Developing Efficient Transition Metal Catalyzed C-C & C-X Bond Construction

This dissertation mainly contains three parts: 1) The synergistic Pd/enamine catalysis for asymmetric hydrocarbon functionalization of unactivated alkenes with ketones; 2) Gold redox catalysis with a selenium cation as mild oxidant; 3) HFIP promoted disulfidation and diselenation of alkyne, alkene, and allene. Palladium-catalyzed alkene activation has its intrinsic limitation: 1) the requirement of a pre-functionalized alkene to form a Pd π-allyl complex; 2) problematic reversible β-H elimination. It always leads to limited reaction scope and losing of the stereochemical control. Synergistic palladium and enamine catalysis was conducted to promote ketone addition to unactivated olefins. A secondary amine-based organocatalyst was identified as the optimal co-catalyst for the directed Pd-catalyzed alkene activation. Furthermore, asymmetric hydrocarbofunctionalization of unactivated alkenes was also achieved with good to excellent yield and stereoselectivity. Au redox catalysis always requires strong oxidants or delicate ligand design, which largely limites the reaction scope. In this part, we utilized selenide cation as mild oxidant to achieve Au oxidation. Excellent regioselectivity (trans) and good to excellent yields were achieved (up to 98% with 2% catalyst loading) with a wide range of substrates. Mechanistic investigation revealed a gold (I/III) redox process was successfully implemented under mild conditions. Among various factors that can affect reactions, the solvent is the one that can dramatically impact the reaction performance. We accidentally observed Hexafluoro-2-propanol (HFIP), as a unique polar organic solvent that can promote the diselenation and disulfidation of C-C unsaturated bonds successfully. In contrast, other solvents, such as isopropanol and dichloroethane, could not promote the same reaction. This method revealed an example of HFIP promoted transformations under mild conditions, which greatly highlighted the unique reactivity of this special solvent. In sum, the combination of transition metal catalyst and organic catalyst can promote a reaction in a highly efficient process and greatly extend the reaction scope, even providing stereoselectivity successfully. Appling mild oxidant in Au redox catalysis is able to achieve Au (III) and holds promise for generating synthetically valuable building blocks, which also enhance the basic understand of this rapidly growing field. HFIP as a magic solvent exhibits the stability to activate diselenides and disulfides to accomplish addition to C-C unsaturated bonds

Developing Efficient Transition Metal Catalyzed C-C & C-X Bond Construction

This dissertation mainly contains three parts: 1) The synergistic Pd/enamine catalysis for asymmetric hydrocarbon functionalization of unactivated alkenes with ketones; 2) Gold redox catalysis with a selenium cation as mild oxidant; 3) HFIP promoted disulfidation and diselenation of alkyne, alkene, and allene. Palladium-catalyzed alkene activation has its intrinsic limitation: 1) the requirement of a pre-functionalized alkene to form a Pd π-allyl complex; 2) problematic reversible β-H elimination. It always leads to limited reaction scope and losing of the stereochemical control. Synergistic palladium and enamine catalysis was conducted to promote ketone addition to unactivated olefins. A secondary amine-based organocatalyst was identified as the optimal co-catalyst for the directed Pd-catalyzed alkene activation. Furthermore, asymmetric hydrocarbofunctionalization of unactivated alkenes was also achieved with good to excellent yield and stereoselectivity. Au redox catalysis always requires strong oxidants or delicate ligand design, which largely limites the reaction scope. In this part, we utilized selenide cation as mild oxidant to achieve Au oxidation. Excellent regioselectivity (trans) and good to excellent yields were achieved (up to 98% with 2% catalyst loading) with a wide range of substrates. Mechanistic investigation revealed a gold (I/III) redox process was successfully implemented under mild conditions. Among various factors that can affect reactions, the solvent is the one that can dramatically impact the reaction performance. We accidentally observed Hexafluoro-2-propanol (HFIP), as a unique polar organic solvent that can promote the diselenation and disulfidation of C-C unsaturated bonds successfully. In contrast, other solvents, such as isopropanol and dichloroethane, could not promote the same reaction. This method revealed an example of HFIP promoted transformations under mild conditions, which greatly highlighted the unique reactivity of this special solvent. In sum, the combination of transition metal catalyst and organic catalyst can promote a reaction in a highly efficient process and greatly extend the reaction scope, even providing stereoselectivity successfully. Appling mild oxidant in Au redox catalysis is able to achieve Au (III) and holds promise for generating synthetically valuable building blocks, which also enhance the basic understand of this rapidly growing field. HFIP as a magic solvent exhibits the stability to activate diselenides and disulfides to accomplish addition to C-C unsaturated bonds

Gold-Catalyzed Oxidative Coupling of Alkynes toward the Synthesis of Cyclic Conjugated Diynes

Gold-catalyzed oxidative coupling of alkynes was developed as an efficient approach for the synthesis of challenging cyclic conjugated diynes (CCD). Compared with the classic copper-promoted oxidative coupling reaction of alkynes, this gold-catalyzed process exhibited a faster reaction rate due to rapid reductive elimination from the Au(III) intermediate. This unique reactivity thus allowed a challenging diyne macrocyclization to take place with high efficiency. Condition screening revealed an [(n-Bu)4N]+[Cl-Au-Cl]− salt as the optimal pre-catalyst. Macrocycles with ring size between 13 and 28 atoms were prepared in moderate to good yields, which highlighted the broad substrate scope of this new strategy. Furthermore, the synthetic utilities of the CCDs for copper-free click chemistry have been demonstrated, showcasing the potential application of this strategy in biological systems

Synergistic Palladium/enamine Catalysis for Asymmetric Hydrocarbon Functionalization of Unactivated Alkenes with Ketones

Synergistic palladium and enamine catalysis was explored to promote ketone addition to unactivated olefins. A secondary amine-based organocatalyst was identified as the optimal co-catalyst for the directed Pd-catalyzed alkene activation. Furthermore, asymmetric hydrocarbon functionalization of unactivated alkenes was also achieved with good to excellent yield (up to 96% yields) and stereoselectivity (up to 96% ee). This strategy presented an efficient approach to prepare α-branched ketone derivatives under mild conditions

Unsafe Mining Behavior Identification Method Based on an Improved ST-GCN

Aiming to solve the problems of large environmental interference and complex types of personnel behavior that are difficult to identify in the current identification of unsafe behavior in mining areas, an improved spatial temporal graph convolutional network (ST-GCN) for miners’ unsafe behavior identification network in a transportation roadway (NP-AGCN) was proposed. First, the skeleton spatial-temporal map constructed using multi-frame human key points was used for behavior recognition to reduce the interference caused by the complex environment of the coal mine. Second, aiming to solve the problem that the original graph structure cannot learn the association relationship between the non-naturally connected nodes, which leads to the low recognition rate of climbing belts, fighting and other behaviors, the graph structure was reconstructed and the original partitioning strategy was changed to improve the recognition ability of the model for multi-joint interaction behaviors. Finally, in order to alleviate the problem that the graph convolution network has difficulty learning global information due to the small receptive field, multiple self-attention mechanisms were introduced into the graph convolution to improve the recognition ability of the model for unsafe behaviors. In order to verify the detection ability of the model regarding identifying unsafe behaviors of personnel in a coal mine belt area, our model was tested on the public datasets NTU-RGB + D and the self-built datasets of unsafe behaviors in a coal mine belt area. The recognition accuracies of the proposed model in the above datasets were 94.7% and 94.1%, respectively, which were 6.4% and 7.4% higher than the original model, which verified that the proposed model had excellent recognition accuracies

Geraniol: A Potential Defense-Related Volatile in “Baiye No. 1” Induced by <i>Colletotrichum camelliae</i>

Plants produce and emit a large variety of volatiles that have multiple defense-related functions in response to abiotic or biotic stresses. In comparison with studies on plant volatile–herbivore interactions, little research has been carried out on plant volatile–microbe interactions. In the present paper, tea volatile–Colletotrichum camelliae interactions were studied. The results of emitted volatiles following infection with C. camelliae in “Baiye No. 1” showed that healthy tea plants contained 68 kinds of volatiles, while infected tea plants contained 76 kinds of volatiles. Five volatiles, namely, geraniol, linalool, methyl salicylate, (E)-3-hexen-1-ol, and α-farnesene, were found to have a relatively large content variation in infected tea plants, with increments of 7.903%, −2.247%, 2.770%, −6.728%, and 3.848%, respectively. The fungicidal activity results of the five volatiles against C. camelliae showed that geraniol had the best activity, with MIC and MBC values of 0.5 and 1 mg·mL−1, respectively. Thus, geraniol was selected for subsequent studies. The effects of geraniol on the mycelia and cell structures of C. camelliae were investigated by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results showed that the mycelia were significantly disrupted, and the cell structures were damaged. The effects of geraniol on the related enzymes of C. camelliae were assessed. The results showed that cellulase activity increased, malondialdehyde content increased, and the activity of defense enzymes was inhibited, thereby inhibiting the growth of pathogens. This study provides the first evidence that geraniol is a defense-related function volatile of “Baiye No. 1” in response to C. camelliae stress. It also provides valuable information and enriches the chemical ecology of tea plant diseases for the research field on defensive substances of microbe-induced plant volatiles

First Appearance of HIV-1 CRF07_BC and CRF08_BC Outside China.

Neither full length genomic sequence of CRF07_BC nor that of CRF08_BC was found in any other countries since they originated in Yunnan, China, in early 1990s. Here, we first report that CRF07_BC and CRF08_BC appeared among intravenous drug users in Shan state of Myanmar bordering Yunnan, and confirmed that they spread from China to Myanmar. The introduction of CRF07_BC and CRF08_BC in northern Myanmar may forebode a changing subtype epidemic in Southeast Asia

First Appearance of HIV-1 CRF07_BC and CRF08_BC Outside China.

Neither full length genomic sequence of CRF07_BC nor that of CRF08_BC was found in any other countries since they originated in Yunnan, China, in early 1990s. Here, we first report that CRF07_BC and CRF08_BC appeared among intravenous drug users in Shan state of Myanmar bordering Yunnan, and confirmed that they spread from China to Myanmar. The introduction of CRF07_BC and CRF08_BC in northern Myanmar may forebode a changing subtype epidemic in Southeast Asia