Proton and 13C NMR spectra of substituted methyl cyanopropionates: Effects of molecular asymmetry

The proton NMR spectra at 220 MHz of two series of substituted cyanopropionates, have been investigated. In addition the ¹³C spectra at 15 MHz of the series I were also studied. In I, where the R groups are diastereotopic, differences are observed in the proton chemical shifts of the CH₃ groups in R for R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉, n-C₅H₁₁ and n-C₆H₁₃. In II [R′ = n-C₃H₇, CH(CH₃)₂, CH₂CH(CH₃)₂ and C(CH₃)₃] diastereoisomers are found with substantial differences in chemical shifts between corresponding protons. Coupling constants are interpreted in terms of conformational preferences for certain molecules in both series.     

Investigations of dithienylglycolic esters—IV : Solvent effects on the chemical shift differences of the diastereotopic thienyl protons in an asymmetric 2,2′-dithienylglycolic ester

The chemical shift differences (Δν) of the diastereotopic thienyl protons of 1-phenyl (-d₅) ethyl 2,2′-dithienylglycolate have been measured for different solvents and at different temperatures. The solvent dependence of the Δν's are interpreted as being due mainly to solvent shifts of the diastereotopic protons.     

Structural discrimination from in situ measurement of 1DCH and 2DHH residual dipolar coupling constants

A fast residual dipolar coupling constant‐assisted strategy involving the simultaneous determination of scalar and total coupling constants from a single ¹J_CH/²J_HH‐resolved NMR spectrum is reported. It is shown that the concerted use of the directly measured ¹D_CH (for all CH_n multiplicities) and ²D_HH residual dipolar couplings allows an on‐the‐fly assignment of diastereotopic CH₂ protons, as well as of an efficient discrimination between diastereoisomeric structures of strychnine which contains six stereocenters. Copyright © 2017 John Wiley & Sons, Ltd.     

Living cationic polymerization route to poly(oligooxyethylene carbonate) vinyl ethers

The addition of dialkyl (R = Me or Et) carbonates to poly(oxyethylene)-based solid polymeric electrolytes resulted in enhanced ionic conductivities. Relatively high conductivities in lithium batteries with solutions of lithium salts in di(oligooxyethylene) carbonates such as R( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR (R = Et, n = 1, 2, or 3, m = 0, 1, 2, or 3) and related carbonates were obtained. In this respect, related comb-shaped poly(oligooxyethylene carbonate) vinyl ethers of the type  CH₂CH(OR) were prepared [R = ( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR′; (1) n = 2 or 3, m = 0, R′ = Et; (2) n = 2 or 3; m = 3, R′ = Me]. The direct preparation of derived target polymers of this class by polymerization of the corresponding vinyl ether-type monomers could not be achieved because of a rapid in situ decarboxylative decomposition of these monomers (as formed) during the final step of their synthesis. Instead, a prepolymer was prepared by a living cationic polymerization of CH₂CH (OCH₂CH₂ )_n O C(O) CH₃ (n = 2 or 3). The hydrolysis of its pendant ester groups, followed by the reaction of the hydrolyzed prepolymer with each of several alkyl chloroformates of the type Cl C(O) O( CH₂CH₂O )_mR′ (m = 0, 2, or 3, R′ = Me or Et) resulted in the corresponding target polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2171–2183, 2002     

Synthesis of Mixed-ring Zirconocene Complexes Containing Alkenyl Group and Ethylene Polymerization Catalyzed with Them

Four new mixed‐ring zirconium completes, [CH₂ = CH(CH₂)_n ‐C₅H₄](RC₅H₄)ZrCl₂ [n = l, R = CH₃OCH₂CH₂(3); n = 2, R = CH₃OCH₂CH₂ (4); n = 2, R=Me₃Si (5); n = 2, R = allyl (6)], have been prepared by the reaction of CH₂ = CH(CH₂)_n C₅H₄ZrCl₃, DME[n = l (1); n = 2 (2)] with RC₅H₄Li. When activated with methylaluminoxane (MAO), the catalytic activities of the above complexes in ethylene polymerization were tested. Complexes 5 and 6 show high activities similar to Cp₂ZrCl₂. Introduction of methoxyethyl group into Cp‐ligand dramatically decreases the catalytic activities of complexes 3 and 4, which can be overcome by increasing the amount of MAO. For complex 5, the dependence of activity and molecular weight (Mη) on the Al/Zr ratio, the polymerization time (t_P), polymerization temperature (T_P) and the polymerization solvent volume (V) was investigated.     

1H-, 31P- and 13C-NMR spectra of some 2-arylsulphonylamido-2-thiono-5-methyl-1,3,2-dioxaphospholanes

Some 2-arylsulphonylamido-2-thiono-5-methyl-1,3,2-dioxaphospholanes (1), containing two chiral centres, give NMR spectra in which splittings of the ¹H and ¹³C signals of the 5-methyl substituent and of the ³¹P signal indicate that they exist in an approximately 70:30% ratio of two racemic mixtures, Z and E respectively, diastereomeric to each other. These splittings were invariably observed for compounds 1a, containing a monosubstituted sulphonylamido group (Y = H) and various substituents at position 4′ of the aryl group, X = H, CH₃, OCH₃, F, CI and Br. The methylenic protons in position 4 of the phospholane ring are diastereotopic and therefore magnetically non-equivalent. Benzene-induced shifts were measured for the Z isomers of compounds 1a, X = H, F and for compound 1b, containing an N-disubstituted sulphonylamido group (Y = CH₃) and X = H; the tentative interpretation of these shifts places the more shielded diastereotopic methylene proton on the same side of the ring as the 5-methyl substituent. The H? P and H? H coupling constants indicate that the preferred conformation of the dioxaphospholane ring should be a ‘twisted envelopey’ shape with the 5-methyl substituent in the equatorial position.     

Resonance assignments of diastereotopic CH2 protons in the anomeric side chain of selenoglycosides by means of 2J(Se,H) spin‐spin coupling constants

Unambiguous resonance assignments of diastereotopic CH₂ protons in the anomeric side chain of nine alkyl‐ and aralkylselenoglycosides have been carried out on the basis of experimental CPMG‐HSQMBC measurements and theoretical second order polarization propagator approach (SOPPA) calculations of geminal ⁷⁷Se‐¹H spin‐spin coupling constants involving diastereotopic pro‐R and pro‐S protons. Theoretical conformational analyses have been performed at the MP2/6‐311G** level. The conformational space of each of the selenoglycosides under study could be adequately described as a mixture of six interconverting conformers with the molar fractions depending on the nature of the side chain substituent at the selenium atom. The good agreement observed between measured and the weighted conformational averaged values of the calculated coupling constants provides a basis for reliable diastereotopic assignments in this type of carbohydrate structures. Copyright © 2012 John Wiley & Sons, Ltd.     

Kinetic study of the reaction of OH with a series of acetals at 298 ± 4 K

Rate coefficients have been measured at 298 ± 4 K and 1000 mbar total pressure for the reactions of OH with a series of symmetrical acetals (R O CH₂ O R, R = C₁ to C₄) using a relative kinetic technique. The investigations have been performed in a laboratory photoreactor and also in the large outdoor EUPHORE simulation chamber facility in Valencia, Spain. The following rate coefficients (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹) have been obtained: dimethoxy methane (R = CH₃), 0.49 ± 0.02; diethoxy methane (R = CH₃CH₂), 1.84 ± 0.18; di‐n‐propoxy methane (R = CH₃CH₂CH₂), 2.63 ± 0.49; di‐iso‐propoxy methane (R = (CH₃)₂CH), 3.93 ± 0.48; di‐n‐butoxy methane (R = CH₃CH₂CH₂CH₂), 3.47 ± 0.42; di‐iso‐butoxy methane (R = (CH₃)₂CHCH₂), 3.68 ± 0.57; di‐sec‐butoxy methane (R = CH₃CH₂C(CH₃)H), 4.68 ± 0.05. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 797–803, 1999     

Studies on the kinetics of decomposition of diacyl peroxides: VI. CIDNP in the products of thermolysis of lauroyl peroxide and 3,5,5-trimethylhexanoyl peroxide

The ¹H NMR spectra recorded during the thermolysis of lauroyl peroxide and of 3,5,5-trimethylhexanoyl peroxide in ODCB containing 2-iodopropane show CIDNP multiplet effect. It was observed that the relative concentrations of 1-iodoundecane and 2-iodopropane, both polarized and normal species, changed with time. The relaxation time T₁ of the α-protons in 1-iodoundecane and vinyl protons of CH₂ in 1-undecene, enhancement factor of the protons of polarized species and the rate constant of decomposition for lauroyl peroxide have been determined. The mechanism of the decomposition of the entitled peroxides is discussed in terms of the radical pair theory.     

Ab initio analysis of monomers and dimers of trialkylphosphine oxides: Structural and thermodynamic stability

Structural and thermodynamic stabilities of monomers and dimers of trialkylphosphine oxides (TRPO) were studied using quantum chemistry calculations. Density functional theory calculations were carried out and the structures of four TRPO have been determined: TMPO (methyl; R = CH₃), TEPO (ethyl; R = CH₃CH₂), TBPO (n‐butyl; R = CH₃(CH₂)₃), and TOPO (n‐octyl; R = CH₃(CH₂)₇). TRPO homodimers were investigated considering two isomeric possibilities for each dimer. Relative binding energies and the enthalpic and entropic contributions to the Gibbs free energy were calculated for all dimers. The formation of dimers from the individual monomeric TRPO species as a function of temperature was also analyzed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Metallation studies of organofunctional trisiloxanes

Summary The organofunctional trisiloxanes Me₃SiOSiMe(R)OSiMe₃ [R=(CH₂)₂PPh₂, (CH₂)₃C₅H₄N, (CH₂)₃CN, (CH₂)₂Ph, (CH₂)₂SPh, CH=CH₂ and CH₂CH=CH₂] have been reacted with metal halide and-carbonyl moieties in order to determine the coordination preferences of materials being used as models for metallated longchain linear functionalised polysiloxanes. The products [Me₃SiOSiMe(R)OSiMe₃]₃ML_n [R=(CH₂)₂PPh₂, ML_n=RhCl],cis-[Me₃SiOSiMe(R)OSiMe₃]₂ML_n [R=(CH₂)₂PPh₂ or (CH₂)₃C₅H₄N, ML_n=Mo(CO)₄],trans-[Me₃SiOSiMe(R)OSiMe₃]₂ML_n[R=(CH₂)₂PPh₂, ML_n=NiCl₂, PdCl₂, PtCl₂ and [Rh(CO)Cl] and [Me₃SiOSiMe(R)OSiMe₃]ML_n [R=(CH₂)₂PPh₂, ML_n=Mo(CO)₃(2,2-bipyridine); R=(CH₂)₂Ph, ML_n=Mo(CO)₃; R=(CH₂)₃C₅H₄N, (CH₂)₃CN, or (CH₂)₂SPh, ML_n=Rh(CO)₂Cl; R=CH=CH₂ or CH₂CH=CH₂, ML_n=Fe(CO)₄] have been isolated and characterised spectroscopically in the course of these studies.     

Mono- and Bis-N-[3-(triorganylsilyl)propyl]guanidines and Their Derivatives

Organosilicon guanidine derivatives RNHC(=NH)NHCH₂CH₂CH₂Si(OC₂H5)_{3 - n} (OH)_n [R = H, n = 1; R = (CH₂)₃Si(OC₂H₅)₃, n = 0] were synthesized by condensation of guanidinium carbonate with (3-aminopropyl)triethoxysilane. The products were brought into ether interchange with thiethanolamine and hydrolytic polycondensation.     

Chiral poly(pyrazolyl)borate ligands and complexes: III. Chiral poly(pyrazolyl)borate isonitrile complexes of molybdenum and tungsten

The syntheses of enantiomeric and diastereoisomeric Bpz₄M★(CO)(NO)(CNR) complexes (M = Mo, W; R = CH₂CH₃, CH₂Ph, C★H(CH₃)(C₆H₅)) are reported. When R = CH₂CH₃ or CH₂C₆H₅ the presence of the diastereotopic methylene hydrogens does not allow the detection of the neighbouring chiral center, because they are magnetically equivalent. The diastereoisomeric complexes show different ¹H NMR signals, but cannot be resolved by liquid chromatography or by crystallization.     

Synthesis of sulphonated aminomethylphosphines and some nickel(II), palladium(II), platinum(II) and rhodium(I) complexes. Crystal structure of [Et3NH][(Ph2PCH2)2 N(CH2)2SO3]

Summary Aminoalkanesulphonic acids H₂N(CH₂) _n SO₃H, (n = 1, 2 or 3) react with phosphonium salts [R₂P(CH₂OH)₂]Cl (R = Ph or Cy, Cy = cyclohexyl) in the presence of Et₃N to give the sulphonated aminomethylphosphines [Et₃NH] [(R₂PCH₂)₂N(CH₂) _n SO₃] (R = Ph, n = 1, 2 or 3; R = Cy, n = 1). The single crystal X-ray structure of [Et₃NH] [(Ph₂PCH₂)₂N(CH₂)₂SO₃] has been determined. Some Ni^II, Pd^II, Pt^II and Rh^I complexes of the phosphines have been prepared.     

Stéréochimie en série aziridine: VI—Etude en Résonance Magnétique Nucléaire d'alcools aziridiniques primaires (configuration à l'azote,isoméries de rotation)

The PMR spectra of six primary aziridinyl carbinols are studied over a temperature range of ?30°C to +100°C. Nitrogen configuration is determined. When the inversion process is effective, kinetic parameters are evaluated. Rotational isomerism about the ‘ring? CH₂OH’ bond is studied from vicinal coupling constants associated with the two diastereotopic protons on the ? CH₂OH group. From the J(HOCH) coupling constant (in CCL₄) rotamer populations of the hydroxyl group are determined in some cases and the overall conformational distribution can be established.     

Trimethylene-bridged Tetraorganodistannoxanes {[Me3SiCH2(RCOO)Sn(CH2)3Sn(OOCR)CH2SiMe3]O}n (R = Ph, 2,4-Me2C6H3): Control of Structure by Variation of R

The synthesis of trimethylene-bridged carboxylate-substituted tetraorganodistannoxanes {[Me₃SiCH₂(RCOO)Sn(CH₂)₃Sn(OOCR)CH₂SiMe₃]O} _n (1, R = Ph; 2, R = 2,4-Me₂C₆H₃) is reported. Depending on the structure of R, in the solid state these compounds are either dimers (1, n = 2, cis-isomer) with a ladder-type structure or tetramers (2, n = 4) with a double ladder-type structure.     

Phenyl(acyloxy)fluorosilanes C6H5Si(OCOR)nF3?n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)FCl

The method of synthesis of the hitherto unknown class of organosilicon compounds, phenyl(acyloxy)fluorosilanes C₆H₅Si(OCOR) _n F_3−n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C₆H₅Si(OCOR) FCl in up to 91% yield has been developed based on the reaction of phenyl(fluoro)chlorosilanes C₆H₅SiCl _n F_3−n (n = 1, 2) with trimethylsilyl esters of carboxylic acids Me₃SiOC(O)R [R = H, CH₃, CF₃, CCl₃, ClCH₂, BrCH₂, CH₂=CHCH₃, CH₂=CHPh, CH(CH₃)=CH₂, Ph].     

Mössbauer studies on ferrocene complexes: XVI. Structure of triorganostannyl derivatives of dimethylaminomethylferrocene and N,N-dimethylbenzylamine

A series of new stannylated derivatives of dimethylaminomethylferrocene (DMAMF) and N,N-dimethylbenzylamine have been synthesised and their structures investigated by ¹H, ¹³C and ¹¹⁹Sn NMR together with ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy. Polystannylated derivatives were synthesised from DMAMF and BuLi in the presence of TMED. The methylene protons of the CH₂NMe₂ group were diastereotopic for all the DMAMF derivatives synthesised. The chemical shift differences of these protons is discussed in terms of conformational changes. ¹³C and 119Sn shifts were used to establish the substitution patterns in the polystannylated derivatives. ¹³C shifts for the 2-substituted derivatives of both DMBA and DMAMF were reasonably additive, for both the free amines and the quaternary ammonium salts. The Mössbauer data show no evidence of pentacoordination in any of the derivatives.     

Structure-based predictions of H NMR chemical shifts of sesquiterpene lactones using neural networks

In this work the prediction of ¹H NMR chemical shifts of CH_n protons of sesquiterpene lactones by means of neural networks is described. This method is based on the incorporation of experimental chemical shifts of protons of sesquiterpene lactones as additional memory of an associative neural network system previously trained with chemical shifts of other organic compounds. One advantage of this method is its ability to distinguish between CH₂ diastereotopic protons belonging to rigid substructures since stereochemistry is considered. This is achieved via the automatic conversion of the 2D structure diagram into a 3D molecular structure. The predicted ¹H NMR chemical shifts of the sesquiterpene lactones showed a high level of accuracy. This is the first report on a fully automatic proton assignment of structures of sesquiterpene lactones of an accuracy that allows its use in structure elucidation.     

Acyl iodides in organic synthesis. Reaction of acetyl iodide with thiols

The direction of reactions of acetyl iodide with aliphatic, aromatic, and heterocyclic thiols is determined by the thiol acidity and steric factors. Acetyl iodide reacted with aliphatic thiols, including trialkylsilylsubstituted derivatives R(CH₂) _n SH (R = Me, n = 3; R = Me₃Si, n = 3; R = Et₃Si, n = 2), to give the corresponding ethanethioates R(CH₂) _n SCOMe. Benzenethiol was oxidized with acetyl iodide to diphenyl disulfide. The reaction of acetyl iodide with 2-sulfanylethanol afforded 2-(2-iodoethyldisulfanyl)ethyl acetate as a result of three consecutive-parallel processes: acylation, iodination, and oxidation of the initial compound. 1,3-Benzothiazole-2-thiol reacted with acetyl iodide only at the nitrogen atom to give quaternary salt, whereas the SH group remained intact.