Synthesis and characterization of polyamides containing octadecanedioic acid: Nylon‐2,18, nylon‐3,18, nylon‐4,18, nylon‐6,18, nylon‐8,18, nylon‐9,18, and nylon‐12,18

High‐aliphatic‐content linear nylons were produced with an 18‐carbon diacid with diamines containing both odd and even methylene segments. The resulting polymers were characterized with viscosimetric, thermal, and spectroscopic techniques. Solid‐state ¹⁵N NMR was used to determine the nylon crystalline form present. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 936–945, 2005     

Synthesis,Structure, and Physical Properties of 5,7,14,16‐Tetraphenyl‐8:9,12:13‐bisbenzo‐hexatwistacene

A novel compound, 5,7,14,16‐tetraphenyl‐8:9,12:13‐bisbenzo‐hexatwistacene ( TBH ), has been successfully synthesized through a retro‐Diels–Alder reaction. Single‐crystal structure analysis indicated that TBH has a twisted configuration with a torsion angle of 27.34°. The HOMO–LUMO gap of TBH calculated from the difference between the half‐wave redox potentials (E_1/2^ox=+0.40 eV and E_1/2^red=?1.78 eV) is 2.18 eV, which is in good agreement with the band gap (2.19 eV) derived from the UV/Vis absorption data. In addition, organic light‐emitting devices using TBH as emitter have been fabricated. The results revealed that TBH is a promising red light‐emitting candidate for applications in organic light‐emitting diodes.     

Sulfenylation of heterocyclic 1,3‐dicarbonyl systems: 4‐Hydroxy‐2‐pyrones, 6‐hydroxy‐4‐pyrimidones, 4‐hydroxy‐2‐pyridones, 4‐hydroxy‐6‐pyridazinones,and 5‐hydroxy‐3‐pyrazolones

Anions of enolized heteroaromatic 1,3‐dicarbonyl systems, such as the title compounds 1, 9,14 , and 19 , react in dimethylformamide in the presence of potassium carbonate with diaryl disulfides 2 to yield arylsulfenyl derivatives ( 3, 10, 15, 20 ). The arylthiolate anions 4 formed in this reaction can be oxidized by air to yield the starting disulfides 2 again. Tetraalkylthiuram disulfides 7 react in the same manner to yield dialkylaminothiocarbonylthio derivatives ( 8, 13, 18 ) of the title compounds. Oxidation of the arylsulfenyl derivatives with hydrogen peroxide in sodium hydroxide solution usually leads to sulfoxides ( 5, 11, 16 ), whereas oxidation with peracetic acid affords sulfones ( 6, 12, 17 ).     

A New Class of Organosuperbases,N‐Alkyl‐ and N‐Aryl‐1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidene Amines: Synthesis,Structure, pKBH+ Measurements,and Properties

A series of stable organosuperbases, N‐alkyl‐ and N‐aryl‐1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidene amines, were efficiently synthesized from N,N′‐dialkylthioureas and 3‐hydroxy‐2‐butanone and their basicities were measured in acetonitrile. The derivatives with tert‐alkyl groups on the imino nitrogen were found to be more basic than the tBu P₁ (pyrr) phosphazene base in acetonitrile. The origin of the high basicity of these compounds is discussed. In acetonitrile and in the gas phase, the basicity of the alkylimino derivatives depends on the size of the substituent at the imino group, which influences the degree of aromatization of the imidazole ring, as measured by ¹³C NMR chemical shifts or by the calculated ΔNICS(1) aromaticity parameters, as well as on solvation effects. If a wider range of imino‐substituents, including electron‐acceptor substituents, is treated in the analysis then the influence of aromatization is less predominant and the gas‐phase basicity becomes more dependent on the field‐inductive effect, polarizability, and resonance effects of the substituent.     

Biocompatible and pH‐responsive triblock copolymer mPEG‐b‐PCL‐b‐PDMAEMA: Synthesis,self‐assembly,and application

A series of well‐defined amphiphilic triblock copolymers [polyethylene glycol monomethyl ether]‐block‐poly(ε‐caprolactone)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (mPEG‐b‐PCL‐b‐PDMAEMA or abbreviated as mPEG‐b‐PCL‐b‐PDMA) were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization. The chemical structures and compositions of these copolymers have been characterized by Fourier transform infrared spectroscopy, ¹H NMR, and thermogravimetric analysis. The molecular weights of the triblock copolymers were obtained by calculating from ¹H NMR spectra and gel permeation chromatography measurements. Subsequently, the self‐assembly behavior of these copolymers was investigated by fluorescence probe method and transmission electron microscopy, which indicated that these amphiphilic triblock copolymers possess distinct pH‐dependent critical aggregation concentrations and can self‐assemble into micelles or vesicles in PBS buffer solution, depending on the length of PDMA in the copolymer. Agarose gel retardation assays demonstrated that these cationic nanoparticles can effectively condense plasmid DNA. Cell toxicity tests indicated that these triblock copolymers displayed lower cytotoxicity than that of branched polyethylenimine with molecular weight of 25 kDa. In addition, in vitro release of Naproxen from these nanoparticles in pH buffer solutions was conducted, demonstrating that higher PCL content would result in the higher drug loading content and lower release rate. These biodegradable and biocompatible cationic copolymers have potential applications in drug and gene delivery. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1079–1091, 2010     

Ring‐Shaped Phosphinoamido‐Magnesium‐Hydride Complexes: Syntheses,Structures, Reactivity,and Catalysis

A series of magnesium(II) complexes bearing the sterically demanding phosphinoamide ligand, L^?=Ph₂PNDip^?, Dip=2,6‐diisopropylphenyl, including heteroleptic magnesium alkyl and hydride complexes are described. The ligand geometry enforces various novel ring and cluster geometries for the heteroleptic compounds. We have studied the stoichiometric reactivity of [(LMgH)₄] towards unsaturated substrates, and investigated catalytic hydroborations and hydrosilylations of ketones and pyridines. We found that hydroborations of two ketones with pinacolborane using various Mg precatalysts is very rapid at room temperature with very low catalyst loadings, and ketone hydrosilylation using phenylsilane is rapid at 70 °C. Our studies point to an insertion/σ‐bond metathesis catalytic cycle of an in situ formed “MgH₂” active species.     

Functionalization of Quinazolin‐4‐ones Part 3: Synthesis,Structures Elucidation,DNA‐PK,PI3K,and Cytotoxicity of Novel 8‐Aryl‐2‐morpholino‐quinazolin‐4‐ones

A series of novel 8‐aryl‐2‐morpholino quinazolines ( 11a – n , 12a – d , 14a – f , and 15 ) were synthesized from the precursor 2‐thioxo quinazolin‐4‐ones 8 . The 8‐aryl‐2‐morpholino quinazolines compounds were assayed for DNA‐PK and PI3K. All compounds showed low DNA‐PK % inhibition activity at 10 μM compound concertation, and the most active was 8‐(dibenzo[b,d]thiophen‐4‐yl) 12d with 38% inhibition. Similar pattern of PI3K α, β, γ, and δ isoforms inhibition activity at 10 μM were observed. The most active isoform was PI3K δ of 41% inhibition for 8‐(dibenzo[b,d]furan‐4‐yl) compound 11 . Most compounds were less active than expected in spite of the strong structural resemblance to known inhibitors ( NU7441 , 3 , 4 , and 6 ). Loss of activity could be attributed to the tautomerization to the aromatic enol (4‐OH), which could specify that the important functional group for the activity is the 4‐carbonyl (C=O) group. Alternatively, the aromatization of the pyrimidine heterocyclic ring could alter the conformation, and thus binding site, of the 2‐morpholine ring, which could reduce the compound‐receptor hydrogen bonding to the morpholine 4‐oxygen. Selected compounds displayed appreciable cytotoxicity with 6‐chloro‐8‐(dibenzo[b,d]thiophen‐4‐yl)‐2‐morpholinoquinazolin‐4(1H)‐one 11j exhibiting the greatest activity with an IC₅₀ of 9.95 μM. Therefore, the mechanism of the cytotoxicity of compound 11j were not through DNA‐PK or PI3K inhibition activity.     

Chain‐extended,hydroxyterminated‐polybutadiene‐based polyurethaneureas: Synthesis,reaction kinetics,and properties

Hydroxyterminated‐polybutadiene‐based prepolyurethanes were prepared with two different catalysts, dibutyltindilaurate (DBTDL) and triethylamine (TEA); chain extension of the prepolyurethanes followed with two different aromatic diamines, oxydianiline and 4,4′‐diaminodiphenylsulfone, in various concentrations. The prepolyurethane synthesis followed second‐order kinetics, with the DBTDL catalyst showing better efficiency for urethane formation than TEA. TEA‐catalyzed synthesis suffered from the self‐association of isocyanates as a major side reaction, following second‐order kinetics with respect to isocyanate concentration. Although there was a gradual increase in the intrinsic viscosity during prepolyurethane synthesis in the presence of DBTDL, the intrinsic viscosity remained almost constant with the progress of the reaction in the presence of TEA. The tensile properties of prepolyurethane and polyurethaneureas synthesized in DBTDL‐catalyzed reactions were higher than the properties of those synthesized in TEA‐catalyzed reactions. The variation of the tensile strength with the diamine concentration was correlated with the crosslink density and sol fraction. The solubility of the hard segment of polyurethaneurea in the reaction medium appeared to be important in influencing the tensile properties. The effects of the diamine concentration (chain extender) on the diffusion coefficient and activation energy of diffusion of toluene in polyurethaneureas were studied. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2978–2992, 2001     

Synthesis of Polyfunctionalized 1,4‐Dihydropyridine‐Fused‐1,3‐Diazaheterocycles: One‐Pot Reaction of 1,1‐Bis(methylthio)‐2‐nitroethylene, 1,n‐Diamine,Arylaldehyde, and Malononitrile

An efficient, one‐pot synthetic protocol for polyfunctionalized 1,4‐dihydropyridine‐fused‐1,3‐diazaheterocycles, a class of biologically active compounds, starting from 1,1‐bis(methylthio)‐2‐nitroethylene, 1,n‐diamine, arylaldehyde, and malononitrile is described. The reactions are completed within 12–15 h under refluxing conditions and in the presence of 10 mol % of piperidine as a basic catalyst to produce the title compounds in 60–75% yields.     

Rose Bengal‐Sensitized Photooxidation of the Dipeptides l‐Tryptophyl‐l‐Phenylalanine,l‐Tryptophyl‐l‐Tyrosine and l‐Tryptophyl‐l‐Tryptophan: Kinetics,Mechanism and Photoproducts¶

The Rose Bengal‐sensitized photooxidations of the dipeptides l ‐tryptophyl‐l ‐phenylalanine (Trp‐Phe), l ‐tryptophyl‐l ‐tyrosine (Trp‐Tyr) and l ‐tryptophyl‐l ‐tryptophan (Trp‐Trp) have been studied in pH 7 water solution using static photolysis and time‐resolved methods. Kinetic results indicate that the tryptophan (Trp) moiety interacts with singlet molecular oxygen (O₂(¹Δ_g)) both through chemical reaction and through physical quenching, and that the photooxidations can be compared with those of equimolecular mixtures of the corresponding free amino acids, with minimum, if any, influence of the peptide bond on the chemical reaction. This is not a common behavior in other di‐ and polypeptides of photooxidizable amino acids. The ratio between chemical (k_r) and overall (k_t) rate constants for the interaction O₂(¹Δ_g)‐dipeptide indicates that Trp‐Phe and Trp‐Trp are good candidates to suffer photodynamic action, with k_rlk_t values of 0.72 and 0.60, respectively (0.65 for free Trp). In the case of Trp‐Tyr, a lower k_rlk_t value (0.18) has been found, likely as a result of the high component of physical deactivation of O₂(¹Δ_g) by the tyrosine moiety. The analysis of the photooxidation products shows that the main target for O₂(¹Δ_g) attack is the Trp group and suggests a much lower accumulation of kynurenine‐type products, as compared with free Trp. This is possibly because of the occurrence of another accepted alternative pathway of oxidation that gives rise to 3a‐oxidized hydrogenated pyrrolo[2,3‐b]indoles.     

N,N′‐Di­methyl‐1,4‐dithiine‐1,2:4,5‐tetracarbox­imide and N,N′‐di­methyl‐1,4‐diselenine‐1,2:4,5‐tetracarbox­imide

The title compounds of sulfur, C₁₀H₆N₂O₄S₂, (I), and selenium, C₁₀H₆N₂O₄Se₂, (II), are isomorphous. The crystallographically centrosymmetric mol­ecules are planar. The bond distances and angles, except for those involving the S and Se atoms, are comparable. The mol­ecules are disposed in layers parallel to the bc plane. The molecular axes differ by 75° for (I) and by 80° for (II) from one layer to the next.     

Pyrenoimidazole‐Based Deep‐Blue‐Emitting Materials: Optical,Electrochemical, and Electroluminescent Characteristics

A series of pyrenoimidazoles that contained various functional chromophores, such as anthracene, pyrene, triphenylamine, carbazole, and fluorene, were synthesized and characterized by optical, electrochemical, and theoretical studies. The absorption spectra of the dyes are dominated by electronic transitions that arise from the pyrenoimidazole core and the additional chromophore. All of the dyes exhibited blue‐light photoluminescence with moderate‐to‐high quantum efficiencies. They also displayed high thermal stability and their thermal‐decomposition temperatures fell within the range 462–512 °C; the highest decomposition temperature was recorded for a carbazole‐containing dye. The oxidation propensity of the dyes increased on the introduction of electron‐rich chromophores, such as triphenylamine or carbazole. The application of selected dyes that featured additional chromophores such as pyrene, carbazole, and triphenylamine as blue‐emissive dopants into multilayered organic light‐emitting diodes with a 4,4′‐bis(9H‐carbazol‐9‐yl)biphenyl (CBP) host was investigated. Devices that were based on triphenylamine‐ and carbazole‐containing dyes exhibited deep‐blue emission (CIE 0.157, 0.054 and 0.163, 0.041), whereas a device that was based on a pyrene‐containing dye showed a bright‐blue emission (CIE 0.156, 0.135).     

Molecular Triangles: Synthesis,Self‐Assembly,and Blue Emission of Cyclo‐7,10‐tris‐triphenylenyl Macrocycles

A set of cyclo‐7,10‐tris‐triphenylenyl macrocycles have been prepared by a Yamamoto cyclotrimerization protocol. In these novel macrocycles, three triphenylene units are covalently linked to each other, resulting in the formation of triangular‐shaped molecules. The fully planar derivative revealed pronounced self‐assembly behavior. NMR spectroscopy was used to determine the association constant in solution. 2D wide‐angle X‐ray scattering was applied to the study of the liquid crystallinity of this new discotic mesogen in the bulk state. Furthermore, nonplanar, laterally substituted derivatives were successfully tested as blue emitters in organic light‐emitting diodes owing to their unique optoelectronic properties and their high stability. In this case, substitution with sterically demanding phenyl groups was efficiently used to suppress intermolecular packing, thus preventing undesired quenching effects.     

Heavy Heparin: A Stable Isotope‐Enriched,Chemoenzymatically‐Synthesized,Poly‐Component Drug

Heparin is a highly sulfated, complex polysaccharide and widely used anticoagulant pharmaceutical. In this work, we chemoenzymatically synthesized perdeuteroheparin from biosynthetically enriched heparosan precursor obtained from microbial culture in deuterated medium. Chemical de‐N‐acetylation, chemical N‐sulfation, enzymatic epimerization, and enzymatic sulfation with recombinant heparin biosynthetic enzymes afforded perdeuteroheparin comparable to pharmaceutical heparin. A series of applications for heavy heparin and its heavy biosynthetic intermediates are demonstrated, including generation of stable isotope labeled disaccharide standards, development of a non‐radioactive NMR assay for glucuronosyl‐C5‐epimerase, and background‐free quantification of in vivo half‐life following administration to rabbits. We anticipate that this approach can be extended to produce other isotope‐enriched glycosaminoglycans.