Synthese, 13C-NMR-Spektren und räumliche Struktur von ‘Push-Pull’-Diacetylenen

Synthesis, ¹³C-NMR Spectra, and X-Ray Investigation of ‘Push-Pull’ Diacetylenes Phenyl-substituted ‘push-pull’ diacetylenes 1f and 1g have been prepared by acetylation and benzoylation of the appropriate lithiodiynylamines 4 (Scheme 2). ¹³C-NMR spectra of diacetylenes 1a–g (Table 1) are discussed with respect to the expected polarisation of the diacetylene unit by ‘push’ and ‘pull’ substituents. X-Ray investigations of 1c , 1e , and 1f have been performed in view of the planned solid-state polymerisation of ‘push-pull’ diacetylenes. In the crystalline state, diacetylenes 1c and 1f are stacked, however, the stacking parameters do not allow a solid-state polymerisation.     

Versuche zur Synthese von ‘Push-Pull’-Diacetylenen

Attempted Synthesis of Push-Pull Diacetylenes Two alternative synthesis of push-pull diacetylenes of type 1 (5-amino-2,4-alkadiynals) are investigated. A bromination-dehydrobromination sequence starting with 5-dimethylamino-2,4-pentadienal ( 2 ) as well as the application of the well-known Cadiot-Chodkiewicz coupling reaction give new intermediates 3–5 , and 7 and 8 , respectively, but fail to give the target molecules 1 .     

Push-pull alkenes by reacting N,N′-dimethyl cyclic ketene N,N′-acetals with isocyanates: synthesis, structures, and reactivities

N,N′-Dimethyl cyclic ketene N,N′-acetals react with two or three equivalents of isocyanates to generate tetrasubstituted push-pull alkene derivatives in one-pot sequential reactions. X-ray crystallography showed significant elongations and out of plane distorsions of the polarized carbon-carbon double bonds.     

Synthese von ‘Push-Pull’-Oligoacetylenen

Synthesis of ‘Push-Pull’-OligoAcetylenes ‘Push-pull’ triacetylenes 11a , b , c , as well as ‘push-pull’ tetraacetylene 13b have been prepared by reaction of the corresponding trichloroene(oligoinyl)amines 9 and 10 with 2 mol-equiv. of BuLi followed by acylation. The sequences (Schemes 3 and 4) are very simple and straightforward, they could in principle be applied to the synthesis of ‘push-pull’ pentaAcetylenes 15 and hexaacetylenes 17 (Scheme 5). Main limitations are the moderate yields as well as the low thermal stability of push-pull oligoacetylenes.     

Polydiacetylene–inorganic clay nanocomposites

Two new diacetylenes, 14-amino-10,12-tetradiynoic acid (a diacetylenic aminoacid) and 10,12-docosadiyndiamine (diacetylenic diamine), were successfully synthesized via Eglinton and Cadiot–Chodkiewicz coupling. These two diacetylenes and 10,12-pentacosadiynyl amine (monoamine) were intercalated in mica-type layered silicates, montmorillonite and vermiculite, via a cationic exchange reaction. The intercalation process was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The interlayer spacing and polymerizability of the intercalated diacetylene were found to depend upon the length of the diacetylene molecule, the layer charge density of the clay and the solvent treatment. The X-ray diffraction pattern of vermiculite–diacetylene showed evidence of the in-plane packing of the diacetylene. The polymerization of the intercalated diacetylene was confirmed by Raman spectra. © 1998 John Wiley & Sons, Ltd.     

“Push-Pull”-Acetylene für die Peptid-Synthese

“Push-Pull” Acetylenes as Reagents for Peptide Synthesis A series of ‘push-pull’ acetylenes 1 is easily available from the corresponding “push-pull” olefins by a simple bromination-dehydrobromination sequence. The versatility of the acetylenes with regard to peptide synthesis is discussed.     

Novel synthesis of 4,5-diarylphenanthrenes via C2-C6 cyclization of benzannulated enyne-allenes.

A new synthetic pathway to the 4,5-diarylphenanthrenes 8 having a helical twist in their structures was developed. The synthetic sequence involves condensation of the diketone 5 with 2 equiv of the lithium acetylides derived from the diacetylenes 4 followed by protonation to produce the propargylic alcohols 6. Reduction of 6 with triethylsilane in the presence of trifluoroacetic acid furnished the tetraacetylenic hydrocarbons 7 in nearly quantitative yields. Treatment of 7 with potassium tert-butoxide under refluxing toluene at 110 degrees C for up to 10 h then furnished the 4,5-diarylphenanthrenes 8. Apparently, the transformation from 7 to 8 involves initial prototropic isomerizations to form the benzannulated enyne-allenes 9. Two subsequent formal intramolecular Diels-Alder reactions via the biradicals 10 and 12 derived from the C(2)-C(6) cyclizations then led to 13, which in turn underwent tautomerizations to give 8. The structure of 8a was established by the X-ray structure analysis, showing that the two phenyl substituents are bent away from each other and the central aromatic system is severely distorted with a helical twist. The existence of a helical twist in 8 imposed by the aryl groups at the 4- and 5-positions was also revealed with a set of AB (1)H NMR signals for the diastereotopic methylene hydrogens on the five-membered rings.     

Liquid crystal properties of novel diacetylenes having a pyridine end group

Asymmetrical diacetylenes with a pyridine ring bonded directly to one end of the diacetylene unit and an aryl system containing a flexible alkoxy chain at the opposite end, have been synthesized and show liquid crystalline behaviour. The mesophase behaviour is shown to be dependent on the length of the flexible alkoxy chain. Incorporation of one of these diacetylenes in a polymer 'guest-host' system at a 15 wt% concentration gave a high X⁽²⁾ non-linear optical susceptibility of 4.27 × 10^-9e.s.u.     

Nitrogen–Carbon Bond Formation by Reactions of a Titanium–Potassium Dinitrogen Complex with Carbon Dioxide,tert‐Butyl Isocyanate,and Phenylallene

Nitrogen–carbon bond‐forming reactions at coordinated dinitrogen in a bifunctional titanium–potassium system are reported. A titanium atrane complex with a tris(aryloxide)methyl ligand ( 1 ) was treated with two equivalents of potassium naphthalenide under N₂ atmosphere to generate a bifunctional complex ( 2 ) in which N₂ binds end‐on to two titanium centers and side‐on to three potassium cations. Dinitrogen complex 2 reacted with carbon dioxide, tert ‐butyl isocyanate, and phenylallene, forming nitrogen–carbon bonds and affording diverse N‐functionalized products. The reaction of 2 with CO₂ followed by addition of Me₃SiCl resulted in the formation of the starting complex 1 with concomitant release of silylated carboxyl hydrazines while the reaction with two equivalents of tert ‐butyl isocyanate proceeded by insertion into the Ti−N bonds. Treatment of 2 with phenylallene afforded vinyl‐substituted hydrazido complexes.     

General synthesis of thiophene and selenophene-based heteroacenes

[reaction: see text] A new intramolecular triple cyclization of bis(o-haloaryl)diacetylenes, via dilithiation followed by reaction with chalcogen elements, produces pi-conjugated compounds containing heterole-1,2-dichalcogenin-heterole fused tricyclic skeletons. The subsequent dechalcogenation with copper metal affords a series of thiophene- and selenophene-based heteroacenes.     

Selective N,O‐Addition of the TEMPO Radical to Conjugated Boryldienes

B(C₆F₅)₂‐containing boryldienes 4 underwent the addition of two molar equivalents of TEMPO to give N,O‐bonded four‐membered heterocyclic products 7 . The reaction is a metal‐free example of the generation of reactive nitrogen‐centered TEMPO radical derivatives, in this case by the addition of TEMPO to the borane, followed by carbon–nitrogen bond formation and subsequent trapping of the resulting allyl radical by the second equivalent of TEMPO.     

Der ‘Push-Pull’-Effekt von ‘Push-Pull’-Oligoacetylenen. Eine 13C-NMR-Untersuchung

The ‘Push-Poll’ Effect of ‘Push-Pull’ Oligoacetylenes. A ¹³C-NMR Investigation According to ¹³C-chemicaI shifts of ‘push-pull’ oligoacetylenes 1 – 4 , the ‘push-pull’ effect (i.e. π delocalization induced by ‘push-pull’ substituents) rapidly decays in this series. To correct for other than π -charge-density effects, Δδ values of symmetrically placed C-atoms of the oligoacetylene chain are discussed. Stereoelectronic resteffects (SER) of the substituents on terminal C-atoms of PP-ketones 1a – 3a and PP -esters 1b – 4b are estimated from the residual Δδ of the asymptotes of Fig. 3. Fig. 4 convincingly shows that Δδ values are dramatically decreasing with increasing number n of acetylene units between the push and pull substituents. Assignment problems of ‘push-pull’ triacetylenes 3 have been solved by ¹³C labelling of the CO group of 3a .     

Alternating diacetylene copolymer utilizing perfluorophenyl-phenyl interactions

The symmetric diacetylenes, 2,4-hexadiynylene dibenzoate 4 and 2,4-hexadiynylene bis(pentafluorobenzoate) 5, as well as the unsymmetric 6-(pentafluorobenzoyloxy)hexa-2,4-diynyl benzoate 6 were prepared and investigated with respect to their reactivity toward topochemical polymerization in the crystalline state. The 1:1 cocrystal 4.5 was successfully polymerized to the corresponding poly(diacetylene) copolymer 7, as evidenced by solid-state (13)C NMR and Raman spectroscopy, as well as single-crystal structure analysis of the monomer-polymer cocrystal. Thus, perfluorophenyl-phenyl interactions were utilized as complementary supramolecular synthons in the cocrystallization of two different diacetylene monomers and their unprecedented conversion into a strictly alternating diacetylene copolymer.     

Preparation of new nitrogen-bridged heterocycles. 55. Reinvestigation of the bromination/dehydrobromination of ethyl 3-[2-(methylthio)indolizin-3-yl]acrylate derivatives

The bromination/dehydrobromination reactions of ethyl 3-[1-alkoxycarbonyl-2-(methylthio)indolizin-3-yl]acrylates were reinvestigated. Reactions of the title compounds with two equivalents of bromine, followed by heating of the resulting reaction mixture and then treatment with a base gave the unexpected dialkyl 7-bromothieno[2,3-b]indolizine-2,9-dicarboxylates, while similar reactions using benzyltrimethylammonium tribromide as a brominating agent afforded only non-brominated thieno[2,3-b]indolizine derivatives, which were converted to the corresponding 7-bromo derivatives upon further treatment with bromine.     

Festkörper-Polymerisation eines ‘Push-Pull’-Diacetylens

Solid-State Polymerisation of a ‘Push-Pull’-Diacetylene Solid-state polymerisation of ‘push-pull’-diacetylene 5-(diphenylamino)-1-phenylpenta-2,4-diyn-1-one ( 1d ), initiated by heating of crystals of 1d at 90°, gives ‘push-pull’ poly-diacetylene 2d . X-Ray results and spectroscopic data of monomer 1d as well as of polymer 2d are discussed.     

Theoretical investigation of two-photon absorption allowed excited states in symmetrically substituted diacetylenes by ab initio molecular-orbital method

Symmetrically substituted diacetylene compounds, which shows large two-photon absorption (TPA) cross sections, have been theoretically investigated by the ab initio molecular-orbital method employing several theoretical models including the configuration interaction with single excitation (CIS), random phase approximation (RPA), and time-dependent density-functional theory (TDDFT) methods. The calculated excited energies are overestimated by CIS or RPA, whereas underestimated by TDDFT with the B3LYP parametrization for both one-photon absorption (OPA) and TPA allowed states. The lowest OPA state is well described by the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) transition. On the other hand, lower TPA allowed states can be represented as the superposition of the HOMO-LUMO+1 and HOMO-1-LUMO transitions, giving rise to two TPA allowed states. The absorption intensity for the lower TPA state of the diacetylenes molecules is discussed in terms of the alternancy symmetry and its breaking. The symmetry property is differently manifested for neutral and dicationic diacetylenes. Introduction of charges breaks the alternancy symmetry, which gives rise to an increase in the TPA cross sections at the lower frequency. The upper TPA state is calculated to show huge TPA cross sections, which reproduces the enhancement of the TPA cross section experimentally observed for one of the diacetylenes at the higher-frequency region. The enhancement is discussed employing an index defined as the ratio of the transition polarizability and its static limit, which represents the degree of influence of one-photon resonance on the TPA intensity. The huge TPA cross sections are found to be due to a near-resonance effect. The present theoretical calculation approves the previously proposed assumption based on the four-state (dual three-state) model, which consists of the ground, one OPA allowed, and two TPA allowed states.     

Synthesis and cytotoxic activity of a series of diacetylenic compounds related to falcarindiol

The synthesis of a series of diacetylenic compounds related to the natural product falcarindiol has been carried out. Unsymmetrical diacetylenes were prepared by a modification of the Cadiot-Chodkiewicz coupling reaction, while a Glaser coupling was used to prepare symmetrical diacetylenes. These compounds have been tested for in vitro cytotoxic activity against Hep-G2, and H-4-II-E cell lines. Diacetylenes with additional unsaturation at C-1, 2, appended with hydroxyl groups at C-3 and C-8, or with long hydrophobic chains, exhibited IC50 values in the micromolar range.     

Dianionic Tris[oxalato(2—)]silicate and Tris[oxalato(2—)]germanate Complexes: Synthesis,Properties, and Structural Characterization in the Solid State and in Solution

Reaction of tetramethoxysilane with three molar equivalents of oxalic acid and two molar equivalents of 1‐(2‐hydroxyethyl)‐pyrrolidine or 1‐(2‐hydroxyethyl)piperidine in tetrahydrofuran yielded the λ⁶Si‐silicates 1‐(2‐hydroxyethyl)pyrrolidinium tris[oxalato(2—)]silicate ( 4 ) and 1‐(2‐hydroxyethyl)piperidinium tris[oxalato(2—)]silicate ( 5 ). The related germanium compounds 1‐(2‐hydroxyethyl)piperidinium tris[oxalato(2—)]germanate ( 6 ) and triethylammonium tris[oxalato(2—)]germanate ( 7 ) were synthesized analogously, starting from tetramethoxygermane and using three molar equivalents of oxalic acid and two molar equivalents of 1‐(2‐hydroxyethyl)piperidine or triethylamine. Compounds 4 — 7 were characterized by elemental analyses (C, H, N), single‐crystal X‐ray diffraction, solid‐state VACP/MAS NMR spectroscopy (²⁹Si), and solution NMR spectroscopy (¹H, ¹³C, ²⁹Si). The structural characterization was complemented by computational studies of the tris[oxalato(2—)]silicate dianion and the tris[oxalato(2—)]germanate dianion. In addition, the stability of compounds 4 — 7 in aqueous solution was studied by ¹³C NMR spectroscopy.     

Alkali and alkaline-earth metal ketyl complexes: isolation, structural diversity, and hydrogenation/protonation reactions

The use of hexamethylphosphoric triamide (HMPA) as a stabilizing ligand allowed successful isolation of a series of structurally characterizable alkali metal and calcium ketyl complexes. Reaction of lithium and sodium with one equivalent of fluorenone and reaction of sodium with one equivalent of benzophenone in THF, followed by addition of two equivalents of HMPA, yielded the corresponding ketyl complexes 1, 2, and 11, respectively, as microketyl-bridged dimers. If one equivalent of HMPA was used in the reaction of sodium with fluorenone, a further aggregated complex, the mu3-ketyl-bridged tetramer 3, was isolated, whereas analogous reaction of benzophenone with sodium afforded the trimeric ketyl complex 13, rather than a simple benzophenone analogue of 3. In the reaction of potassium with fluorenone, the use of two equivalents of HMPA gave the tetramer 4, rather than a dimeric complex analogous to 1 or 2. Compared to the tetrameric sodium complex 3, there is an extra HMPA ligand that bridges two of the four K atoms in 4. When 0.5 equiv of HMPA was used in the above reaction, complex 5, a THF-bridged analogue of 4, was isolated. In the absence of HMPA, the reaction of sodium with an excess of fluorenone yielded the tetrameric ketyl complex 6, in which two of the four Na atoms are each terminally coordinated by a fluorenone ligand, and the other two Na atoms are coordinated by a THF ligand. Two bridging THF ligands are also observed in 6. Reaction of 1,2-bis(biphenyl-2,2'-diyl)ethane-1,2-diol (7) with two equivalents of LiN(SiMe3)2 or NaN(SiMe3)2 in the presence of four equivalents of HMPA easily afforded 1 or 2, respectively, via C-C bond cleavage of a 1,2-diolate intermediate. The reaction of calcium with two equivalents of fluorenone or benzophenone in the presence of HMPA gave the corresponding complexes that bear two independent ketyl ligands per metal ion. In the presence of 3 or four equivalents of HMPA, the fluorenone ketyl complex was isolated in a six-coordinate octahedral form (10), while the benzophenone ketyl complex was obtained as a five-coordinate trigonal bipyramid (13). The radical carbon atoms in both benzophenone ketyl and fluorenone ketyl complexes are still in an sp2-hybrid state. However, in contrast with the planar configuration of the whole fluorenone ketyl unit, the radical carbon atom in a benzophenone ketyl species is not coplanar with any of the phenyl groups; this explains why benzophenone ketyl is more reactive than fluorenone ketyl. Hydrolysis of 2 or 11 with 2N HCI yielded the corresponding pinacol-coupling product, while treatment of 2 or 11 with 2-propanol, followed by hydrolysis, gave the pairs fluorenone and fluorenol or benzophenone and benzhydrol, respectively. A possible mechanism for these reactions is proposed.     

The Behaviors of Metal Acetylides with Dinitrogen Tetroxide

Lithium phenylacetylide ( 1a ) and N₂O₄ ( 2 ) at −78° yield diphenylbutadiyne ( 6a ) by oxidative coupling, phenylacetylene ( 7a ) by oxidation and then solvent H‐abstraction, and benzoyl cyanide ( 8 ) by dimerizative‐rearrangement of nitroso(phenyl)acetylene ( 23 ). Nitro(phenyl)acetylene ( 3 , R=Ph) is not obtained. Benzonitrile ( 9 ), a further product, possibly results from hydrolytic decomposition of nitroso(phenyl)ketene ( 27 ) generated from phenylacetylenyl nitrite ( 26 ). Phenylacetylene ( 7a ) and 2 give, along with (E)‐ and (Z)‐1,2‐dinitrostyrenes ( 34 and 35 , resp.), 3‐benzoyl‐5‐phenylisoxazole ( 10 ), presumably as formed by cycloaddition of benzoyl nitrile oxide ( 40 ) to 7a . Further, 2 reacts with other lithium acetylides ( 1b – 1e ), and with sodium, magnesium, zinc, copper, and copper lithium phenylacetylides, 1f – 1l , to yield diacetylenes 6a – 6c and monoacetylenes 7a – 7c . Conversions of metallo acetylide aggregates to diacetylenes are proposed to involve generation and addition reactions of metallo acetylide radical cationic intermediates in cage, further oxidation, and total loss of metal ion. Loss of metal ions from metallo acetylide radical cations and H‐abstraction by non‐caged acetylenyl radicals will give terminal acetylenes. The principal reactions (75–100%) of heavy metal acetylides phenyl(trimethylstannyl)acetylene ( 44 ) and bis(phenylacetylenyl)mercury ( 47 ) with 2 are directed nitrosative additions (NO⁺) and loss of metal ions to give nitroso(phenyl)ketene ( 27 ), which converts to benzoyl cyanide ( 8 ).