Catalyst-Free Propargylboration of Ketones with Allenyl-Bpins: Highly Stereoselective Synthesis of tert-Homopropargyl Alcohols Bearing Vicinal Stereocenters.

A practical and efficient propargylboration of ketones is presented using general allenylboronic acid pinacol esters (allenyl-Bpins) without a catalyst. This reaction is triggered by in-situ activation of stable allenyl-Bpins through the sequential addition of 1.25 equiv. of n BuLi and the prerequisite 2.0 equiv. of TFAA. Under the optimized reaction conditions, the versatile trisubstituted allenyl-Bpins react with various ketones smoothly to afford a wide range of tert-homopropargyl alcohols bearing vicinal stereocenters in high yields with good to excellent diastereoselectivities. Furthermore, propargylboration of ketones with chiral trisubstituted allenyl-Bpins allows for the asymmetric synthesis of chiral tert-homopropargyl alcohols with a full chirality transfer.

Pd-catalysed cross-coupling of allenylic carbonates with gem-diborylalkanes: efficient synthesis of isoprenylboronates.

A simple and novel Pd-catalysed cross-coupling reaction of allenylic carbonates with different gem-diborylalkanes was developed. Under mild reaction conditions, synthetically useful and versatile isoprenylboronates could be obtained selectively in moderate to high yields. Furthermore, the utility of the novel isoprenylboronate is demonstrated through isoprenylboration and homologation.

[Spectral Characteristics and Catalytic Performances of SO2-4/Ce-TiO2 with Visible Light Response].

Ce doped TiO2 was prepared via sol-gel method. The as-prepared Ce doped TiO2 was impregnated with diluted H2SO4 to obtain a H2SO4-treated Ce doped TiO2. In succession, the characterizations of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), pyridine adsorption-FTIR (Py-FTIR), ultraviolet-visible spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS) were carried out to analyze the reasons for the improvement of the light response performance. The visible light photocatalytic degradation of Rhodamine B (RhB) in an aqueous solution was used as a probe reaction to evaluate the photocatalytic activity of the obtained samples. According to the XRD analysis, Ce doping created the lattice defects in TiO2 and minimized the particle size, which promoted the transfer of photo-generated electrons and then improved catalyst activity. The bridged bidentate coordination mode of SO2-4 was proposed based on the FTIR spectra. The pyridine FTIR spectra showed that both Lewis and Brnsted acid sites were formed on the sample surface. The characteristic absorption band as Lewis acid was more intense than that of the Brnsted acid, exhibiting the major Lewis acidity. The presence of the Lewis acid sites resulted in the transfer of photogenerated electrons to the Lewis acid center because of the electron deficiency of the Lewis acid sites, which contributed greatly to the transport of the photogenerated electrons, inhibiting the recombination of the photogenerated electron/hole pairs and leading to the enhancement of the photocatalytic activity of samples. From UV-Vis results, Ce-doping introduced an impurity energy level in the band gap, narrowing the TiO2 band gap. The impurity energy level could capture the photogenerated electrons on the conduct band and photogenerated holes on the valence band, reducing the recombination probability of photogenerated carriers and exciting the electrons captured on the impurity energy band by the photons with lower energy, thus expanding the light response range of TiO2. The XPS results indicated that the doped Ce existed as a mixture of Ce3+/Ce4+ states, which facilitated the efficient separation of the photo-generated electrons and holes because of the electron transfer, enhancing the system's quantum efficiency. The sulfated Ce doped TiO2 catalysts were very active for the visible photocatalytic degradation of RhB. Results showed that the synergetic effects of Ce doping and acid-treatment improved the visible light response for sulfated Ce-doped TiO2, enhancing the visible photocatalytic activity.

[Preparation and characterization of modified kaolins and their photocatalytic property].

In order to develop the cheap and efficient photocatalysts, kaolins were modified through calcination and acid leaching. In succession, the prepared samples were characterized using thermal gravimetric-differential thermal analysis (TG-DTA), scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis) and BET specific surface area measurements (BET). Methyl orange, used as a model reactant, was degraded under UV light irradiation to evaluate the photocatalytic activities of the prepared samples. From UV-Vis spectroscopy analyses, an obvious increase in the red shift of the absorption edge was observed for the samples treated with acid. The acid sites generated during the modification of kaolin were determined through adsorbed pyridine analysis using infrared spectroscopy (Py-IR). Kaolins modified using over 30% H2SO4 contained both Brönsted and Lewis acid sites. Combining the results of photocatalytic experiment with the conclusions of Py-IR and XRD, the acid properties of the prepared samples were the main factors that affected their catalytic activity.

[Spectralsignatures of nickel and vanadium supported photocatalysts and their photocatalytic properties].

Using SiO2, activated carbon (AC) and Al2O3 as supports, the supported photocatalysts Ni-V-O/SiO2, Ni-V-O/AC and Ni-V-O/Al2O3 were prepared by impregnation method, and their spectralsignatures were investigated. The carbonylation of methanol with CO2 under UV irradiation was used as a probe reaction to compare the photocatalytic performance of the prepared catalysts. Integrated with the testing results of carbonylation, the effects of different supports on selectivity for the carbonylation products of methyl formate (MF) and dimethyl carbonate (DMC) were discussed by pyridine-IR and UV-Vis techniques. XRD results showed that the particles of nickel and vanadium supported on SiO2 had the highest degree of dispersion. Results of pyridine-IR indicated that all catalysts retained Lewis acid sites. The acid strength was different from catalyst samples with different supports but with the same active components. The acid strengths could be arranged as follows: Ni-V-O/SiO2 > Ni-V-O/Al2 O3 > Ni-V-O/AC. Different acid strengths exhibited different influence on the selectivity of products MF and DMC of carbonylation. The surface acid strengths of catalysts were the major factor influencing the selectivity of carbonylation products.

Microfluidic hydrogels for tissue engineering.

With advanced properties similar to the native extracellular matrix, hydrogels have found widespread applications in tissue engineering. Hydrogel-based cellular constructs have been successfully developed to engineer different tissues such as skin, cartilage and bladder. Whilst significant advances have been made, it is still challenging to fabricate large and complex functional tissues due mainly to the limited diffusion capability of hydrogels. The integration of microfluidic networks and hydrogels can greatly enhance mass transport in hydrogels and spatiotemporally control the chemical microenvironment of cells, mimicking the function of native microvessels. In this review, we present and discuss recent advances in the fabrication of microfluidic hydrogels from the viewpoint of tissue engineering. Further development of new hydrogels and microengineering technologies will have a great impact on tissue engineering.

[Spectroscopic study of photocatalytic mechanism of methanol and CO2].

Ni-Ti-O/SiO2 catalyst was prepared by impregnation method, and its photocatalytic performance for carbonylation of methanol with CO2 was investigated under UV light. The in-situ IR, XPS and MS were carried out to analyze the possible photocatalytic reaction mechanism. Results indicated that the Ni-Ti-O/SiO2 exhibited good photocatalytic performance for carbonylation of methanol with CO2, the methanol conversion reached up to 24.9%, and the selectivity for the carbonylated products was more than 60% within 180 min reaction time. The catalyst characterization results showed that the O==C .--O- and CH3OC(O)* might be important intermediate in the carbonylation of methanol with CO2.