Ring‐opening polymerization of 1,4‐dioxan‐2‐one initiated by lanthanum isopropoxide in bulk

Lanthanum isopropoxide (La(OiPr)₃) has been synthesized and employed for ring‐opening polymerization of 1,4‐dioxan‐2‐one in bulk as a single‐component initiator. The influences of reaction conditions such as initiator concentration, reaction time, and reaction temperature on the polymerization were investigated. The kinetics indicated that the polymerization is first‐order with respect to the monomer concentration. The Mechanistic investigations according to ¹H NMR spectrum analysis demonstrated that the polymerization of PDO proceeded through a coordination‐insertion mechanism with a rupture of the acyl‐oxygen bond of the monomer rather than the alkyl‐oxygen bond cleavage. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5214–5222, 2008     

H‐shaped (ABCDE type) quintopolymer via click reaction [3 + 2] strategy

H‐shaped quintopolymer containing different five blocks: poly(ε‐caprolactone) (PCL), polystyrene (PS), poly(ethylene glycol) (PEG), and poly(methyl methacrylate) (PMMA) as side chains and poly(tert‐butyl acrylate) (PtBA) as a main chain was simply prepared from a click reaction between azide end‐functionalized PCL‐PS‐PtBA 3‐miktoarm star terpolymer and PEG–PMMA‐block copolymer with alkyne at the junction point, using Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as a catalyst in DMF at room temperature for 20 h. The H‐shaped quintopolymer was obtained with a number–average molecular weight (M_n) around 32,000 and low polydispersity index (M_w/M_n) 1.20 as determined by GPC analysis in THF using PS standards. The click reaction efficiency was calculated to have 60% from ¹H NMR spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4459–4468, 2008     

Thermally latent synthesis of networked polymers from multifunctional hemiacetal ester and diepoxide catalyzed by Schiff‐base‐zinc chloride complex

Thermally latent reaction of a copolymer ( P1 ) bearing hemiacetal ester and n‐butyl methacrylate moieties and glycidyl phenyl ether ( 2 ) was catalyzed by bis(p‐methoxybenzylidene)‐1,2‐diiminoethane/zinc chloride complex (ZnCl₂/ 3 ) at 30–150 °C for 6 h. No reaction of P1 and 2 took place below 70 °C, and it smoothly proceeded above 120 °C. The latencies and activities mean that ZnCl₂/ 3 meets both the high latencies at ambient conditions and the high activities at desired temperatures. Thermal crosslinking reaction employing multifunctional derivatives was carried out using ZnCl₂/ 3 at 140 °C for 6 h to afford a networked polymer in high yields. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3682–3689, 2008     

Synthesis of 1H‐quinazoline‐2,4‐diones from 2‐aminobenzonitriles by fixation of carbon dioxide with amidine moiety supported polymer at atmospheric pressure

1H‐Quinazoline‐2,4‐diones, which are key intermediates in the synthesis of medicines, were successfully synthesized from 2‐aminobenzonitriles by the fixation of CO₂ in the presence of a polystyrene derivative bearing amidine moiety [poly(amidine)]. A model reaction, that is, the reaction of 2‐aminobenzonitrile ( 1a ) with CO₂ in the presence of N‐methyltetrahydropyrimidine ( MTHP ) revealed that a catalytic amount of MTHP afforded 1H‐quinazoline‐2,4‐dione ( 2a ) quantitatively at atmospheric pressure. Several 1H‐quinazoline‐2,4‐diones ( 2a ‐ 2c ) were successfully synthesized from the corresponding 2‐aminobenzonitriles ( 1a ‐ 1c ) in the presence of poly(amidine). The poly(amidine) could easily be separated from the reaction mixture by filtration and reused in subsequent reactions owing to the heterogeneous system. These demonstrated that poly(amidine) is a useful heterogeneous polymer‐supported reagent for the synthesis of 1H‐quinazoline‐2,4‐diones from CO₂. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 653–657, 2009     

Stereospecific synthesis of a family of novel (E)‐2‐aryl‐1‐silylalka‐1,4‐dienes or (E)‐4‐aryl‐5‐silylpenta‐1,2,4‐trienes via a cross‐coupling of (Z)‐silyl(stannyl)ethenes with allyl halides or propargyl bromide

Stereospecific synthesis of a family of novel (E)‐2‐aryl‐1‐silylalka‐1,4‐dienes or (E)‐4‐aryl‐5‐silylpenta‐1,2,4‐trienes via a cross‐coupling of (Z)‐silyl(stannyl)ethenes with allyl halides or propargyl bromide is described. In the reaction with allyl bromide, either a Pd(dba)₂? CuI combination (dba, dibenzylideneacetone) in DMF or copper(I) iodide in DMSO–THF readily catalyzes or mediates the coupling reaction of (Z)‐silyl(stannyl)ethenes at room temperature, producing novel vinylsilanes bearing an allyl group β to silicon with cis ‐disposition in good yields. Allyl chlorides as halides can be used in the CuI‐mediated reaction. CuI alone much more effectively mediates the cross‐coupling reaction with propargyl bromide in DMSO–THF at room temperature compared with a Pd(dba)₂? CuI combination catalysis in DMF, providing novel stereodefined vinylsilanes bearing an allenyl group β to silicon with cis ‐disposition in good yields. Copyright © 2008 John Wiley & Sons, Ltd.     

Palladium‐catalysed Suzuki cross‐coupling of primary alkylboronic acids with alkenyl halides

The Suzuki reaction of primary alkylboronic acids with alkenyl halides proceeds nicely using the air‐stable catalyst PdCl(C₃H₅)(dppb), Cs₂CO₃ as base and toluene or xylene as solvent. A minor effect of the substituent position of the alkenyl bromide was observed. Quite similar yields were observed in the presence of α‐ or β‐substituted alkenyl bromides such as 2‐bromobut‐1‐ene or 1‐bromo‐2‐methylprop‐1‐ene with this catalyst. This reaction proceeded with a variety of alkylboronic acids such as 2‐phenylethylboronic acid or n‐octylboronic acid. Lower yields of coupling products were obtained in the presence of an alkenyl chloride. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of new complexes of the type [Ru(CO)2Cl2 (2‐phenyl‐1,8‐naphthyridine‐kN) (2‐phenyl‐1,8‐naphthyridine‐kN′)]. Preliminary applications in homogeneous catalysis

Novel ruthenium (II) complexes were prepared containing 2‐phenyl‐1,8‐naphthyridine derivatives. The coordination modes of these ligands were modified by addition of coordinating solvents such as water into the ethanolic reaction media. Under these conditions 1,8‐naphthyridine (napy) moieties act as monodentade ligands forming unusual [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] complexes. The reaction was reproducible when different 2‐phenyl‐1,8‐naphthyridine derivatives were used. On the other hand, when dry ethanol was used as the solvent we obtained complexes with napy moieties acting as a chelating ligand. The structures proposed for these complexes were supported by NMR spectra, and the presence of two ligands in the [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] type complexes was confirmed using elemental analysis. All complexes were tested as catalysts in the hydroformylation of styrene showing moderate activity in N,N′‐dimethylformamide. Copyright © 2008 John Wiley & Sons, Ltd.     

A theoretical investigation on the cycloaddition reaction between azocarbenium ions and nitriles

The 1,3‐dipolar cycloaddition reactions of the cationic 1,3‐dipolarophiles of azocarbenium ion 1 with HCN in the gas phase were examined using the density functional theory, QCISD method (Quadratic configuration interaction using single and double substitutions) and CCSD(T) (Coupled cluster calculations with single and double excitations and a perturbative estimate of triple contributions calculations) calculations. The theoretical results revealed that the reaction takes place via an initial formation of a 1:1 complex of the two reactants, mainly driven by charge interaction, followed by an asynchronous concerted cyclization forming the 3H‐[1,2,4]‐triazolium ion 3, which undergo [1,2]‐H shift to provide the 1H‐[1,2,4]‐triazolium ion 4. The effect of the solvent has been modeled by using the isodensity‐surface polarizable continuum (IPCM) model and the calculation showed that the reaction in CH₂Cl₂ solution proceeds in a similar manner as in gas phase with only a slight derivation of activation barrier. The substituent effects have also been investigated. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

A convenient synthesis of 2‐(1H‐1,2,4‐triazol‐1‐yl)‐2H‐1,4‐benzothiazine derivatives

A series of 2‐(1H‐1,2,4‐triazol‐1‐yl)‐2H‐1,4‐benzothiazines were designed and synthesized by condensation of 1,2,4‐triazole‐substituted ω‐bromoacetophenones and o‐aminothiophenols with the aid of K₂CO₃ under mild conditions with moderate to high yields. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:332–336, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20434     

Preparation of star block copolymers with polystyrene‐block‐poly(ethylene oxide) as side chains on hyperbranched polyglycerol core by combination of ATRP with atom transfer nitroxide radical coupling reaction

The star block copolymers with polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) as side chains and hyperbranched polyglycerol (HPG) as core were synthesized by combination of atom transfer radical polymerization (ATRP) with the “atom transfer nitroxide radical coupling” (“ATNRC”) reaction. The multiarm PS with bromide end groups originated from the HPG core (HPG‐g‐(PS‐Br)_n) was synthesized by ATRP first, and the heterofunctional PEO with α‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy group and ω‐hydroxyl group (TEMPO‐PEO) was prepared by anionic polymerization separately using 4‐hydroxyl‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (HTEMPO) as parents compound. Then ATNRC reaction was conducted between the TEMPO groups in PEO and bromide groups in HPG‐g‐(PS‐Br)_n in the presence of CuBr and pentamethyldiethylenetriamine (PMDETA). The obtained star block copolymers and intermediates were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, fourier transform‐infrared in detail. Those results showed that the efficiency of ATNRC in the preparation of multiarm star polymers was satisfactory (>90%) even if the density of coupling cites on HPG was high. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6754–6761, 2008     

Thermally latent reaction of hemiacetal ester with epoxide catalyzed by recyclable polymeric catalyst consisting of salen‐zinc complex and polyurethane main chain

This article describes the synthesis of and catalysis with a polymeric catalyst (Zn/ 1_NHCOO ) carrying salen‐zinc complex structure in the main chain prepared from polyaddition of zinc/bis(4‐hydroxy)salicylidene‐1,2‐diiminoethane and 4,4′‐diphenylmethane diisocyanate. Poly(Zn/ 1_NHCOO ) promoted the reaction of glycidyl phenyl ether (2) with 1‐propoxyethyl‐2‐ethylhexanoate (3) only at moderately elevated temperatures. Poly(Zn/ 1_NHCOO ) can be recycled by simple filtration from the reaction mixtures, and the recycled polymer is as active as the freshly prepared one. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3673–3681, 2008     

A new strategy to characterize the extent of reaction of thermoset elastomers

A new method for determining the extent of reaction of thermoset elastomers was developed based on equilibrium swelling and dynamic mechanical analysis (DMA). The extent of reaction was defined based on the molecular weight between crosslinks (M_c) of a polymer sample in relation to M_c at the onset of gelation and at complete reaction. The molecular weight between crosslinks was measured using equilibrium swelling, whereas rheology and DMA were used to determine the exact point of gelation and reaction completion, respectively. The extent of reaction of poly(1,8‐octanediol‐co‐citrate) at various polymerization conditions was investigated and this method was used to study the relationship between mechanical properties, molecular weight between crosslinks, and extent of reaction. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1318–1328, 2008     

Synthesis of a hyperbranched polythioketal with 100% degree of branching

A 100% hyperbranched polymer was successfully prepared by using 2‐[4‐(4‐mercaptobutoxy)phenoxy]‐9H‐fluoren‐9‐one as an AB₂ monomer in trifluoroacetic acid. The kinetics of the model reaction between 9‐fluorenone and 3‐mercaptopropionic acid was investigated. The reaction obeyed the second‐order kinetics, indicating that the first reaction, that is, the formation of the intermediate from 9‐fluorenone and 3‐mercaptopropionic acid, is considerably slower than the second one, that is, the reaction of the intermediate with 3‐mercaptopropionic acid. On the basis of this finding, a new monomer expected to produce a 100% branched hyperbranched polymer, 2‐[4‐(4‐mercaptobutoxy)phenoxy]‐9H‐fluoren‐9‐one, was designed and prepared. The obtained polymer was characterized by ¹H and ¹³C‐NMR spectroscopy, which confirmed that the polymer was a 100% branched hyperbranched polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2689–2700, 2008     

Kinetics of ethylene polymerization reactions with chromium oxide catalysts

Principal kinetic data are presented for ethylene homopolymerization and ethylene/1‐hexene copolymerization reactions with two types of chromium oxide catalyst. The reaction rate of the homopolymerization reaction is first order with respect to ethylene concentration (both for gas‐phase and slurry reactions); its effective activation energy is 10.2 kcal/mol (42.8 kJ/mol). The r₁ value for ethylene/1‐hexene copolymerization reactions with the catalysts is ～30, which places these catalysts in terms of efficiency of α‐olefin copolymerization with ethylene between metallocene catalysts (r₁ ～ 20) and Ti‐based Ziegler‐Natta catalysts (r₁ in the 80–120 range). GPC, DSC, and Crystaf data for ethylene/1‐hexene copolymers of different compositions produced with the catalysts show that the reaction products have broad molecular weight and compositional distributions. A combination of kinetic data and structural data for the copolymers provided detailed information about the frequency of chain transfer reactions for several types of active centers present in the catalysts, their copolymerization efficiency, and stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5315–5329, 2008     

Synthesis and structural consideration of 1‐chloro‐N,N′,N″‐tris(pentafluorophenyl)azagermatrane: Azagermatrane with the shortest intramolecular N → Ge bond

Two compounds of a novel‐type azagermatrane, N(CH₂CH₂NC₆F₅)₃Ge‐Hal: HalCl ( 1 ), Br ( 2 ), were prepared via a metathetical reaction of trilithium salt of tetramine, N[CH₂CH₂N(Li)C₆F₅]₃, with corresponding GeHal₄. A single crystal structure of 1 was determined by the X‐ray diffraction study: The compound shows the strongest transannular N_ax → Ge interaction (2.148(7) Å) among other studied azagermatranes. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:738–741, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20476     

Effect of prepolymer molecular weight on solid state polymerization of poly(bisphenol a carbonate) with nitrogen as a sweep fluid

The effect of prepolymer molecular weight on the solid‐state polymerization (SSP) of poly(bisphenol A carbonate) was investigated using nitrogen (N₂) as a sweep fluid. Prepolymers with different number–average molecular weights, 3800 and 2400 g/mol, were synthesized using melt transesterification. SSP of the two prepolymers then was carried out at reaction temperatures in the range 120–190 °C, with a prepolymer particle size in the range 20–45 μm and a N₂ flow rate of 1600 mL/min. The glass transition temperature (T_g), number–average molecular weight (M_n), and percent crystallinity were measured at various times during each SSP. The phenyl‐to‐phenolic end‐group ratio of the prepolymers and the solid‐state synthesized polymers was determined using 125.76 MHz ¹³C and 500.13 MHz ¹H nuclear magnetic resonance (NMR) spectroscopy. At each reaction temperature, SSP of the higher‐molecular‐weight prepolymer (M_n = 3800 g/mol) always resulted in higher‐molecular‐weight polymers, compared with the polymers synthesized using the lower molecular weight prepolymer (M_n = 2400 g/mol). Both the crystallinity and the lamellar thickness of the polymers synthesized from the lower‐molecular‐weight prepolymer were significantly higher than for those synthesized from the higher‐molecular‐weight prepolymer. Higher crystallinity and lamellar thickness may lower the reaction rate by reducing chain‐end mobility, effectively reducing the rate constant for the reaction of end groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4959–4969, 2008     

Synthesis,characterization, and biological activity of phosphorylated/thiophosphorylated compounds of 2‐substituted benzimidazoles

A series of phosphorylated and thiophosphorylated compounds of 2‐substituted benzimidazoles have been synthesized by the reaction of POCl₃ and PSCl₃ with 2‐substituted benzimidazoles in different molar ratios. The compounds have been characterized by elemental analyses, infrared, and ¹H NMR and ³¹P NMR spectral studies. These compounds were found to be insecticidal when tested against Periplenata americana. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:154–157, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20385     

N‐functionalized azolin‐2‐ylidene‐palladium‐catalyzed heck reaction

Novel 1,3‐dialkylimidazolidinium, 1,3‐dialkyl‐3,4,5,6‐tetrahydropyrimidinium, and 1,3‐dialkyl‐1H‐4,5,6,7‐tetrahydrodiazepinium hexafluorophosphates ( 1a–c, 2a–c ) as N‐heterocyclic carbene precursors have been synthesized and characterized. The incorporation of saturated N‐heterocyclic carbenes into palladium precatalysts gives high‐catalyst activity in the Heck coupling of aryl bromide substrates in aqueous media. The complexes were generated in the presence of Pd(OAc)₂ by in situ deprotonation of 1,3‐dialkylazolinium salts 1, 2 . © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:82–86, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20415     

Asymmetric epoxidation of chromenes catalyzed by chiral pyrrolidine SalenMn(III) complexes with an anchored functional group

Chiral pyrrolidine SalenMn(III) complexes with an anchored functional group at the N_aza‐substituent in the pyrrolidine backbone were synthesized, and used as catalysts for asymmetric epoxidation of substituted chromenes. The complex 1 with an anchored imidazole as acceptor could effectively catalyze epoxidation of substituted chromenes in the absence of expensive additive 4‐phenyl pyridine N‐oxide (PPNO) by the coordination of the anchored organic base to the central manganese ion. Complexes 2 and 3 with a quaternary ammonium salt unit at the N_aza‐substituent in the pyrrolidine backbone displayed higher activities than Jacobsen catalyst and the analogous complex 4 without anchored functional group in the aforementioned reaction. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization, and fluorescence phenomena of 1‐naphthoxy and 1‐naphthylamino substituted cyclotriphosphazenes

The reactions of hexachlorocyclotriphosphazene N₃P₃Cl₆ ( 1 ) with 1‐naphthol and 1‐naphthylamine have been examined. The reaction of 1 with sodium 1‐naphthoxy gave the hexakis(1‐naphthoxy)cyclotriphosphazene ( 2 ) in high yield. Geminal 2,2‐di(1‐naphthylamino)‐4,4,6,6‐tetrachlorocyclotriphosphazene ( 3 ) was obtained from the reaction of 1 with 1‐naphthylamine. The structures of phosphazene derivatives were defined by elemental analysis, FTIR, UV‐‐visible, and ¹H, ¹³C, ³¹P NMR spectroscopy. The fluorescence intensity of the compounds was measured in THF and CH₂Cl₂. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:158–162, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20400