bluuebunny/crossref_metadata_2025 huggingface dataset:
Décomposition du percarbonate deO,O‐t‐butyle etO‐isopropényle en solution: Acétonylation des esters, acides et nitriles
Authors: Lalande Robert , Filliatre Claude , Villenave Jean‐Jacques , Jaouhari Rabih
Published: December 2004

The Free‐Radical Decomposition ofO,O‐t‐Butyl andO‐Isopropenyl Peroxycarbonate in Solution: the Acetonylation of Esters, Acides and Nitriles

The free‐radical decomposition ofO,O‐t‐butyl andO‐isopropenyl peroxycarbonate in substratres possessing mobile H‐atoms (SH) consists mainly in an induced chain process leading to acetonylated derivatives of the solvent. Fairly good yields are obtained but teh acetonylation of functional substrates often gives mixtures of isomers.

In the case of methyl acetate, the acetonylation occurs on the C‐atoms adjacent to the carbonyl (acylox moiety) and to the O‐atom (alkox moiety). However, the relative amounts of the isomeric products depend on the concentration of the peroxycarbonate solutions; at lowest concentration, methyl 4‐oxopentanoate (acyloxy moiety) is obtained selectively. It is assumed that the free radicals issued from the solvent are able to abstract H‐atoms of other molecules of solvent before adding to the double bond of the peroxycarbonate; the more the peroxycarbonate solution is diluted the more the transfers from the C‐atom adjacent to the carbonyl to the radicals adjacent to the O‐atom are favoured. In the case of methyl alkanoates, H‐transfers from the α‐C‐atoms to β‐radicals of teh acyloxy moiety may account for the orientation of the process. Owing to similar H‐transfer processes, the acetonylation of functional esters, of acids and nitriles is selective in most cases.
Molecular Ions of Transient Species: Vinylamine‐Cation
Authors: Albrecht Bruno , Allan Michael , Haselbach Edwin , Neuhaus Louis , Carrupt Pierre‐Alain
Published: December 2004

Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured. I = 8.20 eV and I = 8.65 eV were found, the dominant vibrational progression (ṽ = 725 cm−1) indicating that in the course of 1(X)→1+(X̃) flattening around the N‐atom occurs. The Franck‐Condon profile of this band, however, suggests that a skeletal mode of ṽ ≈ 1400 cm−1 (observed also in the iso‐π‐electronic systems vinyl‐alcohol‐cation and allyl radical) may also be excited. Comparison with the data for the isomer acetaldehyde‐imine 2 and its cation s+ shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from the neutrals to the cations.
Photoisomerization pathways of 8,16‐methno[2.2]metacyclopane‐1,9‐diene. A model case for adiabatic electrocyclic ring closure in the excited singlet state
Authors: Wirz Jakob , Persy Gabriele , Rommel Erika , Murata Ichiro , Naksuji Kazuhiro
Published: December 2004

The title compound1bideally meets the theoretical requirements for the occurrence of an adiabatic photoisomerization in the lowest excited state (11b*) and, indeed, the predominant primary photoreaction observed is the conversion to its fluorescent valence isomer 10b, 10c‐methano‐cis‐10b 10c‐dihydropyrene (11a*). The mechanism for the formation often previously observed photoproduct 8b, 9a‐dihydro‐9H‐ cyclopropa[e]pyrene (4a) has been analyzed in some detail (Scheme). Below − 30°C the reaction path consists of a three quantum process (two di‐π‐methane rearrangements and photochemical 1,7‐H shift) involving two thermally stable, but light‐sensitive isomers 8,11b‐methanocyclodeca[cde]naphthalene (2b) and 9H‐cyclohepta[def]‐phenanthrene (3b). At room temperature the rearrangement2b→4aproceeds with a single excitation step bypassing the ground state intermediate3b. Finally, upon prolonged irradiation of (4a), the methylene group is lost to yield pyrene. Compound2bcompletes the series of all possible adducts of methylene to a CC bond of pyrene.
Peduncularistin, Triabunnin und Aristolarin, drei neue Indolalkaloide aus Aristotelia peduncularis (LABILL.) HOOK. F., 191. Mitteilung über organische Naturstoffe
Authors: Kyburz Rolf , Schöpp Emanuel , Hesse Manfred
Published: December 2004

Peduncularistine, Triabunnine and Aristolarine, Three Ne Indole Alkaloids from Aristotelia peduncularis (LLABILL.) HOOK, F.

Peduncularistine (1), triabunnine (2) and aristolarine (3), three new indole alkaloids, have been isolated from Aristotelia peduncularis (LABILL.) HOOK. F.; the structure and absolute configuration of 1 were elucidated on the basis of spectroscopic data and confirmed byt transformation of 1 into aristeserratine (4), a known alkaloid isolated from the same plant. The proposed structure 2 for the second alkaloid and its absolute configuration were established but spectroscopic means and by partial synthesis from 4. The relative configuration of 3 was postulated on the basis of spectroscopic and biogenetic arguments.
The Synthesis and Reactions of 1‐(2‐Propynyl)pyidinium Salts
Authors: Katritzky Alan R. , Schwarz Otto A. , Rubio Olga , Markees Diether G.
Published: December 2004

The synthesis of 1‐(2‐propynyl)pyridinium salts 3 described. Compounds 3 react with a second pyridine molecule, in the presence of the corresponding hydrochloride, to form products of type 4, Certain bases cause the 1‐(2‐propynyl)pyridinium salts 3 to rearrange into 1‐propadienylpyridinium salts. 5. Diethylamine converts compounds 3 into 1‐acetonylpyridinium salts 8. Moreover, treatment of 3 or 5 with sodium methoxide gives enol ether sof type 9, which can be hydrolyzed to teh ketones 8. Addition of bromine to some of teh unsaturated compounds is also reported.
Integrated Systems for Water Cleavage by Visible Light; Sensitization of TiO2 Particles by Surface Derivatization with Ruthenium Complexes
Authors: Duonghond Dung , Serpone Nick , Grätzel Michael
Published: December 2004

Irradiation of acidic (pH 2) solutions of RuL32+ 2Cl− (L = diisopropyl 2,2′‐bipyridine‐4,4′ ‐dicarboxylate) in the presence of TiO2 at 100°C leads to the loss of one bipyridyl ligand and the chemical fixation of RuL2 at the surface of teh TiO2 particles through formation of Ru‐O‐Ti bonds. These surface complexes are very stable and shift the absorption onset of TiO2 beyond 600 mm. Efficient sensitization H2‐generation is achieved with this system beginning in the wave length domain between 590 and 665 nm. Preliminary water cleavage experiments with bifunctional TiO2/Pt/RuO2 redox catalyst are reported.
Fluoro(phenylsufinyl)methyllithium. Note on the 13C‐NMR Spectrum of a Flourocarbenoid
Authors: Nájera Carmen , Yus Miguel , Hässig Robert , Seebach Dieter
Published: December 2004

The title compound is synthesized with 13C‐ and 6Li‐labelling on the fluorinated carbon atom. H/Li‐Exchange in fluoromethyl phenyl sulfoxide (1→2) causes a Δδ(13C) = + 11.4 ppm, a ΔJ(13C,1H) ≈ 0 Hz, and a ΔJ(19F,13C) = + 80.4 Hz. Tentative conclusions bout the struture of the title compound are drawn from these changes.
Studies on the Synthetic Usefulness of the Nitro Function. Part I. A Novel Cyclopentenone Ring Annelation
Authors: Nakashita Yoshihiko , Watanabe Toshio , Benkert Erwin , Lorenzi‐Riatsch Annalaura , Hesse Manfred
Published: December 2004

A novel cyclopentenone ring annelation reaction is described. The treatment of the nitro compound 13 with aqueous sodium hydroxide in the presence of a phase‐transfer catalyst furnished 14a in one step. Similar treatment of 7 led to 8, the reaction of which with t‐BuOK afforded 9a without purification in high yield.
Synthesis of 14‐Membered Lactones from Cyclooctanone
Authors: Aono Tetsuya , Hesse Manfred
Published: December 2004

As shown in the Scheme, 3‐(1‐nitro‐2‐oxocyclooctyl)propanal (1) prepared earlier from cyclooctanone was converted into the 14‐membered lactones 6 and 7. The aldehyde 1 was submitted to allylation to give 2 using allyltitnium or allylsilicon reagents. After lactonizatrion and transformation of the C,C‐double bond to an alcohol, 4 was translactonized under acidic conditions to form 5, from which 6 and 7 were prepared.
Photochemistry of 2‐Allyl‐3‐oxo‐2,3‐dihydro‐1H‐pyrrole‐2‐carboxyalates
Authors: Beyer Michael , Ghaffari‐Tabrizi Ramin , Jung Michael , Margaretha Paul
Published: December 2004

On acetone‐sensitized irradiation the title compounds 3a–c are converted to 2‐allyl‐3‐hydroxy‐1H‐pyrrole‐2‐carboxylates 4 in reasonable yields.
1,2‐Epoxycarotinoide 5. Mitteilung, Synthese von (S)‐1,2‐Epoxy‐1,2,7,8,7′,8′‐hexahydro‐Ψ, Ψ‐carotin ((S)‐1,2‐Epoxy‐1,2‐dihydro‐ζ‐carotin)
Authors: Arm Christoph , Pfander Hanspter
Published: December 2004

1,2‐Epoxycarotenoids, Synthesis of (S)‐1,2‐Epoxy‐1,7,8,7′,8′‐hexahydro‐Ψ, Ψ‐carotene ((S)‐1,2‐Epoxy‐1,2‐dihydro‐ζ‐carotene)

The synthesis of (S)‐1,2‐Epoxy‐1,2‐dihydro‐ζ‐carotene ((all‐E,S)‐1) using (E,E)‐farnesol (3) as starting material, and a Sharpless epoxidation as key step is described.
Deoxy‐nitrosugars 8th communication Convenient preparation of 1‐C‐nitroglycosyl chlorides. Halonitro ethers from hydroxy oximes
Authors: Meuwly Roger , Vasella Andrea
Published: December 2004

Partially protected 4‐ or 5‐hydroxy‐sugar oximes were transformed into 5‐ or 6‐membered 1‐C‐nitroglycosyl chlorides, respectively, by reaction with NaOCl under phase‐transfer conditions. With the exception of the oxidation of the gluco‐derivative 1 giving the anomers 6 and 7, the reactions were completely diastereoselective.
Rearrangement of Derivatives of 1,3‐Dithian‐5‐amineinto Bicyclic 2‐Thiazolidines. Crystal Structures of cis‐ and trans‐1‐(2‐Aryl‐1,3‐dithain‐5‐yl)‐2‐thioureas and cis‐ and trans‐5‐Aryl‐3‐imino‐7,7a‐dihydro‐1H,3H,5H‐thiazolo[3,4‐c]thiazoles
Authors: Borgulya Janos , Daly John J. , Schönholzer Peter , Bernauer Kerl
Published: December 2004

Under conditions normally applied to transform thioureas into the corresponding carbodiimides, cis‐ and trans‐1‐(2‐aryl‐1,3‐dithian‐5‐yl)‐2‐thioureas 7 and 8 undergo a rearrangement to 5‐aryl‐3‐imino‐7,7a‐dihydro‐1H, 3H, 5H‐thiazolo[3,4‐c]thiazoles 9/10 with cis‐ and trans‐fused rings, respectively. The structures of these novel heterocycles were established by X‐ray analysis of compounds 9a, 9d, and 10d. The cis‐fused compounds 9 are the thermodynamically more stable ones. The stereochemical outcome of the rearrangement depends on the carbenium ion stabilizing capability of the aryl moiety and on the reagent system applied. With Ar = Ph, p‐Cl‐Ph, p‐O2N‐Ph, the reaction can be directed to deliver mainly either the cis‐thiazolothiazoles 9 or the trans‐thiazolothiazoles 10. With Ar = 5‐methyl‐4‐imidazolyl or p‐Me2N‐Ph, formation of the cis‐thiazolothiazoles (9a and 9b, resp.) is strongly favored independently of the reaction conditions, In contrast to it 2‐aryl analogs, (1,3‐dithian‐5‐yl)‐2‐thiourea 7g can be transformed into the carbodiimide 11. Under rigorous conditions, 11 also undergoes rearrangement to the corresponding thiazolothiazole 9g. Mechanisms explaining the above findings are discussed. Reaction of trans‐2‐phenyl‐1,3‐dithian‐5‐amine 6d with phosgene or trichloromethyl chloroformate gives the 5‐phenyl‐7,7a‐dihydro‐1H,3H,5H‐thiazolo[3,4‐c]‐thiazol‐3‐ones 12 and 13, whereas the amine 5g lacking an aryl substitutent forms the sable isocyanate 14. Compound 14 is transformed into the corresponding thiazolothiazolone 15 by refluxing in diglyme. Syntheses are described for the 1,3‐dithian‐5‐amines 5/6 and the thioureas 7/8 derived therefrom. The relative configuration of 7d and 8d was determined by X‐ray analysis. NMR data then allowed to assign the configurations of all compounds of types 7 and 8.
Metal complexes with macrocyclic ligands. Part XX. Influence of coordinated ligands onto the complexation rate of Ni2+ with 1,4,8,11‐tetraazacyclotetradecane
Authors: Wu Yi‐he , Kaden Thomas A.
Published: December 2004

The kinetics of the reaction between 1,4,8,11‐tetraazacyclotetradecane (Cy) and Ni2+ in the presence of series of ligands L = fluoride, acetate, glycolate, oxalate, malonate, succinate, methanetriacetate, 1,3,5‐cyclohexanetriacetate, tricarballylate, picolinate, glycinate, iminodiacetate, nitrilotriacetate. N,N′ ‐ethylenediiminodiacetate, ammonia, pyridine, ethylenediamine, 1,3‐propanediamine and diethylenetriamine were studied by pH‐static and spectrophotometric methods at 25° and I = 0.5. By analysis of the log k/log [L] and/or log k/pH profiles the resolved bimolecular rate constants K (Table 3) were determined using a non‐linear least‐square fitting procedure. Practically for all systems the rate constant K, describing the reaction between the 1:1 Ni2+ complex and the monoprotonated form of the macrocycle, was obtained. In some cases, however, also K and K were found. Since the experimental conditions were choosen so that NiL was mainly formed, the reactivity of NiL2 was generally not measurable. The effect of the number of coordinated donor groups in NiL and of the charge of NiL on K is discussed. Both effects seem to indicate that for the reaction between NiL and CyH+ first bond formation is not the rate‐determining step.
Triaziridines. Part III. Triaziridine, azimine, and triazene: A SCF study of the energy and structure of N3H3‐isomers
Authors: Nguyen Minh‐Tho , Kaneti Jose , Hoesch Lienhard , Dreiding André S.
Published: December 2004

The portions of the N3H3 singlet potential energy surface corresponding to triaziridines (1), azimines (2) and triazenes (3) have been calculated by ab initio SCF using 3‐21G, 6‐31G, and 6‐31G** basis sets. Minima and transition states were located by force gradient geometry optimization. The most important computation results are: (1) Triaziridines (1): The configuration at the 3 N‐atoms is pyramidal. There are 2 stereoisomers, 1a and 1b. The c,t‐isomer 1a has less energy than the c,c‐isomer 1b. The 2 stereoisomerizations by N‐inversion hve rather high activation energies. The N,N bonds in 1 are longer and weaker (STO‐3G estimation) than in hydrazine. The N‐homocycle 1 exhibits less ring strain than the C‐homocycle cyclopropane or three‐membered heterocycles. (2) Azimine (2): All 6 Atoms are in the same plane. There are 3 stereoisomers, 2a, 2b, and 2c. The order of ground state energies is (Z,Z) < (E,Z) ≫ (E,E). The 2 N,N bond lengths correspond to multiplicity 1½. The electronic structure of 2 corresponds to a 1,3‐dipole with almost equal delocalization of the 4 π‐electrons over all 3 N‐atoms. The negative net charge at the central N‐atom is much less than that at the terminal N‐atoms. Azimines should behave as π‐donors in complexation with transition metals (3) Triazene (3): All 6 atoms are in the same plane. There are 2 stereoisomers, 3a and 3b. The order of ground‐state energies is (E) < (Z). The stereoisomerization proceeds as pure N‐inversion. N‐Inversion has a high energy barrier inversion at N(1) is faster than at N(2). One of the N,N bond lengths is typical for a double, the other for a single bond. The electronic structure of triazene 3 entails rather localized π‐ and p‐electron pairs at N(1),N(2) and at N(3). Triazenes should behave as p‐donors in complexation with transition metals. (4) ‐N3H3‐Isomers: The order of ground‐state energies is 3 < 2 < 1. The energy differences between these constitutional isomers are much larger than between the stereoisomers of each. The [1,2]‐H shifts for conversions of 2 to 3 and the [1,3]‐H shift for tautomerization of 3 have relatively high activation energies; both shifts can be excluded as modes of thermal, unimolecular transformations.
Benz[cd]indoles. Part III. A New Stereospecific Synthesis of Dihydrolysergic Acid and an Entry to 14‐Substituted Derivatives
Authors: Haefliger Walter E.
Published: December 2004

A new convenient synthesis of dihydrolysergic acid is described, which allows the preparation of substituted derivatives, especially those with different substitutents in the aromatic ring. Starting from appropriately substituted 5‐nitro‐2‐tetralones, the synthesis leads via a tricyclic isonitrile to the indole‐ring closure as the last step, thus circumventing the troublesome protection/deprotection of the latter.
Total Synthesis of (±)‐Clovene. On the Stereoelectronic Requirements of the α‐Alkynone Cyclisation
Authors: Ackroyd John , Karpf Martin , Dreiding André S.
Published: December 2004

The synthesis of the sequiterpenoid tricyclic hydrocarbon (±)‐cleovene (1) by application of the α‐alkynone cyclisation is described. The starting bicyclic carboxylic acid 2 was obtained from ethyl 3‐methyl‐2‐oxocyclohexane‐1‐carboxylate by modified known methods (24%) and converted to the α‐alkynone 3 (86%). The thermolysis of 3 in the gas phase at 620° selectively produced the tricyclo[6.3.1.01,5] dodecenone 4 (80%) which was converted to 1 (37%) by conventional procedures. The selectivity of the α‐alkynone cyclisation is discussed in terms of the stereoelectronic requirements (coplanarity factor) of the carbene insertion. In order to throw further light on the importance of this factor, the (1‐adamantyl) alkynone 16 was synthesised from adamantane‐1‐carboxylic acid (78%) and subjected to thermolysis at 620°. Since this led to the tetracyclo[6.3.1.1.13,10.03,7]tridecenones 17 and 18 (together 72%), we conclude that the planar carbene insertion transition state, while preferred, is not a stringent requirement.
A New Base‐Labile Anchoring Group for Polymer‐Supported Peptide Synthesis
Authors: Mutter Manfred , Bellof Dieter
Published: December 2004

A new base‐labile anchoring group, derived from 9‐(hydroxymethyl)fluorene‐4‐carboxylic acid (HO2CFmoH or HOFmCO2H; 7), for polymer‐supported peptide synthesis os described. The synthesis of 7 starting from 2,2′‐biphenyldicarboxylic acid (1) proceeds in an overall yield of 53%. The group HO2CFmo exhibits properties similar to the well known Fmoc protecting group: It is stable to acidic conditions and cleavable by 15% piperidine in DMF. In combination with acid labile Nα‐protecting groups (e.g. Boc, Ddz, Bpoc, Nps etc.), it renders more flexibility to the stepwise synthesis using polymer supports. The versatility of the new anchoring group in solid‐ and liquid‐phase peptide synthesis is demonstrated for the synthesis of a model peptide.
The Photoisomerization of 1,2,3,4,5‐Pentamethyl‐5‐vinyl‐1,3‐cyclopentadiene
Authors: Burger Ulrich , Etienne Robert
Published: December 2004

The title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone‐sensitized photolysis at 300 nm, the syn‐vinyl‐pentamethylhousene 5, which spontaneously rearranges in a [3,3]0sigmatropic process to give the bicyclo[3.2.0]heptadiene skeleton 2. Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di‐π‐methane rearrangement. The bicyclo[3.2.0]heptadiene derivative 2 give pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.
The Structure of Diastereomeric Oxaprotiline Metabolites. An NMR Study
Authors: Winkler Tammo , Dieterle Walter , Hung Paul , Rihs Grety , Kriemler Hans‐Peter
Published: December 2004

The structure of phenolic metabolites of oxaprotiline, obtained from a study with rats and dogs, are assigned with NMR‐spectroscopic methods in combination with MS data and an X‐ray structure analysis of synthetic (9R*,2′S*)‐2‐chlorooxaprotiline, the metabolites are shown to be (9R*,2′R*)‐2‐hydroxy, 3‐hydroxy‐, and 2‐hydroxy‐3‐methoxyoxaprotiline, and (9R*,2′S*)‐2‐hydroxy‐, 3‐hydroxy‐, and 3‐hydroxy‐2‐methoxyoxaprotiline, as well as 2,6‐dihydroxyoxaprotiline.
An Improved Liquid‐Phase Synthesis of Simple Alkylpyridines
Authors: Grayson J. Ian , Dinkel Rolf
Published: December 2004

The synthesis of pyridines from mixtures of aldehydes or ketones NH3 in the liquid phase has been reinvestigated, using continuous dosage of the carbonyl components to the reaction mixture. The main product from the reaction of acetaldehyde and formaldehyde is 3‐methylpyridine (6), which is also the main product from the reaction of acrolein or a mixture of crotonaldehyde and formaldehyde under the same conditions. The reaction of other aldehydes with formaldehyde give 3,5‐dialklypyridines, e.g. 10, 16. Acetone reacts with either formaldehyde or acetaldehyde to give polysubstituted alkylpyridines. A mechanistic pathway is proposed which accounts for the formation of the observed products.
Monofunctional (Dimethylamino)silane as Silylating Agent
Authors: Szabó Katalin , Ha Ngoc Le , Schneider Philippe , Zeltner Peter , Kováts Ervin sz.
Published: December 2004

The reaction of triorganyl(dimethylamino)silanes with surface‐hydrated silicon dioxide has been studied. These silylating agents are easy to prepare from the corresponding chloro or bromosilanes with dimethylamine. The resulting products are thermally stable and relatively volatile. Reaction with surface‐hydrated silicon‐dioxide preparations at 150–250°C for 170 h yields a dense grafted layer. However, with (dimethylamino)silanes having strongly polar substituents, a retreatment of the surface‐modified silica seems to be necessary in order to attain maximum coverage.
Synthese von N‐(4‐Aminobutyl)‐16‐aza‐19‐nonadecanlactam und N‐(4‐Aminobutyl)‐17‐aza‐20‐icosanlactam (Desoxoinandenin)
Authors: Wälchli Rudolf , Giggisberg Armin , Hesse Manfred
Published: December 2004

Synthesis of N‐(4‐Aminobutyl)‐16‐aza‐19‐nonadecanelactam and N‐(4‐Aminobutyl)‐17‐aza‐20‐icosanelactam (Desoxoinandenine)

According to Scheme 1, the two homologous macrocyclic spermidine derivatives 12 and 23 were synthesized. Key steps in both cases were two different types of ring‐enlargement reactions. Compound 12 was identical with a degradation product of the naturally occurring spermidine alkaloids of inandenine‐type.
Synthesis and Crystal Structure of a Peroxo‐Bridged Binuclear Rhodium (III) Complex and its Superoxo‐Bridged Analogue
Authors: Springborg John , Zehnder Margareta
Published: December 2004

The reaction of the ammonia diol [(NH3)4Rh(OH)2Rh(NH3)4]4+with H2O2 Yields among other products a peroxo‐bridged dimeric species [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](CIO4)3. Its structure was determined by single‐crystal X‐ray diffraction. The crystals are monoclinic with space group P21/n and lattice constants a=12.269 (5) Å, b=10.769(4) Å, c=15.964(4) Å, β=107.17(3)°. The dihedral angle of the RhOORh group in the bimetallic ring deviates by 62δ from planarity. The peroxo‐bridged complex was found to disproportionate in 1M HCIO4 and a red superoxo‐bridged complex. [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](NO3)4, was isolated. Its structure was solved by single‐crystal X‐ray diffraction. The crystals are orthorhombic with space group Pna 2, and lattice constants a=14.997(5) Å, b=11.952(4) Å, C=10.489(4) Å. The dihedral angle off the RhOORh group deviates by 7δ from planarity.
Photoactive cryptands. Synthesis of the sodium cryptates of macrobicyclic ligands containing bipyridine and phenoanthroline groups
Authors: Rodriguz‐Ubis Juan‐Carlos , Alpha Béatrice , Plancherel Dominique , Lehn Jean‐Marie
Published: December 2004

The NaBr cryptates of five macrobicyclic ligands containing bipyridine (bpy) and phenanthroline (phen) groups, i.e, of [bpy.bpy.bpy] 1 [bpy.bpy.phen] 2 [phen.phen.‐phen] 3 [2.1.phen] 4 and [2.2.phen] 5, have been prepared. 1, 2, 4 and 5 have been obtained in high yield by condensation of bis(bromomethyl)bipyridine 6 or ‐phenanthroline 9 with the corresponding macrocyclic diamines in presence of Na2CO3. Direct access to the NaBr complexes of th symmetrical cryptands 1 and 3 was achieved by a one‐step macrobicyclisation procedure. The metal‐ion complexes of ligands 1‐5 have the attractive feature of combining the cation inclusion, nature of cryptates with the photoactivity of bipyridine and phenanthroline groups; they may thus be expected to posses a variety of interesting physical and chemical properties.
Halochrome Molekeln. 6. Mitteilung. Spektrophotometrische Untersuchungen zum acidobasischen Verhalten substituierter 6,6‐Diphenyl‐6H‐chromeno[4,3‐b]indolizine und ihrer Aza‐analogen
Authors: Gunzenhauser Sigmund , Balli Heinz
Published: December 2004

Halochromic Molecules. Spectrophotometric Investigation of the Acidobasic Behaviour of Substituted 6,6‐Diphenyl‐6H‐chromeno[4, 3‐b]indolizines and their Aza‐analogues

Substituted 6,6‐diphenyl‐6H‐chromeno[4,3‐b]indolizines form ring‐opened, intensely coloured (diphenyl)‐indolizinylcarbenium salts with acid. UV/VIS spectra of the coloured salts are discussed on the basis of VEPPPCI calculations. The ϵpH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation equilibria.
The adamantane rearrangement of 1,2‐trimethylenenorbornanes. Part IV. Hydride‐ion abstraction in 1,2‐exo‐trimethylenenorbornane
Authors: Klester Alfred Michael , Ganter Camille
Published: December 2004

In the AlBr3‐catalyzed adamantane rearrangement in CS2of 1,2‐exo‐trimethylenenorbornane (1) to 2‐endo,6‐endo‐trimethylenenorbornane (3), hydride‐ion abstraction occurs at C(6) from theexo‐side. ThekH/kDvalue for competition between1and5(Dexo‐C(6)) was 1.58 ± 0.05, whereas no kinetic isotope effect was operative for competition between unlabeled1and4(Dendo‐C(5)) and between1and6(Dendo‐C(6)).
Über den sterischen Verlauf der Umsetzung von Enaminen aus offenkettigen Aldehyden und Ketonen mit Nitroolefinen zu 2,3‐disubstituierten 4‐Nitroketonen
Authors: Seebach Dieter , Beck Albert K. , Goliński Jerzy , Hay John N. , Laube Thomas
Published: December 2004

On the Steric Course of the Reaction of Enamines Derived from Open‐Chain Aldehydes and Ketones with Nitro‐olefins Yielding 2,3‐Disubstituted 4‐Nitroketones

The relative configuration of the nitro‐ketone 12 obtained by the title reaction has been proved by a Baeyer‐Villiger degradation and subsequent reduction to the amino‐alcohol (±)‐(u)‐20, the relative configuration of which is identical with a sample prepared from 2‐methyl‐3‐hydroxybutyrate of known configuration (Scheme 1). The stereochemical course of the title reaction is thus as predicted by our topological rule. It is assumed that the other nitro‐ketones 13–18 described here are also formed by (lk)‐combination of the trigonal centers of the educts (diastereoselectivity > 90%, see Formulae and Fig. 1). It is not possible to reverse this relative topicity by employing (Z)‐ instead of (E)‐components of the starting materials, due to the reversibility of the primary step of these Michael additions (Schemes 2 and 3, and Fig. 2).
Photochemical reactions. 141st communication. Photochemistry of α,β‐unsaturated δ,ϵ‐epoxyketones of the ionone series
Authors: Mathies Peter , Frei Bruno , Jeger Oskar
Published: December 2004

On n,π*‐ as well as on π,π*‐excitation, the 4,5‐epoxy‐α‐ionones (E)‐1, (E)‐2, and (E)‐3 undergo (E)/(Z)‐isomerization and subsequent γ‐H‐abstraction leading to the corresponding 4‐hydroxy‐β‐ionones (E/Z)‐9, (E/Z)‐13, and (E/Z)‐17 as primary photoproducts. On photolysis of (E)‐3, as an additional primary photoproduct, the β,γ‐unsaturated σ,ϵ‐epoxy ketone 18 was obtained. The other isolated compounds, namely the 2H‐pyrans 10A + B and 14A + B as well as the retro γ‐ionones 11 and 15A + B, represent known types of products, which are derived from the 4‐hydroxy‐β‐ionones (E/Z)‐9 and (E/Z)‐13, respectively.
Camphorsulfonamide‐Shielded, Asymmetric 1,4‐Additions and Enolate Alkylations; Synthesis of a Southern Corn Rootworm Pheromone. Preliminary Communication
Authors: Oppolzer Wolfgang , Dudfield Philip , Stevenson Thomas , Godel Thierry
Published: December 2004

Using readily accessible 10‐sulfonamido‐isoborneols as regenerable, chiral auxiliaries, highly face‐selective C–C‐bond formations at Cα and Cβ of carboxylates could be conveniently achieved. Thus, conjugated additions of RCu to enoates (1→2) furnished, after saponification, β‐substituted carboxylic acids 3 in 94–98% e.e. Similarly, propionates 12 yielded after deprotonation, enolate alkylation, and reductive ester cleavage the (R)‐alcohols 15 in 78–98% e.e. The acid (+)‐3e was converted to the pheromone (–)‐11.
Asymmetric α‐Acetoxylation of Carboxylic Esters. Preliminary Communication
Authors: Oppolzer Wolfgang , Dudfield Philip
Published: December 2004

Using the readily accessible chiral auxiliaries 1–3 the sulfonamide‐shielded O‐silylated esters 5 underwent π‐face‐selective α‐acetoxylation on successive treatment with Pb(OAc)4 and NEt3 HF to give after recrystallization α‐acetoxy ester 6 in 55–67% yields and in 95–100% d.e. Starting from conjugated enoates addition of RCu and subsequent acetoxylation 10→11→12 yielded α,β‐bifunctionalized esters 12 with >95% configurational control at both Cα and Cβ. Nondestructive removal of the auxiliary (6→7, 6→8 and 12→13) gave either α‐hydroxycarboxylic acids or terminal α‐glycols in high enantiomeric purity. The prepared glycols 8c and 13a are key intermediates for previously reported syntheses of the natural products 16 and 17, respectively.
Synthesis of 1,2‐Dihydropyridines, 2,3‐Dihydro‐4(1H)‐pyridinone, and 1,2,3,4‐Tetrahydropyridines via N‐Acyl N,O‐Hemiacetal Formation
Authors: Roduit Jean‐Paul , Wyler Hugo
Published: December 2004

New procedures are described for the synthesis of α,β‐ethylenic and acetylenic aldehydes from 2‐butene‐ and 2‐butyne‐1,4‐diol, respectively (see Scheme 1). These are applied to the preparation of a particular δ‐acetylamino‐α,β‐ethylenic aldehyde ((E)‐5) as well as of its acetylenic analogue 15. On heating in the presence of a silyl enol ether, the former undergoes a complete dehydrative cyclization affording the N‐acetyl‐1,2‐dihydropyridine 19. The addition of HCl to aldehyde (E)‐5 results in the production of the 4‐chloro‐1,2,3,4‐tetrahydropyridine 22 which is hydrolyzed to the corresponding alcohol 23 on silica gel. Similarly, the addition of HCl or HBr to the δ‐acetyl‐amino‐α,β‐acetylenic aldehyde 15 leads to the previously unknown 4‐halo‐1,2‐dihydropyridines 26; these are easily hydrolyzed to the 2,3‐dihydro‐4(1H)‐pyridinone 27. The ring‐forming process involves a N‐acyl N,O‐hemiacetal as intermediate which is eventually dehydrated.
Selektive Reaktionen an den Tetranortriterpenen Bussein A und B
Authors: Guex Matthias , Tamm Christoph
Published: December 2004

Selective Reactions of the Tetranortriterpenes Busseins A und B

Bussein A (1) was transformed to the 1′‐O‐ and 2‐O‐acetyl and the 1′‐O ‐ and 2‐O‐chloroacetyl derivatives 3,5,4, and 6, respectively. By hydrolysis with H2SO4 in MeOH bussein J (7) was obtained from 1 and bussein K (8) from bussein B (2). Treatment of 1 with H2SO4 in H2O and tetrahydrofuran yielded 7, the acid 9, and the dilactone 16. Hydrolysis of 1 with aqueous NH3 in MeOH gave 10; at higher temperature, 12, 13, and 14 were obtained as additional products. With NaOH in aqueous MeOH 7, 10, 15, and 17 – the latter being an isomer of 15 of unknown structure – were formed from 1. Photooxidation of 1 led to 20β,21β:21β,23β‐diepoxybussein A (18).
Variable‐Temperature and Variable‐Pressure17O‐NMR Study of Water Exchange of Hexaaquaaluminium(III)
Authors: Hugi‐Cleary Deirdre , Helm Lothar , Merbach André E.
Published: December 2004

The transverse relaxation rate of H2O in Al(H2O)has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the17O‐NMR line‐broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchange with bulk H2O, whereas at low temperatures quadrupolar relaxation is prevailing. Low‐temperature fast‐injection17O‐NMR was used to extend the accessible kinetic domain. The samples studied contained Al3+(0.5m), Mn2+(0.2–0.5m),H+(0.2–3.1m) and17O‐enriched (20–40%) H2O. Non‐coordinating perchlorate was used as counter ion. The following H2O exchange parameters were obtained:k= (1.29 ± 0.04) s−1, ΔH* = (84.7 ± 0.3) kJ mol−1, ΔS* = +(41.6 ± 0.9)J K−1mol−1, and ΔV= +(5.7 ± 0.2) cm3mol−1, indicating a dissociative interchange,Id, mechanism. These results of H2O exchange on Al(H2O)are discussed together with the available complex‐formation rate data and permit also the assignment of Idmechanisms to these latter reactions.
Esters of 1‐O‐Demethylthiocolchicines: Formation of Isomers in Chloroform Solution
Authors: Kerekes Peter , Brossi Arnold , Flippen‐Anderson Judith L. , Chignell Colin F.
Published: December 2004

1‐O‐Acetyl‐1‐O‐demethylcolchicine, and acylated 1‐O,2‐O‐didemethylthiocolchicines, in contrast to 2‐O‐acetyl‐, 2‐O,3‐O‐diacetyl‐ and 3‐O‐acetyl analogs, showed after standing in CHCl3 solution significant changes in optical rotation, a duplication of 1H‐NMR signals, and the formation of new isomers on TLC. Solid‐state X‐ray diffraction of O‐acetylated colchinoids and thio analogs, showed out of planar arrangements of the aromatic substituents, but the analysis could not help to explain the structures of the newly formed isomers in CHCl3 solution.
Total Synthesis of (−)‐Crinine. Use of Tandem Cationic Aza‐Cope Rearrangement/Mannich Cyclizations for the Synthesis of Enantiomerically Pure Amaryllidaceae Alkaloids
Authors: Overman Larry E. , Sugai Soji
Published: December 2004

The total synthesis of enantiomerically pure (−)‐crinine (1) in 10 steps and 6% overall yield from cyclopentene oxide is reported. The key step was the rearrangement of 7 upon reaction with AgNO3 at 25°C to give cis‐perhydroindolone 8 in 81% yield.
Konformation und Dynamik von [6]Paracyclophan‐8,9‐dicarbonsäure‐dimethylester. Eine 1H‐ und 13C‐NMR Studie
Authors: Günther Harald , Schmitt Peter , Fischer Hartmut , Tochtermann Werner , Liebe Jörg , Wolff Christian
Published: December 2004

Conformation and Dynamics of Dimethyl [6]Paracyclophane‐8,9‐dicarboxylate. A 1H‐ and 13C‐NMR Study

The 1H‐ und 13C‐NMR spectra of dimethyl [6]paracyclophane‐8,9‐dicarboxylate have been assigned and analyzed in the slow‐exchange limit (−20°C) for the ring‐inversion process of the methylene bridge using several 2D‐NMR techniques. The vicinal 1H, 1H coupling constants of the methylene chain show a Karplus‐type dependence on torsional angles. The observed values indicate that the solution conformation of 1 closely resembles that found in the crystal. No significant changes in the 1H‐NMR shielding properties of the boat‐shaped benzene ring were detected. The 13C chemical shifts of the methylene C‐atoms can be explained without invoking ring current contributions, which are too small for unambiguous identification. A lineshape analysis for the AB⇌BA exchange system of the aromatic protons yielded ΔH≠ = 43.25 ± 0.72 kJ/mol, ΔS≠ = −51.27 ± 2.66 J/K mol, and ΔG≠(298) = 58.53 kJ/mol for the dynamic process corresponding to an inversion of the methylene bridge.
Synthesis of a Glyoxalase I Inhibitor from Streptomyces griseosporeus NIIDAet OGASAWARA
Authors: Mirza Sohail , Molleyres Louis‐Pierre , Vasella Andrea
Published: December 2004

The pseudolactones 6 and 12 were prepared in a straightforward way from methyl α‐D‐glucopyranoside and methyl α‐D‐mannopyranoside, respectively. The pseudolactone 6 reacted with tert‐butyl lithioacetate to give the protected, trihydroxylated cyclohexenone carboxylate 7 (51 %). The sterically hindered, L‐ribo‐configurated pseudolactone 12 reacted with diethyl ethylphosphonate and dimethyl methylphosphonate to give the protected trihydroxycyclohexenones 17 (49 %) and 18 (62 %), respectively. The hydroxymethylated cyclohexenone 21 was obtained from 18 by treatment with Me2AlSPh and then formaldehyde, oxidation of the product 19, and elimination. Deprotection of 21 gave 2, identical with KD16‐Ul. Esterification of 2 gave 1, identical with the title compound. Alternatively, 1 was obtained in higher yields by esterification of 21, followed by deprotection of the hydroxy groups. This synthesis gave 1 and 2 from methyl α‐D‐mannopyranoside in an overall yield of 18 and 20 %, respectively, confirming their absolute configuration.
Photochemistry of 4‐Thia‐2‐cycloalkenones. Part 2
Authors: Anklam Elke , Lau Sabine , Margaretha Paul
Published: December 2004

Methyl 2‐allyl‐3‐oxo‐2,3‐dihydrothiophene‐2‐carboxylate (2) photocyclizes selectively to methyl 2‐oxo‐7‐thiatricyclo[3.2.1.03,6]octane‐1‐carboxylate (4). In contrast, 4‐thia‐2‐cyclohexenone 3, on irradiation, affords only low yields of dimers, cycloadducts (2‐methylpropene) or RH reduction products (i‐ProH).
Direct Clay‐Catalyzed Friedel‐Crafts Arylation and Chlorination of the Hydrocarbon Adamantane
Authors: Chalais Stéphane , Cornélis André , Gerstmans André , Kołodziejski Wacław , Laszlo Pierre , Mathy Arthur , Métra Pierre
Published: December 2004

Multiple chlorinations and arylations at the tertiary positions of adamantane are promoted by FeCl3‐doped K10 montmorillonite in CCl4 or in aromatic solvents. The process, remarkably easy to implement, can be tailored to selective formation of monosubstituted 1‐adamantyl derivatives or 1,3‐disubstituted adamantanes. The process achieves alkylation at the meta‐ and para‐positions of toluene leading to a purely statistical distribution and displays no substrate specificity in competition experiments between toluene and benzene.
The Novel Adamantane Isomer Tricyclo[4.4.0.03,9]decane (2‐Homotwistbrendane)
Authors: Känel Hans‐Ruedi , Ganter Camille
Published: December 2004

Two synthetic approaches to the novel C10H16 hydrocarbon tricyclo[4.4.0.03,9]decane (1; 2‐homotwistbrendane), one of the 19 members of the adamantaneland, and its Lewis‐acid‐catalyzed rearrangement are described. One route starts from tricyclo[4.3.0.03,8]nonan‐2‐one (2; 2‐twistbrendanone). The missing tenth C‐atom is introduced by ring enlargement (Tiffeneau‐Demjanov method). Starting from methyl 8,9,10‐trinorborn‐5‐ene‐2‐endo‐carboxylate (8), ring enlargement by one C‐atom, regio‐ and stereoselective introduction of a C1 unit to a 2‐endo,6‐endo‐disubstituted bicyclo[3.2.1]octane, and ring closure by acyloin condensation are the key steps in the second approach.
New Furano‐sesquiterpenoids from Mediterranean Sponges
Authors: Guella Graziano , Mancini Ines , Guerriero Antonio , Pietra Francesco
Published: December 2004

A mixture of sponges of the East Pyrenean Mediterranean is shown to contain the known sponge products longifolin (1), avarol ((+)‐3), and avarone (4) and the terrestrial‐plant product sesquirosefuran (2), besides to the new furano‐sesquiterpenoids tavacfuran (= 3‐methyl‐2‐[(3′Z)‐3′‐methyl‐4″‐methyl‐2″‐furyl‐3′‐butenyl]furan; (5) and tavacpallescensin (= 5,10‐dihydro‐6,9‐dimethyl‐4H‐benzo[5,6]cyclohepta[1,2‐b]furan; 6) and the new furano‐butenolide sesquiterpenoids tavacbutenolide‐1 (= (±‐4‐ethoxy‐2‐methyl‐4‐)[(2′E)‐2′‐methyl‐4′‐(3″‐methyl‐2″‐furyl)‐2′‐butenyl]‐2‐buten‐4‐olide; (±)‐7) and tavacbutenolide‐2 (= (±)‐4‐ethoxy‐3‐methyl‐4‐[2′E)‐3′‐methyl‐4′‐(4″‐methyl‐2″‐furyl)‐2′‐butenyl]‐2‐buten‐4‐olide; (±)‐8). Structural assignments are based on NMR data and on the synthesis of the (E)‐isomer of 5. The sponge Dysidea tupha of the same area is also shown to contain the two sesquiterpenoids ent‐furodysinin ((−)‐14), which is enantiomeric to a product of a Dysidea sp. of Australian waters, and tuphabutenolide ((+)‐15).
Synthesen von Carotinen mit ψ‐Endgruppen und (Z)‐Konfiguration an terminalen konjugierten Doppelbindungen
Authors: Zumbrunn Albrecht , Uebelhart Peter , Eugster Conrad Hans
Published: December 2004

Syntheses of Carotenes with ψ‐End Groups and (Z)‐Configuration at Terminal Conjugated Double Bonds

Five carotenes bearing (5Z)‐ψ‐end groups were synthesized and carefully characterized: (5Z)‐lycopene (6), (5Z5′Z)‐lycopene (7), (5′Z)‐neurosporene (8), (5′Z)‐β,ψ‐carotene (12), and (5′Z)‐ε,ψ‐carotene (14).
Totalsynthese von Decarboxybetalainen durch photochemische Ringöffnung von 3‐(4‐Pyridyl)alanin
Authors: Hilpert Hans , Siegfried Marc‐André , Dreiding André S.
Published: December 2004

Total Synthesis of Decarboxybetalaines by Photochemical Ring Opening of 3‐(4‐Pyridyl)alanine

A photochemical approach is presented for the total synthesis of the decarboxybetalaines, which were previously known from the mild decarboxylation of the natural plant colorants, the betalaines: Irradiation of rac‐3‐(4‐pyridyl)alanine (1) yielded the rac‐2‐decarboxybetalamic‐acid‐imine (4, 86%), presumably via a Dewar pyridine 2, a cyclic aminal 3 and an electrocyclic ring opening. The imine‐zwitterion 4 was treated with three amines, namely (S)‐cyclodopa (6), (S)‐proline (7), and indoline (8), to afford three decarboxybetalaines, namely (2S)‐17‐decarboxybetanidine (9, red, 34%), (2S)‐13‐decarboxyindicaxanthine (10, yellow, 56%), and rac‐16‐decarboxyindobetalaine (11, orange, 78%), respectively. The structures of these coloring matters were confirmed by their electrophoretic behavior and their spectroscopic properties. 17‐Decarboxybetanidine 9 was shown to be a ca. 1:1 mixture of two C(15)‐epimers 9a and 9b, separable by chromatography. The configuration of 9a was determined as (2S, 15S) and that of 9b as (2S, 15R), by correlating their optical rotations with those of betanidine (12a) and isobetanidine (12b), respectively. The decarboxybetalaines 9, 10, and 11 did not show the double‐bond isomerism at C(β), (Cγ) of the chromophore which had been found characteristic for the corresponding betalaines 12, 13, and 14.
Quantitative Line‐Shape Analysis of Temperature‐ and Concentration‐Dependent 13C‐NMR Spectra of 6Li‐ and 13C‐Labelled Organolithium Compounds. Kinetic and Thermodynamic Data for Exchange Processes in Dibromomethyllithium, (Phenylthio)methyllithium, and Butyllithium
Authors: Heinzer Josef , Oth Jean F. M. , Seebach Dieter
Published: December 2004

Using the ‘permutation of indices’ method proposed by Kaplan and Fraenkel, we could formulate the density‐matrix equations required to fit the temperature‐dependent 13C‐NMR spectra observed with the title compounds. For 6Li13CHBr2 (1) and 6Li13CH2SC6H5 (2) an exchange mechanism is proposed by which monomers interchange C‐ and Li‐atoms via a non‐observed dimeric intermediate; the activation parameters of these intermolecular dynamic processes have been found to be ΔH≠ = 10.2 kcal/mol, ΔS≠ = 13.7 cal/mol·K for 1 and ΔH≠ = 11.1 kcal/mol, ΔS≠ = 20.6 cal/mol·K for 2 ((D8)THF as solvent). In the case of (6Li)butyllithium (3), the observed low‐temperature spectra indicate that dimeric (3b) and tetrameric (3a) species are in dynamic equilibrium interchanging the C3HCH2 groups (and THF molecules) bonded to the 6Li‐atoms. The relative concentrations of the dimer and of the tetramer have been determined by peak integration or by line‐shape fitting; the ‘pseudo’‐ equilibrium constant, defined by K′eq = [3b]2/[3a], was found to be 2.6·10−2 mol/1 (at −88°) and corresponds to ΔGR (−88°) = 2 ΔG°f(3b) – ΔG°f(3a) = 1.34 kcal/mol. The activation parameters of the dynamic process responsible for the exchange were estimated as ΔH≠ = 3.78 kcal/mol and ΔS≠ = −31.3 cal/mol·K. Tentative interpretation of the thermodynamic and kinetic parameters is given.
The Radical Anions and Trianions of 1,8‐Diphenylnaphthalene and of Some of its Derivatives Containing a Cyclophane Substructure
Authors: Gerson Fabian , Heckendorn René , Möckel Reinhart , Vögtle Fritz
Published: December 2004

The radical anions of 1,8‐diphenylnaphthalene (1) and its decadeuterio‐(D10‐1) and dimethyl‐(2) derivatives, as well as those of [2.0.0] (1,4)benzeno(1,8)naphthaleno(1,4)benzenophane (3) and its olefinic analogue (4) have been studied by ESR and ENDOR spectroscopy, At a variance with a previous report, the spin population in \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {2}^{-\kern-4pt {.}} $\end{document} is to a great extent localized in the naphthalene moiety. A similar spin distribution is found for \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {3}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {4}^{-\kern-4pt {.}} $\end{document}. The ground conformations of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document}‐\documentclass{article}\pagestyle{empty}\begin{document}$ \rm {4}^{-\kern-4pt {.}} $\end{document} are chiral of C2 symmetry. For \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document}, an energy barrier between these conformations and the angle of twist about the bonds linking the naphthalene moiety with the phenyl substituents were estimated as ca. 50 kJ/mol and ca. 45°, respectively. The radical trianions of 1, D10‐1, and 2, have also been characterized by their hyperfine data. In \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{3-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {2}^{3-\kern-4pt {.}} $\end{document}, the bulk of the spin population resides in the two benzene rings so that these radical trianions can be regarded as the radical anions of ‘open‐chain cyclophanes’ with a fused naphthalene π‐system bearing almost two negative charges. The main features of the spin distribution in both \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{3-\kern-4pt {.}} $\end{document} are correctly predicted by an HMO model of 1.
The Reaction of 4‐Oxo‐4H‐[1]benzopyran‐3‐carbaldehyde with 1,2‐Benzenediamine. X‐Ray Structure Analysis of the Reaction Product
Authors: Rihs Grety , Sigg Ivo , Hass Georges , Winkler Tammo
Published: December 2004

The reaction product of 4‐oxo‐4H‐[1]benzopyran‐3‐carbaldehyde and 1,2‐benzenediamine is 1,8‐dihydro‐6,13‐bis(2‐hydroxybenzoyl)dibenzo[b,i]‐1,4,8,11‐tetraazacyclotetradeca‐4,6,11,13‐tetraene (1), and its dehydrogenation product is 3‐(2‐benzimidazolyl)‐4H‐[1]benzopyran‐4‐one (2) as shown by X‐ray structure analysis confirming our earlier report.
Isolement et identification de l'acide furfurique, nouvelle depsidone du lichen Pseudevernia furfuracea (L.) Ach
Authors: Gunzinger Jan , Tabacchi Raffaele
Published: December 2004

Isolation and Identification of Furfuric Acid a New Depsidone from the Lichen Pseudevernia furfuracea (L.) Ach.

The structure of furfuric acid, (1), a new depsidone, isolated from the lichen Pseudevernia furfuracea (L.) Ach. has been established as 4‐formyl‐3,8‐dihydroxy‐9‐(2,4‐dihydroxy‐5‐methoxycarbonyl‐3,6‐dimethylbenzyl)‐1,6‐dimethyl‐11‐oxo‐11H‐dibenzo[b,e][1,4]dioxepin‐7‐carboxylic acid by spectral and chemical methods.
Ligand Substitution Reaction of Bis(ethylenediamine)glycinatocobalt(III) Complex with Ethylenediamine Catalyzed by the Photo‐excited Tris(2,2′‐bipyridine)ruthenium(II) Complex
Authors: Ishikawa Masahiko , Okamoto Ken‐ichi , Hidaka Jinsai , Einaga Hisahiko
Published: December 2004

Substitution reaction with ethylenediamine of coordinated glycinate ligand in bis(ethylenediamine)‐glycinatocobalt(III) complex has been studied in the presence of photo‐excited tris(2,2′‐bipyridine)ruthenium(II) complex in alkaline aqueous solution (buffered around pH 12) containing 1.0M chloride ion at 25°C. VIS absorption and CD spectra were used for the racemate and the optically active isomers of the Co(III) complexes, respectively. The reaction was catalyzed by the excited Ru(II) complex to give tris(ethylenediamine)cobalt(III) complex. Mechanism of the ligand‐substitution reaction and role of the excited Ru(II) complex were discussed.