bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deoxy‐nitrosugars. 5th Communication. The anomeric effect of the nitro group
Authors: Aebischer Bernard , Hollenstein Roger , Vasella Andrea 
Published: December 2004

AbstractThe 1‐deoxy‐1‐nitro‐D‐manno‐pyranose 4 was transformed into the nitroolefin 5 and hence into the anomeric 1,2‐dideoxy‐1‐nitro‐3, 4, 6‐tri‐O‐benzyl‐D‐arabino‐hexopyranoses (3a and 3b; cf. the Scheme). Conformational analysis of 1‐benzyloxy‐2‐nitroethane (6) by 1H‐NMR spectroscopy (Fig. 2) showed the synclinal conformation to be more stable than the antiperiplanar one by about 1.4 kcal/mol (attractive gauche‐effect). This gauche‐effect favours the 1‐deoxy‐1‐nitro‐2, 3, 4, 6‐tetra‐O‐benzyl‐β‐D‐manno‐hexopyranose (1b) possessing an equatorial nitro group, which is, however, qualitatively the less stable anomer. The relative concentrations of the anomers of 1 and 3, respectively, were determined by 1H‐NMR spectroscopy after base catalyzed equilibration at 37° in CHCl3‐solution (Table). Anomeric effects for the nitro group of approximately 2.4 kcal/mol in 3 and of approximately 3.4 kcal/mol in 1 were calculated.
Stable Liquid Crystals with Large Negative Dielectric Anisotropy. Part IV
Authors: Osman Maged A. , Huynh‐Ba T. 
Published: December 2004

AbstractStable liquid crystals with negative dielectric anisotropy containing the bicyclo [2.2.2]octyl group were synthesized. The incorporation of this moiety in the molecules increased the thermodynamic stability of the mesophase and lowered the smectic tendency. These new compounds can be useful in liquid crystal mixtures for homeotropic nematic displays.
The chemistry of thujone. VIII. Thujone as a chiral synthon for the synthesis of optically active steroid analogues. The enol lactone route
Authors: Kutney James P. , Grice Peter , Pascoe Keith O. , Piotrowska Krystyna , Rettig Steven J. , Szykula Jerzy , Trotter James 
Published: December 2004

AbstractThe thujone‐derived enone 1 is converted via enol lactone intermediates 4 and 5 to the optically active steroidal analogue 13 and the corresponding 19‐norsteroid analogue 14. The structure of 13 was determined by X‐ray diffraction analysis. The acid‐catalyzed cyclopropane‐ring opening of 13 and ozonolysis of the resulting olefin provided the 16‐keto‐steroid analogue 18.
The chemistry of thujone. IX. Thujone as a chiral synthon for the synthesis of optically active steroid analogues. The vinylpicoline route
Authors: Kutney James P. , Grice Peter , Piotrowska Krystyna , Rettig Steven J. , Szykula Jerzy , Trotter James , Van Chu Loc 
Published: December 2004

AbstractThe thujone‐derived enone 1, upon base‐catalyzed reaction with 2‐methyl‐6‐vinylpyridine is converted to the pyridine analogue 5 (Scheme 1). Catalytic reduction of the latter to 6 generates two new centers of chirality which eventually become C(8) and C(14) in the ultimate synthetic steroid analogue 12. An X‐ray analysis of 6 establishes the structure and absolute configuration so as to determine its suitability in subsequent synthetic studies. The acetal derivative 7, via Birch reduction, hydrolysis, and internal aldol cyclization, is converted into the cyclohexenone analogue 10 (Scheme 2). This ‘one‐pot’ process affords an efficient conversion of the pyridine ring into a cyclohexenone system required for A‐ring construction of the steroid skeleton. Finally, conversion of 10, via the unsaturated diketone 11, provides the chiral steroid analogue 12.
Umwandlung von Bicyclo [3.2.0]hept‐2‐en‐6‐on in Cyclopentadienessigsäure‐Derivate
Authors: Wallquist Olof , Rey Max , Dreiding André S. 
Published: December 2004

Conversion of Bicyclo [3.2.0]hept‐2‐en‐6‐one into Cyclopentadienylacetic Acid DerivativesThe reaction of a mixture of 4exo‐bromobicyclo [3.2.0]hept‐2‐en‐6‐one (2) and ‐7‐one (3) with O‐ or N‐nucleophiles yielded cyclopentadien‐5′‐yl‐acetates 4a–f or‐acetamides 4g–h. Due to their rapid isomerization, the products 4 were not isolated, but some of them were demonstrated spectroscopically or captured in situ with maleimide as 10′‐substituted norbornene derivatives 7. The formation of 4 from 2/3 involves a fragmentation of the bond between the carbonyl and the bridge‐head C‐atom, induced by the attacking nucleophile and the leaving Br‐ion and aided by the relief of the four‐membered ring strain. Some of the isomerization products of 4, i.e. the cyclopentadiene‐1′‐yl‐ and 2′‐yl‐acetyl derivatives were captured with maleimide as the 1′‐ and 8′‐substituted norbornene‐derivatives 8 and 9. Two C‐nucleophiles did not induce the fragmentation: sodium acetylacetonate substituted the Br‐atom and sodium (diethoxyphosphoryl)ethoxycarbonylmethide condensed with the carbonyl group of 2/3, yielding 11/12 and 13/14, respectively.
Correction for Inner Filter Effects in Fluorescence Spectroscopy
Authors: Lutz Hans‐Peter , Luisi Pier Luigi 
Published: December 2004

AbstractA method is proposed for correcting experimental fluorescence readings for inner filter effects, i.e. the absorption of the exciting light and/or the absorption of the emitted radiation, which cause the non‐linearity between fluorescence intensity and fluorophor concentration. Basically the method consists of measuring the fluorescence intensity at two different points along the diagonal in the cell. Unlike similar methods proposed in the literature, the two points are corrected simultaneously for both absorption of excitation and of emission radiation without the necessity of reading the optical density of the solution, and with a very simple data elaboration.
Carbon Participation in the Solvolysis of 6‐ and 7‐Substituted 2‐Norbornyl p‐Toluenesulfonates. Norbornanes, Part 11
Authors: Flury Peter , Grob Cyril A. 
Published: December 2004

AbstractThe solvolysis rates and products of several 7‐anti‐substituted 2‐endo‐norbornyl p‐toluenesulfonates 11 have been determined and compared with those of the previously reported 6‐exo‐substituted 2‐exo‐norbornyl p‐toluenesulfonates 1. Although the number of bonds between the substituent and the reaction site is the same in the two series, the inductive effect of the substitutents is transmitted far more strongly in the 6‐exo‐2‐exo‐series 1 than in the 7‐anti‐2‐endo‐series 11; i.e. their inductivities differ widely. It is concluded that through space induction involves graded bridging of the substituent‐bearing C‐atom to the incipient cationic center at C(2) and that this involves differential bridging strain. The different reactivities of unsubstituted 2‐exo‐ and 2‐endo‐norbornyl derivatives can then be ascribed to a stereoelectronic effect.
Die Hydrolyse von 7‐anti‐substituierten p‐Toluolsulfonsäure‐[2‐endo‐und 2‐exo‐norbornyl]estern. Norbornanreihe. 12. Mitteilung
Authors: Flury Peter , Grob Cyril A. 
Published: December 2004

The Hydrolysis of 7‐anti‐Substituted 2‐endo‐ and 2‐exo‐Norbornyl p‐ToluenesulfonatesThe hydrolysis products of the title compounds have been determined. The preparation of the hitherto unknown solvolysis products is described.
Nucleotide, XVII. Synthese von homogenen Adenosyl‐3′,5′‐Oligomeren nach dem Phosphotriester‐Verfahren
Authors: Flockerzi Dieter , Uhlmann Eugen , Pfleiderer Wolfgang 
Published: December 2004

Nucleotides, XVII. Synthesis of Homogeneous Adenosyl‐3′,5′‐oligomers by the Phosphotriester MethodThe chemical synthesis of the fully protected trimer 12, the tetramers 11 and 23 as well as the pentamer 14 was achieved in preparative scales starting from the fully blocked adenosine‐3′‐phosphotriesters 1, 2, and N6‐benzoyl‐2′,3′‐bis‐O‐(tert‐butyldimethylsilyl)adenosine (6). All intermediates and end products have been isolated, purified and characterized by elemental analyses, UV, and CD spectra. Deprotection of the various blocking groups proceeds without difficulties to afford the free trimeric, tetrameric, and pentameric oligoadenylates 15, 16, and 24 in high yields.
The Radical Ions of Indolizino [6,5,4,3‐aij]quinoline and Some of its Derivatives
Authors: Gerson Fabian , Metzger André 
Published: December 2004

AbstractIndolizino [6,5,4,3‐aij]quinoline (1) and its 3,9‐dimethyl‐ (2), di‐tert‐butyl‐ (3) and diphenyl‐(4) derivatives yield persistent radical cations which have been studied by ESR and ENDOR spectroscopy. The corresponding radical anions have also been prepared, but only that of 3 was amenable to a complete characterization by hyperfine data. The π‐spin populations in the radical anions are essentially localized on the 13‐membered C‐perimeter, and thus both the HOMO and LUMO of 1 exhibit an ‘annulenyl character’. The radical anions of 1 and 2 have gradually been converted into those of the corresponding 3,4‐dihydro derivatives (1‐H2 and 2‐H2) which have been unambiguously identified by a combination of preparative and spectroscopic methods.
Synthese von β‐D‐Glucopyranosiden einiger hydroxylierter Vitamin‐D‐Verbindungen
Authors: Fürst Andor , Labler Ludvik , Meier Werner 
Published: December 2004

Synthesis of β‐D‐Glucopyranosides of some Hydroxylated Vitamin‐D CompoundsCholesta‐5, 7‐diene‐1α, 3β‐diol (1a) was glycosylated with ‘α‐acetobromoglucose’ (2) as well as with ‘α‐acetobromocellobiose’ (4) to yield the 3‐(glycosides) 1b and 1c, respectively. Irradiation of these products with UV light followed by thermal isomerization led to the corresponding vitamin‐D derivatives 3a and 3c. Direct glucosylation of vitamin D3 (3f) and vitamin D2 (5a) with 2 gave the derivatives 3g and 5b, respectively. With 25‐hydroxycholecalciferol ( = calcidiol; 6a) as substrate, besides the 3‐(glucoside) 6b small amounts of the C(25)‐analog 6c were formed. The reaction of 1α, 25‐dihydroxycholecalciferol ( = calcitriol; 6e) with 2 furnished the 3‐ and the 1‐(glucoside) (6f and 6g, respectively) as the major components and the C(25)‐analog 6h in minor quantity. From the acetylated 3‐(glucosides) 3a, 3g, 5b, 6b, and 6f, the free glucopyranosides 3b, 3h, 5c, 6d, and 6i, respectively, were prepared as well as the free glucopy‐ranosyl‐glucopyranoside 3d from the acetylated disaccharide 3c.
Discrimination between an Antiparallel and a Parallel β5.6‐Helix Using 1Hα‐NMR Spin‐Lattice Relaxation
Authors: Lorenzi Gian Paolo , Tomasic Lera , Bangerter Felix , Neuenschwander Peter , Di Blasio Benedetto 
Published: December 2004

AbstractThe 1H‐NMR spectrum of Boc‐(L‐Val‐D‐Val)4‐OH in CDCl3 can be attributed either to an antiparallel or to a parallel double‐stranded β5.6‐helical structure. To resolve this ambiguity, T1‐measurements have been carried out for the α‐protons of Boc‐(L‐Val‐D‐Val)4‐OH and its monodeuterated analogue Boc‐(L‐Val‐D‐Val)2 ‐α‐2H‐L‐Val‐D‐Val‐L‐Val‐D ‐Val‐L‐Val‐D‐Val‐OH. The results show that the Hα of the fifth residue in one strand is close to the Hα of the seventh residue in the other strand, as expected for an antiparallel arrangement, a conclusive demonstration that the correct structure of Boc‐(L‐Val‐D‐Val)4‐OH is antiparallel.
Studies related to biological detoxification of kraft pulp mill effluent. VII. The biotransformation of 12‐chlorodehydroabietic acid with mortierella isabellina
Authors: Kutney James P. , Hewitt Gary M. , Salisbury Philip J. , Singh Mahatam , Servizi James A. , Martens Dennis W. , Gordon Robert W. 
Published: December 2004

AbstractA detailed study of the biodegradation of one of the fish‐toxic chlorinated resin acids, 12‐chlorodehydroabietic acid (3), is discussed. When 3 is exposed to the fungus Mortierella isabellina, it is converted into the monohydroxylated metabolites 2α‐hydroxy‐12‐chlorodehydroabietic acid (5) and 16‐hydroxy‐12‐chlorodehydroabietic acid (8) after short‐term (26 h) incubation, and into the 2α, 16‐dihydroxy derivatives 11 and 14 after 96 h incubation. These metabolites show low levels of toxicity to fish.
New Sesquiterpenoids from Clary Sage Oil (Salvia sclarea L.)
Authors: Maurer Bruno , Hauser Arnold 
Published: December 2004

AbstractSix sesquiterpenoids, (R, 5E)‐2, 12‐epoxycaryophyll‐5‐ene (1), (2 R, 5E)‐caryophyll‐5‐en‐12‐al (2), (2S, 5E)‐caryophyll‐5‐en‐12‐al (3), isospathulenol (4), (1R, 5R)‐ 1,5‐epoxysalvial‐4(14)‐ene (5), and salvial‐4(14)‐en‐l‐one (6) have been identified for the first time in clary sage oil (Salvia sclarea L.). The structures and absolute configurations of 1–6 are corroborated by partial syntheses and their organoleptic properties are discussed.The compounds 5, 6 and mintsulfide (14) possess the rare C‐skeleton C, for which the semisystematic name ‘salvialane’ is proposed. The sesquiterpenoids 1–5 are new.
Photochemische Reaktionen 130. Mitteilung. Zur Photochemie von 5,6‐Epoxy‐1,3‐dienen: Der Einfluss eines 7‐Hydroxysubstituenten auf die Carbenbildung
Authors: De Weck Guy , Nakamura Norio , Tsutsumi Kentaro , Wolf Hans Richard , Frei Bruno , Jeger Oskar 
Published: December 2004

Photochemistry of 5,6‐Epoxy‐1,3‐dienes: Influence of a 7‐Hydroxy Substituent on the Carbene FormationOn singlet excitation (λ=254 nm) in MeCN the hydroxy‐epoxydiene (E)‐4 undergoes photocleavage to the carbene intermediates d and e as main processes. The carbene d, showing behaviour typical of vinyl carbenes, undergoes addition to the adjacent double bond furnishing the cyclopropenes 5A + B. The carbene e, however, undergoes an insertion reaction into the neighbouring carbinol C,H‐bond leading to the enol intermediate 21, which gives rise to the compounds 6A + B and 7A + B. To a lesser extent the products 8A + B are formed via another enol intermediate (32). On photolysis of (E)‐4 in MeOH instead of MeCN the enol intermediates 21 and 32 undergo rapid tautomerisation to the ketones 9A + B (main products) and 11.
Über die Enantiomerentrennung durch Verteilung zwischen flüssigen Phasen. 3. Mitteilung. Selektivität der lipophilen Weinsäureester für chirale Ammonium‐Salze verschiedener Konstitution und Konfiguration
Authors: Prelog Vladimir , Mutak Stjepan , Kovačević Krunoslav 
Published: December 2004

Separation of Enantiomers by Partition between Liquid Phases. 3. Communication. Selectivity of Lipophilic Tartaric Acid Esters for Chiral Ammonium Salts of Different Constitution and ConfigurationSeveral methods are described which allow determination on a small scale of the enantiomer distribution constant Q, and the affinity coefficient P, which characterize the enantioselectivity and the affinity of a lipophilic phase for ammonium salts of different constitution and configuration.The influence of concentration of the tartaric acid ester, temperature, concentration and type of the lipophilic anion on Q and P was investigated to find out favourable experimental conditions for resolutions of racemates by iterative process, e.g. partition chromatography.The relationship between Q and the configuration of aminoalcohols 1–12 was explored and the observed regularities are pointed out.In addition it was found that lipophilic tartaric acid esters are enantioselective to salts of threo‐1,2‐diphenyl‐1,2‐ethanediamine 13, and to phenylglycine and its derivatives 14–16.
2‐Vinylcyclobutanones by Cycloaddition of Vinylketenes to Simple Olefins
Authors: Jackson David A. , Rey Max , Dreiding André S. 
Published: December 2004

AbstractSelected [2+2]‐cycloadditions of three alkylvinylketenes 2 to one mono‐ and seven dialkyl‐olefins 3 yielded eleven 2‐alkyl‐2‐vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl‐elimination from α,β‐unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]‐cycloadditions were fully regio‐ and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that ‐ where possible ‐ two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their 1H‐NMR, spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.
The Tricyclooctanone Approach to the Total Synthesis of Steroids. The Cyclization of the A‐CD Unit
Authors: Mikhail Gamal , Demuth Martin 
Published: December 2004

AbstractThe first steps of a novel approach to the total synthesis of 9, 11‐dehydroestrone via tricyclo[3.3.0.02,8]octan‐3‐one (2) are described. One route involves a tandem‐type transformation of the key intermediate 3 (A‐CD unit) consisting of cyclopropane cleavage and ring B closure to afford C, 18‐bisnor‐13 α, 17 α‐estradiol derivatives. E.g. the 3‐methoxy‐9 ζ‐hydroxy‐17 α‐methanesulfonyloxy derivative (‐)‐6 has been synthesized in 8 steps and 10% overall yield from 1,3‐cyclohexadiene. As an alternative, the A‐CD type intermediate 4b has been prepared and could be used for a ring C enlargement prior to cyclization.
Synthesen und chemisches Reaktionsverhalten neuer überbrückter Chinonderivate. Kupplungsreaktionen von Diazoniumsalzen mit 2‐Methoxy‐1,6‐methano [10]annulen
Authors: Neidlein Richard , Radke Christoph Martin 
Published: December 2004

Syntheses and Chemical Properties of New Bridged Quinone Derivatives. Coupling Reactions of Aryldiazonium Salts with 2‐Methoxy‐1,6‐methano[10]annuleneCoupling of 2‐methoxy‐1,6‐methano[10]annulene (3) with the aryldiazonium salts 4a‐4i yields the quinone hydrazones 5a‐5i. The spectroscopic properties of these products are described. The reaction of 3 with 4‐nitrophenyldiazonium tetrafluoroborate buffered with sodium acetate in dry methanol yielded after chromatographic separation the azo derivative 7 on the one hand and a mixture of the valence tautomers 8a and 8b on the other.
Isolement et identification de la C‐galactosyl‐8 apigénine dans les tiges feuillées de Carlina acanthifolia
Authors: Proliac Arlette , Raynaud Jean 
Published: December 2004

Isolation and Identification of 8‐C‐Galactosylapigenin from Leaves of Carlina acanthifolia8‐C‐galactosylapigenin was isolated from the leaves of Carlina acanthifolia (Compositae). This identification represents only the third report of a mono C‐galactosylapigenin in plants and the first report in the Compositae.
Réarrangements en milieu acide trifluoroacétique de deux alcaloïdes indoliques: la desformocorymine et la dihydrocorymine
Authors: Massiot Georges , Lavaud Catherine , Vercauteren Joseph , Le Men‐Olivier Louisette , Lévy Jean , Guilhem Jean , Pascard Claudine 
Published: December 2004

The rearrangement in trifluoroacetic acid of two indole alkaloids of the echitamine series, desformocorymine (14) and dihydrocorymine (9), has been investigated. Desformocorymine (14) was tranformed into a mixture of carbinolamines 17a,b, with the akuammiline skeleton, which were reduced (Et3SiH, CF3CO2H) into an isomer 12 of cathafoline (6). This sequence constitutes the first example of an interconversion of the corymine skeleton into the akuammiline skeleton (Scheme 2). In the case of dihydrocorymine (9), the rearrangement followed a different pathway owing to the formation of a hemiacetal between the primary alcohol CH2(17)‐OH and a carbonyl formed at C(3). Treatment of this hemiacetal 26 with aqueous base led to its opening with concomitant formation of a lactam. 13C‐NMR seems to indicate that this lactam exists under a hydrated form 27. This highly unstable intermediate was cleanly transformed (MeONa‐MeOH) into a 2‐acyl indole 30 (Scheme 4), the structure of which was determined by X‐ray crystallography. The formation of this acylindole involves the rupture of the C(7)C(16) bond; it is the reverse of the reaction generally postulated as occurring in the biogenesis of the pentacyclic alkaloids. The structure of a by‐product 34 was established as 17‐hydroxymethylvincoridine by X‐ray crystallography.The acid‐catalyzed rearrangements involve the rupture of the Ph‐NCN chromophore, with formation of a carbonyl at C(3). The reversibility of these steps is used in an easy correlation of dihydrocorymine and of 3‐epidihydrocorymine via their trifluoroacetates.
Efficient Molecular Catalysis of ATP‐Hydrolysis by Protonated Macrocyclic Polyamines
Authors: Hosseini Mir Wais , Lehn Jean‐Marie , Mertes Mathias P. 
Published: December 2004

AbstractMolecular catalysis of ATP‐hydrolysis by a number of protonated macrocyclic polyamines 1–9 has been investigated by 31P‐NMR spectroscopy, and marked rate enhancements have been obtained. The largest acceleration is produced by the [24]‐N6O2 macrocycle 1, and the process displays the following properties: 1. protonated 1 forms very stable complexes with ATP, as well as with ADP and AMP; 2. it enhances the rate of ATP‐hydrolysis by a factor of 103 at pH = 8.5; the rate of hydrolysis is constant over a wide pH‐range, from pH = 2.5 to 8.5; 3. 1 is more efficient than acyclic analogues; 4. the products of the reaction are orthophosphate (OP) and ADP, which is subsequently hydrolyzed to OP and AMP at a slower rate; 5. at pH > 6.5, a transient species is detected, which is tentatively identified as a phosphoramidate intermediate, resulting from phosphorylation of the macrocycle 1; 6. the reaction presents first‐order kinetics and is catalytic. The mechanism of the process is discussed in terms of initial formation of a complex between ATP and protonated 1, followed by an intracomplex reaction which may involve a combination of nucleophilic or acid catalysis with electrostatic catalysis.
Competitive Formation of Ylide and Carbene Intermediates from 1π,π*‐Excited α,β‐Unsaturated γ,δ‐Epoxyketones
Authors: Bischofberger Norbert , Frei Bruno , Wirz Jakob 
Published: December 2004

AbstractLaser flash photolyses (λ = 265mm) of the γ,λ‐epoxyenones 1–3, 7 and 8, the α,β‐unsaturated γ,δ‐epoxy ester 6, and the epoxytriene 9 at ambient temperature produced short‐lived transients with broad absorption maxima in the visible region, which are identified as carbonyl ylides. Comparison of the rather long‐wavelength absorption maxima with the results of standard PPP SCF SCI calculations suggests that some degree of twisting is present in all the ylides studied. The lifetimes of the order of hundreds of ns of these intermediates and Stern‐Volmer analysis of the trapping of the carbonyl ylide derived from 2 with CH3COOH provide conclusive evidence that the carbene products are not formed via the carbonyl‐ylide intermediate (Scheme 3).
A Novel Pentannulation Sequence. Facile Access to Key Intermediates for the Synthesis of Exaltone® and Muscone
Authors: Fehr Charles 
Published: December 2004

AbstractTreatment of the sulfonyl ketones 1a and 1b with potassium t‐butoxide in toluene or with potassium hydroxide in toluene/dimethyl sulfoxide affords in high yield the bicyclic dienes 3a and 3b, important precursors for Exaltone® and (±)‐muscone. An application of this novel pentannulation sequence is demonstrated for the sulfonyl ketones 6, 10, and 14. An intermolecular variant is exemplified by the synthesis of diene 22.
Photoreduction of Cyclic α‐Fluoroketones
Authors: Reinholdt Karin , Margaretha Paul 
Published: December 2004

AbstractIrradiation of the α‐fluoroketones 1a and 6a in i‐PrOH selectively affords the parent ketone 1b and 6b, respectively. It is concluded that in this solvent heterolytic C‐F bond cleavage of the anion radical‐formed by electron transfer to the excited fluoroketone‐is a faster process than the subsequent protonation by the cation radical of the solvent. In cyclohexane 1b and 6b are only formed in minor amounts, the fluorinated RH‐reduction product 4 now being the major product from 1a. In non‐reducing solvents as t‐BuOH or benzene 2‐fluorocyclohexanone (1a) exhibits a similar behavior as cyclohexanone (1b) on excitation. The quantum yields for α‐cleavage are alike for both compounds, but oxetane formation with 2‐methylpropene as olefinic component occurs much more readily with 1a than with 1b.
Synthesis of Cycloprop[b]anthracenes via Trapping of o‐Naphthoquinodimethane
Authors: Müller Paul , Rodriguez Domingo 
Published: December 2004

AbstractCycloprop[b]anthracenes 1, 1a, 1b are prepared in a 3‐step synthesis starting from o‐di(iodomethyl)benzene. The key step consists of trapping of o‐naphthoquinodimethane (9) with 1,2‐di‐ and tetrahalogenocyclopropenes (3, 3a, 4b).