Catalytic Activity of Amines Hydrochlorides,Intramolecular Catalysis and Stereoselectivity of Phosphorylation of Hydroxylcontaining Nucleophiles with P(III)-N-Ethylanilines

Abstract

The effect of acid-base properties of amines hydrochlorides (AH) on their catalytic activity in methanolysis of P(III)-N-ethylaniline has been studied. The analysis of Bronsted correlation equation was indicative of general acid catalysis and it was thus confirmed, that general regularities had place during alcoholysis of P(III)-amines under catalysis with AH. In addition, the increasing of alcohol polarity leads to the increasing of proton transfer degree (α) from acid catalysts to phospho(III)amine substrate and to the increasing of the positive charge at the phosphorus in the transition state. Besides, the comparison of α values indicates that in more polar methanol (in comparison with tbutanol) the catalysis is more sensitive to the acidity change of used catalysts.     

Alternating RF/DC Isolations for Quantitation with Coeluting Internal Standards in Gas Chromatography/Ion Trap Mass Spectrometry

A new ion trap scan function for gas chromatography/mass spectrometry (GC/MS) quantitation is described that employs alternating mass-selective storage (rf/dc isolation) of ions from an analyte and its coeluting isotopically labeled internal standard. This scan includes two separate ionization/isolation/mass analysis sequences within the same scan function, each optimized for either the analyte or the internal standard. This results in alternating between analyzing the analyte and the internal standard during their coelution. The method is conceptually similar to using two different scan functions to analyze either the analyte or the internal standard in alternating scans; however, it is much faster because it eliminates the slow procedure of continuously downloading alternating scan functions from disk. This allows more data points to be obtained over a GC peak, resulting in more reproducible GC peak profiles as well as better sensitivity and precision. Results of calibration curves spanning four orders of magnitude (0.5 pg to 5 pg injected on column) obtained by using this method give excellent linear correlations (r ² > 0.9990) and precision (relative standard deviations of triplicate injections < 10%).     

Kinetics of solvolysis of 1-acetyl-4-(1-ethoxycarbonyl-1-cyano) methylene-1,4-dihydroquinoline in undried DMSO-d6· formation of Acetic Anhydride as an intermediate

The kinetics of solvolysis of the title compound (QAc) in undried DMSO-d₆ to give 4-(1-ethoxycarbonyl-1-cyano)methylquinoline (QH) and HOAc at ambient temperature were investigated by ¹H nmr spectrometry. With a limited excess of water the solvolysis follows a three-step process of $ {\rm QAc} + {\rm H}_2 {\rm O}\mathop \to \limits^{k_1} {\rm QH} + {\rm HOAc}, $ , and $ {\rm Ac}_{\rm 2} {\rm O} + {\rm H}_2 {\rm O}\mathop \to \limits^{k_3} {\rm 2\,HOAc}, $ where k₂ > k₁ and k₃ < k₁. Addition of pyridine-d₅ to the reaction mixture markedly catalyzes the overall solvolysis, while addition of CF₃CO₂D to the reaction mixture simplifies the kinetics to pseudo first-order in [QAc] with k = 4.3 × 10^?3 min^?1.     

Solid-State 13C-NMR spectral evidence for charge transfer complex formation in aromatic diimides and dianhydrides

Solution and solid-state proton decoupled ¹³C-NMR spectra were determined on two diimides derived from 4, 4′-oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′-isophthaloyldiphthalic anhydride (IDPA) and 4, 4′-terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid-state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides.     

Thermal Degradation and Flammability Properties of Poly(propylene)/Carbon Nanotube Composites

Nanocomposites based on poly(propylene) and multi‐wall carbon nanotubes (up to 2 vol.‐%) were melt blended, yielding a good dispersion of nanotubes without using any organic treatment or additional additives. Carbon nanotubes are found to significantly enhance the thermal stability of poly(propylene) in nitrogen at high temperatures. Specifically, the nanotube additive greatly reduced the heat release rate of poly(propylene). They are found to be at least as effective a flame‐retardant as clay/poly(propylene) nanocomposites.     

The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(μ-X)(μ-PR2)Re cluster (X=halide)

Diphenylphosphine oxidatively adds to the ReRe bonds of Re₂ X ₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) and Re₂Cl₄(-dpam)₂ (dpam=Ph₂AsCH₂AsPh₂) to afford the dirhenium(III) complexes Re₂(-X)(-PPh₂)HX ₃(-LL)₂. The dppm complexes have also been prepared from the reactions of Re₂(-O₂CCH₃)X ₄(-dppm)₂ with Ph₂PH, and a similar strategy has been used to prepare Re₂(-Cl)(-PPh₂)HCl₃(-dmpm)₂ (dmpm=Me₂PCH₂PMe₂) from Re₂(-O₂CCH₃)Cl₄(dmpm)₂. Phenylphosphine likewise reacts with Re₂ X ₄(-dppm)₂ to give Re₂(-X)(-PHPh)HX ₃(-dppm)₂. An X-ray crystal structure determination on Re₂(-Cl)(-PPh₂)HCl₃(-dppm)₂ confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group (No. 148) witha=21.699(3) Å, =84.50(4)°,V=10084(5) ų, andZ=6. The structure was refined toR=0.049 (R _w 0.069) for 5770 data withI>3.0(I). The Re-Re distance is 2.5918(7) Å. Oxidation of the bromide complex Re₂(-Br)(-PPh₂)HBr₃(-dppm)₂ with NOPF₆ produces the unusual dirhenium(III, II) cation [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]⁺ which has been structurally characterized as its perrhenate salt, [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]ReO₄ · 2CH₂Cl₂. This complex crystallizes in the space group (No. 2) witha=14.187(7) Å,b=16.419(5) Å,c=16.729(5) Å, =98.76(2)°, =110.11(3)°, =104.66(3)°,V=3414(6) ų,Z=2. The structure was refined toR=0.040 (R _w =0.051) for 5736 data withI>3.0(I). The presence of a phosphorus-bound [P(O)Ph₂]^– ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) Å.     

Ligand dynamics and reactivity in trimetallic clusters

The general relationships between trinuclear cluster reactivity and the ligand dynamical processes in these systems are explored. Three specific mechanistic studies are presented: (1) the rate and stereochemistry of ligand addition to ₃-imidoyl complexes, (2) the factors influencing the rate of carbon-hydrogen bond activation in ₃-alkyne complexes, and (3) the origin of anomalously large kinetic deuterium isotope effect in metal to ligand and ligand to metal hydrogen transfer in trinuclear and binuclear complexes. In all three cases, the current state of the mechanistic studies are summarized and the possible rate of specific ligand dynamical processes in controlling the mechanism are put forth.     

Total synthesis of dysiherbaine

A convergent total synthesis of the marine natural product dysiherbaine was accomplished. The key steps of the synthesis are an alkylation at the gamma-carbon of a protected glutamate with a highly substituted pyran derived from mannose, which was followed by a ring-contraction cascade reaction, which simultaneously gave the tetrasubstituted carbon and the hexahydrofuro[3,2-b]pyran ring system of the natural product.