bluuebunny/crossref_metadata_2025_split huggingface dataset:
Convenient Synthesis of Biologically Important Retinoids
Authors: Biesalski Hans‐K. , Doepner Gudrun , Kunz Horst , Paust Joachim , John Michael 
Published: July 2007

AbstractThe toxic and teratogenic effects caused by the highly biologically active (all‐E)‐retinoic acid and its derivatives prompted us to synthesize a number of retinoids. We developed synthetic approaches to (all‐E)‐retinyl β‐D‐glucuronide 3, methyl (retinoyl β‐D‐glucopyranoside)uronate 5, (all‐E)‐retinoic acid β‐D‐glucopyranosyl ester 8 and (all‐E)‐retinoyl β‐D‐glucuronide 6 in high purity and yield. Compound 3 was synthesized under Koenigs‐Knorr conditions from (all‐E)‐retinol and an α‐halogenose. Compounds 5 and 8 were prepared by esterification of a silver salt of (all‐E)‐retinoic acid with an α‐glycosyl halide in pyridine. (all‐E)‐Retinoyl β‐D‐glucuronide 6 was prepared by reaction of (all‐E)‐retinoyl fluoride with underivatized β‐D‐glucuronic acid. Compounds 5, 6 and 8 show biological effects similiar to those of retinoic acid.
Synthesis of (4E,7S)‐(−)‐7‐Methoxy‐4‐tetradecenoic Acid, a Major Constituent of the Marine Cyanophyte Lyngbya Majuscula
Authors: Müller Claudia , Voss Gundula , Gerlach Hans 
Published: July 2007

AbstractThe metabolite of the marine cyanophyte Lyngbya majuscula (4E,7S)‐(−)‐7‐methoxy‐4‐tetradecenoic acid (1) has been synthesized for the first time in optically active form in eight steps in 20% overall yield, Heptyloxirane (3) and the alkyne 4 containing the carboxyl group masked as a tricyclic orthoester were prepared by known methods from 5 and 6 as starting materials. Reaction of lithiated 4 with 3 afforded in 74% yield the alkyne 2 which could easily be transformed into the target molecule. Hydrogenation with Lindlar catalyst produced 7 which could be isomerized to 8 with (E) configuration. Methylation of the 7‐hydroxy group in 8 gave 9 which could be transformed into the methyl ester 10 and the (4E,7S)‐acid 1 in high yield.
A reinvestigation of the Meerwein‐Ponndorf‐Verley reduction A highly efficient variation using zirconium catalysts
Authors: Knauer Birgit , Krohn Karsten 
Published: July 2007

AbstractA new variation of the Meerwein‐Ponndorf‐Verley reduction based on mechanistic considerations is presented. Under optimized conditions 1‐(4‐dimethylaminophenyl)ethanol was used as the reducing alcohol (2–4 equiv.), Zr(O‐tBu)4 as the catalyst (0.2 equiv.), and toluene or cyclohexane as the solvent. Aldehydes and ketones (if not extremely sterically hindered) were reduced to the corresponding alcohols at room temperature mostly within 2–4 h in essentially quantitative yield. α,β‐Unsaturated carbonyl compounds cleanly react in a 1,2‐mode to afford the corresponding allylic alcohols.
Eine neue Synthesestrategie zur Darstellung chiraler, polysubstituierter, an Pyranosen anellierter Tetrahydrofurane
Authors: Al‐Tel Taleb H. , Meisenbach Mark , Voelter Wolfgang 
Published: July 2007

A New Synthetic Strategy for the Synthesis of Chiral Polysubstituted Tetrahydrofurans Annulated to PyranosesAn efficient strategy for the regio‐ and stereoselective synthesis of the chiral tetrahydrofurans 2, 3, 5, 6, 10–16, fused to the pyranose skeleton, from the anhydro sugars 1 and 4 and 1,3‐dicarbonyl compounds via 5‐enol‐exo‐exo‐tet ring closure is described. Furthermore, the syntheses of the regioisomeric tetrahydrofuran 9, the γ‐hydroxy‐tetrahydrofulan 19 and the branched‐chain sugar 20 were successfully achieved.
Template synthesis of the first amide‐based rotaxanes
Authors: Vögtle Fritz , Händel Mirko , Meier Stephan , Ottens‐Hildebrandt Stephan , Ott Frank , Schmidt Thomas 
Published: July 2007

AbstractThe first rotaxanes 6a, 6b and 11 with an amide structure are described. Their (supramolecular template) syntheses are strikingly simple. The central part of the „axle”︁ is added to the „wheel”︁ and subsequently capped. The macromonocycle („wheel”︁) provides the receptor cavity for the „axle”︁ and the triphenylmethane stoppers confirm the mechanical bond between „wheel”︁ and „axle”︁.
Chelation control by a second nitrogen atom in formal hetero Diels‐Alder reactions of N‐arylimines
Authors: Linkert Frank , Laschat Sabine , Knickmeier Markus 
Published: July 2007

AbstractLewis acid‐catalyzed cyclization of proline‐derived N‐arylimines 8 gives the tetracyclic decahydro‐7,7,11‐trimethyl‐in‐dolizino[3,4‐b]quinolines 17a, b in a ratio, which is highly dependent on the coordination number of the acidic catalyst. Whereas monodentate Brønsted and Lewis acids as well as octahedral bidentate Lewis acids preferably gave the all‐trans product 17b, the all‐cis product 17a was obtained by tetrahedral aluminium Lewis acids. In contrast to this chelation‐controlled reversal of diastereoselectivity, mixtures of cis/trans undecahydro‐6,6,10‐trimethyl‐11‐azacyclopenta[a]‐anthracenes 18b‐e, h were isolated from the cyclization of the corresponding cyclopentane‐derived N‐arylimines 16 irrespective of the Lewis acid. Force field calculations support a stepwise iminium ion cyclization under thermodynamic control rather than a concerted hetero‐Diels‐Alder mechanism.
A simple synthesis of functionalized rac‐chlorins via allylboration of porphyrin aldehydes
Authors: Höper Frank , Montforts Franz‐Peter 
Published: July 2007

AbstractChlorins rac‐17a, b which bear terminally hydroxy‐substituted butyl side chains were synthesized by allylboration and Claisen rearrangement from readily accessible formylporphyrins 5 and 6. The hydroxyalkyl side chain and the photo‐physical properties of the chlorins rac‐17a, b should open a broad access to chlorins suitable for photodynamic therapy having different residues attached to the hydroxy function. The reported synthetic pathway also should be useful for the synthesis of naturally occurring hydroporphyrins containing geminally dialkylated structural parts and a propionic acid residue on the saturated pyrrole ring.
Synthesis of donor‐substituted 2‐benzopyrans, isoquinolines, and cinnolines with acetal structure
Authors: Wünsch Bernhard , Nerdinger Sven , Höfner Georg 
Published: July 2007

AbstractAt −105°C the aryllithium intermediate 7, which was generated by treatment of the donor‐substituted bromo acetal 6 with n‐butyllithium, was trapped with aromatic and aliphatic aldehydes, with paraformaldehyde, with a ketone, an amide, an imine, and an azo compound to yield the hydroxy acetals 9a–c and 18, the homophthalaldehyde derivative 8, the amino acetal 24 and the hydrazino acetal 28. The acid‐catalyzed ring closure of the hydroxy acetals 9a–c and 18, the amino acetal 24, and the hydrazino acetal 28 provided the 2‐benzopyrans 10a–c, 19 and 20, the isoquinoline 26, and the cinnolines 29 and 30, respectively. Hydrogenolysis (H2, Pd/C) of the benzyl‐protective group led to the phenols 15a–c, 21, 31, and 32. The spiropiperidines 21 and 22 showed a very low affinity for the phencyclidine binding site of the NMDA receptor. In mice weakly sedative effects were caused by application of 21 and 22.
Constituents of tropical medicinal plants, LXIX. The hexalobines, diprenylated indoles from Hexalobus crispiflorus and Hexalobus monopetalus
Authors: Achenbach Hans , Renner Christian , Waibel Reiner 
Published: July 2007

AbstractNineteen individual hexalobines (diprenyl‐substituted indoles) were isolated from petroleum ether and dichloromethane extracts of the stem bark of Hexalobus crispiflorus and H. monopetalus, respectively. The structures were established by spectroscopic methods. The absolute configurations result from chiroptical measurements and from chemical interconversions. Various hexalobines exhibit significant antifungal activity.
Lurlene, the sexual pheromone of the green flagellate Chlamydomonas allensworthii
Authors: Jaenicke Lothar , Marner Franz‐Josef 
Published: July 2007

AbstractThe pheromone produced by the female gametes of the green flagellate Chlamydomonas allensworthii to lure the male gametes for sexual fusion is the plastohydroquinone derivative lurlene, (all‐E)‐14‐[2′‐hydroxy‐3′,4′‐dimethyl‐5′‐(1″;‐β‐D‐xylopyranosyloxy)phenyl]‐4,8,12‐trimethyltetradeca‐4,8,12‐trienoic acid (1).
The diastereoselectivity of zirconium alkoxide catalysed Meerwein‐Ponndorf‐Verley reductions
Authors: Krohn Karsten , Knauer Birgit 
Published: July 2007

AbstractThe new variation of the Meerwein‐Ponndorf‐Verley reduction using 1‐[4‐(dimethylamino)phenyl]ethanol (DMAPE) (6) or 1‐tetralol (12) (3 equiv.) as the reducing alcohols and Zr(O‐tBu)4 as the catalyst (0.2 equiv.) is kinetically controlled and highly stereoselective. Preferential axial attack is achieved with the sterically less bulky alcohol 6 in the case of 4‐tert‐butyl‐ and 3‐methylcyclohexanones (1a → 96% axial and 3a → 93% axial attack). The combination tetralol (12)/Zr(O‐tBu)4 behaves as a very bulky reducing agent, and the thermodynamically less stable alcohols 2c (80%) and 4c (92–96%) are formed preferentially in the reduction of 2a and 4b. The fused bicyclic systems 1‐methyl‐2‐tetralone (14a) and flavanone (15a) and the steroids 16a–18a are reduced with high stereoselectivity to the corresponding cis alcohols 14b and 15b and the (β‐alcohols 16b–18b. The stereochemical outcome is in agreement with the Felkin‐Ahn model.
Synthesis and antiviral evaluation of quinazoline, thieno‐[2,3‐d]pyrimidine, and lumazine analogues of 3′‐fluoro‐3′‐deoxythymidine (FLT)
Authors: El‐Barbary Ahmed A. , El‐Brollosy Nasser R. , Abdel‐Bary Hamed M. , Pedersen Erik B. , Stein Paul , Nielsen Claus 
Published: July 2007

Abstract2,4(1H,3H)‐Quinazolinediones 3a–c, lumazine (3d) and thieno[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione (8) were silylated and condensed with methyl 2,3‐dideoxy‐3‐fluoro‐5‐O‐(4‐phenylbenzoyl)‐β‐D‐erythro‐pentofuranoside (2) by using trimethylsilyl triflate as a catalyst to afford the corresponding cyclic nucleosides 4 and 9 and acyclic nucleosides 5 and 10. Removal of the protecting group from the glycon moiety was achieved in good yields by treatment with sodium methoxide in methanol at room temperature. The new FLT analogues were devoid of activity against HIV‐1 and HSV‐1.
Synthesis of 1‐C‐(2,5‐diphenyl‐3,4‐diarylphenyl)alditols
Authors: Del Valle José L. , Marcaccini Stefano , Torroba Tomás 
Published: July 2007

AbstractTetraarylcyclopentadienones 2a–c react with (E)‐3,4,5,6,7‐penta‐O‐acetyl‐1,2‐dideoxy‐1‐C‐nitro‐D‐galacto‐ (1a) and ‐D‐manno‐hept‐1‐enitol (1b) to give 1‐C‐(2,3,4,5‐tetraarylphenyl)‐D‐galacto‐ (3a–c) and ‐D‐manno‐penta‐O‐acetylpentitol (3d‐f), respectively, after decarbonylation and HNO2 elimination from the Diels‐Alder cycloaddition intermediates.
Synthesis and stereostructure of some spiro[morphinan‐6,2′(3′H)‐[1,3,4]oxa(thia)diazolines]
Authors: Somogyi László , Szabó Zoltán , Hosztafi Sándor 
Published: July 2007

AbstractTreatment of dihydrocodeinone (thio)semicarbazones 1a–d with Ac2O/ZnCl2 afforded (6S)‐spiro[morphinan‐6,2′(3′H)‐[1,3,4]oxadiazolines] (2a, b) and (6R)‐spiro[morphinan‐6,2′‐(3′H)‐[1,3,4]thiadiazolines] (3a, b), respectively. The structure of the products including the configuration of the spiro carbons was determined by 1H‐ and 13C‐NMR measurements.
Umlagerung von 3‐Thioxo‐Δ1,4‐steroiden, ein neuer Zugang zu Steroidthiolen
Authors: Möller Stephanie , Weiß Dieter , Beckert Rainer 
Published: July 2007

Rearrangement of 3‐Thioxo‐Δ1,4‐steroids, a New Approach of Steroid Thiols3‐Thioxoandrosta‐1,4‐dien‐17‐one (1) is subjected to a dienthion‐thiophenol rearrangement in aprotic and protic solvents in the presence of an acid catalyst resulting in the formation of 1‐(acetylthio)‐4‐methylestra‐1,3,5(10)‐trien‐17‐one (2). 1‐mercapto‐4‐methylestra‐1,3,5(10)‐trien‐17‐one (3), and the dimer 1,1′‐(dithio)bis[4‐methylestra‐1,3,5(10)‐trien‐17‐one] (4) as the reaction products. The mercapto compound 3 tends to be autoxidized to the sulfide 4.
A Synthesis of rac‐S‐(2‐Acetoxy‐3‐hexadecyloxypropyl) thiophosphocholine, the isosteric and isopolar PAF analog
Authors: Mlotkowska Barbara , Olejnik Jadwiga 
Published: July 2007

Abstractrac‐S‐(2‐Acetoxy‐3‐hexadecyloxypropyl) thiophosphocholine (5), the isosteric and isopolar thiophosphate analog of Platelet Activating Factor (PAF), was synthesized from bis(2‐acetoxy‐3‐hexadecyloxypropyl) disulfide (12) or O,O‐diethyl S(2‐acetoxy‐3‐hexadecyloxypropyl) thiophosphate (16) as starting materials by two independent „one‐pot”︁ procedures in 65% and 20% overall yield, respectively.
Azachlorins: Synthesis of a novel type of hydroporphyrins from the bile pigment bilirubin
Authors: Gerlach Benjamin , Montforts Franz‐Peter 
Published: July 2007

AbstractAzachlorins rac‐10a,b, rac‐11, and rac‐16, a novel type of hydroporphinoid compounds, were synthesized from azaporphyrins 8 and 13 by regioselective cycloaddition of singlet oxygen and further transformation by amide acetal Claisen rearrangement. The azaporphyrins are readily accessible from the naturally occurring bile pigment bilirubin (5). The photophysical properties of the azachlorins recommend these chlorin derivatives as potential photosensitizers for Photodynamic Therapy (PDT).
Common pathways to 1,3,2‐thiazaphospholidin‐4‐ones
Authors: Weber Martin , Ugi Ivar 
Published: July 2007

Abstract1,3,2‐Thiazaphospholidin‐4‐ones are a relatively new group of five‐membered cyclic phosphorylating agents. They may be used in amino acid phosphorylation and nucleotide coupling. Common pathways to thus compounds are reported. Even sulfurized DNA analogs are accessible by these agents.
Syntheses of putative metabolites of 1,2,3,4‐tetrahydro‐7,12‐dimethylbenz[a]anthracene
Authors: Srivastava Santosh K. , Sharma Pradeep K. 
Published: July 2007

AbstractSyntheses of (8α,9α,10α,11β)‐trans‐1,2,3,4,8,9,10,11‐octahydro‐7,12‐dimethyl‐8,9‐epoxybenz[a]anthracene‐10,11‐diol (3) and (8α,9α,10β,11α)‐trans‐1,2,3,4,8,9,10,11‐octahydro‐7,12‐dimethyl‐8,9‐epoxybenz[a]anthracene‐10,11‐diol (4), the putative D‐ring metabolites of 1,2,3,4‐tetrahydro‐7,12‐dimethyl‐benz[a]anthracene (1), starting from 1,2,3,4‐tetrahydro‐10‐methoxy‐7,12‐dimethylbenz[a]anthracene (11), are reported.
Synthesis of oxochlorins from the red blood pigment heme and their transformation into potentially biologically active chlorin derivatives
Authors: Bats Jan W. , Haake Gerold , Meier Axel , Montforts Franz‐Peter , Scheurich Gerhard 
Published: July 2007

AbstractThe hydroxychlorinrac‐3was prepared from the readily accessible chlorinsrac‐5a, b. The alcohol function ofrac‐3could be used to attach an estrogen residue28and the hydroquinone19to yield the chlorin estrogen ethers32a, band the chlorin hydroquinone etherrac‐30respectively. The prepared chlorin estrogen derivatives might be useful as sensitizers and fluorescence markers for photodynamic therapy and other diagnostic/therapeutic applications. The chlorin hydroquinone ether is of interest as a potential artificial photosynthesis system, which contains a „natural”︁ chlorin as a structural subunit in contrast to previously synthesized model systems based on porphyrins.
Formation of tricyclic compounds in domino reactions of alkenal oximes
Authors: Aurich Hans Günter , Quintero Jose‐Luis Ruiz , Sievers Ulrich 
Published: July 2007

Abstract5‐Alkenal oximes 4, 12, and 13 were prepared by various methods. These oximes undergo a domino reaction with mercaptoacetaldehyde (1‐M) affording tricyclic compounds 6, 17 and 18, respectively. At first the mercapto group adds to the oxime function forming a hydroxyamino moiety which then condenses with the aldehyde group giving the cyclic nitrones 10, 15, and 16, resp., as intermediates. These nitrones undergo spontaneously an intramolecular cycloaddition yielding the tricyclic compounds (6, 17, 18). The regioselectivity of the latter reaction step is opposite to that observed for corresponding intermolecular nitrone cycloadditions. The domino reaction proceeds highly selectively affording only one of the diastereomers. Starting from enantiomerically pure oxime 13, we prepared optically active 18. The stereogenic center of 13 induces the formation of three further stereogenic centers in the product. The configuration at C‐5 of 18 was determined by a NOESY experiment.
Synthesis of 5,5,10,10‐tetramethyl‐1‐oxacyclotridecane‐6,7,8,9‐tetrone – on the mechanism of the Rubottom reaction
Authors: Gleiter Rolf , Staib Michael , Ackermann Uwe 
Published: July 2007

AbstractThe synthesis of 5,5,10,10‐tetramethyl‐1‐oxacyclotridecan‐6,7,8,9‐tetrone (12) was achieved via a multistep procedure involving an oxidation known as the Rubottom reaction. The key intermediates were the dialdehyde (25), the diacid (33), the cyclic diketone (39) and the bis(silyl enol ether) (42). The oxidation of 42 with mCPBA yielded two diastereomers, the syn and anti bis(α‐hydroxy ketones) (44, 45) the ratio of which depends strongly on the solvent used. This result combined with the isolation of the diepoxide (43) gives an insight into the stereochemistry of the Rubottom reaction.
Ab initio and semiempirical calculations of the hetero‐Diels‐Alder reaction of 1‐aza‐1,3‐butadiene with ethene
Authors: Tietze Lutz F. , Fennen Jens , Geißler Holger , Schulz Gerhard , Anders Ernst 
Published: July 2007

AbstractThe transition structures of the hetero‐Diels‐Alder reaction of (E)‐ and (Z)‐1‐aza‐1,3‐butadiene (8 and 11) were studied by means of ab initio (UHF/6‐31+G* and RHF/6‐31+G*) and semiempirical (AM1, PM3) methods. The energy surface of the title reaction was calculated with AM1/CI. Two competing reaction channels exist, a concerted and a two‐step path. All methods used show a preference for the two‐step mechanism in agreement with experimental observations.
A novel synthesis of 1‐(2,4,6‐trihydroxy‐3,5‐dimethylphenyl)ethanone (di‐C‐methylphloracetophenone) and two new non‐aromatic C‐benzylated derivatives
Authors: Hauteville Marcelle , Stomberg Rolf , Gaillard Pascale , Duclos Marie‐Christine 
Published: July 2007

AbstractThe synthesis of the title compound 1e was achieved by an easy three‐step procedure from 1,3,5‐benzenetriol (1a, phloroglucinol). Compound 1a was C‐methylated using MeI. The crude mixture obtained was acetylated to give 1d which was converted into 1e using BF3 AcOH complex. Benzylation of the latter with benzyl chloride afforded the new non‐aromatic compound 2. Reaction of 2 with NaOH and benzoyl chloride (Scheme 1) gave the new compound 4. Its structure was established by X‐ray analysis.
Structure elucidation of yersiniabactin, a siderophore from highly virulent Yersinia strains
Authors: Drechsel Hartmut , Stephan Holger , Lotz Ralf , Haag Hubert , Zähner Hans , Hantke Klaus , Jung Günther 
Published: July 2007

AbstractFrom cultures of Yersinia enterocolitica H1852, an iron‐complexing and iron‐transporting compound named yersiniabactin was isolated. The structure of the siderophore was determined by a variety of spectroscopic methods, including 2D NMR experiments on the metal‐free ligand as well as its gallium complex. The metal‐free ligand, derivatives, as well as iron and gallium complexes were examined by high‐resolution FAB‐MS, API‐MS, API‐MS/MS and GC‐MS. The novel siderophore contains a benzene and a thiazolidine ring, as well as two thiazoline rings (Figure 1). Its stereochemistry is noteworthy for the presence of five chiral centers, one of which is considerably epimerized. The compound forms stable complexes with trivalent cations such as ferric iron and gallium.
π…︁π interactions of flavins, 5. Syntheses, structures and physical properties of flavin systems with covalent bonding to π donors and π acceptors (quinones)
Authors: Staab Heinz A. , Kanellakopulos Johannes , Kirsch Peer , Krieger Claus 
Published: July 2007

AbstractTo study π…︁π interactions of flavins of different redox states with π‐electron donors and acceptors, the syntheses of compounds in which such π systems are linked to flavins by using the „cyclophane concept”︁ were attempted and partially achieved. The syntheses of the metacyclo‐isoalloxazinophanes 1 and 2 are reported as well as the X‐ray structure analysis of 2. The conversion of 1 or 2 to the benzoquinono‐isoalloxazinophanes 3 or 4, respectively, was not achieved, obviously due to the specific sterical shielding of the methoxy groups in the isoalloxazinophanes. Benzoquinone‐isoalloxazine systems in which the two components are linked by only one triethylene chain were obtained. Spectroscopic and electrochemical properties related to intramolecular interactions are reported.
Sulfonamide‐based catenanes — regioselective template synthesis
Authors: Ottens‐Hildebrandt Stephan , Schmidt Thomas , Harren Jörg , Vögtle Fritz 
Published: July 2007

AbstractThe first catenanes containing sulfonamide units were synthesized. Selective formation of the in/out isomer 7 can be explained by host‐guest interactions that cause a regioselective templating effect. Replacement of O2S‐NH by O2S‐NMe increases the yield significantly (from 10 to 19%). The sulfonamide catenane 7 has a topologically chiral structure.
Synthesis of asymmetrical methyl‐branched chiral ketones from the corresponding homologous wax esters. A new synthesis of the insect pheromone lardolure and of 9‐norlardolure
Authors: Morr Michael , Proppe Christiane , Wray Victor 
Published: July 2007

AbstractThe insect pheromone (2R4R6R,8R)‐4,6,8‐trimethyl‐2‐undecyl formate (lardolure, 7c) and (2R,4R,6R,8R)‐4,6,8‐trimethyl‐2‐decyl formate (9‐norlardolure, 7b) have been synthesized from the corresponding homologous chiral methyl‐branched esters 1b and 1c, which have been obtained from the preengland wax of the domestic goose Anser a. f. domesticus. The intermediate (4R,6R,8R)‐4,6,8‐trimethyl‐2‐undecanone (4c) and (4R,6R,8R)‐4,6,8‐trimethyl‐2‐decanone (4b), the (2R)‐alcohols 5c and 5b, as well as some analogous compounds, have been characterized. 9‐Norlardolure (7b) shows a weak pheromone activity.
PE‐spectroscopic investigation of nonconjugated π,π interactions in (seco)dodecahedradienes — on the route to an experimental ethylene/ethylene cycloaddition reaction coordinate
Authors: Martin Hans‐Dieter , Mayer Bernhard , Weber Klaus , Wahl Fabian , Prinzbach Horst 
Published: July 2007

AbstractNature and extent of nonconjugated π,π interactions in (bis)‐secododecahedradienes and (pentagonal, non‐pentagonal) dodecahedradienes with transannular π,π distances ranging from ca. 2.8 to ca. 3.5 Å – representing well defined points on the D2h [π2 + π2] reaction coordinate – were studied by PE spectroscopy. The π,π splitting of 0.68 eV measured at the largest π,π distance of ca. 3.5 Å (1,16‐dodecahedradiene 3a) was attributed to ca. 50% each of through‐space and through‐bond conjugation (analysis of precanonical MOs).
Synthesis of bis(trifluoromethyl)‐substituted olefins: Methods of preparation and properties
Authors: Haas Alois , Lieb Max , Zwingenberger Jörg 
Published: July 2007

AbstractSeveral bis(trifluoromethyl)‐ and trifluoromethyl‐substituted alkenes, dienes, arylalkenes, and α,β‐unsaturated derivatives of carbonyl compounds such as tosylhydrazone 5b and diazomethane 5c were prepared. Their reactivity towards a variety of nucleophiles, resulting from the electron‐withdrawing effect of the trifluoromethyl group, was investigated. Depending on the trifluoromethyl‐ and a bis(trifluoromethyl)‐substituted double bond, different regioselectivities were observed in the reaction with morpholinocyclohexene as a nucleophile. An explanation is given on the basis of the 13C‐NMR data.