Polyrotaxanes based on polyethers and β‐cyclodextrin

A polyrotaxane in which β‐cyclodextrins (β‐CDs) are threaded onto a polyether chain was prepared by polycondensation of a β‐CD/bisphenol A (BPA) inclusion complex with aromatic dihalides. Two dihalides, with and without a side chain, were used. This polycondensation results in a polyrotaxane (or pseudopolyrotaxane for polymers without stoppers) with a 1:1 threading ratio when the side chain is present and 2:3 when there is none. The long side chain prevents dethreading of the macrocycles. The best yield and a good threading ratio were obtained when the polycondensation was performed by liquid?solid phase transfer catalysis without solvent (L/S PTC) using 2,5‐bi(iodomethyl)‐4‐methoxy‐(1‐octyloxy)benzene as dihalide. The ¹H NMR and FTIR spectra show that the products consist of β‐CD and polyether. The 2D NOESY NMR spectrum shows that the polyether chains are included in the β‐CD cavity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4391–4399, 2009     

Novel synthesis of aromatic polysulfides from S,S′-bis(trimethylsilyl)-substituted aromatic dithiols and activated aromatic dihalides

A new method for the synthesis of aromatic polysulfides has been developed by the polycondensation of S,S′-bis(trimethylsilyl)-substituted aromatic dithiols with activated aromatic dihalides. The solution polycondensation of three S-silylated aromatic dithiols with bis(4-chloro-3-nitrophenyl) sulfone afforded readily aromatic polysulfides having inherent viscosities of 0.7 dL/g, and the polymerization with bis(4-fluorophenyl) sulfone gave the polymers with viscosity values of 0.3 dL/g. The silylation method was compared advantageously with a conventional route using parent dithiols and activated aromatic dihalides.     

A facile cesium fluoride-mediated synthesis of aromatic polyethers from bisphenols and activated aromatic dihalides

A facile method for the synthesis of high-molecular-weight aromatic polyethers was developed with the use of cesium fluoride as a base. The high-temperature solution polycondensation between bisphenols and activated aromatic dihalides with cesium fluoride in polar aprotic solvents readily afforded a series of aromatic polyethers having inherent viscosities of 0.5–1.0 dL/g under essentially neutral and milder reaction conditions, compared with the conventinal method using alkali hydroxides or alkali carbonates. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2055–2061, 1997     

Influence of the bisphenol structure on the direct synthesis of sulfonated poly(arylene ether) copolymers. I

New sulfonated poly(arylene ether sulfone) copolymers with high molecular weights were successfully synthesized with controlled degrees of disulfonation of up to 70 mol % via the direct copolymerization of sulfonated aromatic dihalides, aromatic dihalides, and one of four structurally distinct bisphenols. The disodium salts of the 3,3′‐disulfonated‐4,4′‐dichlorodiphenyl sulfone and 3,3′‐disulfonated‐4,4′‐difluorodiphenyl sulfone comonomers were synthesized via the sulfonation of 4,4′‐dichlorodiphenyl sulfone or 4,4′‐difluorodiphenyl sulfone with 30% fuming sulfuric acid at 110 °C. Four bisphenols (4,4′‐bisphenol A, 4,4′‐bisphenol AF, 4,4′‐biphenol, and hydroquinone) were investigated for the syntheses of novel copolymers with controlled degrees of sulfonation. The composition and incorporation of the sulfonated repeat unit into the copolymers were confirmed by ¹H NMR and Fourier transform infrared spectroscopy. Solubility tests on the sulfonated copolymers confirmed that no crosslinking and probably no branching occurred during the copolymerizations. Tough, ductile films were solvent‐cast that exhibited increased water absorption with increasing degrees of sulfonation. These copolymers are promising candidates for high temperature proton‐exchange membranes in fuel cells, which will be reported separately in part II of this series. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2264–2276, 2003     

2,3,4,5‐Tetraethylpentela‐cyclo‐pentadienide (2,3,4,5‐Tetraethylpentolide) der Erdalkalimetalle Magnesium,Calcium, Strontium und Barium

2,3,4,5‐Tetraethylpentela‐cyclo‐pentadienides (2,3,4,5‐Tetraethylpentolides) of the Alkaline Earth Metals Magnesium, Calcium, Strontium, and Barium The reaction of bis(cyclopentadienyl)‐1‐zircona‐2,3,4,5‐tetraethyl‐cyclo‐penta‐2,4‐diene with ECl₃ (E = P, As, Sb) yields 1‐chloro‐tetraethylphosphole ( 1 ), ‐arsole ( 2 ) und ‐stibole ( 3 ). The reduction of these pentoles gives in a first step the corresponding octaethyldiphospholyle ( 4 ), ‐diarsolyle ( 5 ) and ‐distibolyle ( 6 ). Further reduction of these dipentolyles with magnesium and calcium leads in the presence of the corresponding dihalides to the formation of magnesium chlorid (2,3,4,5‐tetraethylphospholide) ( 7 ), ‐arsolide) ( 8 ) and ‐stibolide) ( 9 ) and calcium chlorid (2,3,4,5‐tetraethylphospholide) ( 10 ), ‐arsolide) ( 11 ) and ‐stibolide) ( 12 ), respectively. In the absence of alkaline earth metal dihalides no reaction is observed. For the larger metals strontium and barium the reduction of the dipentolyles succeeds in THF also without the addition of halides and the 1,1′‐dipentela‐octaethylstrontocene [E = P ( 13 ), As ( 14 ), Sb ( 15 )] as well as ‐barocene [E = P ( 16 ), As ( 17 ), Sb ( 18 )] are isolated halogen‐free. The strontocene crystallizes as a THF adduct whereas the barocene precipitates coligand‐free but with a chain structure. The molecular structures of 7 , 10 , and 16 are discussed.     

Selective Formation of Indene through the Reaction of Benzyl Radicals with Acetylene

The combustion of fossil fuels forms polycyclic aromatic hydrocarbons (PAHs) composed of five‐ and six‐ membered aromatic rings, such as indene (C₉H₈), which are carcinogenic, mutagenic, and deleterious to the environment. Indene, the simplest PAH with single five‐ and six‐membered rings, has been predicted theoretically to be formed through the reaction of benzyl radicals with acetylene. Benzyl radicals are found in significant concentrations in combustion flames, owing to their highly stable aromatic and resonantly stabilized free‐radical character. We provide compelling experimental evidence that indene is synthesized through the reaction of the benzyl radical (C₇H₇) with acetylene (C₂H₂) under combustion‐like conditions at 600 K. The mechanism involves an initial addition step followed by cyclization and aromatization through atomic hydrogen loss. This reaction was found to form the indene isomer exclusively, which, in conjunction with the high concentrations of benzyl and acetylene in combustion environments, indicates that this pathway is the predominant route to synthesize the prototypical five‐ and six‐membered PAH.     

Electrochemical Study of Highly Substituted Titanocene Dihalides

Titanocene dihalides are promising alternative to Cisplatin in cancer chemotherapy which should reduce negative side effects and overcome increasing resistance of cancer cells. Since the mechanism of anti‐cancer action is associated with generation of reactive oxygen species (ROS), hence with redox processes, electrochemical investigation of titanocene species would be an important issue, not applied up to now. In this article we report on the electrochemical reduction as well as oxidation of titanocene difluorides and dichlorides where unsubstituted as well as highly substituted titanocene dihalides are compared. The experiments were realized in acetonitrile using various electrode materials. The studied series was completed by a new dimethylsilylene bridged ansa‐titanocene difluoride which was characterized by NMR and x‐ray crystallography. The influence of structure and substitution on the redox properties was evaluated and, in addition to this, cytotoxicity of studied titanocene dihalides against human ovarian cancer cell lines A2780 and SK‐OV‐3, as well as against human embryonic kidney cell line HEK293 were screened. Two of highly substituted titanocenes exhibit cytotoxicity comparable with that of Cisplatin.     

The Palladium Way to N‐Heteroacenes

Novel synthetic methodologies allow increasingly efficient access to known organic materials, as well as the preparation of otherwise inaccessible species. Pd‐catalyzed coupling of aromatic dihalides to ortho‐diaminoarenes furnishes embedded stable N,N′‐dihydropyrazines expediently and in often excellent yields. The embedded N,N′‐dihydropyrazines can then be oxidized by MnO₂ to give substituted azatetracenes, azapentacenes, azahexacenes, and azaheptacenes, which are soluble, processable, and stable. This powerful Pd‐catalyzed methodology allows the preparation of azaacenes, including diaza‐, tetraaza‐ and hexaazaacenes. In combination with a suitable Pd precursor, Buchwald‐type biarylphosphines have been shown to give excellent results. Activated dihalides such as 2,3‐dihaloquinoxalines are coupled easily under simplified conditions, whereas 2,3‐dibromoacenes require more stringent conditions and advanced catalyst precursors. Pd catalysts effect the assembly of azaacenes with otherwise difficult to obtain substitution patterns. High yields and flexibility make this method most attractive.     

Synthesis,kinetics and mechanism of the reaction of a quasi‐aromatic copper(II) complex, [Cu(PnAO)‐6H]0, with aromatic aldehydes

The quasi‐aromatic metal complex (1,1,2,8,9,9‐hexamethyl‐4,6‐dioxa‐5‐hydro‐3,7,10,14‐tetraazacyclotetradecane‐2,7,10,12‐tetraene)copper(II), [Cu(PnAO)‐6H]⁰ (AH), was synthesized. Reactions of AH were studied spectrophotometrically in acidic media (pH = 1 ∼ 2, EtOH:H₂O = 1:4 v/v) with para‐substituted benzaldehydes (ald). The Cu,2N,3C quasi‐aromatic heterocyclic ring in AH is highly reactive at the central‐aromatic‐carbon atom, C12, to most aldehydes. A novel parallel, competitive and consecutive second‐order reaction mechanism is proposed. To obtain the rate constants following this mechanism, the Gauss‐Newton‐Marquardt and Runge‐Kutta methods were employed. Consistent results were obtained. Effects of acidity, solvent, temperature and substituent R (RH, CH₃, OCH₃, Cl) of the aromatic aldehydes on the reaction rate constants were studied. The results support the proposed SN2 mechanism. A linear free energy relationship between the rate constant k₁ and the Hammett parameters for the substituted benzaldehydes as well the activation parameters are presented. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 1–8, 2001     

Nouveaux polyéthers et polyesters à base d'isosorbide: synthèse et caractérisation

A new family of multifunctional polyethers was synthesized with acceptable yields by condensation of isosorbide with aliphatic and aromatic dihalides in solid-liquid heterogeneous medium (solid KOH in DMSO). Molecular weights evaluated by GPC are rather low (polydispersed oligomers with n = 2–9). On the other hand, polycondensation with aliphatic or aromatic acid dichlorides in mass or in solution allowed the elaboration of polyethers with appreciable weights (4000–8000) in good yields.     

The synthesis of diene and of vinyl copolymers containing predetermined quantities of polynuclear hydrocarbon or heterocyclic adducts-III. Copolymers formed from polynuclear hydrocarbons and alkyldihalides

The reaction in tetrahydrofuran between the disodium salt of anthracene (A) and alkyl dihalides (RX₂) results in oligomeric products with a repeat unit -[A-R]-. The same reaction with the dilithium derivative is complicated by the high reactivity of this species toward solvent; oligomers with -(CH₂)₄OH end groups are isolated. The xylylene dihalides undergo metallation and Wurtz coupling, and they produce low yields of oligomers rich in xylylene units.The reaction with dilithium acenaphthylene and alkyl dihalides gives a high yield of copolymer but there is evidence of crosslinking. Although addition occurs principally across the 1.2 position, some 1,5 addition is believed to cause this crosslinking. With dilithium phenanthrene the reaction is mainly one of electron transfer; the oligomers produced in low yield are low in phenanthrene adducts.     

Are water–aromatic complexes always stabilized due to π–H interactions? LMP2 study

Eight complexes of various aromatic molecules with water have been studied theoretically at the local Møller–Plesset 2nd order theory (LMP2)/aug‐cc‐pVTZ(‐f)//LMP2/6‐31+G* level of theory. Two types of complexes can be formed, depending on the electronic structure of aromatic molecules. Donor hydrocarbons form A‐type complexes, while aromatics bearing electron‐withdrawing substituents form B‐type complexes. A‐type complexes are stabilized due to π–H interactions with the OH bond pointing to the aromatic molecule plane, while B‐type complexes have geometry with the oxygen atom pointing to the aromatic molecule plane stabilized by the interaction of highest occupied molecular orbital (HOMO) of water molecule with π* orbitals of the aromatics. It has been found that a (? HOMO–lowest unoccupied molecular orbital (LUMO)/2 value of aromatic molecule, which can be called “molecular electronegativity,” is useful to predict the type of complex formed by aromatic molecule and water. Aromatic hydrocarbons with “molecular electronegativity” of <0.15 tend to form A‐type complexes, while aromatic molecules with “molecular electronegativity” of <0.15 a.u. form B‐type complexes. The binding energy of water–aromatic complexes undergoes a minimum in the area of switching from A‐type to B type complexes, which can be rationalize in terms of frontier orbital interactions. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Nano‐TiO2 as an Efficient Catalyst for Tandem Knoevenagel–Michael‐Cyclocondensation Reaction of Dimedone with Aromatic Aldehydes and Ammonium Acetate or Aromatic Amines under Solvent‐free Conditions

TiO₂ nanoparticles in anatase and rutile forms was characterized and studied by several techniques including X‐ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and successfully applied as an efficient and heterogeneous catalyst in the synthesis of 1,8‐dioxo‐decahydroacridines via the one‐pot multi‐component condensation reaction of dimedone with aromatic aldehydes and ammonium acetate or aromatic amines under mild and solvent‐free conditions.     

Synthesis and properties of poly(arylene ether sulfone)s and poly(arylene ether ketones) derived from 4,4″-dihydroxy-o-terphenyl

Novel poly(arylene ether)s with a rigid and zigzag 4,4″-o-terphenyldiyl structure, introduced into the polymer backbone were synthesized by nucleophilic displacement reaction of 4,4″-dihydroxy-o-terphenyl with several activated aromatic dihalides in virtually quantitative yields. The poly(arylene ether)s having high molecular weight show both good solubility in common organic solvents and high thermal stability up to 545°C. They are amorphous with glass transition temperatures of 160–200°C.     

Synthesis and characterization of poly(arylene ether imidazole)s

Poly(arylene ether imidazole)s were prepared by the aromatic nucleophilic displacement reaction of a bisphenol imidazole with activated aromatic dihalides. The polymers had glass transition temperatures ranging from 230 to 318°C and number-average molecular weights as high as 82,000 g/mol. Thermogravimetric analysis showed a 5% weight loss occurring ～ 400°C in air and ～ 500°C in nitrogen. Typical neat resin mechanical properties obtained at room temperature included tensile strength and tensile modulus of 14.2 and 407 ksi and fracture energy (G_lc) of 23 in. lb/in.² Titanium-to-titanium tensile shear strengths measured at 23 and 200°C were 4800 and 3000 psi, respectively. In addition, preliminary data were obtained on carbon fiber laminates. The chemistry, physical, and mechanical properties of these polymers are discussed.     

Design,Synthesis, and Antimicrobial Evaluation of some Novel Pyridine,Coumarin, and Thiazole Derivatives

Treatment of 2‐cyano‐N′‐(1‐(pyridin‐2‐yl)ethylidene)acetohydrazide 1 with aromatic/heterocyclic aldehydes 2a–f gave arylidene derivatives 3a–f . Polysubstituted pyridine derivatives 4a,b were prepared either from reaction of arylidene 3a,b with malononitrile or from reaction of acetohydrazide 1 with arylidenemalononitrile 5a,b . Cyclocondensation of acetohydrazide 1 with salicylaldehyde derivatives and acetylacetone furnished pyrido‐coumarins 6,7 and 2‐pyridone‐3‐carbonitrile 8, respectively. In addition, pyrido‐thiazoles 13 and 15 were obtained through reaction of 2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinecarbothioamide 11 with hydrazonyl chlorides and α‐haloketones, respectively. The structures of synthesized compounds were elucidated with spectral and elemental data. The antimicrobial activity of the synthesized compounds was studied.     

Synthesis of 1,3-Bis(trialkylammonio)-2-propanol Dihalides Exhibiting Retardant Activity toward Rape

1,3-Bis(trialkylammonio)-2-propanol dihalides were prepared, and their retardant activity was studied in relation to the chemical structure.     

Synthesis of ether‐linked bisoxazolines and their use in step‐growth polymerization reactions with phenolics

Six new ether‐linked bisoxazolines have been synthesized via reaction of p‐hydroxyphenyl‐2‐oxazoline with dihalides. These bisoxazolines may be used as chain extenders or crosslinkers for resins, monomers or polymers containing various acidic groups, including phenolics, via step‐growth (1 : 1) reactions. As an illustration, a phenol‐formaldehyde polycondensate (Alnovol) and an enzyme oligomerized bisphenol A resin, as well as poly (p‐hydroxystyrene), was chain extended and crosslinked to produce thermosets with high glass transition temperatures. The new bisoxazolines were also polymerized with diphenol compounds, such as diphone D and bisphenol P to generate linear or branched oligomers and polymers. Differential scanning calorimetry was used to evaluate the potential for polymerization and crosslinking reactions. Preliminary results showed that the new, ether‐linked bisoxazolines have potential for formulating high performance thermosets. Copyright © 2002 John Wiley & Sons, Ltd.     

Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes

The formation of a bis(μ‐oxido)dicopper complex with the ligand 2‐(diethylaminoethyl)‐6‐phenylpyridine (PPN) and its subsequent hydroxylation of the pendant phenyl group (studied earlier by Holland et al., Angew. Chem. Int. Ed.­ 1999 , 38, 1139–1142) has been reinvestigated to gain a better understanding of such systems in view of the development of new synthetic applications. To this end, we prepared a simple copper imine complex system that also affords selective o‐hydroxylation of aromatic aldehydes by using dioxygen as the oxidant: Applying the ligand N′‐benzylidene‐N,N‐diethylethylenediamine (BDED), salicylaldehyde was prepared in good yields and we show that this reaction also occurs through an intermediate bis‐μ‐oxido copper complex. The underlying reaction mechanism for the PPN‐supported complex was studied at the BLYP‐D/TZVP level of density functional theory and the results for representative stationary points along reaction paths of the BDED‐supported complex reveal a closely related mechanistic scenario. The results demonstrate a new facile synthetic way to introduce OH groups into aromatic aldehydes.     

Molecular structures of a series of substituted bis(η5‐cyclopentadienyl)titanium dihalides CpR2TiX2 [X = F,Cl, Br and I; R = CHPh2, CH(p‐Tol)2 and adamantyl]

Metallocene dihalides and derivatives thereof are of great interest as precursors for catalysts in polymerization reactions, as antitumor agents and, due to their increased stability, as suitable starting materials in salt metathesis reactions and the generation of metallocene fragments. We report the synthesis and structural characterization of a series of eleven substituted bis(η⁵‐cyclopentadienyl)titanium dihalides, namely bis[η⁵‐1‐(diphenylmethyl)cyclopentadienyl]difluoridotitanium(IV), [Ti(C₁₈H₁₅)₂F₂], bis{η⁵‐1‐[bis(4‐methylphenyl)methyl]cyclopentadienyl}difluoridotitanium(IV), [Ti(C₂₀H₁₉)₂F₂], and bis{η⁵‐1‐[bis(adamantan‐2‐yl)methyl]cyclopentadienyl}difluoridotitanium(IV), [Ti(C₁₅H₁₉)₂F₂], together with the bromide and iodide analogues, and the chloride analogues of the diphenylmethyl and adamantyl complexes. These eleven complexes were prepared by the reaction of the corresponding bis(η⁵:η¹‐pentafulvene)titanium complexes with different hydrogen halides (Cl, Br and I). The titanocene fluorides become available via chloride–fluoride exchange reactions.