Synthesis and properties of new soluble aromatic polyamides and polyimides on the basis of N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new N‐phenylated amide (N‐phenylamide) unit containing aromatic diamine, N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 3‐nitrobenzoyl chloride, followed by catalytic reduction. Two series of organosoluble aromatic poly(N‐phenylamide‐imide)s and poly(N‐phenylamide‐amide)s with inherent viscosities of 0.58–0.82 and 0.56–1.21 dL/g were prepared by a conventional two‐stage method and the direct phosphorylation polycondensation, respectively, from the diamine with various aromatic dianhydrides and aromatic dicarboxylic acids. All polyimides and polyamides are amorphous and readily soluble in many organic solvents such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with high tensile strengths. These polyimides and polyamides had glass‐transition temperatures in the ranges of 230–258 and 196–229 °C, respectively. Decomposition temperatures of the polyimides for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2564–2574, 2002     

Rapid and sensitive liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of yonkenafil and its major metabolites in rat plasma

Yonkenafil is a promising drug for treatment of male erectile dysfunction. Previous studies showed that the piperazine‐N,N’‐deethylation metabolite, piperazine‐N‐deethylation metabolite, and piperazine‐N‐deethylation‐N,N’‐deethylation metabolite were the major metabolites of yonkenafil after extensive metabolism. We developed a sensitive and selective method for the simultaneous quantification of yonkenafil and its major metabolites using high‐throughput liquid chromatography with tandem mass spectrometry. Analytes and internal standard were extracted from a small quantity of plasma (50 μL) using liquid–liquid extraction with diethyl ether/dichloromethane (60:40, v/v), and the baseline separation was achieved on Zorbax SB‐C₁₈ column using ammonia/water/methanol (0.2:20:80, v/v/v) as the mobile phase. The assay was performed with an electrospray positive ionization mass spectrometry through the multiple‐reaction monitoring mode within 2 min. Calibration curve of the method was linear within the range of 1.00–1000 ng/mL for all the analytes with the intra‐ and interday precisions of 4.0–5.2 and 4.0–5.3% for yonkenafil, 3.1–4.9 and 3.1–5.2% for the piperazine‐N,N’‐deethylation metabolite, 4.8–6.8 and 4.8–7.3% for the piperazine‐N‐deethylation metabolite, and 2.9–6.1 and 5.4–6.3% for the piperazine‐N‐deethylation‐N,N’‐deethylation metabolite, respectively. The recoveries were above 90% with low matrix effects. The validated assay was successfully applied to support a preclinical pharmacokinetic study in six rats using a single oral dose of yonkenafil (8 mg/kg).     

1,2,3-thiadiazoles. I. Synthesis of sodium (or potassium) 1,2,3-thiadiazole-4-thiolates via thiocarbazonate esters and N-acylthiohydrazonate esters

A general synthesis of 1,2,3-thiadiazole-4-thiolates 1 and their derivatives 2–3 by an extension of the Hurd-Mori 1,2,3-thiadiazole synthesis is described. Treatment of methyl (or ethyl) [1-(alkylthio)alkylidene]hydrazinocarboxylates 11 (thiocarbazonate esters) or other N-acylthiohydrazonate esters [Y = ureido ( 12 ) or arenesulfonyl ( 13 )] with thionyl chloride affords 2–3 efficiently. Intermediates 11–13 are readily obtained from the N²-thioacylcarbazates 8 , N³-thioacylsemicarbazides 9 , or N²-thioacyl-N¹-(p-toluenesulfonyl)hydrazides 10 , respectively, by S-alkylation. Physicochemical properties of the 1,2,3-thiadiazoles 1–3 and N-acylthiohydrazonate esters 11–13 are also described.     

Surface activities and thermodynamic properties of novel cationic surfactants with hydroxymethyl group

A new series of cationic surfactants, N–alkyl–N,N–dimethyl–N–(p–(hydroxymethyl) benzyl) ammonium chlorides (p-DHBA-m), were synthesized and the structures were characterized by ¹HNMR, ¹³CNMR, FT–IR and ESI–MS. The surface activities, thermodynamic properties and aggregation behaviors of p-DHBA-m in aqueous solutions were respectively studied by means of surface tension, isothermal titration calorimetry and steady-state fluorescence methods. Thermodynamic parameters show that the micellization is an entropy-driven process. According to the fluorescence quenching method, the micelle aggregation numbers (N_agg) of p-DHBA-m were calculated and found that the increase of temperature or the elongation of alkyl chain length could lead to the reduction of the N_agg, respectively.     

Characteristic ion clusters as determinants for the identification of pyrrolizidine alkaloid N‐oxides in pyrrolizidine alkaloid–containing natural products using HPLC–MS analysis

Pyrrolizidine alkaloid (PA)–containing plants are widely distributed in the world. PAs are hepatotoxic, affecting livestock and humans. PA N‐oxides are often present together with PAs in plants and also exhibit hepatotoxicity but with less potency. HPLC–MS is generally used to analyze PA‐containing herbs, although PA references are unavailable in most cases. However, to date, without reference standards, HPLC–MS methodology cannot distinguish PA N‐oxides from PAs because they both produce the same characteristic ions in mass spectra. In the present study, the mass spectra of 10 PA N‐oxides and the corresponding PAs were systemically investigated using HPLC–MS to define the characteristic mass fragment ions specific to PAs and PA N‐oxides. Mass spectra of toxic retronecine‐type PA N‐oxides exhibited two characteristic ion clusters at m/z 118–120 and 136–138. These ion clusters were produced by three unique fragmentation pathways of PA N‐oxides and were not found in their corresponding PAs. Similarly, the nontoxic platynecine‐type PA N‐oxides also fragmented via three similar pathways to form two characteristic ion clusters at m/z 120–122 and 138–140. Further application of using these characteristic ion clusters allowed successful and rapid identification of PAs and PA N‐oxides in two PA‐containing herbal plants. Our results demonstrated, for the first time, that these characteristic ion clusters are unique determinants to discriminate PA N‐oxides from PAs even without the availability of reference samples. Our findings provide a novel and specific method to differentiate PA N‐oxides from PAs in PA‐containing natural products, which is crucial for the assessment of their intoxication. Copyright © 2012 John Wiley & Sons, Ltd.     

The effect of ammonium polyphosphate on the mechanism of thermal degradation of polyureas

The thermal decomposition of structurally related N–H and N,N′-disubstituted polyureas (Table I) and their mixtures with ammonium polyphosphate (APP) was investigated by thermogravimetry (TG) and direct pyrolysis in a mass spectrometer (MS). The N–H polyureas (IV–VI) undergo a quantitative depolymerization process with the formation of oligomers with amine and isocyanate end groups. In contrast, the thermal degradation of the N,N′-disubstituted polyureas (I–III) proceeds by a different mechanism as a function of their chemical structure. The addition of APP lowers the thermal stability of the N,N′-disubstituted polyureas, whereas that of the N–H polyureas is unaltered. However, our data show that APP does not change the nature of the pyrolytic products. The destabilizing effect of the additive can be attributed to the catalytic action of the acid species formed by its thermal decomposition.     

Adducts of phenanthrene 9,10-imine and of benz[a]anthracene 5,6-imine to some nitrogen heterocycles

N-4-Pyridinyl-, N-2-quinolinyl-, and 2-pyrazinylphenanthrene 9,10-imines 4–6 , as well as N-4-pyridinyl- and N-2-pyrazinylbenz[a]anthracene 5,6-imines 12 and 13 were prepared by sodium hydride-mediated interaction of the parent arene imines, 1 and 10 , and the respective chloropyridine, chloroquinoline or chloropyrazine. N-Nicotynoyl-, N-2-pyridinoyl- and N-6-quinolinoylphenanthrene 9,10-imines 7–9 were obtained by interaction of N-trimethylsilylphenanthrene 9,10-imine ( 2 ) and the appropriate pyridine- or quinolinecarbonyl chlorides. Reaction of N-methylsulfonylphenanthrene 9,10-imine with thymine, cytosine, 5-fluorocytosine, purine, 6-chloropurine and adenine afforded, in the presence of either potassium carbonate or 1,5-diazabicyclo[3.4.0]non-5-ene, adducts 16–22 , respectively. The structures of the adducts were conformed by multinuclear nmr and by NOESY and C-H correlation 2D nmr spectrometry.     

Boc–Pro–Hyp–Gly–OBzl and Boc–Ala–Hyp–Gly–OBzl,two repeating triplets found in collagen

The protected tripeptides benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­prol­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Pro–Hyp–Gly–OBzl, C₂₄H₃₃N₃O₇, and benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­alan­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Ala–Hyp–Gly–OBzl, C₂₂H₃₁N₃O₇, are the minimum repeating triplets found in collagen. Within the crystal structure of each are two independent peptide mol­ecules with similar structures. The peptides are arranged anti­parallel to one another and inter­act through hydrogen bonds involving the main chains and the 4‐hydroxy­prolyl groups. The structures exhibit characteristics of a triple helix, but the peptides tend to assume a sheet‐like structure.     

Synthesis and characterization of novel poly(amide-imide)s containing hexafluoroisopropylidene linkage

A series of novel soluble poly(amide-imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl]hexafluoropropane, with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl₂ using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.78–1.63 dL g⁻¹. The polymers were amorphous and readily soluble in aprotic polar solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide as well as in less polar solvents such as pyridine and γ-butyrolactone, and also in tetrahydrofuran. The polymer films had tensile strength of 84–129 MPa, an elongation at break range of 6–22%, and a tensile modulus range of 2.0–2.7 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 240–282°C. These polymers were fairly stable up to a temperature around or above 400°C, and lose 10% weight in the range of 450–514°C and 440–506°C in nitrogen and air, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2629–2635, 1999     

Synthesis and properties of aromatic secondary amine-blocked isocyanates

N-Methylaniline-, diphenylamine-, and N-phenylnaphthylamine-blocked toluene diisocyanates (TDI) were prepared and characterized by IR, NMR spectroscopy, and nitrogen content analyses. The structure–property relationship of these adducts was established by reacting with hydroxyl-terminated polybutadiene (HTPB). The cure rate of the adduct increases from the N-phenylnaphthylamine- to diphenylamine- and to N-methylaniline-blocked TDI adduct. Simultaneous TGA/DTA results also confirm this trend, and the thermal stability of the adduct decreases in the following order: N-phenylnaphthylamine–TDI > diphenylamine–TDI > N-methylaniline–TDI. The gas chromatogram of the amine-blocked isocyanate confirms that the thermolysis products are the blocking agent and isocyanate. The solubilities of the adducts were carried out in polyether, polyester, and hydrocarbon polyols, and it was found that the N-methylaniline–TDI adduct shows higher solubility than the rest and also found that the polyester polyol shows higher solvating power against the adducts than the polyether and hydrocarbon polyols. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1815–1821, 1999     

Effects of the acid chain length and copolymer crosslinking on the acylation of N-hydroxysuccinimide copolymers with carbobenzoxyoligo-ϵ-aminocaproic acids

N-Hydroxysuccinimide-type soluble copolymer with styrene and three similar divinylbenzene (3–4 mole-%) crosslinked copolymers with styrene, N-vinylpyrrolidone, and N,N-dimethylacrylamide were prepared from their precursor copolymers of N-acetoxymaleimide. Acylation of these N-hydroxyl polymers with carbobenzoxyoligo-?-aminocaproic acids was conducted in dimethylformamide at room temperature by using dicyclohexylcarbodiimide as condensing agent. The soluble styrene copolymer was acylated in good conversions (76–89%) in every case (n = 1–3), whereas the acylation of the crosslinked copolymers decreased slightly from n = 1 to n = 2, and dropped suddenly to only small conversions (4.7–7.4%) with n = 3, showing a marked inhibitory effect of crosslinking when the acids became longer. The effect of the microenvironment of the polymer did not appear significant. All the acyl polymers, including the precursor polymers, yielded the corresponding cyclohexylamides when treated with cyclohexylamine.     

New synthetic route to alternating copoly(aromatic ester–aliphatic amide)s

The preparation of three novel alternating copoly(aromatic ester–aliphatic amide)s containing the same ordered amide–amide–ester–ester (AAEE), the same para-disubstituted phenyl, and the different long methylene chain structure were described. 1,1′-(Adipoyl)bisbenzotriazole (AdBBT), 1,1′-(suberoyl)bisbenzotriazole (SuBBT), and 1,1′-(sebacoyl)bisbenzotriazole (SeBBT) were synthesized. These diacylbenzotriazoles were preferred to aminoethanol at the amino group because of the selective N-acylation of active acylamide of benzotriazole in excellent yield at room temperature to give diol monomers such as N,N′-bis(2-hydroxyethyl)adipic amide (HEAdA), N,N′-Bis(2-hydroxyethyl)subaric amide (HESuA), and N,N′-bis(2-hydroxyethyl)sebacic amide (HESeA). Polycondensation of 1,1′-(teraphthaloyl)bisbenzotrizole (tPBT) with HEAdA, HESuA, and HESeA gave the corresponding alternating copoly(aromatic ester–aliphatic amide)s: P(tPE–AdA), P(tPE–SuA), and P(tPE–SeA), respectively. The alternating copoly(aromatic ester–aliphatic amide)s were characterized by ¹H-NMR spectra. The resulting polymers have two different chain units; one is chain unit of poly(ethylene terephthalate) and the other is a chain unit of polyamide-2,6, polyamide-2,8, and polyamide-2,10; both are linked via a C? N bond.     

Chemo‐ and Regioselective Reduction of 5,15‐Diazaporphyrins Providing Antiaromatic Azaporphyrinoids

Reagent‐controlled chemo‐ and regioselective reduction of 5,15‐diazaporphyrins has been developed. The selective reduction of carbon–carbon double bonds of diazaporphyrins provides 18 π aromatic isobacteriochlorin‐type products, whereas the reduction of carbon–nitrogen double bonds leads to selective formation of 20 π N,N′‐dihydrodiazaporphyrins in excellent yields. The distinct antiaromatic character of N,N′‐dihydrodiazaporphyrins has been revealed. The free‐base N,N′‐dihydrodiazaporphyrin exhibits slower inner NH tautomerism than that in the corresponding 18 π porphyrins.     

pH‐responsive ionic poly(N,N‐diethylaminoethyl methacrylate‐co‐N‐vinyl‐2‐pyrrolidone) hydrogels: Synthesis and swelling properties

A series of an ionic hydrogels composed of N,N‐diethylaminoethyl methacrylamide (DEAEMA), N‐vinyl‐2‐pyrrolidone (VP), and itaconic acid were synthesized by free‐radical cross‐linking copolymerization in water–ethanol mixture by using N,N‐methylenebis(acrylamide) as the cross‐linker, ammonium persulfate as the initiator, and N,N,N′,N′‐tetramethylenediamine as the activator. The swelling behaviors of these hydrogels were analyzed in buffer solutions at various pH. It was observed that the swelling behavior of cross‐linked ionic poly(N,N‐diethylaminoethyl methacrylamide‐co‐N‐vinyl‐2‐pyrrolidone) [P(DEAEMA/VP)] hydrogels at different pH agreed with the modified Flory–Rehner equation based on the affine network model and the ideal Donnan theory. The swelling process in buffer solutions at various pH was found to be Fickian‐type diffusion. The pH‐reversibility and on–off switching properties of the P(DEAEMA/VP) hydrogels may be considered as good candidate to design novel drug‐delivery system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2819–2828, 2005     

Contrasting chemical and physical properties of [o- and [p-(N,N-dimethylamino) phenyl]phosphines and phosphonium salts

The rate of alkylation of (2-N,N-dimethylaminophenyl)diphenylphosphine with benzyl bromide in chloroform is faster than that of the corresponding reaction of (4-N,N-dimethylaminophenyl)diphenylphosphine. This result is discussed in terms of a through-space N_2p–P(IV) interaction for the former. The rate of alkaline cleavage of benzyl(4-N,N-dimethylaminophenyl)diphenylphosphonium bromide, which gives toluene, is slower than the rate of alkaline cleavage of benzyl(2-N,N-dimethylaminophenyl)diphenylphosphonium bromide, which gives dimethylaniline. This result is also discussed in terms of the through-space N_2p–P(IV) interaction. The ³¹P NMR spectra of a series of ortho-dimethylamino-substituted triarylphosphines and benzyltriarylphosphonium halides show that the phosphorus atom is more shielded than in the corresponding para-dimethylamino compounds, as anticipated on the basis of an N_2p–P(IV) interaction for the former.     

Water‐Soluble N‐(n‐Fatty acyl)chitosans

Chitosan was partially N‐acylated by treatment with n‐fatty acid anhydrides in a homogeneous solution in 2 vol.‐% aqueous acetic acid‐methanol (1:2 v/v). The degree of substitution (d.s.) for N‐acyl groups in the water‐soluble N‐acylchitosan derivatives was in the range of 0.42–0.82 for N‐acetyl, 0.37–0.76 for N‐propionyl, 0.52–0.71 for N‐butyryl and 0.54–0.64 for N‐pentanoyl and ca. 0.58 for N‐hexanoyl, respectively.

Water soluble N‐(n‐fatty acyl)chitosans.     

Theoretical studies on structures and nonlinear optical properties of alkali doped electrides B12N12–M (M = Li,Na, K)

The structures and nonlinear optical properties of a novel class of alkali metals doped electrides B₁₂N₁₂–M (M = Li, Na, K) were investigated by ab initio quantum chemistry method. The doping of alkali atoms was found to narrow the energy gap values of B₁₂N₁₂ in the range 3.96–6.70 eV. Furthermore, these alkali metals doped compounds with diffuse excess electron exhibited significantly large first hyperpolarizabilities (β₀) as follows: 5571–9157 au for B₁₂N₁₂–Li, 1537–18,889 au for B₁₂N₁₂–Na, and 2803–11,396 au for B₁₂N₁₂–K. Clearly, doping of the alkali atoms could dramatically increase the β₀ value of B₁₂N₁₂ (β₀ = 0). Furthermore, their transition energies (ΔE) were also calculated. The results showed that these compounds had low ΔE values in the range 1.407–2.363 eV, which was attributed to large β₀ values of alkali metals doped B₁₂N₁₂ nanocage. © 2016 Wiley Periodicals, Inc.     

arachno-Diazapentaboranes

The reaction of appropriate amounts of BH₃ with diazadiboretidines (RBNtBu)₂ ( 1a–e ; R = Et, Pr, Bu, tBu, tBu(Me₃Si)N) transforms them into cyclic diazapentaboranes either of the type [ RB (H₂) BR NtBu BH NtBu ] ( 2a–c ), of the type [ HB (H₂) BR NtBu BH NtBu ] ( 3a–d ), or of the type [ HB (H₂) BH NtBu BH NtBu ] ( 4 ), or into an acyclic product RBH NtBu BH NtBu BHR ( 2e ). The structure of 3c is characterized by a planar N₂B₃ ring skeleton with an unsymmetrical double-hydrogen bridge.     

Studies on two cadmium(II) and two zinc(II) complexes of 4′-chloro-2,2′ : 6′,2″-terpyridine with 1 : 1 or 1 : 2 ratio of metal and ligand

The reaction between 4′-chloro-2,2′ : 6′,2″-terpyridine (tpyCl) with d¹⁰ transition-metal ions produced two cadmium(II) and two zinc(II) metal complexes, formulated as [Cd(tpyCl-κ ³ N,N′,N″)(NO₃-κ ² O,O′)(NO₃-κO)(H₂O-κO)] (1), [Cd(tpyCl-κ ³ N,N′,N″)₂](ClO₄)₂ (2), [Zn(tpyCl-κ ³ N,N′,N″)₂](ClO₄)₂ (3), and [Zn(tpyCl-κ ³ N,N′,N″)₂](BF₄)₂ (4). Supramolecular interactions include coordinative bonding, O–H ··· O, O–H ··· Cl, C–H ··· F, and C–H ··· Cl hydrogen bonding and π–π stacking, all of which play essential roles in forming different frameworks of 1–4.     

Dicationic ionic liquids as recyclable catalysts for one‐pot solvent‐free synthesis of α‐aminophosphonates

Some task‐specific ionic liquids N,N,N′,N′‐tetramethyl‐N,N′‐dipropanesulfonic acid ethylene‐diammonium hydrogen sulfate, N,N,N′,N′‐tetramethyl‐N,N′‐dipropanesulfonic acid‐1,3‐propanediammonium hydrogen sulfate, N,N,N′,N′‐ tetramethyl‐N,N′‐ dipropanesulfonic acid‐1,6‐hexanediammonium hydrogen sulfate were prepared. These ionic liquids could be used as efficient and recyclable catalysts for the synthesis of α‐aminophosphonates at room temperature via an one‐pot three‐component reaction under organic solvent‐free conditions with good yields of 83–96%. The postprocessing was simple, and the catalysts could be reused at least six times without noticeably decreasing the catalytic activity. The novel clean procedure offers the advantages including short reaction time, good yields, operational simplicity, and environmentally benign. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:1–5, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20647