间溴苯氧丙酸与7-溴苯并二氢吡喃-4-酮的合成

以间溴苯酚和3-溴丙酸为原料,合成了间溴苯氧丙酸,并以间溴苯氧丙酸为原料,进一步合成了7-溴苯并二氢吡喃-4-酮。探讨了投料比、反应时间、反应温度、氢氧化钠的质量分数和加料顺序等因素对间溴苯氧丙酸收率的影响。适宜的反应条件为:n(间溴苯酚)∶n(氢氧化钠)∶n(3-溴丙酸)=1∶1∶1.3,反应温度95℃,氢氧化钠的质量分数8%,反应时间7 h,间溴苯氧丙酸收率71.4%。以间溴苯氧丙酸为原料,以85%的收率合成了7-溴苯并二氢唑喃-4-酮。     

2,6-Dibromo-3,5-dimethyl-4-hydroxybenzyl ether and epoxy systems

Summary Meta-halogenated phenols are generally known to be more chemically and thermally stable than their ortho-or para-halogenated counterparts. A novel compound, 2,6-dibromo-3,5-dimethyl-4-hydroxybenzyl ether, is synthesized and is being used to incorporate this stable meta-bromo-phenol moiety into epoxy resins. In electronic encapsulation applications, epoxy derivatives of novolacs containing meta-bromo-phenol have exhibited exceptional hydrolytic and thermal stability compared to the conventional tetrabromobisphenol-A epoxies which are ortho-brominated phenolics. The meta-bromo-phenol moiety contributes to the extended device reliability life while providing fire retardency property.     

Crosslinkable functional moiety for the formation of highly crosslinked stable microspheres in the precipitation polymerization

The highly crosslinked stable spherical microspheres were successfully synthesized using styrene and three crosslinking agents having different number of crosslinkable functional moiety in comonomer using the precipitation polymerization. The crosslinking agents are ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA) and pentaerythritol tetraacrylate (PETRA). The maximum and minimum concentrations for forming the stable spherical particles were ranging at 20-90 mol% for EGDMA, 15-80 mol% for TMPTMA, and 5-40 mol% for PETRA, respectively. The number-average diameter of stable poly(S-co-EGDMA), poly(S-co-TMPTMA), and poly(S-co-PETRA) particles varied 4.1-3.06, 3.94-3.03 and 2.77-1.66 μm, respectively. Since the prepared microspheres are highly crosslinked, no glass transition temperature was observed. The TGA onset point of the thermal degradation temperature increased with the concentration of crosslinking agent and the number of crosslinkable functional moiety, which is EGDMA < TMPTMA < PETRA. As a result, the minimum and maximum concentrations for the formation of stable spherical particles of poly(S-co-EGDMA), poly(S-co-TMPTMA), and poly(S-co-PETRA), the particle size and its distribution, CV, yield and the TGA onset point are significantly affected by the number of the crosslinkable functional moiety. Thus, the number of the crosslinkable functional moiety and the different reactivity as well as the different copolymerization parameters of styrene with (meth)acrylates would influence the composition as well as the rate of formation of stable microspheres.     

Thiol-ene Reaction as Reversible Covalent Bond for the Design of Shape-Memory Polymers

Besides a stable phase, shape-memory polymers require an additional switchable moiety. In addition to thermal transitions and supramolecular interactions, these units can also be based on covalent bonds. Herein, the use of the reversible thiol-ene reaction as reversible cross-linker for the design of shape-memory polymers is demonstrated. A facile route to polymer networks with a thiol-ene acceptor and a comonomer (butyl methacrylate or 2-ethylhexyl methacrylate) cross-linked by dithiols is introduced. The thermal and mechanical properties of the resulting polymers are characterized in detail. Hereby, the polymers feature excellent shape-memory behavior with fixity and recovery rates above 90%. This study shows that the thiol-ene cross-linker can function as both, the stable and the switchable structural moiety rendering the usage of a covalent cross-linker unnecessary. This partial reversibility can also be proven by temperature-depending Raman spectroscopy.     

One-pot synthesis of stable phosphonium ylides using 2-mercaptopyrimidine derivatives

The reaction of dialkyl acetylenedicarboxylates with 2-mercaptopyrimidine and 2-mercapto-4,6-dimethylpyrimidine in the presence of triphenylphosphine leads to stable phosphorus ylides in excellent yields. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbon group.     

Organotrifluoroborates: protected boronic acids that expand the versatility of the Suzuki coupling reaction

Organotrifluoroborates represent an alternative to boronic acids, boronate esters, and organoboranes for use in Suzuki-Miyaura and other transition-metal-catalyzed cross-coupling reactions. The trifluoroborate moiety is stable toward numerous reagents that are often problematic for other boron species. Consequently, remote functional groups within the organotrifluoroborates can be manipulated, while retaining the valuable carbon-boron bond.     

Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Supramolecular modification of single-walled carbon nanotubes with a water-soluble triptycene derivative

Supramolecular surface modification of single-walled carbon nanotubes (SWCNTs) using an amphiphilic molecule containing a bent triptycene moiety and a hydrophilic oligo(ethylene glycol) chain is described. The surface modification was realized through the binding of the triptycene moiety onto the sidewall of SWCNTs through a π–π stacking interaction, and the oligo(ethylene glycol) chains extend into the water and act as dispersing agents, thus yielding an aqueous SWCNT dispersion. This dispersion is stable for more than six months and contains a high concentration of SWCNTs. The dispersion was characterized by absorption, fluorescence, and Raman spectroscopy. Based on shape-fitting of SWCNTs and the triptycene moiety, the stacking of triptycene moieties on the SWCNT sidewall shows a nice selectivity for SWCNTs with a diameter of 1.0 nm.     

Gold Drugs with {Au(PPh3)}+ Moiety: Advantages and Medicinal Applications

Following the success of Auranofin as an anti-arthritic drug, search for novel gold drugs has afforded a large number of [L−Au(PPh₃)] complexes that exhibit notable salutary effects. Unlike Au(III)-containing species, these gold complexes with {Au(PPh₃)}⁺ moiety are stable in biological media and readily exchange L with S- and Se-containing enzymes or proteins. Such exchange leads to rapid reduction of microbial loads or induction of apoptotic cell death at malignant sites. In many cases the lipophilic {Au(PPh₃)}⁺ moiety delivers a desirable toxic L to the specific cellular target in addition to exhibiting its own beneficial activity. Further research and utilization of this synthon in drug design could lead to novel chemotherapeutics for treatment of drug-resistant pathogens and cancers.     

Photodegradation of polyimides. II. Thermal property changes of polyimides based on a hexafluorinated dianhydride

Polyimides based on a hexafluorinated dianhydride decrease in thermal and thermal-oxidative stability upon photolysis with an unfiltered medium pressure mercury lamp source in air. Additionally, the glass transition of photolyzed polyimides containing the hexafluorinated moiety is lowered with increasing photolysis time. By contrast, pyromellitic-dianhydride-based polymers are relatively thermally stable even after prolonged photolysis under similar conditions.     

Synthesis and Characterization of Ferrocene-Containing Hyperbranched Poly(aroylarylene)s

Ferrocene-containing hyperbranched poly(aroylarylene)s are prepared in satisfactory yields by one-pot copolycyclotrimerization of bis(aroylacetylene)s with a ferrocene-containing monoyne. The ferrocene content of the polymers can be varied by changing the monomer feed ratio, and copolymers with up to 41 mol% of ferrocene moiety can be readily prepared. All the polymers are thermally stable, losing little of their weights when heated to 340 °C. This article is dedicated to Professor Didier Astruc.     

An efficient synthesis of stable sulfur-containing phosphoranes derived from 2-mercapto-1-methylimidazole and 2-thiazoline-2-thiol

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong SH-acids, such as 2-mercapto-1-methylimidazole and 2-thiazoline-2-thiol. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group.     

Biosynthesis of Phenolic Glycosides from Phenylpropanoid and Benzenoid Precursors in <Emphasis Type="Italic">Populus</Emphasis>

Salicylate-containing phenolic glycosides (PGs) are abundant and often play a dominant role in plant-herbivore interactions of Populus and Salix species (family Salicaceae), but the biosynthetic pathway to PGs remains unclear. Cinnamic acid (CA) is thought to be a precursor of the salicyl moiety of PGs. However, the origin of the 6-hydroxy-2-cyclohexen-on-oyl (HCH) moiety found in certain PGs, such as salicortin, is not known. HCH is of interest because it confers toxicity and antifeedant properties against herbivores. We incubated Populus nigra leaf tissue with stable isotope-labeled CA, benzoates, and salicylates, and measured isotopic incorporation levels into both salicin, the simplest PG, and salicortin. Labeling of salicortin from [¹³C₆]-CA provided the first evidence that HCH, like the salicyl moiety, is a phenylpropanoid derivative. Benzoic acid and benzaldehyde also labeled both salicyl and HCH, while benzyl alcohol labeled only the salicyl moiety in salicortin. Co-administration of unlabeled benzoates with [¹³C₆]-CA confirmed their contribution to the biosynthesis of the salicyl but not the HCH moiety of salicortin. These data suggest that benzoate interconversions may modulate partitioning of phenylpropanoids to salicyl and HCH moieties, and hence toxicity of PGs. Surprisingly, labeled salicyl alcohol and salicylaldehyde were readily converted to salicin, but did not result in labeled salicortin. Co-administration of unlabeled salicylates with labeled CA suggested that salicyl alcohol and salicylaldehyde may have inhibited salicortin biosynthesis. A revised metabolic grid model of PG biosynthesis in Populus is proposed, providing a guide for functional genomic analysis of the PG biosynthetic pathway.     

Enhanced antibacterial activity of tetramethylguanidinium-conjugated linear polyethylenimine polymers

In the present study, varying amounts of tetramethylguanidinium moiety have been conjugated to linear polyethylenimine to obtain linear polyethylenimine-tmg (LPTG) polymers. Incorporation of hydrophobic and highly basic moiety in the polymeric backbone resulted in the significant improvement in the antibacterial activity which was confirmed by zone of inhibition and MIC assays. Further, the results of transmission electron microscopy and confocal studies revealed that the projected LPTG polymers possessed higher antibacterial activity than the native polymer. In addition, these modified polyethylenimine (PEI) polymers were capable of reducing auric chloride into stable gold nanoparticles. These polyamine-stabilized gold nanoparticles can be used in various biomedical applications.     

Acridine Variations for Coordination Chemistry

This study describes the synthesis of an acridone through the directed lithiation of a diarylamine, and elaboration via the 4,5-dibromoacridone. The bromo substituents are amenable to Suzuki-Miyaura coupling. Conversion to a 9-chloro-4,5-dibromoacridine, followed by bromine-lithium exchange, allows the preparation of a 4,5-bis (phosphino)-9-chloroacridine. The 9-chloro moiety undergoes nucleophilic aromatic substitution by methoxide or an aryloxide. One-electron reduction of a 9-(aryloxy)-4,5-bis(phosphino)acridine affords a stable radical anion.     

Pyroelectric and dielectric properties of side-chain liquid crystal polymers

Liquid crystal side-chain polymers (LCP), where the polymer architecture consists of a polymer backbone, flexible spacers, and mesogenic groups, are of considerable interest as they promise desirable electro-active properties, including pyroelectricity and electro-optic display phenomena. Induced polarization in the LCP system remains stable at ordinary temperatures, and therefore these systems are suitable for sensor materials for pyroelectric applications where switching times are less important. The dielectric applications of the polarized LCP system are also of importance if they are to be used as thin film electro-active devices. This paper reports the results of the dielectric and pyroelectric characterizations of six different polymers over a wide range of frequencies and temperatures. To elucidate the effect of a variation of chemical structure on the macroscopic properties, the structure of the mesogenic moiety was kept constant, and the length of the spacer and the size of the polymer backbone were varied.     

Effect of poly(acrylic acid) molecular mass and end‐group functionality on calcium oxalate crystal morphology and growth

A number of series of poly(acrylic acids) (PAA) of differing end‐groups and molecular mass were used to study the inhibition of calcium oxalate crystallization. The effects of the end‐group on crystal speciation and morphology were significant and dramatic, with hexyl‐isobutyrate end groups giving preferential formation of calcium oxalate dihydrate (COD) rather than the more stable calcium oxalate monohydrate (COM), while both more hydrophobic end‐groups and less‐hydrophobic end groups led predominantly to formation of the least thermodynamically stable form of calcium oxalate, calcium oxalate trihydrate. Conversely, molecular mass had little impact on calcium oxalate speciation or crystal morphology. It is probable that the observed effects are related to the rate of desorption of the PAA moiety from the crystal (lite) surfaces and that the results point to a major role for end‐group as well as molecular mass in controlling desorption rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Zur Chemie des Triacetonamins. III. Verlauf und Produkte der Umsetzung von Isocyanaten mit 2,2,6,6-Tetramethylpiperidin-4-onoxim

Triacetoneamine Chemistry. III. Course of and Products from the Interaction of Isocyanates with 2,2,6,6-Tetramethylpiperidine-4-one Oxime Reaction between 2,2,6,6-tetramethyl-piperidine-4-one oxime 2 and isocyanates RNCO in equimolar amounts yields the corresponding O-carbamoyl derivatives 3 . These compounds are converted to the N, O-dicarbamoyl derivatives 4 by treating 3 with another mole of the same or a different isocyanate. Under mild conditions the N-carbamoyl moiety of the compounds 4 splits off by thermolysis or hydrolysis resulting in reproduction of the more stable 3 . The regiospecifity of the carbamoylation reaction 1 → 3 and of the reverse reaction 4 → 3 is considered as a consequence of steric hindrance in position 1 of the heterocyclus.     

NMR study and AIM analysis for the ylide rotamers from the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of 2-mercapto-1-methylimidazole

Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reactions between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of an SH-heterocyclic compound, such as 2-mercapto-1-methyl imidazole. These stable ylides exist in solution as a mixture of the two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group. In the recent work, an NMR study and the stability of the Z- and E-isomers were undertaken for the two rotamers of phosphorus ylides involving 2-mercapto-1-methylimidazole by natural population analysis.     

Synthesis of ‘ready-to-adsorb’ polymeric nanoshells for magnetic iron oxide nanoparticles via atom transfer radical polymerization

Polymer-magnetite nanoparticle complexes that respond to both magnetic fields and to temperature have been demonstrated. Novel alkyl halide-functional bis(diethylphosphonate) esters were prepared and utilized as initiators for polymerizing N-isopropylacrylamide by controlled atom transfer radical polymerization. The phosphonate esters were removed after polymerization to afford poly(N-isopropylacrylamide) with a bis(phosphonic acid) moiety precisely placed at one terminus. The bis(phosphonic acid) endgroups were adsorbed onto magnetite nanoparticles to yield nanoscale complexes that were stable against any polymer desorption and that were colloidally-stable in physiological media. Thus, the bis(phosphonate) endgroup provides a robust anchoring moiety onto the magnetite. Hydrodynamic sizes of the complexes were predicted with a density distribution model and using the measured sizes of the magnetite cores. Good agreement between the measured and predicted hydrodynamic sizes suggested that the complexes were primarily discrete, non-agglomerated nanoparticles. The complexes exhibited thermosensitive aggregation behavior near the lower critical solution temperature of the poly(N-isopropylacrylamide) component.