bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation, characterization, crystal and molecular structure of Na2[N(CH2COO)399Tc(IV) (μ‐O)299Tc(IV)N(CH2COO)3] · 6H2O
Authors: Anderegg Giorgio , Müller Edgar , Zollinger Kurt , Bürgi Hans‐Beat
Published: December 2004

The title compound and its potassium analog have been prepared from corresponding aqueous solutions of 99TcO at pH ≈︁ 2 with SO2 as a reducing agent. An X‐ray structure determination of the Na‐salt showed Tc coordinated to the tetradentate N(CH2COO) ligand (NTA). Two Tc‐NTA moieties are joined via two bridging O‐atoms into a four‐membered Tc2O2 ring. The observed diamagnetism, a strong absorption band at 19 950 cm−1, and a short Tc‐Tc distance of 2.363 Å are typical for the Tc2O2‐fragment with its strong metal‐metal interaction. The structural trans‐influence at Tc and the network of H‐bonds are consistent with Tc in oxidation state IV.
Crystal and Molecular Structure of Tricarbonyl‐[(1R*, 4S*, 4aS*, 9aR*)‐1,4‐epoxy‐2, 3‐dimethylidene‐1,2,3,4,4a,9,9a,10‐octahydroanthracene]iron
Authors: Alini Mauro , Roulet Raymond , Chapuis Gervais
Published: December 2004

The thermal cyclodimerization of 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene assisted by Fe2 (CO)9 gives the title complex 1, a precursor for the synthesis of antitumoral anthracyclinones. The crystal structure of 1 has been determined by X‐ray diffraction: a = 11.188 (1); c = 26.968 (3) Å; space group tetragonal, P41212, Z = 8; R = 0.041; RW = 0.033. The tricarbonyliron group is in the exo‐position and the coordination polyhedron is tetragonal pyramidal. The NMR coupling constants are well‐related to the observed dihedral angles between the non‐aromatic protons and now give a reliable criterion for assigning the stereochemistry of the metal in d8‐complexes of 2,3‐dimethylidene‐7‐oxanorbornane derivatives.
Asymmetric Palladium‐Assisted Alkylation of Alkenes
Authors: Solladié‐Cavallo Arlette , Haesslein Jean‐Luc
Published: December 2004

Palladium‐promoted alkylation of alkenes using chiral sulfoxide‐containing carbanions and chiral lithiated oxazolines results in asymmetric induction (AI) ranging from 3–5% (1,5 induction), 20–40% (1,3 induction) to 44–52% (1,4 induction). No general trend allowing predictions of results was found. With 1‐hexene, attack at C(1) is almost exclusive but propene gives a mixture of attack at C(1) and C(2). The use of a chiral ligand together with malonate anion also leads to some asymmetric induction (ca. 20%).
Approaches to the synthesis of cytochalasans. Part 5. Studies on the selectivity of the Diels‐Alder reaction leading to the tetrahydroiso‐indolinone sub‐unit
Authors: Schmidlin Tibur , Gamboni Remo , Strazewski Peter , Tamm Christoph
Published: December 2004

The stereo‐ and regiochemical course in the [2+4]cycloaddition of the chiral alkylidene malonic ester 1 to selected derivatives of (2E, 4E)‐4‐methyl‐2, 4‐hexadien‐l‐ol (2) and (2E, 4E)‐4‐methyl‐2, 4‐hexadien‐l‐al (12) has been investigated. The results are discussed on the basis of semiquantitative PMO theory.
Light‐induced dehydrodimerization of pyrroles. Preliminary communication
Authors: Ghaffari‐Tabrizi Ramin , Margaretha Paul
Published: December 2004

Irradiation (λ>280 nm) of 3‐hydroxypyrroles 1 in acetonitrile leads to the formation of 3,3′‐bi‐3H‐pyrroles 2 in reasonable to good yields.
Photoformation of (Z)‐Isomers in Diarylazomethines. Part IV. Direct and sensitized photoisomerization of pyridyl analogues of benzylidene‐aniline and absorption spectra of their (Z)‐isomers
Authors: Maeda Koko , Fischer Ernst
Published: December 2004

UV irradiation of solutions of the (E)‐isomers of five (out of the possible six) monopyridyl analogues at reduced temperatures results in extensive (80–90%) conversion into the corresponding (Z)‐isomers. The process is reversible both thermally and photochemically. The (Z)‐isomers are stable at temperatures below −80°, and their absorption spectra were estimated. Biacetyl‐photosensitized (E)(Z) isomerization was observed, with (Z)‐contents of ca. 70% at the photo‐stationary state.
Solvent Dependence of Inductivity in the Solvolyses of Substituted Norbornyl p‐Toluenesulfonates. Norbornanes, Part 14
Authors: Bielmann Rolf , Christen Marcus , Flury Peter , Grob Cyril A.
Published: December 2004

A comparison of the solvolysis rates of the substituted 2‐exo‐ and 2‐endo ‐norbornyl p‐toluenesulfonates 1, 2, 3 and 4 and the substituted 1‐ and 2‐adamantyl sulfonates 9 and 10, respectively, in 80% ethanol and 97% trifluoroethanol has shown that the sensitivity of rates to the I‐effect of substituents, i.e. the inductivity of these compounds, varies strongly with structure, configuration and solvent. In 97% trifluoro‐ethanol, a solvent of low nucleophilicity and high ionizing power, the inductivities of the 2‐endo‐norbornyl p‐toluenesulfonates 2 and 4 as well as the inductivities of the adamantyl derivatives 9 and 10 were larger than in 80% ethanol. In contrast, the inductivity of the 2‐exo‐norbornyl p‐toluenesulfonates 1 was practically unchanged. It was, therefore, concluded that the transition states for the former compounds are not, or only weakly, bridged, whereas the transition states for the 2‐exo‐norbornyl p‐tolu‐enesulfonates 1 involve graded bridging by C (6). These results confirm that, due to differential bridging strain, 2‐norbornyl cations are anisotropic to polar effects.
Deoxy‐nitrosugars. 6th communication. Stereoelectronic control in the reductive denitration of tertiary nitro ethers. A synthesis of ‘C‐glycosides’
Authors: Baumberger Franz , Vasella Andrea
Published: December 2004

The separate, radical denitration with Bu3SnH of the pyranose derivatives 3, 4, 9, and 10 gave in good yields exclusively the ‘C‐glycosides’ 5 and 11, respectively (Scheme 1). Similar reduction of the cyclohexyl derivatives 15, 16, 19 and 20 gave 4:1 mixtures of 17, 18, 21 and 22, respectively, always with predominant formation of an axial C,H‐bond. In the furanose series a divergent behaviour was observed for the D‐mannose‐derived nitro ethers 25 and 27 and the D‐ribose‐derived nitro ethers 30 and 31, respectively, in that the former two gave isomerically homogeneous reduction products (26 and 28, respectively; Scheme 3) and the latter a 1:1 mixture of the diastereoisomers 32 and 33 (Scheme 4). The stereochemical results were explained on the basis of the stereoelectronic effect of the ring O‐atom, the preferred conformation of the intermediate, pyramidal alkoxyalkyl radicals and steric effects in the trioxabicyclo [3.3.0]octane ring system.
Orthocarbonsäure‐ester mit 2,4,10‐Trioxaadamantanstruktur als Carboxylschutzgruppe; Verwendung zur Synthese von substituierten Carbonsäuren mit Hilfe von Grignard‐Reagenzien
Authors: Voss Gundula , Gerlach Hans
Published: December 2004

Ortho Esters with 2,4,10‐Trioxaadamantane Structure as Carboxyl Protecting Group; Applications in the Synthesis of Substituted Carboxylic Acids by Means of Grignard Reagents

The surprising stability of 2,4,10‐trioxa‐3‐adamantyl derivatives 1 against nucleophilic substitution by organomagnesium compounds is discussed and shown to be caused by unfavourable stereoelectronic and steric factors governing the substitution of these cage compounds (Scheme 2). As a consequence, a number of Grignard reagents 2 containing the carboxyl group masked as 2,4,10‐trioxa‐3‐adamantyl group could be prepared and have been reacted in a second step with various electrophiles (cf. Scheme 4). In the products 7–13 and 15b the carboxyl masking group is removed by mild acid hydrolysis and saponification (cf. Scheme 3) to yield the corresponding acids 16a–21a, 22, and 23a. Acids 21a and 23a have been further transformed to give the macrocyclic lactones 24 and 26, isolated from Galbanum oleo‐gum‐resin, and acid 22 to give 12‐methyl‐13‐tridecanolide (25), isolated from Angelica root oil. In addition 1‐bromo‐ω‐(2,4, 10‐trioxa‐3‐adamantyl)alkanes 1c and 1b have been used to synthesize (±)‐methyl recifeiolate (29b) and pure cis‐ambrettolic acid ((Z)‐32a).
Silicon‐Directed Nazarov Reactions II. Preparation and Cyclization of β‐Silyl‐substituted Divinyl Ketones
Authors: Jones Todd K. , Denmark Scott E.
Published: December 2004

Two general methods for the preparation of β‐silyl‐substituted divinyl ketones have been developed starting from either α, β‐unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five‐membered ring. The observed effects of substituents on rate can be explained by a rate‐determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction.
Construction of Highly Substituted Nitroaromatic Systems by Cyclocondensation. Part II. Conversion of 4‐nitro‐3‐oxobutyrate to 3‐nitrosalicylates
Authors: Duthaler Rudolf O.
Published: December 2004

The base‐catalyzed reaction of 4‐nitro‐3‐oxobutyrate (6) with acetylacetone (8 Scheme 3), formylacetone (13, Scheme 4), formylcyclohexanone (31, Scheme 5), 2,4‐dioxopentanoates 39 and 40 (Scheme 6), and 2,4,6‐heptanetrione (2, Scheme 7) affords substituted 3‐nitrosalicylates, products of a double aldol condensation. With unsymmetrical dicarbonyl compounds both regioisomers are formed. High selectivity was found in the case of β‐keto‐aldehydes 13 and 31 with preferred addition of the NO2‐substituted carbon to the aldehyde carbonyl. The major products of these cyclocon‐densations, which are isolated in yields ranging from 20% to 80%, are all new compounds. Less successful are the conversions with β‐alkoxy‐ and β‐chloro‐vinyl ketones (23, 25, and 26), and with alkinone 24, where the condensation products are formed in very low yield (Scheme 4).
A Re‐investigation of the Wavelength‐dependent Photoreduction of 1‐Piperidinoanthraquinone: Evidence for a Mechanism of Impurity Sensitization
Authors: Suppan Paul , Huber Stephan , Haselbach Edwin
Published: December 2004

The reported wavelength‐dependence of the photoreactivity of 1‐piperidinoanthra‐quinone (1‐PAQ) in hydrogen‐donor solvents is ascribed to a chemical sensitization by trace amounts of 1‐chloroanthraquinone, as the action spectrum for photoreactivity of the former matches the absorption spectrum of the latter. The photochemistry and photophysics of 1‐PAQ seem therefore not to violate the Kasha‐Vavilov rule, i.e. its photoreactivity does not involve an upper n — π* triplet state.
Photochemical reactions. 133rd Communication. Photochemistry of epoxydienes of the ionone series: Influence of a methyl group at the diene side chain on the oxirane cleavage
Authors: Pascual Alfons , Nishio Takehiko , Frei Bruno , Jeger Oskar
Published: December 2004

On triplet excitation (λ > 280 nm, acetone), the epoxydiene (E)‐2 undergoes (E)/(Z)‐isomerization exclusively, leading to the conformers (Z)‐2A and (Z)‐2B. On singlet excitation (λ = 254 nm), apart from (Z)‐2A + B, the cyclobutenes 3A + B are formed. However, the epoxydiene (E)‐2 does not undergo reactions leading to carbene and C,O‐bond cleavage products, which are normally observed on singlet and triplet excitation, respectively, of the epoxydienes of the ionone series.
Loganin, loganic acid and periclymenoside, a new biosidic ester iridoid glucoside from Lonicera periclymenumL. (Caprifoliaceae)
Authors: Calis Ihsan , Lahloub Mohamed F. , Sticher Otto
Published: December 2004

Loganin (1), loganic acid (2), and periclymenoside (3) have been isolated from Lonicera periclymenum L. The structure of the new compound 3 and the identity of the others have been determined by chemical transformations and interpretation of the spectral data.
C‐Metallierte chirale Aloxide als d2‐ und d3‐Reagenzien für die Synthese enantiomerenreiner Produkte (EPC‐Synthese)
Authors: Nájera Carmen , Yus Miguel , Seebach Dieter
Published: December 2004

C‐Metallated Chiral Alkoxides as d2–‐and d3 ‐Regents for the Synthesis of Enantiomerically Pure Compounds (EPC‐Synthesis)

The chloroalcohols (S)‐1 ‐chloro‐2‐propanol (1), (S)‐1 ‐chloro‐2‐methyl‐2‐pentanol (4), (R)‐3‐chloro‐2‐methyl‐1 ‐propanol (7), (R)‐4‐chloro‐2‐butanol (10), and (2R, 3R)‐ 4‐chloro‐3‐methyl‐2‐butanol (14), really available from the esters of lactic, 3‐hydroxy‐2‐methylpropanoic, and 3‐hydroxybutanoic acid are subjected to sequential metallation first with BuLi (or MeMgCl) and then with lithium naphthalenide (or Li metal powder) to give solutions of the highly reactive C ‐metallated alkoxides 15, 22, 26, 27, and 28, respectively. ‐ These chiral d2‐ and d3 ‐reagents may be added to aldehydes (non‐diastereoselectively), ketones, and CO2 to give 1, 3‐ or 1 4‐dioles (18‐21, 24, 29‐33) or δ‐lactones (35, 36). Thiolations with dibenzyl disulfide (→ 16, 34) and a deuteration (→ 17, (S)‐(1‐2H)propan‐2‐ol) were also carried out. Independent synthesis of (S)‐1‐benzylthio‐2‐propanol (16) and comparison of the specific rotations establish that no loss enantiomeric purity occurs on the metallation route. The results described represent and extension of the applicability of simple chiral building blocks to EPC‐synthesis.
Synthese von para‐substituierten phenyl‐terpyridin liganden
Authors: Spahni Werner , Calzaferri Gion
Published: December 2004

Up to now the synthesis of para‐substituted phenyl‐terpyridine ligands was difficult with respect to the purification of the reaction products. We have found that these compounds can easily be isolated as hydrobromides from acetic acid. Starting from the hydrobromides the purification turned out to be easy. Synthesis of para‐substituted Cl‐, Br‐, H3C‐, H2BrC‐, HO‐ 2,6‐Bis(2‐pyridyl)‐4‐phenylphyridine is reported.
Photochemistry of N‐(2‐Cyclohexen‐1‐ylidene) alkylamines
Authors: Kilger Ralf , Margaretha Pual
Published: December 2004

Irradiation (λ = 254 nm) of N‐(4,4,6,6‐tetramethyl‐2‐cyclohexen‐1‐ylidene)‐1,1,3,3‐tetramethyl‐2‐cyclohexen‐1‐ylidene‐1,1,3,3‐tetramethylbutylamine (7d), which in turn is photodecomposed by light of the same wavelength, but at a four times slower rate than it is formed. The rate of formation of photoproduct 7d is a function of the concentration of starting material 1d, suggesting the involvement of a bimolecular (1d* + 1d) step. The structure of 7d was established by spectroscopy and by its hydrolysis to 3‐cyclohexyl‐4,4,6,6‐tetramethyl‐2‐cyclohexenone (8). The previously made assumption that N‐(2‐cyclohexen‐1‐ylidene)cyclohexylamine (1a) and 2,3,4,4a,5,6‐hexahydroquinolines 2 photorearrange to N‐cyclohexylidenecyclohexanamine 3a and 3,4,4a,5,6,8a‐hexahydroquinolines 4, respectively, via a light‐induced 1,3‐hydrogen shift proves incorrect.
Polarographische und voltammetrische Untersuchungen an symmetrischen Methin‐, Azamethin‐ und Phosphamethincyaninen in Acetonitril
Authors: Hellrung Bruno
Published: December 2004

Polarographic Investigations on Symmetrical Methine‐, Azamethine‐, and Phosphamethinecyanine dyes in Acetonitrile Solution

The reduction and oxidation behaviour of six symmetrical methine‐, azamethine‐, and phosphamethine dyes with different heterocycles in MeCN solutions has been investigated by menas of dc‐ and ac‐polarography (DME, MDE and rotating Pt‐electrode) and cyclic triangular wave voltammetry. The reduction and oxidation mechanism has been found to be of the type ec with the reduction and oxidation step being reversible to irreversible. Reduction and oxidation potentials, transfer coefficients, and specific currents have been measured and compared with known properties of methinecyanines, carbocyanines, and triazacarhocyanines.
Synthesis of Optically Pure Compounds by Enantiotopically Differentiating Monoacetalization of Prochiral Diketones. Part II. Fragmentation of β‐Keto‐Acetals
Authors: Duthaler Rudolf O. , Maienfisch Peter
Published: December 2004

Treatment of β‐keto‐acetals, derived from non‐enolisable β‐diketones, with sulfonic acids in boiling benzene resuots in a smooth retro‐Claisen‐type fragmentation. The acetal‐C‐atom is thereby transformed into a carboxylic ester via a dialkoxycarbenium ion, which is dealkylated by the sulfonate counter‐ion. Application of this reaction to the diastereomeric monoacetals 3 and 4, derived from cis‐9‐methyl‐decalin‐1,8‐dione (1), followed by transesterification with CH3OH, yields optically pure 4‐(2′‐methyl‐3′‐oxocyclohexyl)butyrate 9 ((+)−9 from 3, (−)‐9 from 4) and the monosulfonate of Meso‐2,3‐butanediol (−)‐13 (Scheme 2). Unexpectedly, this cleavage proceeds as well with monoacetal 26, obtained by acetalization of trans‐9‐methyl‐decalin‐1,8‐dione (27) with 2,2‐dimethyl‐1,3‐propanediol (Scheme 7). Some attempts, aiming at an isomerization of the cis‐ and trans‐decalin derivatives 3 and 24, or 25 and 26, via the postulated carboxonium intermediate, were not successful.
Selective Photoinduced Oxidation of Benzylic Methylen Groups through UV Irradiation in Presence of Ferric Chloride
Authors: Barbier Michel
Published: December 2004

Selective oxidation of benzylic methylene groups through UV irradiation in acetone/water/FeCl3mixtures is reported. This method applied to a series of model compounds, provides an easy access to the corresponding 1‐oxo derivative. Thus, tetralin gives a 100% yield of 1‐tetralone, indane leads to 60% of 1‐indanone, and diphenylmethane is oxidized to benzophenone with 80% yield. However, under the same conditions, alkyl‐substituted aromatic hydrocarbons such as toluene, ethyl‐ and propylbenzene lead to low yields of aldehydes or ketones. Isochromane furnishes a mixture of two substances which can be interconverted, namely the expected l‐isochromanone (9%) and the corresponding hydroxy acid (23%). We failed to apply the method to nitrogen heterocycles containing benzylic groups such as 1,2,3,4‐ and 5,6,7,8‐tetrahydroquinoline as they do not react due to the formation of complexes which precipitate from the solutions.
Radical Ions of Conjugated Polycyclic Hydrocarbons Containing Two Phenalenyl π‐Systems
Authors: Gerson Fabin , Knöbel Jürgen , Metzger André , Murata Ichiro , Nakasuji Kazhior
Published: December 2004

The radical cations and the radical of 1,2‐bis(phenalen‐1‐ylidene)ethane (1), 1,2‐bis(phenalen‐1‐ylidene)ethene (2) and pentaleno[1,2,3‐cd: 4,5,6‐c′ d′]diphenalene (3) have been characterized by ESR and ENDOR spectroscopy. The ease of formation of these radical ions and their π‐spin distributions are interpreted in terms of a simple model correlates the frontier orbitals of 1, 2 and 3 with the nonbonding MO's of two phenalenyl π‐systems.
1,2‐Epoxycarotinoide. 4. Mitteilung. Synthese, 1H‐NMR‐ und CD‐Studien von (S)‐1,2‐Epoxy‐1,2‐dihydrolycopin und (S)‐1′,2′‐Epoxy‐1′,2′‐dihydro‐γ‐carotin
Authors: Kamber Matthias , Pfander Hanspeter , Noack Klaus
Published: December 2004

1,2‐Epoxycarotenoids: Synthesis, 1H‐NMR and CD Studies of (S)‐1,2‐Epoxy‐1,2‐dihydrolycopene and (S)‐1′,2′‐Epoxy‐1′, 2′ ‐dihydro‐γ‐carotene

The synthesis of (S)‐1,2‐epoxy‐1,2‐dihydrolycopene ((S)‐1) and (S)‐1′, 2′ ‐epoxy‐ 1′, 2′ ‐dihydro‐γ‐carotene ((S)‐2) are described. The CD spectra of the (all‐E)‐isomers and of the isomers (7Z, S)‐1 and (7′Z, S)‐2 are discussed. The comparison of the CD spectra of the synthetic (S)‐1 and the compound isolated from the tomatoes proves the (S)‐configuration of the natural product.
Synthese und NMR‐Spektren einiger 13C‐markierter Thio‐ und Seleno‐äther, ‐acetale und ‐orthoester
Authors: Gabriel Josef , Seebach Dieter
Published: December 2004

Synthesis and NMR Spectra of Some 13C‐Labelled Thio‐ and Seleno‐ethers, ‐acetals, and ‐orthoesters

Twenty‐seven different open‐chain and cyclic derivatives (RX)nCH4‐n and (RX)nCH3‐nR′ with n = 1−3, X = S or Se, R,R′ = alkyl or aryl, 1,3,5‐trithiane, and bis‐(dimethylsulfonio)methane and ‐methanide with single or multiple 13C‐labelling have been synthesized. The 13C‐NMR spectra of the sulfur and selenim compounds have been measured, and the dependence of the chemical shifts (δc) and coupling constants [′J(C,H), ′J(Se,C)] from the substitution pattern in discussed (Fig. 1) and compared with the polyhalogeno‐methanes (Fig. 2).
On cardioactive steroids. Communication XV. A stereoselective synthesis of (21R)‐21‐methyldigitoxigenin, a fully active cardenolide with a wide margin of safety: A contribution to the topology of the Digitalis receptors
Authors: Wiesner Karel , Tsai Thomas Y. R. , Kumar Ravindra , Sivaramakrishnan Harihran
Published: December 2004

Two efficient preparations of the title compound, one from common C19‐steroids, the other frm digitoxigenin, are described. The less active minor epimer (21S)‐methyldigitoxigenin was also obtained and characterized. The positive inotropic effects and margins of safety of the two C(21)‐epimers (tested as glucosides) are discussed in terms of the topological properties of the Digitalis receptors.
The Non‐planarity of the Bicyclo[2.2.1]hept‐2‐ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct‐2‐ene, Bicyclo[2.2.1]hept‐2‐ene, and Bicyclo[2.1.1]hex‐2‐ene Systems
Authors: Pinkerton A. Alan , Schwarzenbach Dieter , Birbaum Jean‐Luc , Carrupt Pierre‐Alain , Schwager Luis , Vogel Pierre
Published: December 2004

The crystal structures of (1R,4R,5S,8S)‐9,10‐dimethylidentricyclo[6.2.1.02,7]undec2(7)‐ene‐4,5‐dicarboxylic anhydride (3), (1R,4R,5S,8S)11‐isopropylidene‐9,10‐dimethylidenetricyclo[6.2.1.m2,7]undec‐2(7)‐ene‐4,5‐dicarboxylic anhydride (6), (1R,4R,5S8S)‐9,10‐dimethylidenetricyclo[6.2.2.02,7]dodec‐2(7)‐ene‐4,5‐dicarboxylic anhydride (9), (1R4R5S8S)‐TRICYCLO[6.2.2.02,7]dodeca‐2(7), 9‐diene‐4,5‐dicarboxylic anhydride (12) and (4R,5S)‐tricyclo[6.1.1.02.7]dec‐2(7)‐ene‐4,5‐dicarboxylic acid (16) were established by X‐ray diffraction. The alkyl substituents onto the endocyclic bicyclo[2.2.1]hept‐2‐ene double bond deviate from the C(1), C(2), C(3), C(4), plane by 13.5°4 in 3 and by 13.9° in 6, leaning toward the endo‐face. No such out‐of‐plane deformations were observed with the bicyclo[2.2.2]oct‐2‐ene derivatives 9 and 12. The exocyclic s‐cis‐butadiene moieties in 3, 6 and 9 do not deviate significantly from planarity. The deviation from planarity of the double bond n bicyclo[2.2.1]hept‐2‐ene derivatives and planarity in bicyclo[2.2.2]oct‐2‐ene analogues is shown to be general by analysis of all known structures in the Cambridge Crystallographic Data File. The non‐planarity of the bicyclo[2.2.1]hept‐2‐ene double bond cannot be attributed only to bond‐angle deformations which would favour rehybridizatoin of the olefinic C‐atoms since the double bond in the more strained bicyclo[2.1.1]hex‐2‐ene drivative 16 deviates from planarity by less than 4°.
Photochemical reactions. 137th communication. Preparation and photolysis of (E/Z)‐7‐methyl‐β‐ionone
Authors: Ishii Keitaro , Mathies Peter , Nishio Takehiko , Wolf Hans Richard , Frei Bruno , Jeger Oskar
Published: December 2004

The title compounds (E/Z)‐7 were prepared in 66% overall yield by reaction of β‐ionone ((E)‐(1) with lithium dimethylcuprate, trapping of the intermediate enolate with benzeneselenenyl bromide and oxidation with H2O2. Analogously, (E/Z)‐7‐methyl‐α‐inone ((E/Z)‐12) was obtained in 65% yield from α‐ionone ((E)‐11). 1n, π*‐ Excitation (λ > 347 nm, pentane) of (E)‐7 causes rapid (E/Z)‐isomerization and subsequent reaction of (Z)‐7 to 15 (66%). The formation of 15 is explained by twisting of the dienone chromophore due to repulsive interaction of the 7‐CH3‐group with the CH3‐groups of the cyclohexene ring. On the other hand, irradiation λ > 347 nm, Et2O) of (E)‐7 in the presence of acid leads to (Z)‐7 (5%) and to the novel compound 16 (88%).
Ein meta‐Xylylen durch Bamford‐Stevens‐Reaktion eines Fulven‐Keten‐Addukts
Authors: Stadler Heinz , Rey Max , Dreiding André S.
Published: December 2004

A meta‐Xylylene by Bamford‐Stevens Reaction of a Fulvene‐Ketene‐Adduct

Heating the sodium salt 8 of the tosylhydrazone 4 of 4‐isopropyliden‐7,7‐dimethylbicyclo[3.2.0]hept‐2‐en‐6‐one (3; obtained by the addition of dimethylketene to 6,6‐dimethylfulvene (1)), in diglyme at 130° led to the cotamethyl‐[2.2]metacyclophane 10 (17%). The latter probably was formed by dimerization of the non‐Kékulé molecule m‐xylylene 14, which, in turn, could have arisen via the homofulvene 13 from the carbene 12. A second product in the thermolysis of 8 was the tricycle 9 (9 %), as a result of an intramolecular insertion of the carbene C‐atom in 12 into a methyl C,H‐bond. Further products were the azines 11a, 11b (50%), of the type known as byproducts in Bamford‐Stevens reactions. Heating dry 8 afforded 9 (9%) and the two benzene derivatives 15 (9%) and 16 (3%). The tosylhydrazone 4 could be recovered by reaction of 11a, 11b with p‐toluenesulfonohydrazide.
Dimers of 3,7‐dehydrotropones (bicyclo[3.2.0]hepta‐1(7),2,4‐trien‐6‐ones)
Authors: Szechner Barbara , Rey Max , Dreiding André S. , Grieb Rita
Published: December 2004

2‐(tert‐Butyl)‐3,7‐dehydrotropone (7‐(tert‐butyl)bicyclo[3.2.0]hepta‐1(7),2,4‐trien‐6‐one; 1) was found to dimerize reversibly to 2A by [2 + 4]‐cycloaddition/cycloreversion reaction. The equilibrium lies on the side of the highly strained dimer 2A in the solid state, and on the side of the monomer 1 in solution. The [2 + 4]‐reaction is fully perisite‐, regio‐ and stereoselective. Above room temperature, 1 irreversibly formed a decarbonylated dimer 6, probably via the intermediate 9A or 9B, which resulted either from a dimerisation of 1 by [4 + 6]‐cycloaddition or from a sigmatropic rearrangement of the originally formed dimer 2A or 2B. Similary, the 6‐bromo derivative 14 afforded the corresponding decarbonylated dimer 15. Should the formation of 6 and 15 be due to a primary cycloaddition then that reaction is fully peri‐, site‐ and regioselective. Mild LiAlH4‐reduction of 6 and subsequent acetylation yielded the acetate 11, the structure of which was established by an X‐ray analysis. More vigorous LiAlH4‐treatment also reduced the terminal fulvenoid double bond of 6 and acetylation of the crude product led to the acetated 12 and 13.
Preparation of Regioselectively Protected Hydroquinones by Phosphorylation of p‐Benzoquinones with Trialkyl Phosphites
Authors: Duthaler Rudolf O. , Lyle Paulette A. , Heuberger Christoph
Published: December 2004

The title reaction has been applied to 10 monosubstituted p‐benzoquinones (Scheme 2, Table). The regioselectively of the O‐phosphorylation is influenced by bulky substituents (t‐butyl and trimethylsilyl) and, electronically, by the methoxy group. The regioselectivity, which is high in nonpolar media (benzene), is lower in polar solvents (CH2Cl2) and (CH3CN). The synthetic potential of this transformation, exemplified by the preparation of compounds 29 (Scheme 3) and 32 (Scheme 4), is considerably extended by applying milder methods for the phosphate hydrolysis and by using the reagent couple P(OCH3)3/trimethylsilyl chloride, which gives clean access to p‐hydroxyphenyl phosphates. p‐Benzoquinones 4th and 4i with strong π‐acceptor substituents react in a different way, giving phosphonates. The electronically induced regioselectivity of the O‐phosphorylation is in according with the preferences expected for the attack by a nucleophilic phosphorylation agent.
Messkette zur direkten potentiometrischen Bestimmung des Enantiomerenüberschusses von 1‐Phenyläthylmmonium‐Ionen
Authors: Bussmann Walter , Morf Werner E. , Vigneron Jean‐Pierre , Lehn Jean‐Marie , Simon Wilhelm
Published: December 2004

Cell Assembly for the Potentiometric Determinatin of the Enantiomeric Excess of 1‐Phenylethylammonium‐Ions

A cell assembly with two membranes containing each one enantiomer of the ionophor N,N,N′,N′,N″,N″,N‴,N‴‐octabutyl‐1,4,7,10,16‐hexaoxacyclooctadecane‐2,3,11,12‐tetracarboxamide is used for the direct potentiomewtirc determination of the enantiomeric excess ee of 1‐phenylethylammonium ions in aqueous solutions. The preference for the (R)‐over the (S)‐1‐phenylethylammonium ion by the (2R,3R,11R,12R)‐ionophor of 2.7 allows a reliable determination of ee even in the presence of known concentrations of the heavy interferent KCl.
Deoxy‐nitrosugars, 7th communication Synthesis of methyl shikimate and of diethyl phosphashikimate from D‐ribose
Authors: Mirza Sohail , Vasella Andrea
Published: December 2004

The chain elongation of the deoxy‐nitroribose 6 by a Michael addition to the vinyl‐phosphonate 7 followed by a solvolysis gave the heptulosephosphonate 11 (87%). From 11, the key intermediates 15 and 16 (77%) were obtained by a highly diastereoselective reduction, followed by detritylation, periodate cleavage, and silylation. Methoxycarbonylation of 15 and 16 gave 17 and 18 which were converted into methyl shikimate (21; 79%) by intramolecular olefination and partial deprotection. Similarly, phosphonoylation of 16 gave 22 (99%) which was transformed into the diethyl phosphashikimate 2 (53% from 6).
The Persistence of Ribbon Orbitals in Polycyclic Alkanes
Authors: Heilbronner Edgar , Honegger Evi , Zambach Werner , Schmitt Peter , Günther Harald
Published: December 2004

Equivalent bond orbital (EBO) calculations by a procedure based on recalibrated, localized bond orbitals derived from an ab initio model, suggest that the two frontier ‘ribbon’ orbitals φHOMO, φHOMO‐1 of polycyclic hydrocarbons consisting of all‐trans‐connected six‐membered rings are well separated in energy from the remaining manifold of σ‐orbitals. Assuming the validity of Koopmans' theorem, a PE‐spectroscopic investigation of perhydroanthracenes, 2‐methylperhydrophenalene and perhydroperylene have shown that this is indeed the case. According to the theoretical treatment these ribbon orbitals are evenly delocalized over the whole of the molecular frame and they conserve the characteristic phase relationship postulated by Hoffmann et al. [16] for cyclohexane moieties. Their behaviour under the successive introduction of centres of unsaturation, i.e., of double bonds is discussed.
A New Pyranocoumarin Diester from Polygala paniculata L
Authors: Hamburger Matthias , Hostettmann Kurt , Stoeckli‐Evans Helen
Published: December 2004

A new coumarin diester has been isolated from Polygala paniculata L. (Polygalaceae) by a combination of flash chromatography on silica gel and preparative reversed‐phase chromatography. Its structure has been determined as 3′‐O‐acetyl‐4′‐O‐benzoylkhellactone (= 9‐acetoxy‐9,10‐dihydro‐8,8‐dimethyl‐2‐oxo‐2 H,8H‐benzo[1,2‐b:3,4‐b′]dipyranh‐10‐yl benzoate) by spectroscopic methods (UV, IR, 1H‐NMR, EI‐and CI‐MS) and by X‐ray analysis.
Experiments on the total synthesis of Lysolipin I. Part II. Michael addition of 1,3‐cyclohexanedione to quinone acetals
Authors: Duthaler Rudolf O. , Wegmann Urs H.‐U.
Published: December 2004

Base‐catalyzed reaction of 1,3‐cyclohexanedione (3) with the quinone monoacetals 4 and 7 leads to the polycyclic products 5 and 8, respectively, and in the case of 4 to variable amounts of dibenzofuranone 6. The 2‐arylcyclohexanedione 9, on the other hand, is isolated from the reaction of 3 and bisacetal 11 catalyzed by ZnCl2 (Scheme 2). Treatment of the adduct 8 with (CH3O)2SO2/K2CO3 results in cleavage of teh heterocyclic ring by a retro‐Michael reaction affording teh liable enone 23 which was further transformed to 24 by selective hydrogenation. The 8‐acetoxydibenzofuranone 22 is obtainable from 8 by acid treatment and acetylation (Scheme 4). The reactions of the silylenol ethers 27 and 35 with quinone monoacetals were very complex (Scheme 6). The desired arylcyclohexanone derivatives 28 and 36 were formed in very low yields. Under certain conditions (elevated temperature or strong Lewis acids as catalysts), single‐electron transfer or addition to the ene‐acetal rather than to the enone function of the quinone monoacetals became predominant. In connection with this study, the sensitive 2‐methoxy‐p‐benzoquinone monoacetals 15 (Scheme 3) and 29 (Scheme 6) have been prepared and characterized.
Experiments on the total synthesis of Lysolipin I. Part III. Preparation and transformations of substituted 1,2,3,4‐Tetrahydrodibenzofuran‐1‐ones
Authors: Duthaler Rudolf O. , Scherrer Veronica
Published: December 2004

1,2,3,4‐Tetrahydrodibenzofuran‐1‐ones were obtained by Michael addition of 1,3‐cyclohexadione (2) to o‐benzoquinone (3) and to p‐benzoquinones 8 and 11 (Scheme 2). In addition to the expected 7,8‐disubstituted adduct 14, the ZnCl2‐catalyzed reaction of dione 2 with methoxy‐p‐benzoquinone (11) afforded a small amount of the 6,8‐disubstituted regio‐isomer 13 (Scheme 2). The projected cleavage of these dibenzofuranones to 3‐methoxy‐2‐phenyl‐2‐cyclohexenone 22 could be effected by treatment with NaOH followed by methylation (Scheme 3). Attempted acetalization of such dibenzofuranones resulted in a retro‐Claisen‐type cleavage, giving the benzofuryl‐butyrate 16. Other transformations include reduction of the ketone, of the C(4a)=C(9b) bond, and alkylation with Li‐ethoxyacetylide (Scheme 3). Oxidation of 8‐hydroxy‐7‐mehoxydibenzofuran derivatives led to o‐quinones instead of the desired ring cleavage to p‐quinones (Scheme 4).
Photoreaction of (RS,SR)‐3‐Phenyl‐6‐hepten‐2‐ol. Benzene‐Olefin Cycloadditions as a Synthetic Route to [5.5.5.5] Fenestranes. Part III
Authors: Mani Jürg , Cho Jung‐Hyuck , Astik Rameshchandra R. , Stamm Erich , Bigler Peter , Meyer Veronika , Keese Reinhart
Published: December 2004

Irradiation of (RS,SR)‐3‐Phenyl‐6‐hepten‐2‐ol (3n) gave the photoproducts 6n–10n. Some reactions of 6n and 8n are reported. The regio‐ and diastereoselectivity observed in the photoreaction of substituted 5‐phenylpentenes is discussed with respect to conformational preferences of the compounds to be irradiated.
The Reaction of 4‐Hydroperoxy‐2,4,6‐trimethylcyclohexa‐2,5‐dienone with Acetaldehyde. Formatino of the Bis(peroxyacetal)
Authors: Jefford Charles W. , Bernardinelli Gérald , McGoran Ernest C.
Published: December 2004

The reaction of 4‐hydroperoxy‐2,4,6‐trimethylcyclohexa‐2,5‐dienone with acetaldehyde using trimethylsilyl trifluoromethanesulfonate as catalyst gives 1,1′‐bis[(1,3,5‐trimethyl‐4‐oxo‐2,5‐cyclohexadienyl) peroxy]diethyl ether (7) in 70% yield. The structure of this unusual acetal was determined by X‐ray analysis.
Approaches to the synthesis of cytochalasans. Part 7. Synthesis of some building blocks for the construction of the macrocyclic moiety
Authors: Wallach Daniel , Csendes Ivan G. , Burckhardt Peter E. , Schmidlin Tibur , Tamm Christoph
Published: December 2004

The synthesis of ethyl (2E, 4E, 8R)‐8‐methyl‐10‐[(2H‐tetrahydropyran‐2‐yl)oxy]‐2,4‐decadienoate (11), methyl (2E, 8R)‐8‐methyl‐10‐[(2H‐tetrahydropyran‐2‐yl)oxy]‐2‐decenoate (16), synthons for the construction of the macrocyclic moieties of the cytochalasins A, B and F, and of (3R)‐[7‐(1,3‐dioxolan‐2‐yl)‐3‐methylheptyl]triphenyl‐phosphonium bromide (24), a C8‐building block for deoxaphomin, proxiphomin and protophomin is described. In all instances (+)‐(R)‐pulegone (5) served as starting material.
Approaches to the synthesis of cytochalasans. Part 8. Further transformations and optical resolution of the tetrahydroisoindolinone subunit
Authors: Schmidlin Tibur , Wallach Daniel , Tamm Christoph
Published: December 2004

The bicycle aldehyde 7 was prepared from the hydroxy ester 3 for the attachment of teh macrocyclic moiety of the cytochalasans. To protect the C(6),C(7)‐double bond the intermediates 8, 9 and 13 were transformed into the epoxides 10, 11 and 14, respectively. Treatment of 10 and 11 with Al(i‐PrO)3 gave the allylic alcohol 12. Protection of the olefinic double bond was also effected by hydroxylation with OsO4. The triol 17 obtained from 3, after acetalization of 18, was oxidized to the aldehyde 20. Attachment of the ylide of the phosphonium salt 1 to 20 gave 24, an intermediate of proxiphomin (2). Removal of the C(6), C(7)‐diol group was achieved via the thiocarbonate 23.
Milde alkalische Hydrolyse von Aconitin
Authors: Katz Alfred , Rudin Hanspeter
Published: December 2004

Mild Alkaline Hydrolysis of Aconitine

Hydrolysis of aconitine (1) with 0.04N K2CO3 in 90% MeOH at room temperature yields, besides the alkamine aconine 3 considerable amounts of 8‐O‐methylaconine (6) and smaller quantities of desbenzoyl‐pyroaconitine (4) and 16‐epi‐desbenzoyl‐pyroaconitine (5). Better yields of 4 and 5 are obtained when heating a solution of aconitine in 0.04N K2CO3 in 90% EtOH.
Synthese eines 2,5,7,10‐substituierten 1,6‐Methano[10]annulens, seine Methylierung, Ätherspaltung und Deprotonierung
Authors: Neidlen Richard , Hartz Georg
Published: December 2004

Synthesis of a 2,5,7,10‐Substituted 1,6‐Methanol[10]annulene, its Methylation, Ether Cleavage; and Deprotonation

The synthesis of 2,7 ‐di(tert ‐butoxy)‐1,6‐methanol[10]annulene derivatives 2 and 3 are described. Methylation of 3 gave 4, and 4 was transformed, on treatment with p‐toluene sulfonic acid, to the salt 5. Basic reagents deprotonated 5; the resulting solution was analyzed by 1H‐NMR spectroscopy.
Herstellung enantiomerenreiner cis‐ oder trans‐konfigurierter 2‐(tert‐Butyl)‐3‐methylimidazolidin‐4‐one aus den Aminosäuren (S)‐Alanin, (S)‐Phenylalanin, (R)‐Phenylglycin, (S)‐Methionin und (S)‐Valin
Authors: Naef Reto , Seebach Dieter
Published: December 2004

Preparation of the Enantiomerically Pure cis‐ and trans‐Configurated 2‐(tert‐Butyl)‐3‐methylimidazolidin‐4‐ones from the Amino Acids (S)‐Alanine, (S)‐Phenylalanine, (R)‐Phenylglycine, (S)‐Methionine, and (S)‐Valine

In contrast to α‐hydroxy and α‐mercapto carboxylic acids, simple α‐amino acids do not form acetal‐type derivatives (2, X = NH) with pivalaldehyde. For the generation of amino‐acid‐derived chiral, nonracemic enolates (cf. 3), and hence, for the α‐alkylation of amino acids without racemization and without an external chiral auxiliary, the imidazolidinones 12–14 were prepared diastereoselectively. To this end, the methyl or ethyl esters of amino‐acid hydrochlorides were first converted to N‐methylamides of amino acids which in turn were condensed with pivalaldehyde to give (neopentylidenamino)amides (11). These Schiff bases could be cyclized either to trans‐or to cis‐imidazolidinones (12, 14 and 13, respectively), which were obtained in enantiomerically pure form after recrystallization. The enantiomeric purities were confirmed by HPLC with chiral stationary phases or by 1H‐NMR spectroscopy in the presence of chiral shift reagents. The configurations (cis, trans) were assigned by NOE measurements on 300‐ or 360‐MHz 1H‐NMR spectrometers.
Synthèse électrochimique de complexes Ni(O)‐diazabutadiène
Authors: Coulombeix José , Emmenegger Franz‐Peter
Published: December 2004

Electrochemical Synthesis of the Ni(O)‐Diazabutadiene Complexes

The electrochemical reduction of Ni salts in the presence of diazabutadiene ligands (DAB = RNCHCHNR, R = t‐Bu, o‐xylyl, p‐anisoyl, p‐tolyl) has been studied in DMF by cyclic voltammetry and rotating disc polarography. In solutions containing DAB and halide X−, Ni(II) can be reduced to Ni(DAB)2, and the features of this reduction agree with a mechanism where the second DAB replaces X− in the coordination sphere of Ni only after its reduction to Ni(O). Rather concentrated (≃ 0.1M) solutions of NiBr2 · DME and DAB in DMF have been electrolyzed without a supporting electrolyte, making the isolation of the product Ni(DAB)2 particularly easy. Thus, gram quantities of Ni(DAB)2 can be conveniently prepared within a few hours.
Molluscicidal Saponins from Talinum tenuissimum DINTER
Authors: Gafner Frank , Msonthi Jerome D. , Hostettmann Kurt
Published: December 2004

Two new saponins, β‐D‐glucopyranosyl 3‐O[O‐βD‐xylopyranosyl‐(1→3)‐O‐(β‐D‐glucopyranosyluronic acid)]oleanolate (1) and 3‐O‐[O‐β‐D‐xylopyranosyl‐(1→3)‐O‐(β‐D‐glucopyranosyluronic acid)]oleanolic acid (2), have been isolated from the tubers of Talinum tenuissimum. The structures have been established mainly by 13C‐NMR and FAB‐MS. The monodesmosidic saponin 2 exhibits very strong molluscicidal activity against the schistosomiasis‐transmitting snail Biomphalaria glabrata.
Propellanes. Part LXXX. Baeyer‐Villiger Oxidation of [4.3.3]Propellane‐8,11‐dione
Authors: Ashkenazi Pnina , Kapon Moshe , Piantini Umberto , Philipsborn Wolfgang Von , Ginsburg David
Published: December 2004

Oxidation of the title compound with m‐chloroperbenzoic acid affords a keto‐lactone, two bis‐lactones and a bis‐spirolactone, in varying amounts depending upon the reaction conditions. The structures were established by means of X‐ray diffraction, 1H‐ and 13C‐NMR spectroscopy.
Synthese substituierter Cyclononatetraene
Authors: Sabbioni Gabriele , Neuenschwander Markus
Published: December 2004

Synthesis of Substituted Cyclononatetraenes

In the course of an exploration of possible synthetic pathways to nonafulvenes, a series of 1‐substituted cyclononatetraenes (CNT) 4b–1 have been prepared in yields of about 60%. Their structures follow from spectroscopic data as well as from the quantitative valence isomerisation to 1‐endo‐substituted cis‐3a, 7a‐dihydroindenes 8. Both all‐cis‐CNT− 1 and cis,cis,cis,trans‐CNT− 2 have been used as nucleophiles. Whereas 2 is normally more nucleophilic than 1, the yield of cyclononatetraenes 4 prepared with 2 may be reduced due to by‐products such as 9 and 10.
Polar effects. Part 12. Inductivity and carbon participation in the solvolysis of 4‐substituted 2‐adamantyl arenesulfonates
Authors: Grob Cyril A. , Wittwer Gerhard , Rama Rao K.
Published: December 2004

The rate constants (log k) for the solvolysis of 4e‐substituted 2e‐ and 2a‐adamantyl p‐nitrobenzenesulfonates 14 and 15, respectively, in 80% EtOH correlate linearly with the respective inductive substituent constants σ. Therefore, relative rates are controlled by the I effect of the substituents at C(4). The derived reaction constants, or inductivities, ρI of −0.80 and −0.64 for the series 14 and 15, respectively, are far smaller than those previously determined for 6‐substituted 2‐norbornyl and 2‐bicyclo[2.2.2]octyl sulfonates, in which the partial structure containing the substituent and the leaving group is the same. The ratio of the retained and inverted adamantanols obtained upon hydrolysis of the series 14 falls from 2.85 for R = CH3 to ca. 1 for R = CN, i.e. as the substituent at C(4) becomes more electron‐attracting. In the 2a‐series 15 this ratio is uniformly higher. These findings confirm that the 2‐adamantyl cation is weakly bridged and that through‐space induction in carbocations involves graded bridging of the cationic center by neighboring C‐atoms.
Conjugated Biradical Intermediates: Spectroscopic, Kinetic, and Trapping Studies of 2,2‐Dimethyl‐1,3‐perinaphthadiyl
Authors: Hasler Erich , Gassmann Ernst , Wirz Jakob
Published: December 2004

The biradical 2,2‐dimethyl‐1,3‐perinaphthadiyl (a) was generated from two different precursors, the naphthocyclopropane 1 and the azo compound 2, and from each by three different pathways (pyrolysis, direct photolysis, and triplet sensitization, Scheme 1). The combined evidence from flash photolysis, low‐temperature spectroscopy, and product analyses provides a detailed mechanistic picture of the formation and decay of this reactive intermediate which is persistent at 77 K in the triplet ground state (3a) and rather long‐lived (400 μs) at room temperature. When formed in its lowest singlet state (1a), the biradical is too short‐lived to undergo intersystem crossing to 3a or bimolecular reactions. Thus, 3a is formed exclusively from the excited triplet state of the precursor compounds, 31* or 33*. The monomolecular decay of 3a is retarded by the spin barrier; 3a initiates the polymerization of acrylonitrile and is trapped by 3O2.
Aromatic nucleophilic substitution. Part 2. Preparation of novel 3‐substituted xanthone and thioxanthone derivatives
Authors: Fischer Walter , Kvita Vratislav
Published: December 2004

The novel 3‐nitro‐9‐oxo‐9H‐xanthene‐ and 3‐nitro‐9‐oxo‐9H‐thioxanthene‐l‐carboxylic acids 2a–d were prepared by intramolecular acylation of 3‐aryloxy‐ and 3‐arylthio‐5‐nitrophthalic anhydrides 1 (Scheme). The 3‐nitro group was readily substituted by O‐ and S‐nucleophiles and halide and azide ions to give a range of 3‐substituted thioxanthone derivatives 3 with varied λmax.
Chinazolincarbonsäuren. VII. Mitteilung. Ein einfacher Zugang zu (4‐Oxo‐3,4‐dihydrochinazolin‐3‐yl)‐alkansäuren, (4‐Oxo‐3,4‐dihydro‐1,2,3‐benzotriazin‐3‐yl)‐alkansäuren und deren Estern
Authors: Süsse Manfred , Johne Siegfried
Published: December 2004

Quinazoline Carboxylic Acids. An Easy Route to (4‐Oxo‐3,4‐dihydroquinazolin‐3‐yl)‐alkanoic Acids, (4‐Oxo‐3,4‐dihydro‐1,2,3‐benzotriazin‐3‐yl)‐alkanoic Acids and their Esters

A new route was found for the synthesis of (4‐Oxo‐3,4‐dihydroquinazolin‐3‐yl)‐alkanoic acids (8) and (4‐Oxo‐3,4‐dihydro‐1,2,3‐benzotriazin‐3‐yl)‐alkanoic acids (6) by cyclization of the N‐(2‐aminobenzoyl)amino acids 5 with HCOOH or HNO2. 2H‐3,1‐Benzoxazine‐2,4(1H)‐diones (1) reacted with glycine esters to 2, which were cyclized by HNO2 to the esters 4. Ester 4 was hydrolyzed to 6 (X = CH2). Diones 1 reacted with the most common amino acids (as the ammonium salt of tertiary amine) to amino‐alkanoic acids 5, which were cyclized with orthoformate to 7 or 8 depending on the reaction conditions.
Reactivité de composés carbonylés avec des cétènes en présence d'alkoxydes de titane ou de zirconium. 3e communication
Authors: Hofer Roger , Evard Daniel , Jacot‐Guillarmod André
Published: December 2004

Reactivity of Carbonyl Compounds with Ketenes in the Presence of Titanium or Zirconium Alkoxides

The reaction of ketene or dimethylketene with aldehydes or ketones in the presence of titanium or zirconium alkoxides gives essentially β‐hydroxyesters. By polyinsertion of ketene and aldehydes in the TiO bond, di‐ tri‐ and tetraesters are formed. An excess of ketene produces acetyl derivatives of esters and 6‐alkyl‐3,4,5,6‐tetrahydro‐2,4‐pyrandiones.
Totalsynthese von (–)‐Norgestrel
Authors: Baier Helmut , Dürner Gerd , Quinkert Gerhard
Published: December 2004

Total‐Synthesis of (–)‐Norgestrel

(–)‐Norgestrel (1a) or (–)‐norethindrone (1b), two active progestational ingredients of currently used contraceptives have been synthesized stereoselectively. Compound 1a has been obtained starting from m‐cresol methyl ether, dimethyl malonate, and (E)‐1,4‐dibromo‐2‐butene. The steroid skeleton has been constructed using an intramolecular Diels‐Alder reaction of an o‐quinodimethane derivative preceeded by a photo‐enolization of an appropriate methyl‐substituted acetophenone derivative. Chirality has been introduced at an early stage during an ScN′ reaction (cf. Scheme 1). Compound 1b has been obtained similarly using a previously reported mixture of the enantiomerically pure constitutional isomers 18b/19b (cf. Scheme 3).
The Synthesis of (±)‐11‐Deoxydaunomycinone via Regioselective Tandem Diels‐Alder Reactions
Authors: Tornare Jean‐Mare , Vogel Pierre
Published: December 2004

The 2,5‐dimethylidene‐3,6‐bis[(Z)‐(2‐nitrophenyl)sulfenylmethylidene]‐7‐oxabicyclo[2.2.1]heptane (13) can be used to generate polyfunctional and multicyclic molecules with high regio‐ and stereoselectivity via two successive Diels‐Alder additions using two different dienophiles. This principle has been applied to the synthesis of (±)‐11‐deoxydaunomycinone (7), the aglycone of an important antitumor drug. The 2,3‐didehydroanisole adds to 13 and gives the monoadduct 14 with high regioselectivity. No trace of bis‐adduct is observed. The 1,4‐epoxy‐1,2,3,4‐tetrahydro‐5‐methoxy‐3‐methylidene‐2‐[(Z)‐(2‐nitrophenyl)sulfenylmethylidene]anthracene (15) obtained on treating 14 with K2CO3 adds to methyl vinyl ketone to give [(1RS, 2SR, 5RS,12RS)‐5,12‐epoxy‐1,2,3,4,5,12‐hexahydro‐7‐methoxy‐1‐(2‐nitrophenyl)sulfenyl‐2‐naphthacenyl]methyl ketone (16) with high regio‐ and stereoselectivity. The acid‐catalyzed 7‐oxanorbornadiene→phenol rearrangement of 16 is regioselective and gives (5‐acetoxy‐3,4‐dihydro‐7‐methoxy‐2‐naphthacenyl) methyl ketone (20) which was transformed into (±)‐7,11‐dideoxydaunomycinone ((±)‐24), a known precursor of 7.
Physicochemical Properties of Deuterated Compounds. 7th Communication. The H/D exchange between hydrogen and methane over Ni Catalyst
Authors: Poretti Marc , Gäumann Tino
Published: December 2004

The isotopic exchange between hydrogen and methane over Ni catalyst has been studied as a function of temperature, isotopic substitution, and ratio of hydrogen to methane. The experimental results can be described by means of a model in which methane is adsorbed either as methyl or as methylene. The adsorbed species undergo one or several exchanges. The four required parameters are adjusted to the experimental results. The exchange of partially deuterated methane with H2 or D2 allowed us to study the isotopic effect on the adsorption and the exchange processes.