Angular distributions of photoelectrons in resonantly enhanced multiphoto ionization via the 7s[1 1/2]0 1 and 8s[1 1/2]0 1 states of Xe

Photoelectron angular distributions have been measured for the three-photon resonant one-photon ionization, (3+1), of Xe via the 7s[1 1/2]⁰ ₁ and 8s[1 1/2]⁰ ₁ states. The results are in good agreement with the theoretical predictions of Tang and Lambropoulos [13] for the 8s[1 1/2]⁰ ₁, but not for the 7s[1 1/2]⁰ ₁ state. Furthermore, the results are compared to those which have been obtained by Blazewicz et al. [1] for the three-photon resonant two-photon ionization, (3+2), of Xe via the 6s[1 1/2]⁰ ₁ state.     

Observation of the electric-field-inducedE1 transition between 5s4d 1 D 2 and 5s 2 1 S 0 levels in Sr I

The angular distribution of the electric-field-inducedE1 radiation is asymmetric with respect to the external electric field direction. Measurement of this asymmetry for the 5s4d ¹ D ₂ → 5s ^{2 1} S ₀ transition in strontium permits the experimental determination of the 5s5p ¹ P ₁ → 5s4d¹ D ₂ decay rate. The result is:A(¹ P ₁ →¹ D ₂)=(4.37±0.93±0.66) × 10³ s ^?1.     

Rearrangements of 1-(1-methylprop-1-en-1-yl)-1,2-dimethylacenaphtyylenonium ions

It was discovered by means of dynamic NMR that the 1-(cis-1-methylprop-1-en-1-yl)-1,2-dimethylacenaphthylenonium ion generated under conditions of “long life” for carbocations underwent fast (ΔG^#35.8 kJ mol^?1 at ?103°C) degenerate 1,2-shift of the cis-dimethylvinyl group. Quantum-chemical calculations by DFT method predict lower rate of 1,2-shift for the trans-dimethylvinyl group compared to cis-dimethylvinyl group and dependence on the cations conformation of the rates of these processes and of the rearrangement mechanism into the ions of phenalenyl type.     

Vibrational spectra of 1-chloro-2-methylpropane and 1-chloro-2,2-dimethylpropane

Infrared and Raman spectra are obtained for 1-chloro-2-methylpropane and 1-chloro-2,2-dimethylpropane. The former compound exists as a mixture of P_C and P_H' conformers in the liquid and unannealed solid states, but only the P_C conformer is present in the crystalline solid. Vibrational assignments are made for both conformers of 1-chloro-2-methylpropane and for 1-chloro-2,2-dimethylpropane with the aid of normal coordinate calculations.     

Correlation of the Solubilizing Abilities of 1-Butyl-1-methyl-pyrrolidinium Tris(pentafluoroethyl)trifluorophosphate, 1-Butyl-1-methylpyrrolidinium Triflate and 1-Methoxyethyl-1-methylmorpholinium Tris(pentafluoroethyl)trifluorophosphate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]⁺[FAP]^?), 1-butyl-1-methylpyrrolidinium triflate, ([BMPyrr]⁺[Trif]^?), and 1-methoxyethyl-1-methylmorpholinium tris(pentafluoroethyl)trifluorophosphate, ([MeoeMMorp]⁺[FAP]^?), stationary phases at (323, 353 and 383) K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. The three sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.11 and 0.15 log₁₀ units, respectively.     

A method for the regioselective synthesis of 1-alkyl-1H-indazoles

A method for the regioselective synthesis of 3-unsubstituted 1-alkyl-1H-indazoles, starting with 2-halobenzonitriles and N-alkylhydrazines, is described. The two-step reaction pathway proceeds through the intermediacy of 1-alkyl-3-amino-1H-indazoles followed by reductive deamination.     

The reaction of perfluoroalkylcopper compounds with 1-bromo-1-perfluoroalkylethylenes

Perfluoroalkylcopper compounds [F_FCU], when they react with 1-bromo-1-perfluoroalkylethylenes 1, do not give the expected gem-disubstituted compounds 3, but the vic-disubstituted products 2 in 60–70% yields. These results show that the reaction does not proceed through a simple vinylic substitution. ¹H and ¹⁹F NMR data are given for the new compounds.     

The molecular orientation of CO on Pd(1 1 1): a polarization-dependent SFG study

The molecular orientation of carbon monoxide adsorbed on Pd(1 1 1) was examined by sum frequency generation (SFG) vibrational spectroscopy utilizing different polarization combinations of the visible and SFG light. This allows to determine the CO tilt angle with respect to the substrate, provided that a proper optical model for the interface can be defined. It is demonstrated that it is essential to invoke the β_aac hyperpolarizability into the analysis and that polarization-dependent SFG of CO/Pd(1 1 1) yields information on β_aac/β_ccc rather than the tilt angle.     

Densities and viscosities for binary mixtures of phenetole with 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol,and 1-decanol at different temperatures

Density (ρ) and viscosity (η) values of the binary mixtures of phenetole+1-pentanol, + 1-hexanol, + 1-heptanol, + 1-octanol, + 1-nonanol, and + 1-decanol over the entire range of mole fraction at 293.15, 298.15, 308.15, and 318.15 K have been measured at atmospheric pressure. The excess molar volume (V^E), viscosity deviations (Δη), and excess Gibbs energy of activation (G*^E) have been calculated from the experimental measurements. These results were fitted to Redlich and Kister polynomial equation to estimate the binary interaction parameters. The viscosity data were correlated with equations of Grunberg and Nissan, Hind et al., Frenkel, and McAllister. While the excess molar volumes of phenetole+1-pentanol, + 1-hexanol are positive, the remaining binary mixtures are negative. The viscosity deviations and excess Gibbs energy of activation are negative for all investigated systems. As the chain length of 1-alkanols increases, both viscosity deviations and excess molar volume values decrease while excess Gibbs energy of activation value increase. The temperature has no effect on excess molar volume, slight effect on excess Gibbs energy of activation, and significant effect on viscosity deviations. The calculated functions have been used to explain the intermolecular interaction between the mixing components.     

Rotational isomerism. A gas-phase 1H nuclear magnetic resonance study of 1-bromo-2-chloroethane

The average vicinal coupling constants of 1-bromo-2-chloroethane at different temperatures have been obtained in a gas-phase ¹H NMR study of 1,2-disubstituted ethanes. Analysis of the experimental data, assuming a ”static” model with constant values for the vicinal coupling constants of the individual rotamers, yielded unacceptable results. A ”dynamic” model, which takes into account the torsional vibrations, has therefore been developed and used to analyse the gas-phase results. The values at 305 K for the vicinal coupling constants of the individual rotamers are: trans rotamer J_T = 13.6 Hz, J'_t = 4.9 Hz; gauche rotamer $\text{1}\text{2}$(J_G1 + J_G2) = 0.9 Hz, $\text{1}\text{2}$(J'_G1 + J'_G2) = 7.8 Hz. These couplings are temperature-dependent with J_T changing about four times as much as the other coupling constants. Analysis of the average vicinal coupling constants, measured in different solvents, with the “dynamic” model gave values for the vicinal coupling constants of the individual rotamers in excellent agreement with those from the gas-phase data. The value of $\text{1}\text{2}$(J_G1+ J_G2) decreases noticeably with increasing dielectric constant of the solution. This can be explained by changes in the average dihedral angle between the coupling protons, in the gauche rotamers, which leads to changes of J_G1 and J_G2 in the same direction.     

Enzymatic resolution of methyl (1RS)-N-tBoc-6-hydroxy-3,4-dihydro-1H-isoquinoline-1-carboxylate by Seaprose S

An efficient biocatalytic process has been developed for the resolution of methyl (1RS)-N-tBoc-6-hydroxy-3,4-dihydro-1H-isoquinoline-1-carboxylate rac-1 by means of Seaprose S-mediated enantioselective hydrolysis to afford (1S)-2 and (1R)-1 in 87% and 93% isolated yield, 101% and 96% potency, and ee >99.8% and >99.5%, respectively.     

Asymmetric synthesis of tert-butyl ((1R,4aR,8R,8aR)-1-hydroxyoctahydro-1H-isochromen-8-yl)carbamate

The asymmetric synthesis of methyl (E)-4-((1R,2S,3R)-3-amino-2-((E)-2-methoxycarbonyl-eten-1-yl)cyclohexyl)but-2-enoate 14 has been achieved from dimethyl (2E,7E)-nona-2,7-dienedioate 2. A key step is the asymmetric synthesis of 1-hydroxyoctahydro-1H-isochromene derivative 5 whose X-ray analysis corroborated the stereochemistry of the new stereocenters. The asymmetric synthesis of the isochromenyl acetate derivative 11 shows the potential of this methodology for fused cyclohexanic system heterocyclic synthesis.     

Oxidation of 1-methyl-1H-imidazole-2-thiol with chlorine dioxide

Oxidation of 1-methyl-1H-imidazole-2-thiol with chlorine dioxide was performed for the first time, and the results were shown to depend on the oxidation conditions. Optimal conditions were found for the preparation of 1-methylimidazole-2-sulfonic acid, 2,2′-disulfanediylbis(1-methylimidazole) hydrochlorite, and 1-methyl-3-sulfo-3H-imidazolium chloride. A new salt, 4-methylanilinium 1-methyl-1H-imidazole-2-sulfonate, was isolated.     

Fine structure of the 1s5f and 1s5g levels of He I

The fine structure of the 1s5f and 1s5g levels of He I was measured using microwave spectroscopy. The helium atoms were excited by ion impact, and the eleven allowed 1s5f ^2S+1 F _J –1s5g ^2S′+1 G _J , transitions near ν≈15 GHz were induced and detected by measuring the 1s4d–1s2p or 1s3d–1s2p spectral-line intensities of the impact radiation as a function of the microwave frequency. The measured transition frequencies are in accord with theoretical values and, except for one transition frequency, with earlier experimental data. The existing discrepancy between these earlier data and theory could be solved.     

Synthesis of 1-(pyrrolidin-2-ylmethyl)-1H-azoles and their piperidine-derived homologues

A convenient preparation of 1-(pyrrolidin-2-yl)-1H-pyrazoles, -imidazoles, and -1H-1,2,4-triazoles, 1-(piperidin-2-yl)-1H-pyrazoles and -1H-1,2,4-triazoles, and 1-(piperidin-3-yl)-1H-1,2,4-triazoles by alkylation of azoles (viz. pyrazoles, imidazoles, and triazoles) with N-Cbz-prolinol mesylate or its analogues and subsequent deprotection is reported. The two-step method allows for synthesis of the title compounds in 16–65% yields. The utility of the procedure has been demonstrated by multigram preparation of a 15-member building block mini-library for the lead-oriented synthesis of compound libraries. These building blocks perfectly fit the definition of low-molecular-weight hydrophilic three-dimensional templates, which leave much room for the lead-oriented synthesis of the compound libraries.      

Asymmetric microbial reduction of ketones: absolute configuration of trans-4-ethyl-1-(1S-hydroxyethyl)cyclohexanol

A set of five fungal species, Botrytis cinerea, Trichoderma viride and Eutypa lata, and the endophytic fungi Colletotrichum crassipes and Xylaria sp., was used in screening for microbial biocatalysts to detect monooxygenase and alcohol dehydrogenase activities (for the stereoselective reduction of carbonyl compounds). 4-Ethylcyclohexanone and acetophenone were biotransformed by the fungal set. The main reaction pathways involved reduction and hydroxylations at several positions including tertiary carbons. B. cinerea was very effective in the bioreduction of both substrates leading to the chiral alcohol (S)-1-phenylethanol in up to 90% enantiomeric excess, and the cis–trans ratio for 4-ethylcyclohexanol was 0:100. trans-4-Ethyl-1-(1S-hydroxyethyl)cyclohexanol, obtained from biotransformation by means of an acyloin-type reaction, is reported here for the first time. The absolute configurations of the compounds trans-4-ethyl-1-(1S-hydroxyethyl)cyclohexanol and 4-(1S- and 4-(1R-hydroxyethyl)cyclohexanone were determined by NMR analysis of the corresponding Mosher’s esters.     

Total synthesis of (+)-piericidin A1 and (−)-piericidin B1

The convergent syntheses of (+)-piericidin A₁ 1 and (?)-piericidin B₁ 2 have been achieved based on classical Julia-Lythgoe olefination between 4-hydroxy-5,6-dimethoxy-3-methyl-2-[5-oxo-3-methyl-pent-(2E)-enyl]-pyridine 3 corresponding to the left half of the final molecule, and chiral phenyl sulfones, (4R,5R)-2,4,6-trimethyl-5-methoxy-1-phenylsulfonyl-octa-(2E,6E)-diene 20 and (4R,5R)-5-tert-butyldimethylsiloxy-2,4,6-trimethyl-1-phenylsulfonyl-octa-(2E,6E)-diene 33, corresponding to the right halves. The construction of the two stereogenic centers in the right half of piericidins was achieved based on lipase-catalyzed hydrolysis of methyl (2,3)-anti-3-acetoxy-2,4-dimethyl-hex-(4E)-enoate (±)-22.     

The crystal structures of the 1-methyl-3,4-benzo-1-telluracyclopentane and 1-phenyl-1-telluracyclopentane cations in their tetraphenylborate salts,C8H8TeMe+ BPh4− and C4H8TePh+ BPh4−

The crystal structures of C₈H₈TeMe⁺ BPh₄^? (I) and C₄H₈TePh⁺ BPh₄^? (II) have been determined from three-dimensional X-ray counter data.I is monoclinic, space group P2₁/n with a 9.175(1), b 17.402(3), c 16.998(3) Å, β 98.92(6)°, Z = 4, R = 5.1% for 1641 observed reflections.II is triclinic, space group P$\text{1}$ with a 9.635(3), b 17.721(3), c 16.858(8) Å, α 89.77(2), β 104.36(4), γ 90.16(2)°, Z = 4, R = 9.0% for 6466 observed reflections.In both I and II tellurium is three-coordinate in a pyramidal geometry, with TeC distances in the range 2.07(1)–2.14(1) Å (I) and 2.10(1)–2.17(1) Å (II). In both structures short contacts of 3.4—3.5 Å occur between tellurium and carbon atoms of the tetraphenylborate anion.     

Vibrational analysis of alkyl iodides: 1-iodo-2- methylpropane and 1-iodo-3-methylbutane

Liquid and solid-state infrared spectra were obtained for 1-iodo-2-methylpropane and 1-iodo-3-methylbutane. The C-I stretching bands of the P_C and P_H' conformers of the propane were observed at 601 and 582 cm^?1, respectively, and those of the P_C and P_H conformers of the butane were observed at 595 and 512 cm^?1. Both conformers of each compound are present in the amorphous solid. Only the more sterically hindered P_H' conformer is present in the crystalline solid of the propane, and only the P_H conformer is present in the crystals of the butane. Vibrational assignments were made for both conformers of each compound with the aid of normal coordinate calculations. The increase in C-I stretching frequency of the P_H' conformer of the propane from the normal value in alkyi iodides (from ca. 500 to 582 cm^?1) is attributed to the increased contribution of C-C stretch and decreased contribution of C-I stretch.     

Calorimetric study of thermodynamics of production of polybutene-1, polypentene-1, 4-methylpentene-1 and properties of reagents between 0 and 670 K

The heat capacitiesC ₀ ^p of polybutene-1, polypentene-1, poly-4-methylpentene-1 and 4-methylphentene-1 were studied calorimetrically from 6 to (500–700) K. Temperatures, enthalpies of melting of various crystalline forms and the parameters of the glass transition were determined. The thermodynamic functionsH ⁰(T)?H⁰(0), S⁰(T) andG ⁰(T)?H⁰ (0) were calculated between 0 K and (500–700) K. From the calorimetric values obtained and literature data, the thermodynamic characteristics of the following processes were estimated for the corresponding alkenes-1, andcis-andtrans-alkenes-2: the polymerization of alkenes-1, the monomer-isomerization polymerization ofcis- andtrans-alkenes-2 to polyaklenes-1 and the isomerization ofcis- andtrans-aklenes-2 to alkenes-1 in the same temperature interval at standard pressure.