bond Formation with C‐Terminal α,α‐Disubstituted α ‐ Amino Acids via Intermediate Oxazol‐5(4H)‐ones

The formation of peptide bonds between dipeptides 4 containing a C‐terminalα,α‐disubstituted α‐amino acid and ethyl p‐aminobenzoate (5) using DCC as coupling reagent proceeds via 4,4‐disubstituted oxazol‐5(4H)‐ones 7 as intermediates (Scheme 3). The reaction yielding tripeptides 6 (Table 2) is catalyzed efficiently by camphor‐10‐sulfonic acid (Table 1). The main problem of this coupling reaction is the epimerization of the nonterminal amino acid in 4 via a mechanism shown in Scheme 1. CSA catalysis at 0° suppresses completely this troublesome side reaction. For the coupling of Z‐Val‐Aib‐OH (11) and Fmoc‐Pro‐Aib‐OH (14) with H‐Gly‐OBu1 (12) and H‐Ala‐Aib‐NMe2 (15), respectively, the best results have been obtained using DCC in the presence of ZnCl2 (Table 3).
The Synthesis of Trimethylcyclopentane‐carboxylic Acids
Authors: Šolaja Bogdan , Huguet Joan , Karpf Martin , Dreiding André S.
Published: December 2004

(1RS, 5SR)‐2,2,5‐Trimethylcyclopentane‐1‐carboxylic acid (17) and (1r, 2RS, 5SR)‐1,2,5‐trimethylcyclopentane‐1‐carboxylic acid (19) are the starting materials for the α‐alkynone routes to (±)‐capnellene and for similar efforts towards ptychanolide. Since 17 and 19 have, so far, been available only by a branching reaction from the same precursor, the cyanohydrin mixture 2/3, a modified synthesis for 17 and a new one for 19 was developed (Scheme 1). The common precursor 2/3 was treated with POCl3 which effected normal dehydration to 6 (47%, major path) in competition with Me migration to 8 and 9 (17%). The minor path to 8 and 9 could be reduced to 3% when SOCl2 was used for the dehydration of 2/3. This reaction was the basis for an improved synthesis of 17 from 1, using the steps b, e, i, r, and v see Scheme 1 in an overall yield of 35%. The POCl3 reaction was also studied with the pure cyanohydrins 2 and 3, the configurations of which were determined by an X‐ray analysis of 2. Me migration did not occur form 2 but only from 3 (25%), which has HOC(1) and HC(5) in a cis position. With SOCl2, 3 underwent only 5% Me migration. The new synthesis of 19 started with 4 using the steps h, n, p, and s (see Scheme 1) in an overall yield of 68%.
Poly(dipeptamidinium)‐Salze: Definition und Methoden zur präparativen Herstellung
Authors: Moser Heinz , Fliri Anton , Steiger Arthur , Costello Gerard , Schreiber Jakob , Eschenmoser Albert
Published: December 2004

Poly(dipeptamidinium) Salts: Definition and Methods of Preparation

Poly(dipeptamidines) are polypeptide derivatives in which the carbonyl oxygen of each second backbone amide group is replaced by an imine nitrogen (see A). So far, such derivatives have been unknown. Polyprotonated salts of them ( = poly(dipeptamidinium) salts) are of interest in view of their intrinsic constitutional relationship to the structure of polynucleotides: the number of covalent bonds between neighboring centers of positive charge in poly(dipeptamidinium) salts is identical to the number of covalent bonds between neighboring centers of negative charge in natural polynucleotides (see D). Poly(dipeptamidinium) polycations and polynucleotide polyanions are constitutionally and electrostatically complementary structures. Since poly(dipeptamidines) are (formally) polymers of dipeptide nitriles, and, since they can be expected to give polypeptides on hydrolysis, the relationship mentioned above deserves attention and experimental study in context with the problem of designing chemical models of biogenesis.

This paper describes methods for the chemical preparation, the spectral characterization, and some chemical properties of homodipeptidic poly(dipeptamidinium) salts in the L‐alanyl‐glycyl and L‐phenylalanyl‐glycyl series. The methods of preparation include a stepwise construction of defined lower oligomers (up to hexamer) as well as, in the L‐alanyl‐glycyl series, a one‐operation poly‐condensation procedure leading to polymers containing an average of ca. 20 dipeptamidinium units (Schemes 4,6 and 7).
Structural isomerism in Polycondensates. Part IV. Synthesis and characterization of liquid crystalline poly(azomethines) and low molecular weight model compounds
Authors: Deschenaux Robert , Neuenschwander Peter , Pino Piero
Published: December 2004

With the aim to investigate the influence of structural isomerism on the mesomorphic thermal stability in main chain thermotropic polycondensates, a series of poly(azomethines) and low molecular weight models have been prepared. The model compounds exhibit smectic and/or nematic mesophases whose stabilites are very sensitive to structural modifications. On the basis of the above results, monomers 2, 5, 6, 8, 9, 23, 25, and 26 were selected to synthesize oligomers 27–23. The oligomer 33 obtained from the nonsymmetric diamine 23 has a lower melting point than the symmetric oligomer 28, but a similar liquid crystalline range.
C45‐ und C50‐Carotinoide. 5. Mitteilung
Authors: Wolleb Heinz , Pfander Hanspeter
Published: December 2004

C45‐ and C50‐Carotenoids. Synthesis of an Optically Active Cyclic C20‐Building Block and of (2R,2′S)‐3′,4′‐Didehydro‐1′,2′‐dihydro‐2‐(4‐hydroxy‐3‐methylbut‐2‐enyl)‐2′‐(3‐methylbut‐2‐enyl)‐β,ψ‐caroten‐1′‐ol (= C. p. 473)

The synthesis of the optically active C20‐building block (R)‐16 and of the optically active C50‐carotenoid C.p. 473 (1) starting from (−)‐β‐pinene is reported.
Tetrazinodi(heteroarene): Voltammetrische und cyclovoltammetrische Untersuchung der Oxidation in Methanol, Acetonitril und Dichlormethan
Authors: Hellrung Bruno , Balli Heinz
Published: December 2004

Tetrazinodi(heteroarenes): Voltammetric and Cyclovoltammetric Studies of the Oxidation in Methanol, Acetonitrile, and Dichloromethane

The oxidation of seven symmetrical [1,2,4,5]tetrazinodi(heteroarenes) with different heterocycles has been investigated by means of dc, ac, and cyclic triangular voltammetry in MeCN and CH2Cl2 (containing Bu4NClO4), MeOH (containing LiCl) and in MeOH/H2O (equimolar mixture). The two step oxidation mechanism has been found of type ‘e‐e’ with quasi‐reversible electrochemical steps. Oxidation potentials and transfer coefficients have been measured (0 to +0.5 V vs. Ag/AgCl/3.5M KCl for the first oxidation step and potential differences of 0.8 to 1.3 V to the second oxidation step), indicating a high radical‐ion stability.
Deoxy‐nitrosugars. 16th Communication. Synthesis of N‐acetyl‐4‐deoxyneuraminic acid
Authors: Baumberger Franz , Vasella Andrea
Published: December 2004

The synthesis of 5‐acetamido‐4‐deoxyneuraminic acid (1) is described. Acetylation of a mixture of the epimeric triols 4 and 5 gave the tetraacetates 7 and 8 (Scheme 1). Ozonolysis of a mixture of these acetates followed by base‐promoted β‐elimination led to the (E) ‐configurated α,β‐unsaturated keto ester 10, which was hydrogenated to give the saturated keto ester 11. Saponification of 11 and hydrolytic removal of the benzylidene group followed by anion‐exchange chromatography gave the 5‐acetamido‐4‐deoxyneuraminic acid (1, Scheme 1 and 2). De‐O‐acetylation (NaOMe/MeOH) of the keto ester 11 gave a mixture of the tert‐butyl ester 12 and the methyl ester 13, which were converted to tert‐butyl N‐acetyl‐4‐deoxyneuraminate (14) and to methyl N‐acetyl‐4‐deoxyneuraminate (15), respectively. Hydrogenolysis of the benzylidene acetal 11 followed by de‐O‐acetylation gave the pentahydroxy ester 16.
Preparation of 3,4‐Fused Cyclopropabenzenes and Cyclopropabenzenyl Cations
Authors: Müller Paul , Rodriguez Domingo
Published: December 2004

A series of 3,4‐disubstituted (4a, b) or 3,4‐fused (4c‐e) 1,1‐di‐fluorocyclopropabenzenes, including the very strained 1,1‐difluoro‐3,4‐dihydro‐1 H‐cyclobuta[a]cyclopropa[d]benzene (4e) have been synthesized and characterized. Dissolution of these difluoro derivatives in fluorosulfonic acid affords the fluoro cations 3a–e. 1H‐, 19F‐, and 13C‐NMR data of the cations are reported and discussed with respect to those of the precursors.
The Relative Stabilities of Substituted cis‐ and trans‐1,2,3,4,4a,9,10,10a‐Octahydrophenanthrenes, Including Configurational Corrections in the Elad‐Ginsburg Morphine Synthesis
Authors: Duthaler Rudolf O. , Ginsburg David
Published: December 2004

The relative configuration of the title compounds has been determined by 1H‐NMR measurements at 300 MHz. In contradistinction to prevailing opinion, it was found that 4‐oxo derivatives prefer the cis‐configuration. While the cis/trans ratio is 82:18 for the parent 1,2,3,4,4a,9,10,10a‐octahydrophenanthrene‐4,9‐dione, the trans‐isomers of C(5)‐substituted derivatives cannot be detected under the conditions of equilibration. The cis‐configuration is retained upon acetalization of the 4‐oxo derivative. A warning is issued regarding the assigned configurations of certain intermediates in the Elad‐Ginsburg synthesis of morphine.
Sarcodictyeone, a ring‐reduced, optically active linear tetraprenylquinone from the mediterranean stolonifer Sarcodictyon roseum ( = Rolandia rosea)
Authors: D'Ambrosio Michele , Guerriero Antonio , Fabbri Daniele , Pietra Francesco
Published: December 2004

The Mediterranean stolonifer Sarcodictyon roseum ( = Rolandia rosea) (Cnidaria, Anthozoa, Alcyonaria, Stolonifera, Clavulariidae) contains the first example of a chiral, optically active prenyl derivative of a reduced benzoquinone, sarcodictyenone (= (+)‐(4R*,5R*)‐5‐geranylgeranyl‐4‐hydroxy‐2‐methylcyclohex‐2‐en‐1‐one; (+)‐1a).
Nukleophile Addition von Lithiumorganylen an das N,N‐Diethyl‐10‐(trimethylsilyl)‐1, 6‐methano[10]annulen‐2‐carboxamid
Authors: Neidlein Richard , Kramer Walter , Wirth Wolfgang
Published: December 2004

Nucleophilic Addition of Lithiumorganyles to N,N‐Diethyl‐10‐(trimethylsilyl)‐1,6‐methano[10]annulene‐2‐carboxamide

Reaction of lithiumorganyles with N,N‐diethyl‐10‐(trimethylsilyl)‐1,6‐methano[10]annulene‐2‐carboxamide followed by quenching with H2O or MeI yields 2,3‐dihydro derivatives of 1,6‐methano[10]annulene.
Generation and Reactions of Lithiated tert‐Butyl and 2,6‐Di(tert‐butyl)‐4‐methylphenyl Cyclopropanecarboxylates
Authors: Häner Robert , Maetzke Thomas , Seebach Dieter
Published: December 2004

tert‐Butyl and 2,6‐di(tert‐butyl)‐4‐methylphenyl (BHT) cyclopropanecarboxylates (4, 6, 24, 25) are lithiated with LiN(i‐Pr)2 and t‐BuLi, respectively. Reactions with alkyl halides, aldehydes, acyl chlorides, and heteroelectrophiles give α‐substituted BHT esters which can be cleaved (t‐BuOK/H2O/THF) to the corresponding carboxylic acids or reduced (LiAlH4/THF) to the cyclopropanemethanols.
Stoffwechselprodukte von Mikroorganismen. 237. Mitteilung. (2S, 3R, 4R, 6R)‐2,3,4‐Trihydroxy‐6‐methylcyclohexanon aus zwei Actinomyceten‐Stämmen
Authors: Müller André , Keller‐Schierlein Walter , Bielecki Jacek , Rak Gabriele , Stümpfel Joachim , Zähner Hans
Published: December 2004

(2S, 3R, 4R, 6R)‐2,3,4‐Trihydroxy‐6‐methylcyclohexanone from Two Strains of Actinomycetes

A tetrazolium‐blue positive compound was isolated from two strains of acinomycetes. Its constitution and relative configuration 1 were determined by spectroscopic methods, and the absolute configuration by degradation to (+)‐(R)‐methylsuccinic acid.
Synthesis of 3β‐Hydroxy[21‐14C]‐5β‐pregn‐8(14)‐en‐20‐one from Chenodeoxycholic Acid
Authors: Deluca MóNica E. , Seldes Alicia M. , Gros Eduardo G.
Published: December 2004

3β‐Hydroxy[21‐14C]5β‐pregn‐8(14)‐en‐20‐one (17) was prepared from chenodeoxycholic acid (1a). The synthetic sequence involved: (i) degradation of the bile‐acid side chain to an etianic acid; (ii) formation of the 8(14)‐double bond; (iii) inversion of the configuration at C(3); (iv) construction of the acetyl side chain at C(17) with the required isotopic label at C(21). Structures of all described products were confirmed by chemical and spectroscopic (IR, 1H‐NMR, 13C‐NMR, MS) methods.
Highly Stereoselective Photochemical Oxidative Addition Reactions. Preliminary Communication
Authors: Chassot Laurent , von Zelewsky Alex
Published: December 2004

Cyclometallated complexes of the type cis‐bis(2‐phenylpyridine)platinum(II) (C22H16N2Pt) and cis‐bis(2‐(2′‐thienyl)pyridine)platinum(II) (C18H12N2S2Pt) undergo thermal or photochemical oxidative addition (TOA or POA) reactions with a number of substrates. TOA (with CH3I, CH3CH2I etc.) yield mixtures of several isomers which rearrange slowly (within ca. one week at room temperature) to one of the possible cis‐isomers. CH2Cl2, CHCl3, or (E)ClCHCHCl, e.g., do not react thermally. POA yield directly complexes of Pt(IV) with the halide and a σ‐bonded C‐atom in cis‐position. The configuration, as assigned by extensive use of 1H‐NMR data, can be characterized for the two chelating ligands C …︁ N and C′ …︁ N′ by C,C′‐cis; N,N′‐cis and C(chelate), Cl‐trans.
[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)‐blastmycinone. Preliminary Communication
Authors: Fráter Georg , Müller Urs , Günther Wulf
Published: December 2004

[2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis‐ethyl propenyl ether showed a ca. 3:1 diastereo‐selectivity. A two‐step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)‐compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis‐ benzyl 1‐hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (−)‐blastmycinone. Accordingly, the preferred transition state has been deduced as 15.
Metaboliten der 1,5‐Dihydroimidazo[2,1‐b]chinazolin‐2(3H)‐one. Synthese und Reaktionen einiger 1,5‐Dihydro‐3‐hydroxyimidazo[2,1‐b]chinazolin‐2(3H)‐one
Authors: Stalder Henri
Published: December 2004

Metabolites of 1,5‐Dihydroimidazo[2,1‐b ]quinazolin‐2(3H)‐ones. Preparation and Reactions of Some 1,5‐Dihydro‐3‐hydroxyimidazo[2,1‐b]quinazolin‐2(3H)‐ones

Hydroxylated 1,5‐dihydroimidazo[2,1‐b]quinazolin‐2(3H)‐ones 2–4 and 6 were isolated as metabolites of imidazoquinazolinones 1a and 1b, respectively. The synthesis of 1,5‐dihydro‐3‐hydroxy‐3‐methylimidazo[2,1‐b]quinazolin‐2(3H)‐ones 3, 4, and 6, and the preparation of some derivatives thereof is described.
Reaktion von 3‐(Dimethylamino)‐2H‐azirinen mit 1,3‐Thiazolidin‐2‐thion
Authors: Ametamey Simon M. , Prewo Roland , Bieri Jost H. , Heimgartner Heinz , Obrecht Jean Pierre
Published: December 2004

Reaction of 3‐(Dimethylamino)‐2H‐azirines with 1,3‐Thiazolidine‐2‐thione

Reaction of 3‐(dimethylamino)‐2H‐azirines 1 and 1,3‐thiazolidine‐2‐thione (6) in MeCN at room temperature leads to a mixture of perhydroimidazo[4,3‐b]thiazole‐5‐thiones 7 and N‐[1‐(4,5‐dihydro‐1,3‐thiazol‐2‐yl)alkyl]‐N′,N′‐dimethylthioureas 8 (Scheme 2), whereas, in i‐PrOH at ca. 60°, 8 is the only product (Scheme 4). It has been shown that, in polar solvents or under Me2NH catalysis, the primarily formed 7 isomerizes to 8 (Scheme 4). The hydrolysis of 7 and 8 leads to the same 2‐thiohydantoine 9 (Scheme 3 and 5). The structure of 7a, 8c, and 9b has been established by X‐ray crystallography (Chapt. 4). Reaction mechanisms for the formation and the hydrolysis of 7 and 8 are suggested.
Intramolecular Carbenoid Reactions of Pyrrole Derivatives. A Total Synthesis of (±)‐Ipalbidine
Authors: Jefford Charles W. , Kubota Tadatoshi , Zaslona Alexander
Published: December 2004

A new method for alkaloid synthesis is described. The rhodium(II)‐acetate‐catalyzed decomposition of 3‐(4‐acetoxyphenyl)‐1‐diazo‐4‐(pyrrol‐1‐yl)‐2‐butanone (5d) gave 6‐(4‐acetoxyphenyl)‐5,6‐dihydro‐7(8H)‐indolizinone (6d) in 82% yield via an intramolecular carbenoid reaction. The latter compound was converted in four steps in 13% overall yield to (±)‐ipalbidine (1b).
The radical anion of 1,2:9,10‐dibenzo[2.2]paracyclophane.. An ESR, ENDOR, and TRIPLE resonance study
Authors: Gerson Fabian , Martin William B. , Wong Henry N. C. , Chan Chin Wing
Published: December 2004

The radical anion of 1,2:9,10‐dibenzo[2.2]paracyclophane (3) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck‐benzene rings, and of the four inner and four outer protons in the side‐benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2‐dimethoxyethane; counterion: K+). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane (1) points to similar nodal properties of the singly occupied orbitals in and . Notwithstanding this similarity, seems to associate less readily than with alkali metal counterions, since tight ion pairs of with K+ are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane‐1,9‐diene (2), are not apparent for in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative 4 which has a CH3 substituent in one of the side‐benzene rings of 3.
3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin als Aib‐Äquivalent: Synthese von Aib‐Oligopeptiden
Authors: Obrecht Daniel , Heimgartner Heinz
Published: December 2004

3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine as an Aib Equivalent; Synthesis of Aib Oligopeptides

3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) reacts with carboxylic acids at 0–25° to give 2‐acylamino‐N,N,2‐trimethylpropionamides ( = 2‐acylamino‐N,N‐dimethylisobutyramide, acyl‐Aib‐NMe2) in excellent yields (Scheme 2 and 3). Examples of α‐amino‐, α‐hydroxy‐, and α‐mercapto‐carboxylic acids are given. On treatment with HCl in toluene, the terminal dimethylamide group is selectively converted to the corresponding carboxylic acid (→acyl‐Aib) via an amide cleavage (Scheme 4 and 5); 1,3‐oxazol‐5(4H)‐ones are intermediates of this amide hydrolysis. This reaction sequence has been used for the extension of peptide chains (Scheme 6). The synthesis of Aib‐oligopeptides using this methodology is described (Scheme 8).
Photochemical Synthesis of Octahydro‐ and 3a,4,5,6,7,7a‐Hexahydro‐benzo[b]thiophenes from Methyl (E)‐4‐Mercapto‐2,6‐heptadienoate and Alkenes or Alkynes via Consecutive Radical Ring Closure. Preliminary Communication
Authors: Kiesewetter René , Margaretha Paul
Published: December 2004

On irradiation (λ = 300 nm) in MeOH 5‐(2‐propenyl)‐2(5H)‐thiophenone (1c) affords methyl (E)‐4‐mercapto‐2,6‐heptadienoate (2c) which undergoes light‐induced homolysis of the S–H bond to give the alkylthio radical 3c. This species can be trapped by 2,3‐dimethyl‐2‐butene or 2‐butyne to afford octahydrobenzo‐[b]thiophene 9 or 3a,4,5,6,7,7a‐hexahydrobenzo[b]thiophene 13, respectively, as main products via consecutive radical ring closure. In the absence of unsaturated hydrocarbons, 3c cyclizes to give methyl (E)‐3(thiolan‐2‐yl)‐2‐propenoate (8).
Complexes of 3,3′‐Oxybis[(diphenylphosphino)methylbenzene] with Ni(II), Pd(II), Pt(II), Rh(I), and Ag(I). How Important is Backbone Rigidity in the Formation of trans‐Spanning Bidenatate Chelates??
Authors: Marty Werner , Kapoor Pramesh N. , Bürgi Hans‐Beat , Fischer Erwin
Published: December 2004

The bidentate diphosphine ligand, 3,3′‐oxybis[(dipenylphosphino)methylbenzene] (1) forms monomeric, trans‐square‐planar complexes MX2(1) (M = Ni, Pd, Pt; X = Cl−, Br− I−, and, in part, N, NCS−, CN−, NO) as well as Pt(H)Cl(1), Pt(H)Br(1), and RhCl(CO)(1). Polymeric species have been observed with substitutionally inert metal centres: trans‐[PtCl2(1)]2 and cis‐[PtCl2(1)]n (mean value of n ≈ 4–5) 31P‐NMR, and selected IR and UV/VIS parameters are reported. Ligand 1 shows a marked preference for trans‐spanning and monomeric chelate formation, despite its various degrees of freedom of internal rotation in the lignad backbone. The readily available ligand 1 as well as analogues with other donor atoms, therefore, appear useful in most potential applications of trans‐spanning chelate ligands. The crystal structure of AgCl(1)·0.5 (CH3)2CO·0.39 C6H12 (space group C2/c,a = 21.02 Å, b = 14.57 Å, c = 24.79 Å, β = 99.77°, V = 7531.4 Å3, Z = 8) confirms the presence of three‐coordinate Ag(I), with a coordination intermediate between a trigonal‐planar and a T‐shaped geometry (P‐Ag‐P = 145.61(8)°).
Nucleotides. Part XXVI.. A new synthesis of 9‐(′‐D‐ribofuranosyl)uric acid and its 5′‐monophosphate
Authors: Schulz Bernd S. , Pfleiderer Wolfgang
Published: December 2004

Syntheses for 9‐(β‐D‐ribofuranosyl)uric acid (16) and its 5′‐monophosphate 14 have been achieved starting from guanosine and applying the 2‐(p‐nitrophenyl)ethyl group for protection of the aglycon moiety as well as the phosphate function. A more efficient and direct approach to 14 uses O6, O8‐dibenzyl protection and phosphorylation by the Yoshikawa procedure. The various protected intermediates have been characterized by spectroscopic means and elemental analysis.