Aliphatic Hydrosilanes via Nickel-Catalyzed Reductive Csp3-Si Coupling of Primary Alkyl Bromides and Chlorohydrosilanes.

The reductive C-Si coupling of chlorosilanes offers efficient access to organosilanes, but its potential for constructing aliphatic ones remains largely unexplored. This manuscript presents a nickel-catalyzed Csp3-Si coupling reaction of unactivated alkyl-Br and R2Si(H)Cl. This work establishes a new approach for synthesizing highly functionalized aliphatic hydrosilanes from readily available chemical feedstocks. The reaction is easily scalable and can accommodate various functional groups, including carboxylic acids, which are usually incompatible with basic conditions.

Nickel-Catalyzed Reductive [4 + 1] Sila-Cycloaddition of 1,3-Dienes with Dichlorosilanes.

Transition-metal-catalyzed sila-cycloaddition has been a promising tool for accessing silacarbocycle derivatives, but the approach has been limited to a selection of well-defined sila-synthons. Herein, we demonstrate the potential of chlorosilanes, which are industrial feedstock chemicals, for this type of reaction under reductive nickel catalysis. This work extends the scope of reductive coupling from carbocycle to silacarbocycle synthesis and from single C-Si bond formation to sila-cycloaddition reactions. The reaction proceeds under mild conditions and shows good substrate scope and functionality tolerance, and it offers new access to silacyclopent-3-enes and spiro silacarbocycles. The optical properties of several spiro dithienosiloles as well as structural variations of the products are demonstrated.

Nickel-Catalyzed Reductive C(sp2 )-Si Coupling of Chlorohydrosilanes via Si-Cl Cleavage.

We report here a new method for the synthesis of organohydrosilanes from phenols and ketones. This method is established through reductive C-Si coupling of chlorohydrosilanes via unconventional Si-Cl cleavage. The reaction offers access to aryl- and alkenylhydrosilanes with a scope that is complementary to those of the established methods. Electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled successfully. Functionalities, including Grignard-sensitive groups (e.g., primary amine, amide, phenol, ketone, ester, and free indole), acid-sensitive groups (e.g., ketal and THP protection), alkyl-Cl, pyridine, furan, thiophene, Ar-Bpin, and Ar-SiMe3 , were tolerated. Gram-scale reaction, incorporation of -Si(H)R2 into complex biologically active molecules, and derivatization of formed organohydrosilanes are demonstrated.

Regiocontrolled Reductive Vinylation of Aliphatic 1,3-Dienes with Vinyl Triflates by Nickel Catalysis.

The regiocontrolled functionalization of 1,3-dienes has become a powerful tool for divergent synthesis, yet it remains a long-standing challenge for aliphatic substrates. Herein, we report a reductive approach for a branch-selective 1,2-hydrovinylation of aliphatic 1,3-dienes with R-X electrophiles, which represents a new selectivity pattern for diene functionalization. Simple butadiene, aromatic 1,3-dienes, and highly conjugated polyene were also tolerated. The combination of Ni(0) and the phosphine-nitrile ligand generally resulted in >20:1 regioselectivity with the retention of the geometry of the C3-C4 double bonds. This reaction proceeds with a broad substrate scope, and it allows for the conjugation of two biologically active units to form more complex polyene molecules, such as tetraene and pentaene as well as heptaene.

Transpedicular screw fixation for thoracolumbar fracture based on finite element analysis / 中国组织工程研究

BACKGROUND: Thoracolumbar fracture is commonly seen in spinal injuries, which causes loss of stability of the spine, as well as spinal cord and nerve compression, even deformity and paralysis. The diagnosis and treatment of thoracolumbar fracture remain controversial.OBJECTIVE: To summarize the mechanism of thoracolumbar fracture based on finite element method, its classification and transpedicular screw fixation.METHODS: The first author retrieved CNKI and PubMed databases for the relevant literature published between January 2000 and December 2016. The keywords were "finite element method, thoracolumbar spine fracture,transpedicular screw fixation" in Chinese and English, respectively.RESULTS AND CONCLUSION: (1) The finite element analysis method can simulate the mechanism of thoracolumbar fracture and provides a reference for the studies on the occurrence, development and treatment of thoracolumbar fracture. (2) The classification of thoracolumbar fracture is beneficial for planning a rational treatment strategy and evaluating prognosis. (3) Compared with the traditional screw fixation, the transpedicular screw fixation holds advantages in biomechanical stability and postoperative correction effect. (4) There are various classifications for thoracolumbar fracture; differences in severity and cartilage injury are difficult to simulate completely. (5) The finite element analysis method shows certain application limitations due to long learning curve and modeling time as well as complicated calculations.

The effect of treatment stages on the coking wastewater hazardous compounds and their toxicity.

This study investigated the change of hazardous materials in coking wastewater at different treatment stages (anaerobic, anaerobic/aerobic, anaerobic/aerobic/photo degradation, anaerobic/aerobic/ozone oxidation treatment) and the effects of them on the development of maize embryos and the activity of amylase and protease in maize seeds. Moreover the interaction of refractory organic matters in the wastewater at different treatment stages with amylase and protease also were determined in vitro. The results show that the biodegradable and the refractory organic compounds in the wastewater both can affect maize embryo development (germination inhibition rate is 19.3% for biodegradable organic compounds). As the treatment stage preceding, the inhibition effect of coking wastewater on the development of the maize embryo (for germination inhibition rates change from 49.3% to 24.6%) and on enzymatic activity (inhibition rates change from 63.9% to 22.4% for amylase) decreases gradually, but the photo-degradation treatment to anaerobic/aerobic effluent can increase its toxicity. The changes in the ability of the refractory organic compounds to bind with enzyme proteins, combined with the analysis of the organic components by GC/MS, show that in the process of coking wastewater treatment no new toxic chemicals were produced.

Responses in the morphology, physiology and biochemistry of Taxus chinensis var. mairei grown under supplementary UV-B radiation.

The effects of supplemental UV-B radiation on Taxus chinensis var. mairei were studied. Leaf traits, gas exchange parameters and the concentrations of photosynthetic pigments, cellular defense system products, secondary metabolites and ultrastructure were determined. UV-B radiation significantly decreased leaf area (p<0.05). Leaf number, secondary branch number, leaf weight per plant and leaf moisture all increased dramatically (p<0.05). Neither the leaf weight nor the specific leaf weight (SLW) exhibited significant differences between ambient and enhanced UV-B radiation. Gas exchange parameters were all dramatically reduced by enhanced UV-B radiation (p<0.05). The contents of chlorophyll and the chlorophyll a/b ratio were not distinctly affected by UV-B radiation, while carotenoids content significantly decreased (p<0.05). Supplemental UV-B treatment induced significant flavonoid accumulation (p<0.05), which was able to protect plant from radiation damage. Meanwhile, the appendage content, abaxial stomatal density, papilla density and particulate matter content in substomatic chambers increased noticeably by supplemental UV-B radiation, whereas the aperture size of single stomata was diminished. The number and area of plastoglobuli were apparently reduced by UV-B radiation, but stroma and grana lamellae were not destroyed. Our results demonstrated that T. chinensis var. mairei can activate several defense mechanisms against oxidative stress injury caused by supplemental UV-B radiation.