Isolation of donor-stabilized N-silylphosphoranimine cations and the discovery of an ambient temperature route to Poly(alkyl/aryl)phosphazenes

This account describes the formation of nitrogen and phosphorus donor-stabilized phosphoranimine cations from N-silylphosphoranimines. A novel phosphine-mediated dehalogenation reaction is also described, as well as the discovery of an ambient temperature route to poly(alkyl/aryl)phosphazenes.     

Hydrazines in the synthesis of N-substituted 1,5,3-dithiazocan-3-amines catalyzed by Ti and Cu compounds

Efficient preparation method was developed for N-aryl(benzyl, alkyl)-1,5,3-dithiazocan-3-amines consisting in the transamination of 3-tert-butyl-1,5,3-dithiazocane with aryl(benzyl)hydrazines, and also in the reaction of N ¹,N ¹,N ⁷,N ⁷-tetramethyl-2,6-dithiaheptane-1,7-diamine with aryl(benzyl, alkyl)hydrazines in the presence of catalytic amounts of Ti and Cu compounds.     

Synthesis and characterization of new thermally stable poly(amide-imide)s based on bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide and aromatic diamines

N,N′-bis-(4-carboxyphenyl)bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide was prepared by reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetra carboxylic dianhydride with p-aminobenzoic acid in a mixture of acetic acid and pyridine (3: 2). Polycondensation of N,N′-bis-(4-carboxyphenyl)bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide with six different aromatic diamines produced a series of new poly(amide-imide)s (PAIs) in high yields with inherent viscosities between 0.49–0.95 dl/g. All PAIs were characterized by means of elemental analysis, viscosity measurement, solubility test, FTIR spectroscopy and ¹H-NMR spectroscopy. Dynamic TGA of PAIs shows 10% weight loss temperatures from 410 to 435°C under nitrogen.     

Copolymerization of N-carboxy Nϵ-carbobenzoxy L-lysine anhydride with N-carboxy β-benzyl L-aspartate anhydride in acetonitrile

Copolymerization of N-carboxy N^?-carbobenzoxy L -lysine anydride with N-carboxy β-benzyl L -aspartate anhydride was initiated with n-butylamine in acetonitrile. The copolymerization proceeded almost homogeneously except for the initial stage, when the proportion of N-carboxy anhydride (NCA) in the polymerization mixture varied from 25 to 75 mol %. This was due to the fact that the copolypeptides formed were soluble or highly swollen in the solvent, in contrast to the homopolymerization of NCAs such as N^?-carbobenzoxy L -lysine NCA and β-benzyl L -aspartate NCA in acetonitrile, which proceeds heterogeneously. The compositions of the copolymers obtained were, within experimental error, the same as their monomer feed compositions. The initial rates of copolymerization were almost the same as the rate of homopolymerization of β-benzyl L -aspartate NCA, which propagates with a nonhelical polypeptide, but were slower than the rate of homopolymerization of N^?-carbobenzoxy L -lysine NCA, which propagates with a helical polypeptide.     

Synthesis, characterization and thermal properties of small R2R2NX-type quaternary ammonium halides

Twenty-one R₂R^′₂N⁺X⁻ -type (R=methyl or ethyl, R^′=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with ¹H-NMR, ¹³C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. The thermal properties of all compounds were studied using TG/DTA and DSC methods. The smallest compounds decomposed during or before melting. The decreasing trend of melting points was observed when the alkyl chain length was increased. The liquid ranges of 120-180 °C were observed for compounds with 5-6 carbon atoms in the alkyl chain. The low melting points and wide liquid ranges suggest potential applicability of these compounds for example as ionic liquids precursors.     

The effect of feed conditions in the emulsion catalytic chain transfer polymerization of alkyl methacrylates

([bis[μ-[(2,3-butanedione dioximato)(2-)-O:O′]] tetrafluorodiborato(2-)-N,N′,N″,N‴] cobalt), CoBF, has been used for the effective catalytic chain transfer of alkyl methacrylate homo- and copolymers under emulsion polymerization conditions. The catalytic chain transfer process reduces the rate of polymerization such that when the monomer is fed over 60 min the instantaneous conversion is low enough for the particle to be swollen with monomer, allowing diffusion of the catalysts between the aqueous and monomer phases. When the amount of the catalyst is reduced, the rate is increased, eventually leading to viscous, glassy particles that prevent catalyst mobility, which is observed as a breakdown in the polymerization mechanism. This can be circumvented by the addition of a 20% shot of monomer at the start of the reaction. The effective chain transfer coefficient decreases on increasing the length of the ester group of the methacrylate. The analysis of the polymers made by the technique described shows that the T_g of the polymers observe a broad transition due to the effect of chain length being pronounced at low molecular mass. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3549–3557, 1999     

Radical polymerization of N-vinylcaprolactam in benzene solutions in a wide conversion range

The kinetics of radical polymerization of N-vinylcaprolactam initiated by the thermal decomposition of AIBN at 60°C in monomer solutions in benzene has been studied in a wide range of conversions. The heat of polymerization of N-vinylcaprolactam is 76.0 ± 0.9 kJ/mol; at initial conversions, the polymerization of N-vinylcaprolactam is of the first order with respect to the monomer and of the 0.5th order with respect to the initiator. The ratio of chain propagation and chain termination rate constants k _p/k _ter ^0.5 is 0.578 l^0.5/(mol s)^0.5, thus suggesting a high propagation rate constant k _p > 10³ l/(mol s). At a high initial concentration of the monomer, the kinetic curves demonstrate a weakly pronounced gel effect, and, in the gel permeation chromatography curves of the polymers, the second high-molecular-mass mode emerges, whose intensity grows with conversion. The observed kinetic features are interpreted in terms of the diffusion control of the gel effect.     

3-ethyl-3-phenylazetidinone-2—I. Synthesis of (R)-, (S)- and (RS)-monomer,polymerization and properties of polymers

Synthesis and optical resolution of 3-ethyl-3-phenylazetidinone-2 were improved to obtain (RS)-, (R)- and (S)-monomers having optical purities up to 98%, which could successfully be determined by ¹H-NMR 250 MHz using tris[3-(2,2,2-trifluoro-l-hydroxymethylidene)d-camphorato]europium III as a shift reagent. These monomers were polymerized anionically in HMPT using potassium salt as a catalyst and by the addition of 1-acetyl-4,4-dimethylazetidinone-2 as a chain initiator. Optical purity of the starting monomer seemed to be maintained in the resulting polymers, the thermal properties of which were found to depend on the mean length of the stereoblocks contained in the chain. While the reactivity, in particular the case of polymerization, of monomer increased with the optical purity, no evidence could be obtained for stereoregulation by a preferential incorporation of a monomer enantiomer according to the configuration of the growing chain end unit.     

On the electro-initiated polymerization of β-N-carbazolyl ethyl vinyl ether

β-N-carbazolyl ethyl vinyl ether, a monomer having the carbazolyl substituent at a distance from the vinyl group, was submitted to electro-initiated polymerization. Polymers with η_red = 0.015–0.07 dlg⁻¹ were obtained in the anodic compartment of a two compartment cell. The i.r., NMR and u.v. spectra show structural characteristics similar to those obtained by conventional cationic polymerization of the monomer but also some peculiarities associated with the conditions of electrochemical synthesis.     

Polymerization of ethene with zirconocene catalysts: an experimental and quantum chemical study of the influence of para-substituent in benzyl in bis{η-(1-benzyl)indenyl}zirconium dichlorides

The meso- and rac-like isomers of bis{η⁵-(1-benzyl)indenyl}zirconium dichloride (5), bis{η⁵-(1-para-methoxybenzyl)indenyl}zirconium dichloride (6), bis{η⁵-(1-para-fluoro-benzyl)indenyl}zirconium dichloride (7) and bis{η⁵-(1-phenylethyl)indenyl}zirconium dichloride (8) were synthesized and isolated. Solid-state structures of meso- and rac-like 5 were determined by X-ray structure analysis. Polymerization properties of the methylaluminoxane (MAO) activated diastereomers of complexes 5-8 were studied in ethene polymerizations under different monomer concentrations. The rac-like isomer of 1-phenylethyl-substituted 8/MAO showed significantly higher activity than the 1-benzyl substituted analogs 5-7/MAO. In addition, rac-8/MAO behaves like a single center catalyst producing polyethene with narrow molar mass distribution (1.8-1.9), while diastereomers of 5-7/MAO produce polymers with molar mass distributions varying from 2.7 up to 10.3. The rac and meso-like isomers of 5-7/MAO have different response on the monomer concentration. Quantum chemical calculations suggest a strong interaction between the benzyl substituent and the electron deficient zirconium center. The phenyl metal coordination energies depend on the electronic properties of the para-substituent. In 8/MAO, due to the ethyl spacer, the coordination does not have a significant role and therefore much higher activity and single center polymerization behavior is observed.     

Synthesis and cationic polymerization of oxyranyl-functionalized triphenylamine

Synthesis and cationic polymerization of N-{4-[(oxiranylmethoxy)methyl]phenyl}-N,N-diphenylamine is reported. Diaryliodonium salts and iron-arene complex were used as photoinitiators. Iodonium salts have appeared to be much more effective photoinitiators for polymerization of the monomer than iron-arene complex. The effect of the temperature on the rate of photopolymerization of the monomer with iron-arene complex has been studied.     

Novel synthesis of isoxazoline indolizine amides for potential application to tropical diseases

Synthetically challenging isoxazoline indolizine amide compounds were designed and prepared for potential application to tropical diseases. Indolizine core structures were synthesized strategically as common intermediates for efficient derivatization. The chemistry for the syntheses of 8-(5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)-N-(2-oxo-2-((2,2,2-trifluoroethyl)amino)ethyl)indolizine-5-carboxamide (3) and 5-(5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)-N-(2-oxo-2-((2,2,2-trifluoroethyl)amino)ethyl)-indolizine-8-carboxamide (4) is described in this Letter.     

Reactions of phenylenedioxytrihalophosphoranes with arylacetylenes: XIII. Reaction of 5-tert-butyl-2,2,2-trihalo-1,3,2λ5-benzodioxaphospholes with acetylenes

Reactions of 5-tert-butyl-2,2,2-trichloro-, 2,2,2-tribromo-5-tert-butyl-, and 2,2-dibromo-5-tert-butyl-2-fluoro-1,3,2λ⁵-benzodioxaphospholes with aryl- and alkylacetylenes lead to quantitative formation of 2-halo-1,2λ⁵-benzoxaphosphinine 2-oxides which may be regarded as phosphorus analogs of natural heterocyclic compounds, coumarin and chromene. The major products (>70%) are 4-aryl-7-tert-butyl-2,6-dichloro-, 4-aryl-2-bromo-7-tert-butyl-, and 4-aryl-7-tert-butyl-2-fluoro-1,2λ⁵-benzoxaphosphinine 2-oxides. Hydrolysis of these compounds and their treatment with amines gives the corresponding 2-hydroxy and 2-amino derivatives, as well as ammonium salts. The structure of some compounds was proved by X-ray analysis.     

A synthetic approach for water soluble hyperbranched poly(N,N-ethylidenebis(N-2-chloroacetyl acrylamide)) with high degree of branching via atom transfer radical polymerization/self-condensing vinyl polymerization

A novel acrylamide A2B2* (A = alkene, B* = alkyl chlorine) type inimer was obtained from commercially available 1,2-ethylenediamine, chloroacetyl chloride and acryloyl chloride. The as-prepared monomer can form water-soluble hyperbranched poly(N,N-ethylidene bis(N-2-chloroacetyl acrylamide))s (HPECA) through atom transfer radical polymerization/self-condensing vinyl polymerization method in the presence alkyl chlorine/CuCl/2,2-bipyridine activation system which can effectively suppress the gelation formation. 1H-NMR spectra and dual detector size exclusion chromatography proved the hyperbranched structure indisputably, and the degree of branching was determined by the detailed analyses of 1H-NMR spectra. The trend of the degree of branching was in consistent with the result of Mark-Houwink exponent a. The experiment results suggested that the conversion was 67%, Mw = 13.2 ? 104, Mark-Houwink a = 0.282 and the degree of branching = 64% when the reaction temperature was 120 oC, reaction time = 168 h and N,N-ethylidene bis(N-2-chloroacetyl acrylamide):Cu(I) = 50:0.62.     

Approaches to the enantioselective synthesis of ferrugine and its analogues

A four-step synthetic route, to ferrugine (2α-benzoyltropane), its methyl analogue (2-acetyltropane) and their N-benzyl analogues is reported. The reaction sequence uses tropinone or N-benzylnortropinone aldols as key intermediates. Reduction of aldol derived N-tosylhydrazones and oxidation of the side chain hydroxyl group followed by spontaneous diastereomer equilibration provides the final products. Relative configuration of the exo,anti N-methyl and N-benzyl aldols was retained during N-tosylhydrazone formation. The relative stereochemistry of N-tosylhydrazones was assigned by single crystal diffraction. The final products, ferrugine and its methyl analogue, were synthesized in enantiomerically pure form via asymmetric deprotonation of tropinone using chiral lithium amide/lithium chloride aggregate prepared in situ from (S,S)-N,N-bis(1-phenylethyl)amine hydrochloride.     

Indenyl and fluorenyl transition metal complexes: XIV. Synthesis and reactions of chromium tricarbonyl complexes of 5,10-dihydroindeno[2,1-α]indene

1-4,4a,10b-η⁶-5,10-dihydroindeno[2,1-α]indene chromium tricarbonyl (III) has been obtained by Rausch's method. Deprotonation of III by t-BuOK in THF solution, by potassium solution in HMPTA or by KH in THF at −65°C yields an η⁶-anion IV, which is irreversibly rearranged into η⁵-anion V at 20°C. Action of n-BuLi/t-BuOK mixture in THF at −65°C results in the formation of η⁶-dianion VI, which is irreversibly converted into η⁵-dianion VII above 0°C. Alkylation of IV with benzyl iodide yields 5-exo-benzyl(III). Reaction of V with benzyl iodide leads to the σ-benzyl derivative, which is isomerized into 5-endo-benzyl(III). The reaction of V with N-nitroso-N-methyltosylamide yields the η⁵-nitrosodicarbonyl complex of chromium (XI).     

Sulfonamidation of halogen-substituted electrophiles with <Emphasis Type="Italic">N</Emphasis>-(2,2,2-trichloroethyl)arenesulfonamides

Reactions of N-(2,2,2-trichloroethyl)arenesulfonamides with primary alkyl bromides and iodides, allyl bromide, chloroacetonitrile, and benzyl chloride in acetonitrile on heating in the presence of potassium carbonate gave the corresponding N-alkyl-N-(2,2,2-trichloroethyl)arenesulfonamides.     

One-pot synthesis of highly functionalized stable ketenimines of 2,2,2-trifluoro-N-aryl-acetamides

Three-component reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of 2,2,2-trifluoro-N-aryl-acetamides in dichloromethane at ambient temperature afforded dialkyl 2-(N-(aryl)-2,2,2-trifluoroacetamido)-3-(alkylimino) methylene-succinate derivatives in excellent yields.     

Atom transfer radical polymerization of 2-methoxy ethyl acrylate and its block copolymerization with acrylonitrile

2-Methoxy ethyl acrylate (MEA), a functional monomer was homopolymerized using atom transfer radical polymerization (ATRP) technique with methyl 2-bromopropionate (MBP) as initiator and CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst system; polymerization was conducted in bulk at 60 °C and livingness was established by chain extension reaction. The kinetics as well as molecular weight distribution data indicated towards the controlled nature of polymerization. The initiator efficiency and the effect of initiator concentration on the rate of polymerization were investigated. The polymerization remained well-controlled even at low catalyst concentration of 10% relative to initiator. The influence of different solvents, viz. ethylene carbonate and toluene on the polymerization was investigated. End-group analysis for the determination of high degree of functionality of PMEA was determined with the help of ¹³C{¹H} NMR spectra. Chain extension experiment was conducted with PMEA macroinitiator for ATRP of acrylonitrile (AN) in ethylene carbonate at 70 °C using CuCl/bpy as catalyst system. The composition of individual blocks in PMEA-b-PAN copolymers was determined using ¹H NMR spectra.