bluuebunny/crossref_metadata_2025_split 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

AbstractThe 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

AbstractThe 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

AbstractPalladium‐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

AbstractThe 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

AbstractIrradiation (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

AbstractUV 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

AbstractA 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

AbstractThe 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 ReagentsThe 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

AbstractTwo 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

AbstractThe 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

AbstractThe 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

AbstractOn 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

AbstractLoganin (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

AbstractUp 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

AbstractIrradiation (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 SolutionThe 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

AbstractTreatment 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

AbstractSelective 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

AbstractThe 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‐caroteneThe 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 ‐orthoestersTwenty‐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

AbstractTwo 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

AbstractThe 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

AbstractThe 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%).