Darstellung und Polymerisation von S-Vinyl-methylendisulfonen

Zusammenfassung S-Vinylmethylendisulfone (CH₂=CH-SO₂-CH₂-SO₂-R; R=C₂H₅, iso-C₃H₇, C₆H₅, CH=CH₂) wurden durch selektive Oxydation von Formaldehyd-S-vinylmercaptalen und durch Wasserabspaltung aus-Hydroxyäthylmethylendisulfonen dargestellt. Die Monomeren wurden in Dioxan-Lösung radikalisch mit AIBN und anionisch mit K-t. butylat polymerisiert. Versuche zur thermischen Polymerisation in der Schmelze (110 °C) und zur strahlungsinduzierten Polymerisation im festen Zustand waren ergebnislos. Aus kinetischen Messungen (dilatometrisch) ergab sich, daß die anionisch initiierte Polymerisation etwa 10 mal schneller verläuft als die Radikalpolymerisation. Besonders bei der anionisch initiierten Polyreaktion wird der Reaktionsverlauf stark durch die acide -SO₂-CH₂-SO₂-Gruppe beeinflußt. Dadurch kommt es bei der Bildung der Polymeren zu einer Überlagerung von Polymerisations- und Polyadditionsschritten. Die Polymeren sind durch Salzbildung in Natronlauge löslich und lassen sich mit -Chlormethyläthern polymeranalog in die entsprechenden Derivate überführen.

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Summary S-Vinyl-methylenedisulfones (CH₂=CH-SO₂-CH₂-SO₂-R; R=C₂H₅, iso-C₃H₇ C₆H₅, CH=CHb=0. were prepared by oxydation of Formaldehyd-S-vinyl-mercaptales and by dehydration from -Hydroxyethylmethylenedisulfones. The monomers were polymerized in dioxan with AIBN and K-t-butoxide as initiators. They could not be polymerized thermally neither in the melt (110 °C) nor by radiation in the solid state. Kinetic measurements (dilatometer) showed that the anionically initiated polymerization is about 10 times faster than the radically initiated reaction. The ionic polyreaction is especially strongly influenced by the acidity of the -SO₂-CH₂-SO₂-group. Thus, for the formation of the polymers, both — polymerization and polyaddition-steps — have to be considered. The poly-S-vinyl-methylenedisulfones are soluble in sodium hydroxide solution and react with -chloromethyl ethers to give the corresponding derivatives in a polymeranalogous reaction.

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Vorgetragen auf dem IUPAO-Symposium (Prag 1965).

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Teil IV,H. Ringsdorf u. Mitarb., Makromolekulare Chemie92, 122 (1966).

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FrauU. Gollmer danken wir für die Mitarbeit bei der Durchführung dieser Arbeit.Die Badische Anilin- und Sodafabrik AG Ludwigshafen, die Farbwerke Hoechst AG Frankfurt/M.-Höchst und die Farbenfabriken Bayer AG Leverkusen unterstützten diese Arbeit durch Überlassen von Chemikalien.     

The electronic structure and spectrum of tropone

The electronic structure and spectrum of tropone were studied by paying special attention to an assignment of the 300 m band. The band was shown to have a single ^* character overlapped by an n ^* transition from the following experimental and theoretical studies: (i) From the comparison of the observed transition energies and intensities with theoretical values obtained by the Pariser-Parr-Pople calculation in which the values of W _X ^2p (valence state ionization potential of the oxygen atom) and k (bond alternation parameter) taken as guiding parameters were changed widely and their adequateness was carefully examined, (ii) From the correlation among the electronic absorption spectra of tropone, troponeimine, and heptafulvene. (iii) From the finding that the 300 m band increases its intensity with the increasing polarity of the solvent. (iv) From the position and intensity of a band newly observed in the vacuum ultraviolet region.

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Zusammenfassung An Tropon wurden Elektronenstruktur und Spektrum untersucht, speziell die 300 m-Bande. Diese entsteht aus einem einzigen - ^*-Übergang, überlagert von einer schwachen n-^*-Bande, und nicht aus 2 - ^*-Banden. Als Stütze dienen: 1. eine PPP-Rechnung, bei der das Valenzzustandsionisationspotential von Sauerstoff und der Bindungsalternierungsparameter sorgfältig variiert wurden, 2. die Korrelation der Spektren von Tropon, Troponimin und Heptafulven, 3. der Lösungsmitteleinfluß auf die Bande, 4. eine neuaufgefundene UV-Bande.

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Résumé La structure électronique et le spectre de la tropolone ont été étudiés en accordant une attention particulière à l'identification de la bande à 300 m. Cette bande a été caractérisée comme résultant d'une transition ^* recouverte par une transition n ^*, à l'aide des arguments théoriques et expérimentaux suivants: 1. à partir de la comparaison des énergies et des intensités de transition observées, avec les valeurs théoriques obtenues par un calcul Pariser-Parr-Pople où les valeurs de W _X ^2p (potentiel d'ionisation de l'état de valence de l'atome d'oxygène) et de k (paramètre d'alternance des liaisons), considérés comme paramètres régulateurs, ont été largement variées et soigneusement analysées. 2. à partir de la corrélation entre les spectres d'absorption électronique de la tropolone, de la tropolonéimine et de l'heptafulène. 3. à partir du fait que la bande à 300 m voit son intensité croitre avec la polarité du solvent. 4. à partir de la position et de l'intensité d'une bande nouvelle observée dans la région de l'ultra-violet lointain.

     

High peak capacity separations of peptides in reversed-phase gradient elution liquid chromatography on columns packed with porous shell particles

The performance of 5 and 15 cm long columns packed with shell particles (Halo, AMT) is compared in gradient elution separations of the tryptic digests of myoglobin and bovine serum albumin. The influences of the temperature and the mobile phase flow rate on the column efficiency for two peptides are discussed. The influences of this flow rate, of the temperature, and of the gradient slopes on the peak capacities are also considered. Peak capacities in excess of 400 were achieved in 6h with the longer column. Peak capacities of 200 could be achieved in 30 min with the shorter column.     

Investigation of the thermal lens effect in water-ethanol mixtures: composition dependence of the refractive index gradient, the enhancement factor and the Soret effect.

The thermal lens effect produced in binary mixtures of water and ethanol has been investigated. It is shown that the sensitivity of the thermal lens method upon the addition of ethanol in water varies as the temperature-dependent refractive index gradient to thermal conductivity ratio of the mixture. The dependence of k and dn/dT upon the ethanol volume fraction follows a second-order and fourth-order polynomial, respectively, and cannot be precisely predicted using the additive rule. Moreover, depending on the experimental conditions and the mixture composition, the temperature gradient produced subsequently to relaxation of the excited species induces mutual migration of the solvent molecules and the formation of a concentration gradient in the irradiated area. This effect, known as the Soret effect, can locally change the thermo-optical properties of the solution and produce an additional signal, especially when steady-state experiments are done. This may result in errors as large as 20% when quantitative informations have to be derived from experimental data.     

Multifunctional Core–Shell Upconverting Nanoparticles for Imaging and Photodynamic Therapy of Liver Cancer Cells

Lanthanide‐doped upconversion nanoparticles (UCNPs) have attracted considerable attention for their application in biomedicine. Here, silica‐coated NaGdF₄:Yb,Er/NaGdF₄ nanoparticles with a tetrasubstituted carboxy aluminum phthalocyanine (AlC₄Pc) photosensitizer covalently incorporated inside the silica shells were prepared and applied in the photodynamic therapy (PDT) and magnetic resonance imaging (MRI) of cancer cells. These UCNP@SiO₂(AlC₄Pc) nanoparticles were uniform in size, stable against photosensitizer leaching, and highly efficient in photogenerating cytotoxic singlet oxygen under near‐infrared (NIR) light. In vitro studies indicated that these nanoparticles could effectively kill cancer cells upon NIR irradiation. Moreover, the nanoparticles also demonstrated good MR contrast, both in aqueous solution and inside cells. This is the first time that NaGdF₄:Yb,Er/NaGdF₄ upconversion‐nanocrystal‐based multifunctional nanomaterials have been synthesized and applied in PDT. Our results show that these multifunctional nanoparticles are very promising for applications in versatile imaging diagnosis and as a therapy tool in biomedical engineering.     

Crystal Engineering of Stable Temozolomide Cocrystals

The antitumor prodrug temozolomide (TMZ) decomposes in aqueous medium of pH≥7 but is relatively stable under acidic conditions. Pure TMZ is obtained as a white powder but turns pink and then brown, which is indicative of chemical degradation. Pharmaceutical cocrystals of TMZ were engineered with safe coformers such as oxalic acid, succinic acid, salicylic acid, d,l ‐malic acid, and d,l ‐tartaric acid, to stabilize the drug as a cocrystal. All cocrystals were characterized by powder X‐ray diffraction (PXRD), single crystal X‐ray diffraction, and FT‐IR as well as FT‐Raman spectroscopy. Temozolomide cocrystals with organic acids (pK_a 2–6) were found to be more stable than the reference drug under physiological conditions. The half‐life (T_1/2) of TMZ–oxalic and TMZ–salicylic acid measured by UV/Vis spectroscopy in pH 7 buffer is two times longer than that of TMZ (3.5 h and 3.6 h vs. 1.7 h); TMZ–succinic acid, TMZ–tartaric acid, and TMZ–malic acid also exhibited a longer half‐life (2.3, 2.5, and 2.8 h, respectively). Stability studies at 40 °C and 75 % relative humidity (ICH conditions) showed that hydrolytic degradation of temozolomide in the solid state started after one week, as determined by PXRD, whereas its cocrystals with succinic acid and oxalic acid were intact at 28 weeks, thus confirming the greater stability of cocrystals compared to the reference drug. The intrinsic dissolution rate (IDR) profile of TMZ–oxalic acid and TMZ–succinic acid cocrystals in buffer of pH 7 is comparable to that of temozolomide. Among the temozolomide cocrystals examined, those with succinic acid and oxalic acid exhibited both an improved stability and a comparable dissolution rate to the reference drug.     

Extended Fluorochromism of Anthracene Trimers with a meta‐Substituted Triphenylamine or Triphenylphosphine Core

Combining meta‐triphenylamine or triphenylphosphine with three anthracene fluorophores gives rise to fluorescent non‐planar triskelions 1 and 2 . The emissive properties of 1 are highly solvatochromic, yielding blue to pale green and even pale yellow fluorescence, whereas the blue emission of 2 is solvent‐insensitive. Anthracene trimers 1 and 2 are both emissive in the solid state, displaying yellow and pale green fluorescence, respectively, with moderate quantum yields.     

4‐(N,N‐Dimethylamino)pyridine‐Embedded Nanoporous Conjugated Polymer as a Highly Active Heterogeneous Organocatalyst

We report herein for the first time the incorporation of a versatile organocatalyst, 4‐(N,N‐dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the “bottom‐up” approach. The resulting DMAP‐NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g^?1). DMAP‐NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the “bottom‐up” monomers. As a result, DMAP‐NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92–99 %. The DMAP‐NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous‐flow conditions for at least 536 h of continuous work with the same catalyst activity.     

Asymmetric Synthesis of Densely Functionalized Medium‐Ring Carbocycles and Lactones through Modular Assembly and Ring‐Closing Metathesis of Sulfoximine‐Substituted Trienes and Dienynes

An asymmetric synthesis of densely functionalized 7–11‐membered carbocycles and 9–11‐membered lactones has been developed. Its key steps are a modular assembly of sulfoximine‐substituted C‐ and O‐tethered trienes and C‐tethered dienynes and their Ru‐catalyzed ring‐closing diene and enyne metathesis (RCDEM and RCEYM). The synthesis of the C‐tethered trienes and dienynes includes the following steps: 1) hydroxyalkylation of enantiomerically pure titanated allylic sulfoximines with unsaturated aldehydes, 2) α‐lithiation of alkenylsulfoximines, 3) alkylation, hydroxy‐alkylation, formylation, and acylation of α‐lithioalkenylsulfoximines, and 4) addition of Grignard reagents to α‐formyl(acyl)alkenylsulfoximines. The sulfoximine group provided for high asymmetric induction in steps 1) and 4). RCDEM of the sulfoximine‐substituted trienes with the second‐generation Ru catalyst stereoselectively afforded the corresponding functionalized 7–11‐membered carbocyles. RCDEM of diastereomeric silyloxy‐substituted 1,6,12‐trienes revealed an interesting difference in reactivity. While the (R)‐diastereomer gave the 11‐membered carbocyle, the (S)‐diastereomer delivered in a cascade of cross metathesis and RCDEM 22‐membered macrocycles. RCDEM of cyclic trienes furnished bicyclic carbocycles with a bicyclo[7.4.0]tridecane and bicyclo[9.4.0]pentadecane skeleton. Selective transformations of the sulfoximine‐ and bissilyloxy‐substituted carbocycles were performed including deprotection, cross‐coupling reaction and reduction of the sulfoximine moiety. Esterification of a sulfoximine‐substituted homoallylic alcohol with unsaturated carboxylic acids gave the O‐tethered trienes, RCDEM of which yielded the sulfoximine‐substituted 9–11‐membered lactones. RCEYM of a sulfoximine‐substituted 1,7‐dien‐10‐yne showed an unprecedented dichotomy in ring formation depending on the Ru catalyst. While the second‐generation Ru catalyst gave the 9‐membered exo 1,3‐dienyl carbocycle, the first‐generation Ru catalyst furnished a truncated 9‐membered 1,3‐dieny carbocycle having one CH₂ unit less than the dienyne.     

Mechanistic Studies on the Gas‐Phase Dehydrogenation of Alkanes at Cyclometalated Platinum Complexes

In the ion/molecule reactions of the cyclometalated platinum complexes [Pt(L? H)]⁺ (L=2,2′‐bipyridine (bipy), 2‐phenylpyridine (phpy), and 7,8‐benzoquinoline (bq)) with linear and branched alkanes C_nH_2n+2 (n=2–4), the main reaction channels correspond to the eliminations of dihydrogen and the respective alkenes in varying ratios. For all three couples [Pt(L? H)]⁺/C₂H₆, loss of C₂H₄ dominates clearly over H₂ elimination; however, the mechanisms significantly differs for the reactions of the “rollover”‐cyclometalated bipy complex and the classically cyclometalated phpy and bq complexes. While double hydrogen‐atom transfer from C₂H₆ to [Pt(bipy? H)]⁺, followed by ring rotation, gives rise to the formation of [Pt(H)(bipy)]⁺, for the phpy and bq complexes [Pt(L? H)]⁺, the cyclometalated motif is conserved; rather, according to DFT calculations, formation of [Pt(L? H)(H₂)]⁺ as the ionic product accounts for C₂H₄ liberation. In the latter process, [Pt(L? H)(H₂)(C₂H₄)]⁺ (that carries H₂ trans to the nitrogen atom of the heterocyclic ligand) serves, according to DFT calculation, as a precursor from which, due to the electronic peculiarities of the cyclometalated ligand, C₂H₄ rather than H₂ is ejected. For both product‐ion types, [Pt(H)(bipy)]⁺ and [Pt(L? H)(H₂)]⁺ (L=phpy, bq), H₂ loss to close a catalytic dehydrogenation cycle is feasible. In the reactions of [Pt(bipy? H)]⁺ with the higher alkanes C_nH_2n+2 (n=3, 4), H₂ elimination dominates over alkene formation; most probably, this observation is a consequence of the generation of allyl complexes, such as [Pt(C₃H₅)(bipy)]⁺. In the reactions of [Pt(L? H)]⁺ (L=phpy, bq) with propane and n‐butane, the losses of the alkenes and dihydrogen are of comparable intensities. While in the reactions of “rollover”‐cyclometalated [Pt(bipy? H)]⁺ with C_nH_2n+2 (n=2–4) less than 15 % of the generated product ions are formed by C? C bond‐cleavage processes, this value is about 60 % for the reaction with neo‐pentane. The result that C? C bond cleavage gains in importance for this substrate is a consequence of the fact that 1,2‐elimination of two hydrogen atoms is no option; this observation may suggest that in the reactions with the smaller alkanes, 1,1‐ and 1,3‐elimination pathways are only of minor importance.