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     

Simultaneous determination of NG‐monomethyl‐l‐arginine,NG,NG‐dimethyl‐l‐arginine,NG,NG′‐dimethyl‐l‐arginine,and l‐arginine using monolithic silica disk‐packed spin columns and a monolithic silica column

We have developed and validated a high‐performance liquid chromatography method that uses monolithic silica disk‐packed spin columns and a monolithic silica column for the simultaneous determination of N^G‐monomethyl‐l ‐arginine, N^G,N^G‐dimethyl‐l ‐arginine, and N^G,N^G′‐dimethyl‐l ‐arginine in human plasma. For solid‐phase extraction, our method employs a centrifugal spin column packed with monolithic silica bonded to propyl benzenesulfonic acid as a cation exchanger. After pretreatment, the methylated arginines are converted to fluorescent derivatives with 4‐fluoro‐7‐nitro‐2,1,3‐benzoxadiazole, and then the derivatives are separated on a monolithic silica column. l ‐Arginine concentration was also determined in diluted samples. Standard calibration curves revealed that the assay was linear in the concentration range 0.2–1.0 μM for methylated arginines and 40–200 μM for l ‐arginine. Linear regression of the calibration curve yielded equations with correlation coefficients of 0.999 (r²). The sensitivity was satisfactory, with a limit of detection ranging from 3.75 to 9.0 fmol for all four compounds. The RSDs were 4.3–4.8% (intraday) and 3.0–6.8% (interday). When this method was applied to samples from six healthy donors, the detected concentrations of N^G‐monomethyl‐l ‐arginine, N^G,N^G‐dimethyl‐l ‐arginine, N^G,N^G′‐dimethyl‐l ‐arginine and l ‐arginine were 0.05 ± 0.01, 0.41 ± 0.07, 0.59 ± 0.11, and 83.8 ± 30.43 μM (n = 6), respectively.     

Synthesis,characterization, and crosslinking of methacrylate‐telechelic PDMAAm‐b‐PDMS‐b‐PDMAAm copolymers

The synthesis and molecular characterization of a new amphiphilic conetwork (APCN) designed for silicone hydrogel use is described. The synthesis strategy, outlined in Scheme 1 , calls for the preparation, by the RAFT technique, of a new methacrylate‐telechelic amphiphilic pentablock, MA‐PHEA‐b‐PDMAAM‐b‐PDMS‐b‐PDMAAm‐b‐PHEA‐MA, and its crosslinking to the target APCN. The sketch shows the architecture of the APCN (dotted lines, PDMAAm; solid lines, PDMS; clusters, MA‐based crosslinking sites; see Fig. 3 ). All six synthesis steps proceed smoothly and efficiently, and the products are optically clear, colorless membranes exhibiting properties appropriate for ophthalmic use. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4284–4290, 2007     

Synthesis,solid‐state,and charge‐transport properties of conjugated polythiophene‐S,S‐dioxides

An alkylated semiconducting polymer comprising alternating bithiophene‐[all]‐S,S‐dioxide and aromatic monothiophene units in the polymer backbone was synthesized with the intent of modifying the energy gap and lowest unoccupied molecular orbital for use as a stable n‐type semiconductor. Films spun from this semiconducting polymer were characterized utilizing X‐ray scattering, near edge X‐ray absorption fine structure spectroscopy, ultraviolet photoelectron spectroscopy, and thin‐film field effect transistors to determine how oxidation of the thiophene ring systems impacts the structural and electronic properties of the polymer. The thiophene‐S,S‐dioxide polymers have lower optical and electrical band gaps than corresponding thiophene polymers. X‐ray scattering results indicate that the polymers are well ordered with the π–π stacking distances increased by 0.4 Å relative to analogous thiophene polymers. The electrical stability of these polymers is poor in transistors with a drop in the field effect mobility by approximately one order of magnitude upon addition of just 5% of the thiophene‐S,S‐dioxide unit in a copolymer with thiophene. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Synthesis and Characterization of donor‐functionalized ansa‐Cyclopentadienyl‐Indenyl and ansa‐Indenyl‐Indenyl Complexes of Yttrium,Samarium, Thulium,and Lutetium

The stepwise reaction of Me₂SiCl₂ with K[C₅H₃ ^tBuMe‐3] or Li[C₉H₇] and then with K[C₉H₆CH₂CH₂‐ NMe₂‐1] followed by double deprotonation with NaH or LiBu, yields the two dimethylsilicon bridged cyclopentadienyl‐indenyl and indenyl‐indenyl donor‐functionalized ligand systems K₂[(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)] ( 1 ), and Li₂[(1‐C₉H₆)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)] ( 2 ), respectively. Treatment of 1 with YCl₃(THF)₃, SmCl₃(THF)_1.77, TmI₃(DME)₃, and LuCl₃(THF)₃ gives the mixed ansa‐metallocenes [(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]LnX (X = Cl, Ln = Y ( 3 ), Sm ( 4 ), Lu ( 5 ); X = I, Ln = Tm ( 6 )), respectively. The reaction of 2 with LuCl₃(THF)₃ yields [(1‐C₉H₆)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]LuCl ( 7 ). Compound 4 reacts with LiMe to give the corresponding alkyl derivative [(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]Sm(CH₃) ( 8 ). The new complexes were characterized by elemental analyses, MS spectrometry, and NMR spectroscopy. The molecular structures of 5 and 6 were determined by single crystal X‐ray diffraction.     

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.     

Rhodium(I) and Silver(I) Complexes of 4, 5‐Dicyano‐1, 3‐dimesityl‐ and 4, 5‐Dicyano‐1, 3‐dineopentylimidazol‐2‐ylidene

The new N‐heterocyclic carbene (NHC) precursors 4, ‐dicyano‐1, ‐dimesityl‐ ( 9 ) and 4, 5‐dicyano‐1, 3‐dineopentyl‐2‐(pentafluorophenyl)imidazoline ( 14 ) were synthesized. The structure of 9 could be determined by X‐ray crystallography. With the 2‐pentafluorophenyl‐substituted imidazolines 9 and 14 , the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO)₂(NHC)] complexes [NHC = 4, 5‐dicyano‐1, 3‐dimesitylimidazol‐2‐ylidene ( 3 ) and 4, 5‐dicyano‐1, 3‐dineopentylimidazol‐2‐ylidene ( 4 )] were obtained. Crystal structures of [AgCl( 3 )] ( 15 ), [RhCl(COD)( 3 )] ( 17 ), [RhCl(COD)( 4 )] ( 18 ), and [RhCl(CO)₂( 3 )] ( 19 ) were solved and with the crystal data of 19 , the percent buried volume ( %V_bur) of 31.8(±0.1) % was determined for NHC 3 . Infrared spectra of the imidazolines 9 and 14 and of the complexes 15 – 20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the Tolman electronic parameters of the newly obtained NHCs 3 (TEP: 2060 cm^–1) and 4 (TEP: 2061 cm^–1), thus proving that 1, 3‐substitution of maleonitrile‐NHCs does not have a significant effect for the high π‐acceptor strength of these carbenes.     

Synthesis and Structure of a 2, 8, 9‐Trioxa‐3, 5, 7‐trisila‐1‐titanaadamantane

The title compound has been prepared from [Ti(η⁵‐C₅Me₅)Cl₃] and cis‐cis‐(t‐BuSi(OH)—CH₂)₃ in hexane solution in the presence of Et₃N. The pale yellow complex was characterized by NMR and MS spectra, as well as by a crystal structure determination. The two crystallographic independent molecules in the triclinic unit cell (space group P1¯, No. 2, Z = 4) both have a nearly identical adamantane‐like TiO₃Si₃C₃ cage of approximate C_3v symmetry. The exocyclic C—C—C bond angles in the Cp‐ligand range from 123° to 129°. A quantum chemical calculation of the free molecule predicts this range to be 124° to 127°. The arrangement of the molecules in the crystal is characteristic for an offset face‐to‐face ππ stacking of the aromatic η⁵‐C₅Me₅ rings.     

Syntheses,Structure, Electrochemistry,and Optical Properties of 1,3‐Diethyl‐2,3‐dihydro‐1‐H‐1,3,2‐pyrido‐[4,5‐b]‐diazaboroles

Reaction of 2,5‐bis(dibromoboryl)thiophene ( 4 ) or 1,4‐bis(dibromoboryl)benzene ( 6 ) with two equivalents of N,N′‐dilithiated 2,3‐diaminopyridine ( 3 ) led to the generation of the pyridodiazaboroles 5 and 7 in which the two diazaborole rings are linked by 2,5‐thiophen‐diyl or 1,4‐phenylene units via the boron atom. The novel compounds were characterized by elemental analyses and spectroscopy (¹H‐, ¹¹B‐, ¹³C‐NMR, MS, and UV‐VIS). The molecular structure of 5 was elucidated by X‐ray diffraction. Cyclovoltammograms of 5 and 7 show two irreversible oxidation waves at 0.76 and 0.73 V, respectively vs Fc/Fc⁺. The novel compounds display intense blue luminescence with Stokes shifts of 76 and 74 nm and relative quantum yields of 39 and 43 % vs Coumarin 120 (Φ = 50 %).     

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 ).     

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     

One‐pot Synthesis,Crystal structure,and Bioactivity of N‐Phenoxyacetyl‐2,4,5‐trisubstituted‐1,3‐oxazolidines

N‐phenoxyacetyl‐1,3‐oxazolidine derivatives were synthesized by the cyclization and acylation with β‐amino alcohol, ketone, and phenoxyacetyl chloride as the starting materials. All compounds were characterized by IR, ¹H NMR, ¹³C NMR, ESI‐MS, and elemental analysis. The configuration of 4a was determined by X‐ray crystallography. The preliminary biological tests showed that all products could protect soybean against injury caused by 2,4‐D butylate to some extent.     

Ligand‐Free Copper‐Catalyzed Arylation of Imidazole and N,N′‐Carbonyldiimidazole,and Microwave‐Assisted Synthesis of N‐Aryl‐1H‐imidazoles

Microwave‐assisted arylation of 1H‐imidazoles and N,N′‐carbonyldiimidazole under ligand‐free copper‐mediated conditions in tetraethyl orthosilicate is reported. Valuable evidence for understanding of the Cu‐catalyzed mechanism of the Ullmann reaction is also presented.     

Synthesis,Characterization, and Crystal Structure of 1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine

1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine ( 1 ) was synthesized by the reaction of [(C₆F₅)NPCl₃]₂ with trimethylsilyl azide in CH₂Cl₂ and characterized by multinuclear NMR and vibrational spectroscopy. The molecular structure of the compound was determined by single‐crystal X‐ray structure analysis. [(C₆F₅)NP(N₃)₃]₂ crystallizes in the monoclinic space group P2₁/n with a = 9.6414(2), b = 7.4170(1) and c = 15.9447(4) Å, β = 94.4374(9)°, with 2 formula units per unit cell. The bond situation in [(C₆F₅)NP(N₃)₃]₂ has been studied on the basis of NBO analysis. The antisymmetric stretching vibration of the azide groups is discussed. The structural diversity of 1 and 1,3‐diphenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine in solution and in the solid state depending on the aryl substituent at the nitrogen atom is discussed.     

Substituent chemical shifts of N‐arylsuccinanilic acids,N‐arylsuccinimides,N‐arylmaleanilic acids,and N‐arylmaleimides

NMR spectra of a series of N‐arylsuccinanilic acids, N‐arylsuccinimides, N‐arylmaleanilic acids, and N‐arylmaleimides were examined to estimate the electronic effect of the amide and imide groups on the chemical shifts of the hydrogen and carbon nuclei of the benzene ring. Copyright © 2009 John Wiley & Sons, Ltd.     

Syntheses,antitumor activities,and antiangiogenesis of exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidoethanoyl‐ 5‐fluorouracil and its polymers

A new monomer, exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidoethanoyl‐5‐fluorouracil (ETFU), was synthesized by the reaction of exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidoethanoyl chloride (ETPC) and 5‐fluorouracil (5‐FU). The homopolymer of ETFU and its copolymers with acrylic acid (AA) and vinyl acetate (VAc) were prepared via photopolymerizations with 2,2‐dimethoxy‐2‐phenylacetophenone at 25 °C for 48 h. The structures of the synthesized monomer and polymers were identified by Fourier transform infrared, ¹H NMR, and ¹³C NMR spectroscopy and elemental analysis. The ETFU contents in poly(ETFU‐co‐AA) and poly(ETFU‐co‐VAc) were 26 mol % and 26 mol %, respectively. The number‐average molecular weights of the polymers, as determined by gel permeation chromatography, ranged from 5600 to 17,000. The in vitro cytotoxicities of 5‐FU and the synthesized samples against mouse mammary carcinoma and human histiocytic lymphoma cancer cell lines increased in the following order: ETFU > 5‐FU > poly(ETFU‐co‐AA) > poly(ETFU) > poly(ETFU‐co‐VAc). The in vivo antitumor activities of the polymers against Balb/C mice bearing the sarcoma 180 tumor cells were greater than those of 5‐FU at all doses tested. The inhibitions of the samples for SV40 DNA replication and antiangiogenesis were much greater than the inhibition of the control. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4272–4281, 2000     

Gas‐phase pyrolytic reactions of N‐ethyl,N‐isopropyl,and N‐t‐butyl substituted 2‐aminopyrazine and 2‐aminopyrimidine

The rates of gas‐phase elimination of N‐ethyl (1), N‐isopropyl (2), N‐t‐butyl (3) substituted 2‐aminopyrazine and N‐ethyl (4), N‐isopropyl (5), and N‐t‐butyl (6) substituted 2‐aminopyrimidine have been measured. The compounds undergo unimolecular first‐order pyrolytic reactions. The relative rates of the primary:secondary;tertiary alkyl homologues at 600 K are 1:14.4:38.0 for the pyrazines and 1:20.8:162.5 for the pyrimidines, respectively. The reactivities of these compounds have been compared with those of the alkoxy analogues and with each other. Product analyses, together with the kinetic data, were used to outline a feasible pathway for the elimination reaction of the compounds under study. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 403–407, 2000     

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.