Copper(I)-Catalyzed Enyne Oxidation/Cyclopropanation: Divergent and Enantioselective Synthesis of Cyclopropanes.

An efficient copper(I)-catalyzed enyne oxidation/cyclopropanation for the modular synthesis of cyclopropane derivatives is described, which represents the first non-noble metal-catalyzed enynes oxidation/cyclopropanation by the in situ generated α-oxo copper carbenes. This protocol allows the assembly of valuable cyclopropane-γ-lactams in generally good to excellent yields with excellent diastereoselectivity. More significantly, the enantioselective version of enyne oxidation/cyclopropanation has been disclosed with chiral copper catalysts.

Cu(I)-Catalyzed Oxidative Cyclization of Enynamides: Regioselective Access to Cyclopentadiene Frameworks and 2-Aminofurans.

An efficient Cu(I)-catalyzed oxidative cyclization of alkynyl-tethered enynamides for the construction of fused bicyclic cyclopentadiene derivatives is disclosed. The cascade proceeds through alkyne oxidation, carbene/alkyne metathesis, and formal (3 + 2) cycloaddition. Employing aryl-tethered enynamides as starting materials, substituted 2-aminofurans can be exclusively formed.

Vibrational spectra of guaiacylglycerol-ß-guaiacyl ether: experiment and theory.

As an important inter-unit of lignin, guaiacylglycerol-ß-guaiacyl (GG) ether has been synthesized, and characterized using terahertz time-domain spectroscopy in the frequency range of 5-85 cm(-1). Seven absorption peaks have been observed. Among these peaks, the 49.8 cm(-1) and 57.6 cm(-1) vibrations are propose to be characteristic absorption peaks of GG ether. Raman spectra were also measured in the range of 50-3500 cm(-1). The vibrations of the two lowest energy forms, i.e., erythro 1r4s and threo 1s4s, were calculated using density functional theory at the B3LYP/6-311G∗∗ level and assigned according to potential energy distribution. In addition, the contents of erythro and threo forms in GG sample could be estimated by comparing the waveform similarities between theoretical and observed curves in the 33.0-80.0 cm(-1) range. Results showed that the observed curve of GG sample is a combination of erythro 1s4r and threo 1s4s. The four absorption vibrations below 33.0 cm(-1) could be assigned to phonon, inter-molecular modes and/or hydrogen bond vibrations. Terahertz spectra and Raman spectra, together with theoretical calculations, could be powerful methods for predicting contents of different isomers in sample.

[Study on terahertz spectra of multi-walled carbon nanotubes].

In the present paper, the authors report the characterization of multiwalled carbon nanotube at terahertz (THz) frequency range using terahertz time-domain spectroscopy. The surface appearances and microanalysis of multiwalled carbon nanotubes were measured by scanning electron microscope in order to fully understand the unique features and applications of multiwalled carbon nanotube. The results show that the refractive indexes of the sample decrease with increasing frequency in the frequency range of 0.2 to 2 THz, while the absorption coefficients of the sample increase with increasing frequency. In addition, the curve of terahertz absorption coefficients can be fitted by a straight line with a slope of 1.92. From the results of scanning electron microscope, the ranges of inner diameter and outer diameters of the sample were from 5 to 15 nm and from 15 to 25 nm, respectively, and its length was in the order of micrometer. The results of microanalysis of its elemental composition showed that the content of element C was about 94% and the rest were O and Cl elements, which were impurity elements. Mathematical modes of terahertz absorption and refractive indexes in the frequency range of 0.2 to 2.0 THz were established after taking into account Taylor expansion and Maxwell's equations, and the calculation was in relatively good agreement with the observed values of the sample in general. The terahertz refractive indexes and absorption properties of multiwalled carbon nanotube were mainly attributed to the chemical compositions and molecular weight, and carbon nanotubes with different content of carbon could show different terahertz absorption spectra and disclose different unique functions.