Amino Ether Research Articles

Organolithium-Induced Alkylative Ring Opening of Aziridines: Synthesis of Unsaturated Amino Alcohols and Ethers

Organolithium-induced alkylative ring opening of N-sulfonyl-protected aziridinyl ethers is described. The reactions were efficiently carried out with a variety of organolithiums, providing a promising new strategy to unsaturated amino alcohols and ethers. Cis- and trans-1,4-dimethoxybut-2-ene-derived aziridines were prepared, and their propensity to undergo organolithium- induced alkylative desymmetrization is detailed. Use of a single enantiomer of the latter aziridine provides a route to enantiopure unsaturated amino ethers.

High Compatibility and Improved Barrier Performance in Blends Based on a Copolyester Modified with a Poly(amino ether) Resin

AbstractSummary: The structure and properties of blends of a PCTG and a PAE resin obtained by direct injection molding have been studied. The blends were almost immiscible, and were composed of a nearly pure PAE phase and a mixed PCTG‐rich phase containing minor PAE amounts. Electron microscopy observations showed a high intermixing level between both components. The permeability data indicated an improved barrier protection of PCTG upon PAE addition. The Young's modulus and the yield stress of the blends followed a linear behavior with respect to composition, while values close or slightly below linearity were observed for the break properties. The combined effects of the small dispersed particle size and the proposed good interfacial adhesion are stated as the main factors responsible for the positive mechanical behavior. The impact strength showed an unexpected variability for PCTG‐rich blends, which is attributed to a ductile‐brittle transition of PCTG.Ductility of PCTG/PAE blends vs. composition.magnified imageDuctility of PCTG/PAE blends vs. composition.

Lithium Diisopropylamide-Mediated Enolization: Catalysis by Hemilabile Ligands

Structural, kinetic, and computational studies reveal the mechanistic complexities of a lithium diisopropylamide (LDA)-mediated ester enolization. Hemilabile amino ether MeOCH2CH2NMe2, binding as an eta1 (ether-bound) ligand in the reactant and as an eta2 (chelating) ligand in the transition structure, accelerates the enolization 10,000-fold compared with n-BuOMe. At the onset of the reaction, a dimer-based enolization prevails. As the reaction proceeds, significantly less reactive LDA-enolate mixed dimers appear and divert the reaction through monomer- and mixed dimer-based pathways. The mechanistic and computational investigations lead to a proof-of-principle ligand-catalyzed enolization in which an ancillary ligand allows the catalytic ligand to re-enter the catalytic cycle.

N-Cyanomethyl-β-chloro amines: chiral building blocks for the synthesis of azacrown ethers

(1 R,2 S)-Ephedrine and norephedrine derived N-cyanomethyl-β-chloro amines react with tri-, tetra- and penta-ethylene glycol to stereoselectively give the corresponding amino ethers. Further transformation into chiral monoaza 12-, 15- and 18-crown-4, -5 and -6 ethers was realized in three steps and good overall yields by: (i) mesylation, (ii) deprotection of the N-cyanomethyl group and (iii) intramolecular alkylation. Binding affinities of these azacrown ethers for alkali cations was studied by FAB-MS.

Structure and properties of a poly(amino ether) resin after reprocessing in the melt state

AbstractThe effects of reprocessing by extrusion for up to five cycles, at both the usual (200°C) and an extreme (230°C) temperature, on the structure and mechanical properties of a poly(amino ether) (PAE) resin were studied. A slight darkening and viscosity increase was observed, mainly upon reprocessing at 230°C. The melt flow index and solubility analysis indicated that grafting and crosslinking reactions took place, respectively, after reprocessing at 200 and 230°C. The Young′s modulus and the yield stress of PAE increased slightly with successive extrusion cycles. This was attributed to the viscosity‐induced increase in orientation, and to a minor extent to the partially grafted/crosslinked nature of the samples. The decrease in the ductility was more noticeable in the samples reprocessed at 230°C, and was attributed to the reduced ability to elongate of partially grafted and partially crosslinked structures present after reprocessing, respectively, at 200 and 230°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1368–1373, 2006

Ring‐Opening Polymerization of Lactide with Group 3 Metal Complexes Supported by Dianionic Alkoxy‐Amino‐Bisphenolate Ligands: Combining High Activity, Productivity, and Selectivity

A series of new alkoxy-amino-bis(phenols) (H2L 1-6) has been synthesized by Mannich condensations of substituted phenols, formaldehyde, and amino ethers or diamines. The coordination properties of these dianionic ligands towards yttrium, lanthanum, and neodymium have been studied. The resulting Group 3 metal complexes have been used as initiators for the ring-opening polymerization of rac-lactide to provide poly(lactic acid)s (PLAs). The polymerizations are living, as evidenced by the narrow polydispersities of the isolated polymers, together with the linear natures of number average molecular weight versus conversion plots and monomer-to-catalyst ratios. Complex [Y(L6){N(SiHMe2)2}(THF)] (17) polymerized rac-lactide to heterotactic PLA (Pr = 0.90 at 20 degrees C) and meso-lactide to syndiotactic PLA (Pr = 0.75 at 20 degrees C). The in situ formation of [Y(L6)(OiPr)(THF)] (18) from 17 and 2-propanol resulted in narrower molecular weight distributions (PDI = 1.06). With complex 18, highly heterotactic PLAs with narrow molecular weight distributions were obtained with high activities and productivities at room temperature. The natures of the ligand substituents were shown to have a significant influence on the degree of control of the polymerizations, and in particular on the tacticity of the polymer.

Kinetic and NMR Spectroscopic Studies of Chiral Mixed Sodium/Lithium Amides Used for the Deprotonation of Cyclohexene Oxide

The mixed-metal complex formed from n-butylsodium, n-butyllithium, and a chiral amino ether has been studied by NMR spectroscopy. Three different mixed-metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium-amido ethers, lithium-amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are more reactive than the single sodium and lithium amides, whereas the stereoselectivities are higher when lithium amides are used. The alkali-metal/gamma-amido ethers exhibit both higher initial reaction rates and stereoselectivities than their beta-amido ether analogues. NMR spectroscopic studies of mixtures of n-butylsodium (nBuNa), n-butyllithium (nBuLi), and the gamma-amino ethers in diethyl ether show the exclusive formation of dimeric mixed-metal amides. In diethyl ether, the lithium atom of the mixed-metal amide is internally coordinated and the sodium atom is exposed to solvent; however, in tetrahydrofuran, both metals are internally coordinated.

A novel photochemical approach to the synthesis of naphthalene-containing lariat-type crown ethers and an evaluation of their metal cation binding and fluorescence sensing properties

A novel method has been developed for the synthesis of naphthalene chromophore containing, lariat-type crown ethers. The route employs SET-promoted photocyclization reactions of polyether-tethered 2,3-naphthalimides to generate the variously ring-sized crown ether cores and an allylsilane N-acyliminum ion addition process to install amino ether side chains. The metal cation binding properties of the lariat-crown ethers, prepared in this manner, were evaluated. In addition, the ability of the lariat-crown ethers to serve as SET-based, fluorescence sensors of metal cations was probed. The results show that although the novel lariat-crown ethers strongly complex alkali metal cations (Na, K, Rb, Cs), this complexation is not associated with enhanced fluorescence from the naphthalene chromophores as would be expected if cation binding impeded SET quenching by the tertiary amine donor in the side chains. In contrast, the novel lariat-crown ethers serve as sensitive sensors for the divalent metal cations of Mg and Cu and the monovalent cation of Ag.

Stereodynamic Coordination Complexes. Dependence of Exciton Coupled Circular Dichroism Spectra on Molecular Conformation and Shape

Chiral amino alcohols, amino ethers, and amino thioethers were converted to tetradentate ligands by alkylation with a variety of chromophore-bearing alkyl heterocycles. Copper(II) complexes of the ligands display conformational diastereomerism in solution. The resultant propeller-shaped compounds were characterized by a variety of techniques, including exciton coupled circular dichroism (ECCD). Three X-ray crystal structures of complexes are described that partially support structural assignments, but also suggest that solid state structures are not always indicative of solution species. Thus, ECCD may in some cases provide data that is strongly complimentary to X-ray crystallography. These results are presented in a larger context of coordination complexes that display dynamic behavior that can be studied by chiroptical spectroscopy.

Unsaturated 1,2‐Amino Alcohols and Ethers from Aziridines and Organolithiums.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of new chiral amino ether derivatives: synthetic application of meso aziridinium ions prepared from β-amino alcohols

Methods of synthesis of new chiral amino ether derivatives through the opening of aziridinium ions, prepared in situ using trans-(±)-2-(1- N, N-dialkylamino)cyclohexyl mesylate with ( R)-(+)-1,1′-bi-2-naphthol, are described. The ( R, R, R)-diastereomer was obtained as the major product and isolated as an enantiopure salt, and characterized by single crystal X-ray analysis. The C 2-chiral ( R, R, R, R, R)-diamino ether was obtained as the major product by opening of the aziridinium ion, prepared using trans-(±)-2-(1-pyrrolidino)cyclohexyl mesylate and ( R)-(+)-1,1′-bi-2-naphthol in the presence of aq NaOH. This was also characterized by single crystal X-ray analysis.

Preparation of Poly(ethylene terephthalate)/Poly(amino ether) Blends by means of the Addition of Poly(butylene terephthalate)

AbstractSummary: Blends based on poly(ethylene terephthalate), PET, with poly(amino ether) (PAE) contents up to 40% were obtained by the addition of 20% poly(butylene terephthalate) (PBT) to the PET matrix. PBT mixed with PET led to a decrease in the Tm of the matrix that was enough to produce homogeneous blends by mixing in the melt state. Despite the presence of a single peak observed by dynamic‐mechanical analysis, the blends were biphasic, with amorphous phases in which minor amounts of the other component, both reacted and mixed, were present. This presence of minor components gave a fine morphology and significant adhesion that, together with the higher orientation of PAE in the blends, produced blends with a clear synergism in the modulus of elasticity, notched impact strength similar to that of the neat components, and high ductility up to 30% PAE.Young's modulus of the PET‐PBT/PAE blends.magnified imageYoung's modulus of the PET‐PBT/PAE blends.

Boc–phenylglycine: a chiral solvating agent for the assignment of the absolute configuration of amino alcohols and their ethers by NMR

The absolute configuration of β-amino alcohols and their ethers can easily be determined by comparison of the 1H NMR spectra of the mixture formed by the substrate amino alcohol or amino ether plus one equivalent of ( R)-Boc–α-phenylglycine (BPG) with that of the mixture formed by the substrate plus one equivalent of ( S)-BPG. Several examples of known absolute configuration have been used to validate the results, which are explained in terms of the selective shielding experienced by protons of the substrate located on the complex on the same side of the phenyl group of BPG. A graphical model has been proposed in which the use of the Δ δ RS parameters for Cα–H, Cβ–H and the L group allow the direct configurational assignment from the NMR data.

Zirconium‐Mediated Coupling Reactions of Amines and Enol or Allyl Ethers: Synthesis of Allyl‐ and Homoallylamines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Unsaturated 1,2-amino alcohols and ethers from aziridines and organolithiums.

Organolithium-induced ring-opening of aziridines of 2,5-dihydrofuran (5 and 8) and 1,4-dimethoxybut-2-ene (16, 17 and 23) gives 3-substituted 2-aminobut-3-en-1-ols 9-15 and amino ethers 18-20 and 24-26.

Zirconium-mediated coupling reactions of amines and enol or allyl ethers: synthesis of allyl- and homoallylamines.

An easy and efficient zirconium-mediated synthesis of allylamines from simple amines and enol ethers is described. This strategy also allows the synthesis of amino alcohol derivatives containing a Z double bond in their structure when 2,3-dihydrofuran is used. Simple conventional modification of these amino alcohols leads to 2-substituted piperidine derivatives. By applying this approach, a formal total synthesis of the alkaloid coniine is easily achieved from a protected butylamine. Finally, the zirconium-mediated reaction of amines and allyl phenyl ether furnishes homoallylamines or amino ethers depending on the structure of the starting amine.

Hemilabile ligands in organolithium chemistry: substituent effects on lithium ion chelation.

The lithium diisopropylamide-mediated 1,2-elimination of 1-bromocyclooctene to provide cyclooctyne is investigated using approximately 50 potentially hemilabile polyethers and amino ethers. Rate laws for selected ligands reveal chelated monomer-based pathways. The dependence of the rates on ligand structure shows that anticipated rate accelerations based on the gem-dimethyl effect are nonexistent and that substituents generally retard the reaction. With the aid of semiempirical and DFT computational studies, the factors influencing chelation are discussed. It seems that severe buttressing within chelates of the substitutionally rich ligands precludes a net stabilization of the chelates relative to nonchelated (eta(1)-solvated) forms. One ligand-MeOCH(2)CH(2)NMe(2)-appears to promote elimination uniquely by a higher-coordinate monomer-based pathway.

Phase behavior and mechanical properties of blends of poly(butylene terephthalate) and poly(amino-ether) resin

The structure, thermal and mechanical properties of blends of poly(butylene terephthalate) (PBT) and a poly(amino–ether) (PAE) barrier resin obtained by direct injection molding are reported. The slight shift of the glass transition temperatures (Tg) of the pure components when blended is attributed to partial miscibility rather than interchange reactions. Both the small strain and the break properties of the blends were close or even above those predicted by the direct rule of mixtures. The specific volume of the blends appeared to be the main reason for the modulus behavior. The linear values of the elongation at break indicated that the blends were compatible, and were attributed to a combination of good adhesion between the two phases of the blends and the small size of the dispersed phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 132–139, 2004

Effect of De-hulling on Ileal Amino Acids Digestibility of Soybean Meals Fed to Growing Pigs

A study was carried out to determine the effect of de-hulling on apparent and true ileal amino acids digestibility of soybean meals for growing pigs. Twenty barrows (Duroc×Large white×Longer white) were fitted with a simple T-cannula at the distal ilium. Digestibility of 20 experimental diets was determined, nine of them were de-hulled soybean meal diets, and nine of them were regular soybean meal diets and two low protein casein diets for determination of endogenous amino acid correction for true digestibility determination. A 5×5 Latin Squares Design was adopted in this trail. The results showed that de-hulling increased apparent ileal digestibility of isoleucine,threonine, aspartic, tyrosine and indispensable and dispensable amino acid (p 0.05). Similar responses were found for true ileal digestibility. In three dehulled and non-dehulled pairs soybean meals from the same respective sources, de-hulling increased apparent digestibility of lysine, methionine, threonine and cystine 1.42%, 2.06%, 2.18% and 1.40% respectively. True digestibility of lysine, methionine, threonine and cystine was increased 1.65%, 1.94%, 2.30% and 1.82% respectively. A prediction equation for true ileal amino acid digestibility (including lysine and arginine) was established by multivariate linear regression. The independent variables included relevant amino acid, organic matter, crude protein, ether extract and nitrogen free extract. The coefficient R 2 values of lysine and agrinine were 0.596 and 0.531 respectively. According to the crude protein content, a prediction equation for lysine and arginine content in soybean meal was also established by single linear regression. The coefficient R 2 values of lysine and agrinine were 0.636 and 0.636 respectively. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 6 : 928-938)

Ceric Ammonium Nitrate (CAN) Catalyzed Ring Cleavage of N‐Tosyl Aziridines: A Potential Tool for Solution Phase Library Generation.

AbstractFor Abstract see ChemInform Abstract in Full Text.