A variable importance criterion for variable selection in near-infrared spectral analysis

Science China Chemistry - Variable selection is a universal problem in building multivariate calibration models, such as quantitative structure-activity relationship (QSAR) and quantitative...     

Photo–thermo Catalytic Oxidation over a TiO2-WO3-Supported Platinum Catalyst

Photo–thermo catalysis, which integrates photocatalysis on semiconductors with thermocatalysis on supported nonplasmonic metals, has emerged as an attractive approach to improve catalytic performance. However, an understanding of the mechanisms in operation is missing from both the thermo- and photocatalytic perspectives. Deep insights into photo–thermo catalysis are achieved via the catalytic oxidation of propane (C₃H₈) over a Pt/TiO₂-WO₃ catalyst that severely suffers from oxygen poisoning at high O₂/C₃H₈ ratios. After introducing UV/Vis light, the reaction temperature required to achieve 70 % conversion of C₃H₈ lowers to a record-breaking 90 °C from 324 °C and the apparent activation energy drops from 130 kJ mol⁻¹ to 11 kJ mol⁻¹. Furthermore, the reaction order of O₂ is −1.4 in dark but reverses to 0.1 under light, thereby suppressing oxygen poisoning of the Pt catalyst. An underlying mechanism is proposed based on direct evidence of the in-situ-captured reaction intermediates.     

A Versatile Method for Kinetic Resolution of Protecting-Group-Free BINAMs and NOBINs through Chiral Phosphoric Acid Catalyzed Triazane Formation

A versatile kinetic resolution of protecting-group-free BINAMs and NOBINs has been realized through chiral phosphoric acid catalyzed triazane formation with azodicarboxylates. A series of mono-N-protected and unprotected BINAMs, diphenyl diamines and NOBIN derivatives could be kinetically resolved with excellent performances (with s factor up to 420). The gram-scale reactions and facile derivatizations of the chiral products demonstrate the potential of these methods in the asymmetric synthesis of chiral catalysts and ligands.     

Nanoscaled Copper Metal–Organic Framework (MOF) Based on Carboxylate Ligands as an Efficient Heterogeneous Catalyst for Aerobic Epoxidation of Olefins and Oxidation of Benzylic and Allylic Alcohols

Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu₃(BTC)₂] (BTC=1,3,5‐benzenetricarboxylate) as a high‐performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal–organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as‐synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity.     

Synthesis,Crystal Structure,and Properties of a New Lead Aluminum Fluoride Borate,Pb6AlB2O7F7

A new compound, Pb₆AlB₂O₇F₇, was synthesized from the PbF₂/B₂O₃ flux system, which is the first compound found in the PbF₂/Al₂O₃/B₂O₃ system. It crystallizes in the orthorhombic system, space group Cmca (No. 64) with unit cell parameters a = 11.649(7) Å, b = 18.300(11) Å, c = 6.394(4) Å, Z = 4. The crystal structure of Pb₆AlB₂O₇F₇ contains the group [Pb₆BO₁₁F₁₀] as basal building unit, which connects with each other forming two‐dimensional _∞[Pb₆BO₁₁F₁₀] layers, whereas aluminum atoms are filled in the interlayers. The IR spectrum further confirms the presence of BO₃ groups. The calculated band structures and the density of states of Pb₆AlB₂O₇F₇ suggest that its indirect gap is 2.968 eV. The DSC analysis and X‐ray diffraction technique prove that Pb₆AlB₂O₇F₇ is a congruent‐melting compound.     

Simultaneous Determination of Resibufogenin and Its Major Metabolite 3-epi-Resibufogenin in Rat Plasma by HPLC Coupled with Tandem Mass Spectrometry

A rapid, sensitive and specific method for the simultaneous quantification of resibufogenin (RBG) and 3-epi-resibufogenin (3-ERBG) in rat plasma was developed by using a liquid–liquid extraction procedure and liquid chromatography–electrospray ionization/tandem mass spectrometric (LC–ESI–MS/MS) analysis. The separation was performed by HPLC on a reversed phase C₁₈ HPLC column (150 × 2.1 mm, 3.5 μm) using a mobile phase of acetonitrilel-0.1% formic acid aqueous solution (45:55, v/v). The determination was performed by a triple-quadrupole mass spectrometer in the multiple reaction monitoring using positive mode of electrospray ionization (ESI). The calibration curves were both linear (R > 0.995) over the concentration range of 3.0–5,000 ng mL⁻¹, and the lower limits of quantification were 3.0 ng mL⁻¹ for both RBG and 3-ERBG. The intra-day and inter-day precisions (% RSD) were all less than 15%, and the accuracies (%RE) were within the range of ±15%. The mean recoveries of RBG, 3-ERBG and IS were over 82.7, 84.8 and 90.0% (n = 6), respectively. The method was proved to be rapid, sensitive and specific, and has been successfully applied to determine RBG and its major metabolite 3-ERBG in rat plasma after oral administration of RBG for pharmacokinetic study. Comparison of pharmacokinetic data with anti-tumor activities of RBG and ERBG suggested that 3-ERBG, as a major metabolite of RBG in rats, was perhaps also a bioactive form of RBG in vivo.