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Unknown spiro-cyclopropanated 1-aminopyrrol-2-ones are regioselectively prepared in high yields by Bi(OTf)3-catalyzed one-pot ‘Mukaiyama-Michael addition/cyclization/ring-contraction’ reactions of 1,2-bis(trimethylsilyloxy)cyclobutene with 1,2-diaza-1,3-butadienes at room temperature. 相似文献
95.
Bongiorno D Ceraulo L Filizzola F Fontana G Natoli MC 《Rapid communications in mass spectrometry : RCM》2006,20(20):3081-3088
The electron ionization (EI)-induced fragmentations of a series of 1,1-(2,2'-dimethoxyphenyl)-substituted 2-methylpropanes (1-20) in both 70 eV and mass-analyzed ion kinetic energy (MIKE) spectra have been investigated. The EI-MS spectra of these compounds are characterized by the presence of abundant benzyl ions. These ions result from competitive hydrogen migration from the 2- and 2'-methoxy groups on the carbenium center of the diphenylmethyl cations formed by benzylic cleavage of the molecular ions. The relative abundances of the benzyl ions arising from such competitive processes are discussed and rationalized. The steric effect of the 3- or 3'-substituents is the main discriminating factor between the two competitive processes. The structural information, arising either from the 70 eV or the MIKE spectra, is discussed. 相似文献
96.
The interaction of Pd and Au atoms with a silica surface and SiO2Mo(112) ultrathin films has been studied with periodic density-functional theory-generalized gradient approximation calculations. On both unsupported and supported silica, Pd and Au are weakly bound. No charge transfer occurs to the empty Pd and Au orbitals. Differently from Au, Pd can easily penetrate with virtually no barrier into the hexagonal rings of the supported silica film and binds strongly at the SiO2-Mo interface. The same process for Au implies overcoming a barrier of 0.9 eV. Completely different is the behavior of Ti-doped silica films. Au forms a direct covalent bond with substitutional Ti at the expense of the Ti...O-Mo interface bond which breaks. The global process is exothermic by 1 eV and nonactivated, showing that Ti doping results in solid anchoring points for the adsorbed Au atoms and for nucleation and growth of small gold particles. The effect of Ti doping is less pronounced for Pd but still visible with substantial enhancement of the Pd adsorption strength. 相似文献
97.
Unambiguous and complete assignments of 1H and 13C NMR chemical shifts for five clerodane diterpenes, four of them isolated from Salvia splendens (salviarin, splendidin and splenolides A and B) and one obtained by acetylation of splenolide A, are presented. The assignments are based on 2D shift-correlated [1H,1H-COSY, 1H,13C-gHSQC-1J(C,H) and 1H,13C-gHMBC-nJ(C,H) (n=2 and 3)] and nuclear Overhauser effect (NOE) experiments. The conformation of the rings of these compounds is supported by the 3J(H,H) values and NOE results. 相似文献
98.
Sanguineti A Monguzzi A Vaccaro G Meinardi F Ronchi E Moret M Cosentino U Moro G Simonutti R Mauri M Tubino R Beverina L 《Physical chemistry chemical physics : PCCP》2012,14(18):6452-6455
A new oxyiminopyrazole-based ytterbium chelate enables NIR emission upon UV excitation in colorless single layer luminescent solar concentrators for building integrated photovoltaics. 相似文献
99.
Kordatos Konstantinos Prato Maurizio Menna Enzo Scorrano Gianfranco Maggini Michele 《Journal of Sol-Gel Science and Technology》2001,22(3):237-244
We report on the synthesis of fullerene derivatives containing a trialkoxysilane moiety that exhibit enhanced solubility in solvents commonly used for sol-gel processing. These derivatives have been successfully embedded in glassy bulk samples and thin films that show very promising optical limiting properties. 相似文献
100.
Adriana Predoi−Cross Michel Herman Luciano Fusina Gianfranco Di Lonardo 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(11):1134-1137
The far infrared spectrum of HCOOH was recorded at a high resolution (0.0009 cm?1) and long path length (72 m) at the far-infrared beamline, Canadian Light Source. Spectra were recorded in the region 62–300 cm?1, showing transitions from the trans-isomer.Ground state rotational transitions with Ka up to 30, were identified up to 175 cm?1, extending the observation reported in the literature. A total of 3321 transitions were assigned and fitted together with previous (4149) published data. An improved set of rotational parameters was obtained adopting the symmetric top (A) reduction of the rotational Hamiltonian in the Ir representation. The newly measured far infrared transitions allowed the determination of all diagonal and off diagonal 8th order parameters L and of some of the diagonal 10th order parameters P. 相似文献