bluuebunny/crossref_metadata_2025 huggingface dataset:
The Photoenolization of 2‐Methylacetophenone and Related Compounds
Authors: Haag Roland , Wirz Jakob , Wagner Peter J.
Published: December 2004

A reinvestigation of 2‐methylacetophenone (1) by ns flash photolysis has provided detailed evidence for the reaction sequence of photoenolization. The triplet reaction proceeds adiabatically from the lowest excited triplet state of the ketone, 3K (1), to the enol excited triplet state, 3E (1), which decays both to enol and ketone ground state. The Z‐ and E‐isomers of the photoenol, Z‐E (1) and E‐E (1) are formed in about equal yield by the triplet pathway, while direct enolization from the lowest excited singlet state of 1 yields (predominantly) the Z‐isomer. Intramolecular reketonization from Z‐E (1) to 1 proceeds at a rate of ca. 108s−1 in cyclohexane, but can be retarded to ca. 104s−1 in hydrogen‐bond‐acceptor solvents. The proposed mechanism is summarized in Scheme 1 and rationalized on the basis of a state correlation diagram, Scheme 2. 3,3,6,8‐Tetramethyl‐1‐tetralone (2) was used as a reference compound with fixed conformational position of the carbonyl group, and some results from a brief investigation of 2,4‐dimethylbenzophenone (3) are also reported.
Der 2‐Trimethylsilyläthyl‐Rest als selektiv abspaltbare Carboxy‐Schutzgruppe
Authors: Sieber Peter
Published: December 2004

The 2‐trimethylsilylethyl residue, a selectively cleavable carboxyl protecting group

In a search for new carboxyl protecting groups suitable for use in peptide synthesis, 2‐trimethylsilylethyl esters [‐COOCH2CH2Si(CH3)3] of several N‐protected amino acids have been prepared. These esters can be synthesized in good yields from Na‐benzyloxycarbonyl‐amino acids and 2‐trimethylsilylethanol with dicyclohexylcarbodiimide in the presence of pyridine. They are stable under a wide variety of conditions used during coupling and work‐up in peptide synthesis. For removal the 2‐trimethylsilylethyl group is readily cleaved by fluoride ions, preverably using a quaternary ammonium fluoride in dimethylformamide. Some side reactions which occurred during the removal of the 2‐trimethylsilylethyl group are discussed.

Special attention has been paid to the question of racemization during the treatment with fluoride ions. No. evidence of racemization was found in any of the cases examined.
Transition metal complexes with bidentate ligands spanning trans‐positions. IV. Preparation and properties of some rhodium and iridium complexes of 2,11‐bis(diphenylphosphinomethyl)benzo [c]phenanthrene
Authors: Reed Frank J. S. , Venanzi Luigi M.
Published: December 2004

The bidentate phosphine 2,11‐bis(diphenylphosphinomethyl)benzo [c]phenanthrene (1) has been used to prepare the mononuclear, square planar complexes trans‐[MX(CO)(1)] and trans‐[M(CO)(CH3CN)(1)][BF4] (M = Rh, Ir; X = Cl, Br, I, NCS). It is found that the tendency of these complexes to form adducts with CO, O2 and SO2 is significantly lower than that of the corresponding Ph3P complexes. The oxidative‐addition reactions of complexes trans‐[IrX (CO) (1)] with hydrogen halides give the six‐coordinate species [IrHX2(CO) (1)]. The complexes [IrH2I (CO) (1)] and [IrH2L (CO) (1)] [BF4] (L = CO and CH3CN) have been obtained from hydrogen and the corresponding substrates. The model compounds trans‐[MCl (CO) (Ph2PCH2Ph)2] (M = Rh, Ir), trans‐[Ir (CO) (CH3CN) (Ph2PCH2Ph)2] [BF4], [IrHCl2(CO)(Ph2PCH2Ph)2] and [IrH2(CO)2(Ph2PCH2Ph)2] [BF4] have been prepared and their special parameters are compared with those of the corresponding complexes of ligand 1. The influence of the static requirements of this ligand on the chemistry of its rhodium and iridium complexes is discussed.
Synthesis of 1‐ and 5‐Aryl‐2,4‐benzothiazepines. 25th Communication on Seven‐membered Heterocycles
Authors: Bream John B. , Schmutz Jean
Published: December 2004

α‐Aryl‐o‐xylyl dibromides 1 reacted with thioureas to give the mono‐isothiouronium salts 2, bis‐isothiouronium salts 4 being formed as by‐products in some cases. Compounds 2, which readily reacted with water or alcohols to form 3, were cyclized with Na2CO3 in anhydrous acetone to yield 5‐aryl‐2,4‐benzothiazepines 5, 6 and 7, but the 2′‐chlorophenyl‐derivative 21 exceptionally cyclized to the cyclobutene 20. The 1‐aryl‐2,4‐benzothiazepines 14, 15 and 16 were prepared unequivocally by acid‐catalysed cyclizations of thioureas 13 and 19.
Crystal and Molecular Structure of trans‐[(2‐chlorophenyl)‐1‐benzocyclobutenyl]‐1,4,5,6‐tetrahydro‐ 2‐pyrimidyl‐sulfide
Authors: Weber Hans Peter , Petcher Trevor J. , Loosli Hans Rudolf
Published: December 2004

Kristalline und molekulare Struktur von trans‐[(2‐chlorphenyl)‐1‐benzocyclobutenyl]‐(1,4,5,6‐tetrahydro‐ pyrimidyl)‐sulfid.

Zur Abklärung von Konstitution und Konfiguration der Titelverbindung wurde eine Röntgenstrukturanalyse durchgeführt. Die Kristalle gehören zur monoklinen Raumgruppe C2/c, a = 17.221 (6), b = 7.846 (2), c = 25.031 (8) Å, β = 104.55 (2)°, Z = 8. Die Struktur wurde mit 2188 signifikanten Daten bis R = 0.055 verfeinert. Die mittlere Standardabweichung der Lagekoordinaten der C‐ und N‐Atome beträgt 0.003 Å.
Chemical selectivities disguised by mass diffusion. IV. Mixing‐disguised nitrations of aromatic compounds with nitronium salts. 4th communication on the selectivity of chemical processes
Authors: Nabholz Felix , Rys Paul
Published: December 2004

The disguise of the intrinsic selectivity of competitive, consecutive reaction systems by the mixing process is demonstrated experimentally using the fast nitration of a number of aromatic compounds with nitronium salts in nitromethane. The measured product distributions were compared with the distributions predicted from our mixing‐reaction model developed previously [2] [4]. This comparison enabled the relative intrinsic rate constants for the second nitration step of the aromatic compounds investigated to be determined.
Trimers of Aliphatic Monosubstituted Ketenes from Acid Chlorides
Authors: Osman Maged A. , Seibl Josef , Pretsch Erone
Published: December 2004

A new synthesis of trimers of aliphatic monosubstituted ketenes from acid chlorides is described. The structures of the products are shown to be alkyl substituted γ‐hydroxy‐α‐pyrones by NMR. and mass spectroscopy. 13C‐NMR. studies indicate, that an acetanilide/aluminium‐chloride complex catalyses the formation of the products.
Thermisch und photochemisch induzierte intramolekulare, 1,3‐dipolare Cycloadditionen von 5‐(2‐Allyloxyphenyl)‐2‐phenyltetrazol. Vorläufige Mitteilung. 54 Mitteilung über Photoreaktionen
Authors: Meier Hansruedi
Published: December 2004

Thermal and Photochemically Induced Interamolecular 1,3‐Dipolar Cycloaddition Reactions of 5‐(2‐Allyloxyphenyl)‐2‐phenyltetrazole

The title compound 5 is easily obtained by a recently described procedure (Scheme 2). The tetrazole 5 reacts at 165–170° or on irradiation at room temperature to yield 2‐phenyl‐3,3a‐dihydrochromano[4,3‐c]pyrazole (7, Scheme 3), which probably arises by intramolecular [3+2]‐cycloaddition of the intermediate nitrilimine. Dehydrogenation of 7 with chloranil leads to 2‐phenylchromano[4,3‐c]pyrazole (8, Scheme 3).
Stickstoffhaltige Dieisen‐hexacarbonyl‐Komplexe aus 3‐Phenyl‐2H‐azirinen
Authors: Nakamura Yushin , Bachmann Kurt , Heimgartner Heinz , Schmid Hans , Daly John J.
Published: December 2004

Nitrogen‐containing diiron‐hexacarbonyl complexes from 3‐phenyl‐2H‐azirines

Reaction of 2,2‐dimethyl‐3‐phenyl‐2H‐azirine (1) with diiron‐enneacarbonyl yields as an insertion product, and in addition to other products, the diiron‐hexacarbonyl complex 2 (Scheme 1), whose structure was derived from spectral data, in particular 13C‐NMR.‐data (Table 1). With trimethylamine oxide in benzene, 2 is converted into the urea derivative 3, and yields with cerium (IV) ammonium nitrate the nitrate 4 (Scheme 1). The analogous complexes 6 and 9 have been obtained by irradiation of 1‐phenyl‐vinyl azide (5) and ironpentacarbonyl (Scheme 1) and from vinyl isocyanate (8) and diiron‐enneacarbonyl at 40° (Scheme 2), respectively.

The azirine 1, an acetylenic compound and diiron‐enneacarbonyl in benzene react to give complexes of type 10 as the main product (Scheme 3). The structure of complex 10 has been established by X‐ray single crystals analysis. On the 13C‐NMR. time scale the carbonyl groups of compound 10 show a fluxional behaviour: below −50° the CO‐groups of one of the two Fe(CO)3‐groups undergo intranuclear exchange, above −50° the CO‐groups of both Fe(CO)3‐groups undergo intranuclear exchange.

Tentative reaction mechanisms for the formation of the complexes of type 2 and 10 are formulated in Schemes 5, 6 and 7.
Tieftemperatur‐Photochemie von 2‐Alkyl‐indazolen
Authors: Heinzelmann Willy
Published: December 2004

Photochemistry of 2‐Alkyl‐indazoles at Low Temperatures

2‐Alkyl‐indazoles 1 undergo a variety of photoreactions (Scheme 1) which have been shown to proceed via excited singlet states of the neutral and protonated indazole, respectively [6]. The quantum yields of these reactions decrease with decreasing temperature; around 150°K the 2‐alkyl‐indazoles are practically reactivity of both neutral and protonated indazoles is observed (Fig. 3), yielding 2‐amino‐acylbenzenes 7, obviously formed by hydrolysis of the corresponding imines 6 (Scheme 2). Yellow ‘intermediates’ (Figs. 1 and 2) which are observable only at low temperatures upon irradiation of neutral indazoles but are rather stable even at room temperature in acid solutions, could be identified as quinoid tautomers 8 of the imines (Scheme 4). It is assumed that the formation of the imines 6 proceeds via an arylnitrene or arylnitrenium‐ion 13 (Scheme 5) and subsequent hydrogen abstraction, the nitrenes being formed directly in their triplet ground‐state from the triplet state of the indazoles.
Photochemische Reaktionen. 95. Mitteilung. Zur Photochemie konjugierter Epoxy‐enone: Die UV.‐Bestrahlung von 9‐Isopropyl‐6‐methyl‐9, 10‐epoxybicyclo [4.4.0] dec‐1‐en‐3‐on
Authors: Dey Ashesh Kumar , Wolf Hans Richard
Published: December 2004

The Photochemistry of Conjugated Epoxy‐enones: Photolysis of 9‐Isopropyl‐6‐methyl‐9,10‐epoxybicyclo [4.4.0]dec‐l‐en‐3‐on

The title compound 1 undergoes on π, π*‐excitation vinylogous β‐cleavage of the C(γ), O‐bond and isomerizes to the unsaturated 1, 5‐diketone8(58%) and the tricyclic diketone9 (14%). On n, π*‐excitation, however, 1 undergoes only desoxygenation to the dienone 7 (ca. 15%) besides polymerization. UV.‐irradiation of 1 (λ ≥ 347 nm) in the presence of tributyl‐stannane gives 7 in 85% yield; in the presence of tributylstannane‐d1 1 yields 13, the deuterated analogon of 7 (85% yield; d1 ca. 50%); 7 has been proven to be stable on π, π* ‐ as well as on n, π*‐excitation.
Reduction of 5,6‐Dimethylidene‐exo‐2,3‐epoxynorbornane with Metal Hydrides. Efficient syntheses of 6‐methyl‐5‐methylidene‐anti‐3‐ nortricyclanol and of 2,3‐dimethylidene‐anti‐7‐norbornanol
Authors: Chollet André , Vogel Pierre
Published: December 2004

5,6‐Dimethylidene‐exo‐2,3‐epoxynorbornane (1) is reduced slowly by LiAlH4 in boiling tetrahydrofuran (THF) and furnishes a mixture of 5,6‐dimethylidene‐exo‐2‐norbornanol (2), 2,3‐dimethylidene‐anti‐7‐norbornanol (3) and principally 6‐methyl‐5‐methylidene‐anti‐3‐nortricyclanol (4). The yield of 4 is the highest for low initial concentrations of LiAlH4; it decreases in favour of alcohols 2 and 3 at high concentration of LiAlH4. The reduction of 1 with AlH3 in THF yields 3 as the major product, thus revealing an efficient synthesis of 7‐substituted‐2, 3‐dimethyl‐idenenorbornane derivatives. No alcohol 2could be isolated by LiEt3BH reduction of 1. LiAlD4 reduces 1 into the monodeuterated alcohols 2‐d, 3‐d and 4‐d. The deuterium label is found in the endo‐position at C (3) in 2‐d, in the exo‐position at C(5) in 3‐d and in the methyl group of the tricyclic alcohol 4‐d. Mechanistic limits for the formation of 2, 3 and 4 are discussed briefly.
Vibrational Spectra of Anhydrous Lanthanum, Europium, Gadolinium, and Dysprosium Nitrates and Oxinitrates
Authors: Bünzli Jean‐Claude G. , Moret Etienne , Yersin Jean‐Robert
Published: December 2004

IR. and Raman spectra of LnONO3 (50–4,000 cm−1, LnLa, Gd, Eu, and Dy) are reported and discussed. The low frequency region of the spectra reflects the cubic structure of these compounds. The dimensions of the cubic unit cells determined by X‐Ray powder diagrams are: 12.81 ± 0.05 Å for EuONO3, 12.69 ± 0.05 Å for GdONO3, and 12.67 ± 0.05 Å for DyONO3. The vibrational frequencies of the nitrato group are consistent with a bidentate nitrate of C2v symmetry. The synthesis of anhydrous Ln (NO3)3 (LnLa, Gd, Eu, and Dy) by dehydration of the corresponding penta‐ or hexahydrates is described. The IR. and Raman spectra (50‐4,000 cm−1) are analysed. Splitting of the bands point to a complex structure of these compounds. All six vibrational modes of the nitrato group are observed and the data are again consistent with bidentate NO−3 moieties. Finally, an analytical control of the purity of Ln (NO3)3 is suggested.
Synthese und Chiralität von (5S, 6R)‐5,6‐Epoxy‐5,6‐dihydro‐β,β‐carotin und (5R, 6R)‐5,6‐Dihydro‐β,β‐carotin‐5,6‐diol, einem Carotinoid mit ungewöhnlichen Eigenschaften
Authors: Eschenmoser Walter , Eugster Conrad Hans
Published: December 2004

Synthesis and Chirality of (5S,6R)‐5,6‐Epoxy‐5,6‐dihydro‐β,β‐carotene and (5R,6R)‐5,6‐Dihydro‐β,β‐carotene‐5,6‐diol, a Compound with Unexpected Solubility Characteristics

Wittig‐condensation of azafrinal (1e) with the phosphorane derived from 7 leads to a (1:3)‐mixture of (E)‐9′‐ and (Z)‐9′‐β,β‐carotene‐diol 3, from which pure and optically active 3 ((5R,6R)‐5,6‐dihydro‐β,β‐carotene‐5,6‐diol) has been isolated as bright violet leaflets, m.p. 168°. Due to the trans‐configuration of the diol moiety and to severe steric hindrance, hydrogen bonding is reduced to such an extent, that 3 behaves much more as a hydrocarbon than as a diol. There is good evidence that the so‐called ‘β‐oxycarotin’ obtained by Kuhn & Brockmann [15] by chromic acid oxidation of β, β‐carotene is the corresponding racemic cis‐diol. 3 has been converted into (5S, 6R)‐5,6‐epoxy‐5.6‐dihydro‐β,β‐carotene (4), m.p. 156°. This transformation establishes for the first time the chirality of a caroteneepoxide (without other O‐functions).

Full spectral and chiroptical data including a complete assignement of 13C‐chemical shifts for azafrin methyl ester and 3 are presented.
Studies on the Synthesis of (2R,4′R,8′R)‐α‐Tocopherol Alternative Syntheses of 2‐Chroman‐acetic Acid Intermediates
Authors: Cohen Noal , Scott John W. , Bizzaro Fred T. , Lopresti Rocco J. , Eichel Wayne F. , Saucy Gabriel , Mayer Hans
Published: December 2004

As an extension of previous studies on the total synthesis of (2R,4′R,8′R)‐α‐tocopherol (1) [1] [2], (S)‐(−)‐2‐(6‐benzyloxy‐2,5,7,8‐tetramethylchroman)acetic acid (6), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11. the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.‐3‐hydroxy‐3‐methylpent‐4‐en‐l‐yl acetate (16) giving rac. ethyl 2‐(6‐hydroxy‐2,5,7,8‐tetramethyl‐chroman)acetate (12).
Drüsenfarbstoffe aus Labiaten: Strukturen von 16 Diterpenen (Coleone und Royleanone) aus Coleus coerulescensGÜRKE
Authors: Grob Konrad , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Leaf‐gland pigments from labiatae: structures of 16 diterpenoids (coleons and royleanones) from Coleus coerulescens GÜRKE

The Abyssinian labiate Coleus coerulescens has been investigated for its leaf‐gland pigments. From the very complex mixture of abietanoic diterpenoids the following pure constituents were isolated and their structures established:

Diosphenols: coleon C (1a), 16‐O‐acetyl‐coleon C (1b), coleon W (1f);

A/B‐trans‐6, 7‐diketones: coleon D (2b), 16‐O‐acetyl‐coleon D (2c), coleon V (2a);

Spiro‐coleons: 7,12‐bis(O‐desacetyl)‐coleon N(3a), 12‐O‐desacetyl‐coleon N (3b), coleon O (4), 6,12‐bis (O‐desacetyl)‐coleon R (5a), 12‐O‐desacetyl‐coleon R (5b), 3‐O‐desacetyl‐3‐O‐formyl‐coleon Y (5g);

Royleanones: The abeo‐compounds 6a, 6b, and 7.

Main compounds are 3b, 5e and 5g. This is the first record of a co‐occurrence of diosphenols, 6,7‐dioxo‐coleons, spiro‐coleons and royleanones. Preliminary experiments show that solvolytic opening of the cyclopropane‐ring followed by tautomerisation, oxidation to hydroxy‐p‐benzoquinones or elimination to quinomethanes and subsequent nucleophilic attack of the solvent leads to compounds with a 2′‐substituted propyl group at C(13), thus supporting the biosynthesis of the unusual coleon E side chain.
Structural Requirements for the Enzymatic Deamination of Cytosine Nucleosides
Authors: Kreis W. , Watanabe K. A. , Fox J. J.
Published: December 2004

Thirty‐three 1‐β‐D‐pentofuranosylcytosine nucleosides were examined as substrates of crude cytidine deaminase from mouse kidney. In addition to previous observations of structural features in substrates required for enzymatic deamination [e.g., a free 3′‐hydroxyl in the ‘down’ ribo (arabino)configuration] we find that: modification of the aglycon by substitution of a fluorine atom at C(5) results in a several‐fold increase in the deamination velocity relative to cytidine whereas insertion of a methyl group at C(5) decreases the deamination velocity. This decrease is even more pronounced when a methyl group is substituted at C(6).

Though xylosylcytosine and 3′‐deoxy‐3′‐fluoro‐xylo‐C are not substrates for this deaminase, those xylofuranosylcytosines bearing good leaving groups (e.g., bromo, mesyloxy, or tosyloxy) at C(3′) are deaminated with substantial deamination velocities. This is probably due to a prior chemical reaction leading to arabino nucleosides bearing a free ‘down’ 3′‐hydroxyl.

A different situation is obtained with arabino nucleosides. Though ara‐C and 2′‐deoxy‐2′‐fluoro‐ara‐C are substrates for this deaminase, substitution of bulky groups (e.g., chloro, bromo, or mesyloxy) at C(2′) substantially decreases the susceptibility to deamination. An hypothesis is offered to explain these differences between xylo‐and arabino‐cytosines.

The presence of a free hydroxyl group at position 5′ is not essential for enzymatic deamination.
Vergleichende Untersuchung von Reaktivitäten und Ionenstrukturen beim monomolekularen Abbau isomerer Hydroxyzimtsäuremethylester unter Elektronenbeschuss
Authors: Kuster Thomas , Mändli Hugo , Robbiani Richard , Seibl Josef
Published: December 2004

Comparative investigation of reactivities and ion structures upon electron impact induced degradations of the isomeric hydroxy cinnamic acid methyl esters

By analysis of energy release data in metastable peaks it is shown that m‐ and p‐hydroxy cinnamic acid methylesters retain specific structural features upon degradation under electron impact, although their spectra are very similar and the shapes of the metastable peaks due to the initial methoxy cleavage are identical. A pronounced charge radical localization in the molecular ion is indicated. The o‐isomer is found to yield a coumarin type structure by elimination of methanol, whose further degradation by decarbonylation involves at least three different mechanisms. The resulting ion structures are different from benzofuran.
Umamidierungsreaktionen an offenkettigen Amino‐amid‐Systemen. 1. Mitteilung über Umamidierungsreaktionen
Authors: Guggisberg Armin , Dabrowski Boleslaw , Kramer Urs , Heidelberger Christian , Hesse Manfred , Schmid Hans
Published: December 2004

Transamidation Reaction of Open Chaine Amino‐amides

Amino‐amides of type 11 with a primary amino and a N, N‐disubstituted amide group isomerize under base catalysis completely to amino‐amides 16 with a secondary amino and a N‐monosubstituted amide group (see Scheme 3). Amino‐amides having a secondary instead of the primary amino group are under base catalysis in equilibrium with the corresponding isomeres (Scheme 4). The opening of the proposed tetrahedral intermediate 13 (Scheme 3) takes place under stereo‐electronic control (Schemes 5 and 6).
Umamidierungsreaktionen an cyclischen Amino‐amid‐Systemen. 3. Mitteilung über Umamidierungsreaktionen
Authors: Guggisberg Armin , Kramer Urs , Heidelberger Christian , Charubala Ramamurty , Stephanou Euripides , Hesse Manfred , Schmid Hans
Published: December 2004

Transamidation Reactions with Cyclic Amino‐amides

Lactames which are substituted at the nitrogen atom by a 3‐aminopropyl residue are transformed under base catalysis to cyclic amino‐amides enlarged by 4 ring atoms. The formed ring must be at minimum 12‐membered. Scheme 2 illustrates this result: the 8‐membered 7 is transamidated in 96% yield to the 12‐membered ring 8 (in the presence of potassium 3‐aminopropylamid in 1, 3‐propanediamine), the 9‐membered 10 to the 13‐membered ring 11 (97%) and the 11‐membered 14 to the 15‐membered ring 15. Furthermore, the 13‐membered ring 27 (Scheme 5) is transformed to the 17‐membered 28. In the case of the 15‐membered lactame 15 it is demonstrated that 14 is not formed back under the conditions of the transamidation.

Large ring lactames which are substituted at the nitrogen atom by a 3‐(alkylamino) propyl group lead under base catalysis to an equilibrium mixture, e.g. the 17‐membered 26 is in equilibrium with the 21‐membered 29. This result is similar to the behavior of the corresponding open‐chain amino‐amides [2].

Because of transannular interactions, the 11‐membered ring 2 is not stable: transamidation of the 7‐membered 1 (Scheme 1) doesn't give the expected 2, but its water elimination product 3 in small yield. The N‐tosyl derivative of 2, namely 20, is synthesized by an independent route (Scheme 3). Detosylation of 20 yields the 7‐membered 1 instead of 2. Concerning the mechanism of this interesting reaction see Scheme 4.
Kristallstruktur eines überbrückten 1,2,3‐Oxadiazolidin‐5‐ons
Authors: Bieri Jost H. , Meier Hansruedi , Heimgartner Heinz
Published: December 2004

The Crystal Structure of a Bridged 1,2,3‐Oxadiazolidin‐5‐one Derivative

3‐(2‐Allylphenyl)‐4‐phenylsydnone (1) undergoes in solution an intramolecular, 1,3‐dipolar cycloaddition reaction to give 2‐oxo‐1‐phenyl‐1,5‐methano‐1,2,4,5,6,11‐hexahydro [1,2,3] oxadiazolo [3,2‐a] cinnoline (2). The unique 1,2,3‐oxadiazolidin‐5‐one structure of this molecule has been proved by X‐ray analysis. The crystal structure has been solved by direct methods and refined by full‐matrix least squares calculations to R = 0,046. The crystal system is orthorhombic, space group Pbca, with unit cell dimensions a = 10,546, b = 15,482, c = 16,531 Å.
An Efficient Stereoselective Synthesis of (±)‐Sweroside and (±)‐secologanin aglucone O‐methyl ethers. Preliminary communication
Authors: Hutchinson C. Richard , Mattes Kenneth C. , Nakane Masami , Partridge John J. , Uskoković Milan R.
Published: December 2004

A seven‐step stereoselective synthesis of (±)‐sweroside aglucone O‐methyl ether (16a) was achieved in 27% overall yield from 1, 4‐cyclohexadiene (4) and methyl diformylacetate (5). Secologanin aglucone O‐methyl ether (18a) was then formed from 16a in 90% overall yield by a straightforward process. The key step in the synthesis was a [2+2]‐enone‐photoannelation of 4 and 5 to form the key intermediate 6 which possessed the desired cis‐fused ring configuration, and all the caron atoms needed to complete the synthesis of 16a and 18a.
Heterocyclic Spiro‐naphthalenones. Part I: Synthesis and reactions of some spiro [(1 H‐naphthalenone)‐1,3′‐piperidines]
Authors: Berney Daniel , Schuh Karlheinz
Published: December 2004

The title compounds 14–16 were obtained via an intramolecular Mannich condensation by treating 11–13 with CH2O at RT. The unsaturated ketones 14 and 15 were reduced to the allylic alcohols 18 and 19 respectively. Ring cleavage of compound 18 on treatment with 2N HCl gave the substituted aminopropanol 20. The allylic alcohols 18 and 19 were hydrogenated to 22 and 23 respectively. With CH2O, the amino‐alcohol 23 gave the methano‐naphthoxazocine 24, whereas 22 and 23, on heating in polyphosphoric acid (PPA), afforded the naphthazepines 25 and 26 respectively. With organolithium compounds, the unsaturated ketones 14 and 16 gave the teriary allylic alcohols 27–29, which were hydrogenated and dehydrated to the olefins 36–40; these were cyclized via an intramolecular alkylation to the methanodibenzo‐octahydrocyclooctapyridines 41–43. On heating in PPA, the allylic alcohol 29 was converted into the naphthazepine 44. With CH2O, the naphthol 49 gave the naphthoxazocine 50, in equilibrium with the spiro‐naphthalene‐pyrrolidinone 51 in solution. Finally, in the presence of CH2O, the naphthazepine 57 afforded the methano‐naphthazepinone 58, which, by a 4‐stage degradation, was transformed to the benzisoquinoline 62.
Über die Reaktion von Phenolen mit N‐substitutierten Maleinimiden
Authors: Renner Alfred , Forgo Imre , Hofmann Walter , Ramsteiner Klaus
Published: December 2004

The Reaction of Phenols with N‐substituted Maleinimides

Phenoxysuccinimides are formed by the base catalysed addition of phenols to N‐substituted maleinimides. In the presence of catalytic amounts of tertiary aliphatic amines yields as high as 90% are obtained. A series of adducts of mono‐and di‐phenols to mono‐ and bismaleinimides is described. Pure phenoxysuccinimides are stable compounds but the basic catalysts of their formation give rise to their decomposition into the phenolic component and oligomeric maleinimide. A nucleophilic reaction mechanism both for the formation and the decomposition is discussed. A new crosslinked addition polymer from a diphenol and a bismaleinimide with a surprisingly high heat stability is described.
Complexes of the Lighter Lanthanoid Nitrates with 15‐crown‐5 and 18‐crown‐6 ethers: Synthesis and characterization
Authors: Bünzli Jean‐Claude G. , Wessner Denis
Published: December 2004

Complexes of lanthanoid trinitrates Ln(NO3)3 with 15‐crown‐5 ether 1 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and with 18‐crown‐6 ether 2 (Ln = La, Ce, Pr, Nd) having a 1:1 stoichiometry as well as 4:3 complexes with 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. All the isolated complexes are solvent free. At 170–220° the 1:1 complexes of 2 are quantitatively transformed into 4:3 complexes. X‐Ray powder diagrams of the neodymium complexes with 2 indicate that both the 1:1 and 4:3 complexes are genuine compounds. All the 1:1 complexes show a characteristic IR. absorption band at 875–880 cm−1 absent from both the spectra of the free ligands and of the 4:3 complexes.

The spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce‐Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2.
Struktur und Eigenschaften von 5‐epi‐Flavoxanthin und 5‐epi‐Chrysanthemaxanthin
Authors: Cadosch Herbert , Vögeli Ulrich , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Structure and properties of 5‐epi‐flavoxanthin and 5‐epi‐chrysanthemaxanthin

The absolute configurations of 5‐epi‐flavoxanthin (6) and 5‐epi‐chrysanthemaxanthin (7) prepared by acid catalysed rearrangement of semi‐synthetic lutein epoxide 5 are shown to be (3S, 5S, 8R, 3′R, 6′R) and (3S, 5S, 8S, 3′R, 6′R), respectively. Contrary to published data [5] the relationship of the polyene chain and H3(18) on the dihydrofurane ring is cis for the pair of stereoisomers having a Δδ = δ (HC(7)) − δ (HC(8)) = 0,22 ppm and 3J ≡ 0. These conclusions are in full accord with the chiroptical data.
Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana ciliataL
Authors: Goetz Michel , Maniliho Faustin , Jacot‐Guillarmod André
Published: December 2004

Study of the flavonic and xanthonic compounds in the leaves of Gentiana ciliata L.

Fifteen 1,3,7,8‐oxygenated xanthones (1–15) were isolated from the leaves of Gentiana ciliata L. (genus Gentianopsis). Among these were six new glycosides: glucosyl‐1‐decussatin 6, glucosyl‐1‐gentiacaulein (8), primeverosyl‐8‐isogentiacaulein (9), glucosyl‐3‐isogentiacaulein (10), glucosyl‐1‐swertianin (12) and primeverosyl‐7‐swertianin (13). Three known flavone C‐glucosides were also found (16–18).
Ein synthetisches Modell für die Aktivstelle der Coenzym‐B12‐abhängigen Methylmalonyl‐CoA‐Mutase
Authors: Flohr Helmut , Pannhorst Wolfgang , Rétey János
Published: December 2004

A synthetic model of the active site of the coenzyme B12 dependent methylmalonyl‐CoA mutase

The synthesis of a bridged cobaloxime with a built‐in methylmalonic ester moiety is described. 2‐Brommethyl‐2‐methylmalonic acid dichloride (5) afforded upon reaction with 5‐heptin‐1‐ol (4) the corresponding diester 6. Subsequent treatment of 6 with ozone, dimethylsulfide and hydroxylamine hydrochloride led to the pentadentate ligand: 10‐brommethyl‐10‐methyl‐9, 11‐dioxo‐8, 12‐dioxa‐nonadecane‐2, 3, 17, 18‐tetraone tetraoxime (8). Reaction of 8 with cobalt (II) chloride, pyridine and sodium borohydride furnished in 7% yield the bridged cobaloxime 10, which was spectroscopically characterized. Short term irradiation of 10 in methanol caused the exchange of the axial pyridine ligand by a solvent molecule affording 10a, the structure of which has been determined by X‐ray crystallography. Long term irradiation of 10 in methanol or ethanol led to irreversible cleavage of the Co, C‐bond. Upon alkaline hydrolysis the degradation product afforded methylsuccinic acid in 82–95% yield. No incorporation of solvent protons into this product could be observed. Implications of these findings for the mechanism of the coenzyme‐B12 catalysed rearrangement of methylmalonyl‐CoA are discussed.
Die Aminoalkylierung von Carbonylverbindungen mit Hilfe der Wittig‐Reaktion
Authors: Marxer Adrian , Leutert Thomas
Published: December 2004

The Aminoalkylation of Carbonyl Compounds by the Wittig‐Reaction

The Wittig reaction would be a very suitable way to replace the carbonyl group in aldehydes and ketones by a 2‐amino‐ethylidene group if a simple and convenient method could be devised for synthesizing (2‐amino‐ethyl)triphenylphosphonium bromides 3. We have synthesized compounds of type like (2‐dialkylaminoethyl)‐, (2‐morpholino‐ethyl)‐, (2‐(1‐imidazolyl)ethyl)‐, and (2‐(1‐triazolyl)ethyl)‐triphenylphosphonium bromides (cf. Table 1), by melting at 150° the hydrobromides of triphenylphosphine and of the appropriate 2‐amino‐ethanol. The phosphonium bromides of type 3 could be converted with ketones by the Wittig reaction into the desired amino‐ethylidene compounds of type 2, e.g. 18–22 (Table 2). In the case of the reaction with 4‐chlorobenzaldehyde the steric course of the transformation was studied, and conditions were found favoring either cis or trans compounds (e.g. 27a or 27b in the reaction of the phosphonium bromide 11, cf. Table 3).
Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations
Authors: Szele Ivanka , Zollinger Heinrich
Published: December 2004

In heterolytic dediazoniations arenediazonium salts form aryl cations. The reaction rates are relatively slow; they depend only to a small extent on the solvent. It is shown that the solvents in which the heterolytic dediazoniation mechanism is predominant have a low nucleophilicity, whereas in solvents of high nucleophilicity homolysis of arenediazonium salts, i.e. the formation of aryl radicals and related intermediates, is favoured. Under comparable conditions, homolytic rates are faster than the corresponding rates of heterolysis. Homolysis is strongly enhanced by addition of nucleophiles which form relatively stable radicals by electron transfer. The ability of additives to catalyze homolysis of arenediazonium salts can be explained using the concept of a nucleofugic

In the original proposal [32] we used the word nucleofugal. In keeping with a forthcoming proposal on nomenclature in physical organic chemistry by Commission III.2 (Physical Organic Chemistry) of IUPAC we now use the word nucleofugic.

homolytic leaving group.
Schiff‐Basen aus 1,3‐Dicarbonylverbindungen und Triaminen und ihre Fe (III)‐, Co (III)‐, Ni(II)‐ und Cu(II)‐Komplexe
Authors: Flückiger Jean‐Rodolphe , Schläpfer Carl Wilhelm
Published: December 2004

Schiff bases of 1,3‐dicarbonyl compounds with triamines and their Fe(III), Co(III), Ni(II) and Cu(II) complexes

The preparation of new hexadentate ligands obtained by the reaction of cis, cis‐1,3,5‐triaminocyclohexane (tach) or 1,1,1‐tris (aminomethyl)ethane (tame) with an 2‐ethoxymethylidene‐1,3‐dicarbonyl compound as well as their Fe(III), Co(III), Ni(II) and Cu(II) complexes is reported. Fe(III) and Co(III) yield neutral complexes with an octahedral N3O3‐coordination sphere, Ni(II) and Cu(II) complexes with a square‐planar coordination‐sphere. In the later complexes one of the bidentate branches of the ligand is not deprotonated and stays uncoordinated.
Synthèse et caractérisation du phosphate de hafnium comme échangeur d'ions
Authors: Simona Marco G. , Balsenc Lucette R. , Jørgensen Christian K.
Published: December 2004

The preparation, crystalline structure, properties and behaviour of the hafnium bis (monohydrogen phosphate) monohydrate as a cationic exchanger have been studied. The crystalline product has been characterized by elemental analysis, X‐ray Powder patterns, thermal analysis, photoelectron spectrometry and infra red spectroscopy. A layered structure in which the hafnium and phosphorus atoms are disposed in such a way as to form zeolitic‐type cavities is suggested. The reversibility of the exchange with respect to sodium ions is discussed and can be related to the water content of the exchanger.
Radikalinduzierte intramolekulare 1, 4‐Verschiebung einer Formylgruppe
Authors: Kalvoda Jaroslav , Grob JÜRgen
Published: December 2004

Radical‐induced Intramolecular 1,4‐Transfer of a Formyl Group

A further example of a radical‐induced intramolecular shift of a functional group in steroids is described. In analogy to the sequence leading to the 1, 4‐transfer of cyano groups [3], 11 β‐nitrite photolysis was used to generate the appropriate C (18) radical in the 20‐hydroxy‐11 β‐nitrosyloxy‐pregnene‐21‐al 6. Intramolecular addition of the radical center to the double‐bond of the specially adjacent aldehyde function, followed by fragmentation of the intermediate cyclic alkoxy radical and subsequent oxidation lead directly to the rearranged 18‐formyl compound 10.
Electronic states of di‐t‐butylpolyacetylene radical cations
Authors: Heilbronner Edgar , Jones Taylor B. , Kloster‐Jensen Else , Maier John P.
Published: December 2004

The π‐ionization energies of the di‐t‐butylpolyacetylenes with two, three, four and five conjugated triple bonds have been determined by He (Iα) photoelectron spectroscopy. The assignment of the bands to the Π‐states of the corresponding radical cations follows from simple correlations in agreement with previous experience. The influence of the t‐butyl groups on the ionization energies is rationalized in terms of traditional, qualitative arguments assuming an inductive and/or hyperconjugative mechanism. However, a more careful analysis shows that the ‘The ‐higher‐the‐ionization‐energy‐the‐higher‐the‐alkyl‐induced‐shift’ rule is not always true.
Chemistry of Benzocyclopropenes. 1H‐and 13C‐NMR. Spectra of 2, 5‐dideuterio‐1‐fluorobenzocyclopropenium ion
Authors: Müller Paul , Pfyffer Jean , Wentrup‐Byrne Edeline , Burger Ulrich
Published: December 2004

Preparation of 1, 1‐difluorobenzocyclopropene (4) and of its 2, 5‐ and 3, 4‐dideuterio derivatives 4a and 4b is reported. Upon ionization in cold fluorosulfonic acid, 4 affords 1‐fluorobenzocyclopropenium ion (6). 1H‐ and 13C‐NMR. spectra of 4 and 6 are assigned on the basis of the data for the specifically deuteriumlabelled compounds 4a and 6a. Hydrolysis of 6a leads to 2, 5‐dideuteriobenzoic acid (7a).
Reaktionsprodukte aus 3‐Dimethylamino‐2, 2‐dimethyl‐2H‐azirin und Phthalohydrazid bzw. Maleohydrazid
Authors: Link Helmut , Bernauer Karl , Chaloupka Stanislav , Heimgartner Heinz , Schmid Hans
Published: December 2004

Reaction Products from 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine and Phthalohydrazide or Maleohydrazide

3‐Dimethylamino‐2, 2‐dimethyl‐2H‐azirine (1) reacts in dimethylformamide at room temperature with the six‐membered cyclic hydrazides 2, 3‐dihydrophthalazin‐1, 4‐dione (2) and 1, 2‐dihydropyridazin‐3, 6‐dione (15) to give the zwitterionic compounds 3 and 16, respectively (Scheme 1 and 7). The mechanism of these reactions is outlined in Scheme 1 for compound 3 (cf. also Scheme 8). The first steps are thought to be similar to the known reactions of 1 with the NH‐acidic compounds saccharin and phthalimide (cf. [1]). Instead of ring expansion to the nine‐membered heterocycle i (X=CONH, Scheme 8), a proton transfer followed by the loss of water gives 3 (Scheme 1).

The structure of the zwitterionic compounds 3 and 16 is deduced from spectral data and the reactions of these compounds (see Schemes 2, 3, 4, 6 and 7). Methylation of 3 yields the iodide 4, which is hydrolysed easily to the 2‐imidazolin‐5‐one derivative 5 (Scheme 2). Hydrolysis of 3 under basic conditions leads to the amide 6, which undergoes cyclization to 7 at 220–230° (Scheme 3). The analogous cyclization has been realized under acidic conditions in the case of 17 (Scheme 7).

Catalytic reduction of 3 yields the tertiary amine 14 (Scheme 6), whereas the reduction with sodium borohydride leads to a mixture of 14 and the 2‐imidazoline derivative 13. The alcohol 11, corresponding to the amine 14, is obtained by sodium borohydride reduction of the 2‐imidazolin‐5‐one 7 or of the amide 6 (Scheme 3). This remarkably easy reaction of 7 shows the unusual electrophilicity of the lactamcarbonyl group in this compound. The reduction of 6 to 11 is understandable only by neighbouring group participation of N (2′) in the dihydrophthalazine residue.
Reaction of aminoalcohols with butadiene catalyzed by palladium complexes. Preliminary communication
Authors: Umpleby J. David
Published: December 2004

The aminoalcohols 1, react with 2 equivalents of butadiene in the presence of catalytic quantities of bis (acetylacetonato)palladium/triphenylphosphine to give exclusively the corresponding N‐octadienyl amninoalcohols. In the presence of excess butadiene, subsequent O‐octadienylation occurs only for N‐octadienylimino‐diethanol 2g, affording the monoether 4g. O‐octadienylation of 2a‐f and 4g can be effected by the addition of molar quantities of triethylamine to the reaction mixture.
The intramolecular ene reaction: The thermal rearrangement of linalool and 1, 2‐dehydrolinalool
Authors: Pickenhagen Wilhelm , Ohloff GÜNther , Russel Ronald K. , Roth Wolfgang D.
Published: December 2004

A kinetic analysis of the thermal rearrangement of linalyl trimethylsilylether (1b) shows that four diastereoisomeric 1, 2‐dimethyl‐3‐isopropenyl‐l‐cyclopentyl trimethylsilyl ethers (2b‐5b) are formed directly in parallel first order reactions. Kinetic analysis of the thermal rearrangement of dehydrolinalool (6) shows that two diastereoisomeric 1‐methyl‐2‐methylidene‐3‐isopropenyl‐1‐cyclopentanols (7 and 8) are formed in parallel first order reactions. The configurations of 7 and 8 are determined by correlations with the known iridenols.
Thiosucres. III. Réactions du substituant (benzylthio)‐acétyle. Communication préliminarie
Authors: Tronchet Jean M. J. , Eder Hansjörg
Published: December 2004

Thiosugars. III. Some reactions of the (benzylthio)‐acetyl substituent Preliminary Communication

The (benzylthio)‐acetyl substituent as found in 6‐benzylthio‐6‐deoxy‐1, 2‐O‐isopropylidene‐3‐O‐methyl‐α‐D‐xylo‐hexofuranos‐5‐ulose (1) constitutes and useful synthon which can be transformed into ‘second generation’ synthons as, for example, the sulfylidene 10 or the chlorinated derivative 14. S‐Debenzylating C‐acylation of 10 leading to 11 is described as well as the ring‐forming condensation of 10 with the sulfene 12. Depending on the nature of the nucleophile reacted with 14, one can obtain the product of the substitution of the chlorine atom or of the chlorine atom and the benzylthio group or reactions taking place at both the carbonyl group and the terminal carbon atom, among them binucleophilic cyclizations. Some reactions of the conjugate base of 14 are also described.
Is water critical to the formation of micelles in apolar media??
Authors: Eicke Hans‐Friedrich , Christen Heinz
Published: December 2004

Photon correlation studies in H2O/sodium di‐2‐ethylhexylsulfosuccinate (AOT)/i‐C8H18‐systems, pertinent IR. investigations, and vapor pressure osmometric measurements with alkylated quaternary ammonium di‐2‐ethylhexylsulfosuccinates strongly suggest water to be pre‐requistite for the micellization in apolar media.
A convenient high yield version of the ester Claisen rearrangement. Preliminary communication
Authors: Petrilka Martin
Published: December 2004

Regiospecific addition of benzeneselenenyl bromide to ethyl vinyl ether followed by alcoholysis of the initially formed β‐bromoalkyl selenide 1 by primary, secondary or tertiary allylic alcohols 2a‐e gave the mixed acetals 3a‐e. Subsequent oxidation and thermal treatment of the corresponding selenoxides 4a‐e furnished after saponification the γ, δ‐unsaturated acids 7a‐e in excellent overall yields. The entire sequence (Scheme 2) represents a new version of the ester Claisen rearrangement.
Photochemische Reaktionen 100. Mitteilung. Photochemistry of N‐Acylimidazoles. V. Photolysis of the N‐Acylimidazoles of Dehydroabietic Acid and of 13‐Deisopropyl‐10‐epi‐dehydroabietic Acid
Authors: Iwasaki Shigeo
Published: December 2004

The irradiation of 1‐(dehydroabietoyl) imidazole (3) gave no Type II elimination product but yielded instead compounds 6 and 7 by migration of the imidazolylcarbonyl group from C(4′) to C(6′) of the abietan moiety, probably via a cyclobutanol intermediate. Similarly, irradiation of 1‐(13′‐deisopropyl‐10′‐epi‐dehydro‐abietoyl)imidazole (13) gave only a small amount of Type II fragmentation product 20, the main products derived from γ‐hydrogen abstraction being the cyclobutanol derivatives 16 and 17.
On Excited States of Alkyl Bridged [14] Annulenes
Authors: Spanget‐Larsen Jens , Gleiter Rolf
Published: December 2004

The linear dichroic absorption spectrum of 1,3,6,8‐trans‐15, 16‐hexamethyl‐dihydropyrene has been measured in stretched polyethylene at 77K, and CNDO‐CI calculations with inclusion of singly and doubly excited configurations have been carried out on a series of alkyl bridged [14] annulenes with pyrene‐ and anthracene‐shaped perimeters. Transitions to e3g → e4u type 1B states are well described, and the results indicate that additional low‐energy excited states originate from e3g→ e5g and e2u → e4u type configurations interacting strongly with doubly excited configurations of the e3g, e3g → e4u, e4u type. The second excited singlet state responsible for the weak transition observed between the 1L bands may be assigned to one of these additional states, but it is probably of complex nature, similar to the ‘phantom’ state in linear polyenes.
The Conversion of α‐Hydroxythioacetals to Functionalized Ketene Thioacetals
Authors: Lottenbach Willi , Graf Walter
Published: December 2004

The conversion of α‐hydroxythioacetals to ketene thioacetals possessing an unprotected carbonyl function is described. Besides the intrinsic utility of this transformation it is of interest to recognize that ketene thioacetals are protected carboxyl groups.
Stoffwechselprodukte von Mikroorganismen. 178. Mitteilung. Die Avilamycine A und C: Chemischer Abbau und spektroskopische Untersuchungen
Authors: Keller‐Schierlein Walter , Heilman William , David Ollis W. , Smith Christopher
Published: December 2004

Hydrolysis and methanolysis of Avilamycin C yielded a series of mono‐ and oligosaccharide‐like products, which were, with one exception, identical with degradation products of flambamycin. Instead of evalose (6‐deoxy‐3‐methyl‐D‐mannose), a building stone of Flambamycin and Everninomicin B, evermicose (2, 6‐dideoxy‐3‐methyl‐D‐mannose) was identified as a constituent of the Avilamycins. This sugar was known as a degradation product of the Everninomicins C and D. From the degradation results a structure of Avilamycin A was postulated which differs from that of Flambamycin only by the lack of a hydroxyl group in position 2 of the evalose residue. This hypothesis was confirmed by a careful 1H‐ and 13C‐NMR. study.
Etude dans la série des radicaux hétérocycliques. Partie XV. Décomposition aprotique de l'amino‐6‐éthyl‐2‐benzothiazole dans des substrats aromatiques et hétéroaromatiques: préparation des mésityl‐6‐ et furyl‐6‐éthyl‐2‐benzothiazoles, des sels quaternaires et des spiropyrannes correspondants
Authors: Vernin Gaston , Kister Jacky , Metzger Jacques
Published: December 2004

Study of heteroaromatic radicals. Part XV.

Partie XIV: cf. [1].

Aprotic decomposition of 6‐amino‐2‐ethylbenzothiazole in aromatic and heteroaromatic substrates: preparation of 6‐mesityl‐ and 6‐furyl‐2‐ethylbenzothiazoles and of the corresponding quaternary salts and spyropyrans

In the presence of excess isopentyl nitrite in aprotic solvent, the 6‐amino‐2‐ethyl‐benzothiazole leads to 6‐aryl‐ and 6‐heteroaryl‐2‐ethylbenzothiazoles 1 to 14 in ca. 20–50% yield (Scheme 1, Table 1). The 2‐ethyl‐6‐benzothiazolyl radicals generated during these reactions exhibit a weak electrophilic character (Table 2).

Preparatively this method has been applied to the synthesis of 6‐mesityl‐ and 6‐furyl‐2‐ethylbenzothiazoles 6 and 7, which were used to prepare the corresponding quaternary salts 15, 16 and the spiropyrans 19, 20 (Scheme 4).
γγ‐Disubstituted Itaconic Acids. Part 1. The Stobbe condensation of 1‐arylnaphthyl ketones with diethyl succinate
Authors: Baghos Victorine B. , Nasr Farid H. , Gindy Munir
Published: December 2004

Arylnaphthyl ketones condense with diethyl succinate yielding the stereoisomeric half‐esters 2a–2d which were subjected to a series of reactions leading to 1‐phenylphenanthrene and 1,1′‐binaphthyl derivatives. (E)‐3‐Ethoxycarbonyl‐4‐(4‐methoxynaphth‐1‐yl)‐4‐arylbut‐3‐enoic acids (2b–d) were converted finally into the corresponding naphtho[1,2‐c]fluorenones (9). The structure of the products was established by IR. and UV. spectroscopy. The effect of substituents on the relative proportions of (E)‐ and (Z)‐half‐esters 2 was determined by chromatography and UV. spectroscopy.
(Z)‐4,7‐Octadiensäure‐äthylester und (Z)‐Buttersäure‐3,5‐hexadienylester, zwei neue Aromastoffe der roten Passionsfrucht
Authors: Winter Max , Näf Ferdinand , Furrer Anton , Pickenhagen Wilhelm , Giersch Wolfgang , Meister Alain , Willhalm Bruno , Thommen Walter , Ohloff Günther
Published: December 2004

Ethyl (Z)‐4,7‐Octadienoate and (Z)‐3,5‐Hexadienyl Butyrate, two New Aroma Components of the Purple Passionfruit

The isolation of ethyl (Z)‐4,7‐octadienoate (1) and (Z)‐3,5‐hexadienyl butyrate (2), two new and important aroma constituents of the purple passionfruit (Passiflora edulis SIMS) is reported.

Ester 1 was synthesized by two different routes: (1) via a Wittig reaction between the known 4‐oxobutyrate 4 and 3‐butenylidenephosphorane, and (2) by thermolysis of (Z)‐8‐acetoxy‐4‐octenoate 7 which was readily accessible from (Z,Z)‐1,5‐cyclooctadiene.

Ester 2 was prepared from the known hex‐3‐yn‐5‐en‐1‐ol (8) by a stereoselective (Z)‐reduction of the triple bond to 9, using Rieke's active metallic zinc, followed by esterification.

The organoleptic properties and the taste threshold values of 1 and 2 are given.