Search results for "oxazoline"

TI: Cyclophosphazenes as polymer modifiers

2003

The utilization of cyclophosphazenes as polymer modifiers is reviewed, with particular concern to their exploitation as versatile chain extenders, possibly for recycle problems, crosslinkers, to enhance mechanical properties of polymeric materials, branchers, to selectively introduce ramifications in linear polymers, and compatibilizers, to favor the formation of blends between originally incompatible organic macromolecules. The great versatility of the synthetic methods put forward for these substrates, together with the ease of controlling their modification, functionalization and reactivity are important parameters for the evaluation of which type of use is more feasible for these trimer…

Synthesis, reactions and structural features of monofluorinated cyclopropanecarboxylates

2002

Abstract Monofluorinated cyclopropanecarboxylates are available in racemic or optically active form by transition metal-catalyzed reactions of vinylfluorides with diazoacetates. From α-fluorostyrene and tert-butyl diazoacetate in the presence of 2 mol% of an enantiopure bis(oxazoline) copper complex, a 81:19 mixture of tert-butyl trans- and cis-2-fluoro-2-phenylcyclopropanecarboxylates was obtained with high enantiomeric excess (ee) of 93 or 89%, respectively. The corresponding racemic ethylesters were used as starting materials for the synthesis of carboxamides, of the cis- and trans-isomers of analogues of tranylcypromine, an anti-depressive drug and several of its homologous fluorinated …

Conformational properties of oxazoline-amino acids

2016

Abstract Oxazoline-amino acids (Xaa-Ozn) occur in natural peptides of potentially important bioactivity. The conformations of the model compounds: Ac-(S)-Ala-Ozn(4R-Me), Ac-(S)-Ala-Ozn(4S–Me), and (gauche+, gauche−, anti) Ac-(S)-Val-Ozn(4R-Me) were studied at meta-hybrid M06-2X/6–311++G(d,p) method including solvent effect. Boc- l -Ala- l -Ozn-4-COOMe and Boc- l -Val- l -Ozn-4-COOMe were synthesized and studied by FT-IR and NMR-NOE methods. The conformations in crystal state were gathered from the Cambridge Structural Data Base. The main conformational feature of the oxazoline amino acids is the conformation β2 (ϕ,ψ ∼ −161°, −6°), which predominates in weakly polar environment and still is …

CaCl2, Bisoxazoline, and Malonate: A Protocol for an Asymmetric Michael Reaction

2015

A mild protocol for the asymmetric Michael addition of dimethyl malonate to various α,β-unsaturated carbonyl compounds was developed. The salient feature of this methodology is that a cheap and environmentally friendly Lewis acid, CaCl2, was used as a catalyst. An aminoindanol- and pyridine-derived ligand provided in the presence of CaCl2 Michael adducts in moderate to high enantioselectivities. The scope of the reaction was demonstrated.

Bisoxazoline-Fullerene Hybrid Systems for Asymmetric Catalysis

Use of PP-g-OXA in the Compatibilization of PP/LCP Blends

1999

Abstract Adding small amounts of liquid crystalline polymers (LCP) to flexible thermoplastic matrices (FTP) allows to enhance the mechanical and thermomechanical properties. Therefore it is possible to obtain materials with new properties only by simple mixing. A strong shortcoming is the incompatibility between LCP and FTP that leads to materials with very poor properties unusable for commercial pourposes. The presence of a compatibilizer is therefore required. Oxazoline functionality is known to be highly reactive toward many other functional groups and then oxazoline functionalized polymers can be efficiently used as compatibilizer precursors. In this work the compatibilizazion of polypr…

2-Alkenoyl Pyridine N-Oxides, Highly Efficient Dienophiles for the Enantioselective Cu(II)−Bis(oxazoline) Catalyzed Diels−Alder Reaction

2007

2-Alkenoyl pyridine N-oxides are introduced as a new kind of efficient dienophiles for the Cu(II)−bis(oxazoline) (BOX) catalyzed enantioselective Diels−Alder reaction affording higher reactivity and enantioselectivity (ee's up to 96%) than the corresponding nonoxidized 2-alkenoyl pyridines.

ChemInform Abstract: N1-Functionalized Indole-Phosphane Oxazoline (IndPHOX) Ligands in Asymmetric Allylic Substitution Reactions.

2012

N-Functionalized IndPHOX ligands bearing various groups have been synthesized and the effects of the N1-substituent on the reaction rate, yield, and asymmetric induction in a palladium-catalyzed allylic substitution reaction are reported. The presence of an oxygen atom in the ligands, namely an N-MOM or N-THP group, led to enhancement of the enantioselectivity in the allylic amination reaction. In addition, a ligand with a chiral oxazoline ring at C-1 and a phosphane substituent at C-2 provided high enantioselectivity in good yield in an asymmetric allylic alkylation reaction.

Oxazoline-containing compatibilizers for polyamide/SAN and polyamide/ABS blends

2002

Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN-m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN-m was found to reduce the SAN-domain size in the PA/SAN-blends. The initial acrylonitrile content of SAN-m had a strong influence on the degree of conversion into o…

On the modification of the nitrile groups of acrylonitrile/butadiene/styrene into oxazoline in the melt

2000

Oxazoline functionality is well known to be highly reactive toward a lot of other functional groups like carboxyls, hydroxyls, mercaptans, and amines. In this work we report the possibility to modify the nitrile groups of an acrylonitrile/butadiene/styrene (ABS) copolymer into oxazoline in the molten state in the presence of aminoethanol as modifier agent and zinc acetate as a catalyst. The reaction has been carried out in a batch mixer and in a corotating twin screw extruder. The conversion of the nitrile groups into oxazoline has been verified by infrared spectroscopy, NMR analysis microanalysis and confirmed by thermomechanical characterization. The results indicate that the kinetic of g…