Polyaniline doped with α, ω‐alkanedisulfonic acids: preparation and characterization

The use of α, ω‐alkanedisulfonic acid, HO₃S(CH₂)_nSO₃H (n = 1, 4, 6 and 12), as a dopant for polyaniline (PANi) was investigated. This series of disulfonic acids with varying chain lengths were synthesized and used in the doping of PANi. The doped polymers showed conductivity in the range 10^?2 to 10^?1 S cm^?1. Thermal studies showed that the doped polymers, depending on the chain length of α,ω‐alkanedisulfonic acid, were stable up to ca 300 °C and the thermal stability decreased with increasing dopant chain length. The thermal stability of α,ω‐alkanedisulfonic acid‐doped PANi was higher than that of alkanesulfonic acid‐doped PANi which typically degrades around 250 °C, suggesting a moderately broader processing window for α,ω‐alkanedisulfonic acid‐doped PANi for blending with other thermoplastics. Copyright © 2012 Society of Chemical Industry     

Synthesis and thermomechanical characterization of polyurethane elastomers extended with α,ω‐alkane diols

A series of polyurethane (PU) elastomers was prepared by the reaction of poly(?‐caprolactone) and 4,4′‐diphenylmethane diisocyanate, which was extended with a series of chain extenders (CEs) having 2–10 methylene units in their structure. The completion of the reaction was confirmed by Fourier transform infrared spectroscopy. The chemical structures of the synthesized PU samples were characterized with Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopy, and the thermal properties were determined by thermogravimetric analysis, DSC, and dynamic mechanical thermal analysis techniques. The mechanical properties were also studied and are discussed. The thermogravimetric analysis and DSC analysis showed that CE length had a considerable effect on the thermal properties of the prepared samples. The dynamic mechanical thermal analysis and damping peaks were also affected by the number of methylene units in the CE length. The elastomer extended with 1,2‐ethane diol exhibited optimum thermal properties, whereas the elastomer based on 1,10‐decane diol displayed the worst thermal properties. Tensile strength and elongation at break decreased with increasing CE length, whereas hardness showed the opposite trend. The glass‐transition temperature moved toward lower temperatures with increasing CE length. The decrease in the glass‐transition temperature and tensile properties were interpreted in terms of decreasing hard segments and increasing chain flexibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Iridium‐Catalyzed [2+2+2] Cycloaddition of α,ω‐Diynes with Cyanamides

The complex [Ir(cod)Cl]₂/DPPF or rac‐BINAP is an efficient catalyst for the [2+2+2] cycloaddition of α,ω‐diynes with cyanamides. A wide range of cyanamides derived from secondary amines are good coupling partners for α,ω‐diynes. The reaction of unsymmetrical α,ω‐diynes possessing two different internal alkyne moieties with cyanamides is regioselective. A competitive experiment showed that cyanamide is more reactive than nitrile. This higher reactivity of cyanamide than nitrile was analyzed based on density functional theory (DFT) calculations at the B3LYP level.

     

Direct Access to Medium‐Chain α,ω‐Dicarboxylic Acids by Using a Baeyer–Villiger Monooxygenase of Abnormal Regioselectivity

Baeyer–Villiger monooxygenases (BVMOs) are versatile biocatalysts in organic synthesis that can generate esters or lactones by inserting a single oxygen atom adjacent to a carbonyl moiety. The regioselectivity of BVMOs is essential in determining the ratio of two regioisomers for converting asymmetric ketones. Herein, we report a novel BVMO from Pseudomonas aeruginosa (PaBVMO); this has been exploited for the direct synthesis of medium‐chain α,ω‐dicarboxylic acids through a Baeyer–Villiger oxidation–hydrolysis cascade. PaBVMO displayed the highest abnormal regioselectivity toward a variety of long‐chain aliphatic keto acids (C₁₆–C₂₀) to date, affording dicarboxylic monoesters with a ratio of up to 95 %. Upon chemical hydrolysis, α,ω‐dicarboxylic acids and fatty alcohols are readily obtained without further treatment; this significantly reduces the synthetic steps of α,ω‐dicarboxylic acids from renewable oils and fats.     

Synthesis of Oligoester α,ω‐diols by Alcoholysis of PET through the Reactive Extrusion Process

The alcoholysis of PET with diols in the presence of dibutyltinoxide was carried out in a twin‐screw extruder with residence times of 1 min and without solvent. The reaction led to scissions of PET chains and to the synthesis of oligoester α,ω‐diols with average number molecular weights of about 1000 g·mol^—1 characterised by conventional techniques such as NMR, SEC and MALDI‐TOF. The alcoholysis kinetics was studied with a rheological tool under selected conditions, and it was shown that this reaction is quite compatible with the residence times in an extruder. This study clearly shows that the oligoesters synthesised by reactive extrusion have characteristics similar to the oligoesters synthesised by batch processes over many hours. Furthermore, the melting temperature of these oligoesters can be controlled between room temperature and 220°C by using diols with different structures for the alcoholysis.     

Asymmetric Synthesis of 3,4‐Dihydrocoumarins Bearing an α,α‐Disubstituted Amino Acid Moiety

An organocatalytic approach for the stereoselective synthesis of 3,4‐dihydrocoumarins with an α,α‐disubstituted amino acid moiety incorporated is presented. The developed methodology is based on the cascade reaction between α‐substituted azlactones and 2‐hydroxychalcones. It is initiated by a chiral Brønsted base‐catalyzed enantio‐ and diastereoselective Michael reaction followed by the azlactone ring opening to construct a 3,4‐dihydrocoumarin framework. Products bearing two adjacent stereogenic centers, one being quaternary, were formed with high enantioselectivities and excellent diastereoselectivities. Furthermore, the complete regioselectivity of the new cascade reactivity is worthy of notice.

     

Synthesis and characterization of α‐butyl‐ω‐N,N‐dihydroxyethylaminopropylpolydimethylsiloxane

α‐Butyl‐ω‐N,N‐dihydroxyethylaminopropylpolydimethylsiloxane, a monotelechelic polydimethylsiloxane with a diol‐end group, which is used to prepare polyurethane–polysiloxane graft polymer, was successfully synthesized. The preparation included five steps, which are hydroxyl protection, alkylation, anionic ring‐opening polymerization, hydrosilylation, and deprotection. The products were characterized by FTIR, GC, LC‐MS, ¹H NMR, and elemental analysis. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Combined Biocatalytic and Chemical Transformations of Oleic Acid to ω‐Hydroxynonanoic Acid and α,ω‐Nonanedioic Acid

A practical chemoenzymatic method for the synthesis of 9‐hydroxynonanoic acid and 1,9‐nonanedioic acid (i.e., azelaic acid) from oleic acid [(9Z)‐octadec‐9‐enoic acid] was investigated. Biotransformation of oleic acid into 9‐(nonanoyloxy)nonanoic acid via 10‐hydroxyoctadecanoic acid and 10‐keto‐octadecanoic acid was driven by a C‐9 double bond hydratase from Stenotrophomonas maltophilia, an alcohol dehydrogenase from Micrococcus luteus, and a Baeyer–Villiger monooxygenase (BVMO) from Pseudomonas putida KT2440, which was expressed in recombinant Escherichia coli. After production of the ester (i.e., the BVMO reaction product), the compound was chemically hydrolyzed to n‐nonanoic acid and 9‐hydroxynonanoic acid because n‐nonanoic acid is toxic to E. coli. The ester was also converted into 9‐hydroxynonanoic acid and the n‐nonanoic acid methyl ester, which can be oxygenated into the 9‐hydroxynonanoic acid methyl ester by the AlkBGT from P. putida GPo1. Finally, 9‐hydroxynonanoic acid was chemically oxidized to azelaic acid with a high yield under fairly mild reaction conditions. For example, whole‐cell biotransformation at a high cell density (i.e., 10 g dry cells/L) allowed the final ester product concentration and volumetric productivity to reach 25 mM and 2.8 mM h⁻¹, respectively. The overall molar yield of azelaic acid from oleic acid was 58%, based on the biotransformation and chemical transformation conversion yields of 84% and 68%, respectively.

     

Microbial Synthesis of Medium‐Chain α,ω‐Dicarboxylic Acids and ω‐Aminocarboxylic Acids from Renewable Long‐Chain Fatty Acids

Biotransformation of long‐chain fatty acids into medium‐chain α,ω‐dicarboxylic acids or ω‐aminocarboxylic acids could be achieved with biocatalysts. This study presents the production of α,ω‐dicarboxylic acids (e.g., C₉, C₁₁, C₁₂, C₁₃) and ω‐aminocarboxylic acids (e.g., C₁₁, C₁₂, C₁₃) directly from fatty acids (e.g., oleic acid, ricinoleic acid, lesquerolic acid) using recombinant Escherichia coli‐based biocatalysts. ω‐Hydroxycarboxylic acids, which were produced from oxidative cleavage of fatty acids via enzymatic reactions involving a fatty acid double bond hydratase, an alcohol dehydrogenase, a Baeyer–Villiger monooxygenase and an esterase, were then oxidized to α,ω‐dicarboxylic acids by alcohol dehydrogenase (ADH, AlkJ) from Pseudomonas putida GPo1 or converted into ω‐aminocarboxylic acids by a serial combination of ADH from P. putida GPo1 and an ω‐transaminase of Silicibacter pomeroyi. The double bonds present in the fatty acids such as ricinoleic acid and lesquerolic acid were reduced by E. coli‐native enzymes during the biotransformations. This study demonstrates that the industrially relevant building blocks (C₉ to C₁₃ saturated α,ω‐dicarboxylic acids and ω‐aminocarboxylic acids) can be produced from renewable fatty acids using biocatalysis.

     

Synthesis and Characterization of Segmented Block Copolymers Based on Hydroxyl‐Terminated Liquid Natural Rubber and α,ω‐Diisocyanato Telechelics

Summary: Segmented block copolymers, consisting of non‐polar soft segments from hydroxyl‐terminated liquid natural rubber (HTNR) and polar hard segments from α,ω‐diisocyanato telechelics obtained by “criss‐cross”‐cycloaddition, have been synthesized. The block copolymer formation took place under relatively mild reaction conditions at 80 °C in dichloroethane in the presence of dibutyltin dilaurate as a catalyst. The resulting block copolymers were characterized by spectroscopic techniques (¹H NMR, FTIR, UV‐vis spectroscopy) as well as GPC for molar mass determination. The block copolymers were compression molded in a hot stage press, and the resulting samples were characterized by DSC and stress‐strain measurement. The solubility and phase morphology of the materials have also been studied.

Segmented block copolymer from HTNR and α,ω‐diisocyanato telechelics     

Copper‐Catalyzed Oxidative α‐Alkylation of α‐Amino Carbonyl Compounds with Ethers via Dual C(sp3)‐H Oxidative Cross‐ Coupling

A novel copper‐catalyzed oxidative alkylation of α‐amino carbonyl compounds with ethers has been established for the selective synthesis of α‐etherized α‐amino carbonyl compounds. This oxidative alkylation is achieved by dual C(sp³) H bond oxidative cross‐coupling, and its scope is expanded to α‐amino ketones, α‐amino esters and α‐amino amides.

     

Convenient Preparation of Chiral α,β‐Epoxy Ketones via Claisen–Schmidt Condensation‐Epoxidation Sequence

A novel Clasisen–Schmidt condensation‐epoxidation sequence of aldehydes and ketones was developed to produce a series of chiral α,β‐epoxy ketones under asymmetric phase‐transfer catalytic conditions. The organocatalytic method reported here can afford chiral α,β‐epoxy ketones under mild conditions with moderate to good yields and up to 96 % ee.     

Palladium‐Catalyzed Decarboxylative sp‐sp2 Cross‐Coupling Reactions of Aryl and Vinyl Halides and Triflates with α,β‐Ynoic Acids using Silver Oxide

Palladium‐catalyzed decarboxylative sp‐sp² cross‐coupling reactions of aryl and vinyl halides and triflates with α,β‐ynoic acids using silver oxide have been developed. A variety of α,β‐ynoic acids were readily decarboxylated in the presence of silver oxide and then, generated in situ, silver acetylides were coupled with electrophiles in the presence of a palladium(0) catalyst under neutral conditions, producing either symmetrical or unsymmetrical diarylacetylenes, arylalkylacetylenes and arylvinylacetylenes in good to excellent yields.     

Atom‐transfer radical polymerization of methyl methacrylate with α,α′‐dichloroxylene/CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine initiation system under microwave irradiation

The atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA), using α,α′‐dichloroxylene as initiator and CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst was successfully carried out under microwave irradiation (MI). The polymerization of MMA under MI showed linear first‐order rate plots, a linear increase of the number‐average molecular weight with conversion, and low polydispersities, which indicated that the ATRP of MMA was controlled. Using the same experimental conditions, the apparent rate constant (k) under MI (k = 7.6 × 10^?4 s^?1) was higher than that under conventional heating (k = 5.3 × 10^?5 s^?1). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2189–2195, 2004     

Three‐Component Reactions of 2‐Alkynylbenzaldoximes and α,β‐Unsaturated Carbonyl Compounds with Bromine or Iodine Monochloride

The three‐component reaction of 2‐alkynylbenzaldoximes and α,β‐unsaturated carbonyl compounds with bromine or iodine monochloride is described, which generates the unexpected 2‐(4‐haloisoquinolin‐1‐yl)ethanol derivatives in good to excellent yields.     

Modification of epoxy resin with α,ω-oligo(butylmethacrylate)diols

Novel liquid rubbers based on bishydroxy-terminated oligo(butylmethacrylate) were used to toughen anhydride-cured epoxy resins. Concentration and molecular weight of the toughening agents were varied in order to examine the effects on important mechanical properties, such as toughness, strength, stiffness, and glass transition temperature. Experimental data show that telechelic methacrylates are suitable toughening agents for epoxies. The compatibility between resin and toughener can be adjusted by varying the molecular weight of the rubber. The best results are obtained by modifying an epoxy resin with 10 wt% of bishydroxy-terminated oligo(butylmethacrylate) of a molecular weight of 5000 g/mol. Fracture toughness K_lc increases by 150% accompanied by a decrease in modulus of only 11% and in strength of 16%, as compared to the corresponding properties of the neat resin. Due to an almost complete phase separation of the rubber upon curing, the glass transition temperature is scarcely affected. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 785–796, 1998     

Synthesis of ω‐amino‐α‐phenylcarbonate alkanes and their polymerization to [n]‐polyurethanes

Aliphatic [n]‐polyurethanes have recently been synthesized from ω‐isocyanato‐α‐alkanols or, more traditionally, by cationic ring‐opening polymerization of cyclourethanes or by the Bu₂Sn(OMe)₂‐promoted polycondensation of ω‐hydroxy‐α‐O‐phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. In contrast, the polymerization of ω‐amino‐α‐phenylcarbonate alkanes is expected to occur under milder conditions. ω‐Amino‐α‐phenylcarbonate alkanes have been synthesized from 6‐aminohexanol (1) and 3‐aminopropanol (6). The procedure involves the N‐Boc protection of the amino group, followed by activation of the alcohol. Removal of the N‐Boc affords the corresponding ω‐amino‐1‐O‐phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]‐polyurethanes. The procedure described is useful for the preparation of stable ω‐amino‐α‐phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]‐polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. Copyright © 2010 Society of Chemical Industry     

Copper‐Catalyzed C−N Bond Formation via Oxidative Cross‐Coupling of Amines with α‐Aminocarbonyl Compounds

A novel and selective method for the simple copper‐catalyzed α‐amination of α‐aminocarbonyl compounds to afford 2‐amino‐2‐iminocarbonyl and 2‐amino‐2‐oxocarbonyl compounds is reported. This transformation is achieved by C(sp³)−H and N−H bond oxidative cross‐coupling and selective C−N bond oxidative cleavage. This reaction system has a broad reaction scope, providing a facile pathway for the α‐functionalization of α‐amino ketones.

     

Copolymerization of styrene with an α‐olefin via atom transfer radical polymerization

This investigation reports the preparation of styrene–α‐olefinic random copolymers, using 1‐octene as an α‐olefin, via atom transfer radical polymerization. Atom transfer radical copolymerization of styrene with 1‐octene was successfully carried out using phenylethyl bromide as initiator and CuBr as catalyst in combination with N, N, N′, N″, N″‐pentamethyldiethylenetriamine as ligand. The copolymers had controlled molecular weight, narrow dispersity and well‐defined end groups with significant 1‐octene incorporation in the polymer. Incorporation of 1‐octene in the copolymers was confirmed using ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy. An increase in 1‐octene content in the monomer feed led to an increase in the level of incorporation of the α‐olefin in the copolymer. An increase in the concentration of 1‐octene led to a decrease in the rate of polymerization and an increase in dispersity. The glass transition temperature of the copolymer gradually decreased as the incorporation of 1‐octene increased. Copyright © 2011 Society of Chemical Industry