Palladium-catalyzed reactions of cyclopropanols bearing oxazoline directing group

Cyclopropanols bearing oxazoline directing group were investigated in palladium-catalyzed reactions. When the directing group and cyclopropanol unit were bonded through two- or three-carbon spacer, formation of unusual products was observed. Oxidative ring opening proceeded with uncommon regioselectivity providing linear enones as main products. The reaction of such cyclopropanols with aryl iodides and silver acetate furnished diarylated α-methylene ketones, which cannot be obtained from cyclopropanols lacking oxazoline ring under the same conditions.     

Novel phthalocyanines bearing four 4-phenyloxyacetic acid functionalities

Metal-free (2) and Co(II), Zn(II), Ni(II), Cu(II) metallophthalocyanines (2a–d) with four 4-phenyloxyacetic acid groups on the periphery were prepared by cyclotetramerization of new p-(3,4-dicyanophenoxy)phenylacetic acid (1) and the corresponding divalent metal salts. Further reactions of these products with thionylchloride and then benzylamine in tetrahydrofuran, and octanol in pyridine gave amide (3, 3a–d) and ester (4, 4a–d) derivatives, respectively. The new compounds have been characterized by elemental analyses, IR, UV–Vis, mass and ¹H NMR spectroscopy. The redox properties of compounds 2 and 2a–d were identified by cyclic voltammetry.     

Self-assembly of rectangles via building units bearing salen and oxazoline ligands

Rigid spacer-chelator with the framework of 3 has been prepared. Building units with two parallel coordination sites such as salen and oxazoline units have also been synthesized. The spacer-chelators, 11 and 15, readily self-assembled with metal complexes such as Zn⁺⁺ and Co⁺⁺ to form molecular rectangles. The overall dimensions of the rectangles, 13 and 17, are 6.2 Å × 23.5 Å. The characterization of the supramolecules by NMR, mass spectroscopy, and X-ray crystal structures is also reported.     

One-pot synthesis and characterization of a new, branched polycarbosilane bearing allyl groups

A highly branched polycarbosilane bearing allyl groups has been prepared by a one-pot synthesis with chloromethyltrichlor-osilane, chloromethylmethyldichlorosilane and allyl chloride as the starting materials. The resultant polymer, with the approximate formula [SiH1.2(CH3)0.71(CH2CH=CH2)0.09CH2]n, has been characterized by 1H, 13C, and 29Si NMR, GPC, TG and elemental analysis. It could be cross-linked thermally at 170℃in the absence of oxygen. Pyrolysis of the polymer gave a ceramic with a yield of about 70%.     

Oxazoline‐terminated macromonomers by the alkylation of 2‐methyl‐2‐oxazoline

Well‐defined macromonomers of poly(ethylene oxide) and poly(tert‐butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2‐methyl‐2‐oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε‐caprolactone in an anionically coordinated way was synthesized, and this led to well‐defined poly(ε‐caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2440–2447, 2005     

Synthesis and anionic polymerization of optically active N-phenylmaleimides bearing bulky oxazoline substituents

Anionic polymerizations of chiral N-phenylmaleimide derivatives bearing an oxazoline pendant (OPMI) were carried out with n-BuLi initiator to obtain optically active polymers. The polymer yields and specific optical rotations () were found to be significantly influenced by the reaction solvent, temperature, and the molar ratio of initiator to monomer. Particularly, the specific optical rotations exhibited a linear dependence on the molecular weights for the formed polymers, and the inversion from levo- to dextro-specific rotation was also observed with an increase in the molecular weights. On the basis of the results from circular dichroism (CD) and ¹³C NMR spectral analyses, the optical activity of poly(OPMI)s was attributed not only to the chirality of oxazolinyl groups in monomeric units but also to the partial helical structure due to an excess of threo-diisotactic configuration in the main chain.     

Selective metal sensor phthalocyanines bearing non-peripheral functionalities: Synthesis,spectroscopy, electrochemistry and spectroelectrochemistry

A novel alcohol-soluble ionophore ligand and its non-peripherally tetrasubstituted functional 1,8,15,22-tetrakis(6-hydroxyhexylsulfanyl) metallophthalocyanines M[Pc(α-SC₆H₁₂OH)₄] (M = Cu(II), Zn(II), Co(II); Pc = phthalocyanine) are reported. The aggregation and cation binding behaviors of the phthalocyanine compounds in the presence of soft Ag^I and Pd^II metal ions were investigated by using UV–Vis spectroscopy. The new compounds have been characterized by elemental analysis, IR, ¹H, ¹³C NMR, UV/Vis spectroscopy, ESI and MALDI–TOF–MS mass spectra. Voltammetric and in-situ spectroelectrochemical studies show that while copper and zinc phthalocyanine complexes give well-defined ring-based reduction and oxidation processes, the cobalt phthalocyanine gives both metal-based and ring-based redox processes which have reversible and diffusion controlled character.     

Self-assembled graphitic nanotubes from an amphiphilic hexabenzocoronene bearing thiol functionalities: Redox-mediated polymerization and depolymerization

A hexabenzocoronene derivative consisting of lipophilic dodecyl side chains and thioacetyl-appended hydrophilic oxyethylene chains was newly synthesized. The self-assembly of this hexabenzocoronene amphiphile in tetrahydrofuran gave a nanotubular object, for which the thioacetyl functionalities were located on the inner and outer surfaces. The removal of the acetyl group under alkaline conditions, followed by autoxidation, allowed the conversion of the noncovalent architecture into a covalently stabilized form via disulfide linkages. The resulting surface-polymerized nanotubes were completely insoluble in common organic solvents. Scanning and transmission electron microscopy showed that the tubular morphology mostly remained after the oxidative polymerization. Disulfide oligomers involved in the polymerized nanotubes were transformed into a thiol monomer upon reduction with dithiothreitol. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5120-5127, 2006     

MALDI-TOF characterization of macromonomers

Methacryloyl endfunctionalized oligostyrene macromonomers were characterized by matrix assisted laser desorption ionization/time of flight (MALDI-TOF) spectroscopy and by isocratic and gradient high performance liquid chromatography (HPLC). The molar mass distribution derived by the different techniques coincide for the investigated oligomers. Mixing experiments revealed that the MALDI-TOF peak areas do not necessarily represent the mixing ratio of the components. Combination of gradient HPLC and MALDI-TOF has resolved the chemical composition of the coupling products formed by reaction of the living anion with oxygen.     

Synthesis of macromonomers bearing hydrolyzable segments derived from α‐hydroxyalkanoic acids

Methacrylic macromonomers bearing hydrolyzable oligoester segments are prepared by derivatization of oligo(α‐hydroxyalkanoic acids) (obtained by thermal polycondensation) with methacrylic acid and copolymerized with tert‐butyl acrylate.     

Electroactive oxazoline ligands

This review deals with the synthesis, properties and applications of electroactive oxazoline ligands. The redox active units include ferrocene and tetrathiafulvalene derivatives. The different synthetic methods for their preparations are reviewed, together with the solid state structures. Metal complexes based on these ligands are described. The ferrocene–oxazolines have been mainly used as electrochemical sensors, while tetrathiafulvalene (TTF)–oxazolines have served as precursors for chiral molecular precursors, in which the role of chirality is emphasized. Moreover, examples of catalytic reactions in which TTF–oxazolines are involved are also discussed. Finally, an example of a poly(thiophene-oxazoline) provided with supramolecular chirality which can be modulated by various factors is presented.     

Transition metal-based homopolymerisation of macromonomers

Since their first utilisation in 1958 for the synthesis of graft copolymers, macromonomers have raised increasing interest because of their ability to provide an easy access to a large number of (co)polymers of different chemical natures and various controlled topologies (comb-like, bottlebrush, star-like, graft copolymers...) exhibiting very different solution or solid-state properties compared to their linear homologues. During the first decades, the (co)polymerisation of macromonomers was based on poorly controlled free radical polymerisations. Therefore, it was difficult to obtain polymers in a controlled manner. With the appearance of Ring Opening Metathesis Polymerisation (ROMP) or of new free radical processes such as Atom Transfer Radical Polymerisation (ATRP) that allow control of molar masses, and of Ziegler–Natta-type polymerisation that allows control of the tacticity of the polymacromonomer backbone, these processes have been increasingly utilised for macromonomer (co)polymerisations. In this paper, a review of the results published in the literature regarding the homopolymerisation of macromonomers in the presence of transition metal is presented.     

Optically active polyacrylamides bearing an oxazoline pendant: Influence of stereoregularity on both chiroptical properties and chiral recognition

Enantiopure acrylamide derivatives, N‐[o‐(4‐methyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl) phenyl]acrylamide (MeOPAM), N‐[o‐(4‐isopropyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenyl]acrylamide (PrⁱOPAM), and N‐[o‐(4‐phenyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenyl]acrylamide (PhOPAM), were synthesized and radically polymerized in the presence of rare earth metal trifluoromethanesulfonates (Ln(OTf)₃, Ln = La, Nd, Sm, and Y) to yield corresponding optically active polymers. Among these Lewis acids, Y(OTf)₃ was found to be most effective for increasing the isotactic specificity during the radical polymerizations when using n‐butanol as solvent. Also, the effect of the Lewis acids was significantly influenced by the ratio of Ln(OTf)₃ to monomer. The relationship of both chiroptical property and the chiral recognition with the stereoregularity was then examined for the resulting polymers having various tacticity by spectroscopic techniques such as NMR, fluorescence, and circular dichroism. The results indicated that the polymers rich in isotacticity exhibited a favorable enantioselective discrimination ability toward 1,1′‐bi‐2‐naphthol as evidenced by ¹H NMR study, where the characteristic hydroxyl proton signal was split into two peaks that ascribed respectively to the levo‐ and dextro‐isomer; furthermore, the splitting magnitude was linearly correlated with the diad isotacticity of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Hyperbranched polycyclocarbosiloxane

A new cross-linkable naphthalene-cyclocarbosiloxane was synthesised starting from bis[1,4-bis(methylhydrosiloxanyl)-dihydronaphthalene] via catalytic addition of the Si-H reactive groups to the unsaturated bond of triethoxyvinylsilane. Hyperbranched polycyclocarbosiloxane networks were formed by condensation of the alcoxyl groups in the presence of dibutyltin dilaurate as catalyst. The cross-linking process was studied in order to obtain information concerning the values of the reaction parameters and to determine the position of the gelation point relative to conversion.GPC analysis, IR, and 1H-NMR spectral analysis techniques were used to investigate the chemical structures of the intermediates and of the product.     

Epoxy and hydroxy functional polyolefin macromonomers

Methods for preparing saturated polyolefin oligomers with Si(SINGLE BOND)H, epoxy groups, and with dihydroxy groups have been developed. Anionic polymerization of butadiene, then termination of the chains with chlorodimethylsilane leads to controlled molecular weight oligomers with silane functionality, and wherein the microstructure can be tailored. Hydrogenation of these materials proceeds smoothly using colloidal nickel catalysts to yield the corresponding saturated materials, which are stable to conditions used for melt polyesterifications. Hydrosilation of allyl glycidyl ether with the Si(SINGLE BOND)H end groups produces epoxy functional oligomers, and subsequent hydrolysis of the epoxy rings yields oligomers with a dihydroxy group at one end. Melt copolymerization of the olefin macromers with 1,4-butanediol and 1,4-dimethylcyclohexanedicarboxylate in the presence of titanium isopropoxide affords poly(ester-g-olefin) graft copolymers. These copolymers are under study as model interfacial agents for polyester/polyolefin blends and as suspension agents for polyester particles in nonpolar media. © 1996 John Wiley & Sons, Inc.     

Coordination of a chiral tin(ii) cation bearing a bis(oxazoline) ligand with tetrahydrofuran derivatives

The reaction of SnCl(2) with the lithio derivative of a bis(oxazoline) ligand precursor afforded the enantiomeric chlorostannylene whose chloride ion can be substituted by several neutral or anionic Lewis donors. Abstraction of the chloride ion from the chlorostannylene with silver salts gave the corresponding tetrahydrofuran (THF) complexes of a chiral tin(ii) cation in 1,2-dimethoxyethane (DME) containing THF. That is, the reaction with silver hexafluoroantimonate (AgSbF(6)) afforded the THF complex without interaction with the counteranion. In contrast, reaction with silver triflate (AgOTf) gave the THF complex whose tin center had a pseudo-trigonal bipyramidal structure with two nitrogen atoms of a bidentate ligand and a lone pair at the equatorial positions and one of the oxygen atoms of triflate and an oxygen atom of THF at the apical positions in the solid state. Use of 3-methyltetrahydrofuran (3-MeTHF) instead of THF afforded the 3-MeTHF complexes, where the R-enantiomer of 3-MeTHF predominantly coordinates to the tin center. The previously reported germanium(ii) analogue of the tin(ii) cation indicated a similar enantioselectivity for the coordination of 3-MeTHF on the germanium center.     

Synthesis of levoglucosenone oxazoline derivative

Russian Journal of Organic Chemistry -     

Dimetallic functionalities in liposome bilayers

A dicopper(II) complex can be covalently linked to palmitate/palmitoyl-oleoyl-phosphatidylcholine (PA/POPC) liposomes using the following one-pot strategy: preformed [Cu₂(bpbp)(PA)](ClO₄)₂ (bpbp^?  = 2,6-bis((N,N′-bis(2-picolyl)amino)methyl)-4-tertbutylphenolato) was incorporated into POPC liposomes with a loading of up to 10 mol%. Despite its shape and charge, the decoration of PA/POPC liposomes with {Cu₂(bpbp)}³⁺ did not disrupt the liposome structure; however, the mean liposome diameter increased from about 130 nm (0 mol% dicopper complex) to about 150 nm (10 mol% dicopper complex). Single-crystal X-ray structures furnish ‘snapshots’ of the pH-dependent solution state derivatives of {Cu₂(bpbp)}³⁺, and model the structure of the [Cu₂(bpbp)(PA)]²⁺ head group at the surface of the liposomes. An impressive plasticity in the intramolecular non-bonded Cu….Cu distance for these ions, ranging from 3 to 4 Å, in [Cu₂(bpbp)OH]²⁺, [Cu₂(bpbp)(OAc)(H₂O)]²⁺ and [Cu₂(bpbp)(H₂O)₂]³⁺ allows for their utility as labile reagents in water. Remarkably, the flexible dicopper site is selective for a single carboxylate ligand, so that [Cu₂(bpbp)(PA)]²⁺ is favoured even in the presence of other chemically similar oxoanions, such as CO₃^2 ? , HCO₃^? , NO₃^? , ClO₄^? , ReO₄^?  and CF₃SO₃^? .     

Aminophosphine–oxazoline and phosphoramidite–oxazoline ligands and their application in asymmetric catalysis

The synthesis of a novel series of aminophosphine–oxazoline and phosphoramidite–oxazoline is described. The efficacy of these aminophosphine–oxazoline ligands was investigated in the palladium catalysed asymmetric allylic alkylation of 1,3-diphenylprop-2-enyl acetate leading to a maximum of 38% ee at 64% conversion. Phosphoramidite–oxazoline ligands, however, gave ees of up to 87% at 71% conversion in the same reaction and also proved to be effective in the palladium catalysed asymmetric Suzuki coupling between 2-methylnaphthylboronic acid and 1-bromonaphthalene, leading to a maximum of 46% ee in 54% isolated yield at room temperature.