Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain...Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain modified glycals in one step through palladium catalysis was reported for the first time,and the modified glycals contained stereodefined tetrasubstituted olefins.Using this method,various difunctionalized glycals that were difficult to form by other routes were synthesized in moderate to good yields.Control experiments and density functional theory calculations show that the palladium catalyst played dual roles in this transformation,namely,inducing nucleophilic substitution and catalyzing Suzuki coupling.The reaction intermediate was isolated and confirmed by X-ray crystallographic analysis.Furthermore,the gram-scale synthesis and facile deprotection of the target compound enhances the practicality of this strategy.展开更多
Hot stamping has been widely used in car industry to produce safety components. Most existing re- searches focused on the stamping and quenching process, but less on the mechanical properties of stamped parts. The fra...Hot stamping has been widely used in car industry to produce safety components. Most existing re- searches focused on the stamping and quenching process, but less on the mechanical properties of stamped parts. The fracture behaviors of hot stamped boron steel B1500HS have been studied, and other four commonly used sheet metals with different strengths, including Q235, TRIP780, QP980 and MS1300, were also introduced for comparison. Both uniaxial tests and mechanical trimming tests were performed, and the fracture surfaces under different stress states were observed and discussed. The SEM observations showed that the fracture models are closely related to the stress states, i. e., the tensile surfaces have ductile rupture characters while the trimming surfaces have brittle rupture characters. Compared with other steels, the quenched boron steel has smaller dimple size accompa- nied by shear planes in the tensile surface, and has smaller burnish zone in the trimming surface, and its cutting surface with ＇S＇ like shape is also very different with others. Furthermore, two fitted em pirical models were derived to describe the quantitative correlations between the average dimple diam- eter and the steel strength and between the percentage of burnish zone and the steel strength.展开更多
基金We thank the National Natural Science Foundation of China(NSF 22171114 and 21772075)for its financial support.
文摘Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain modified glycals in one step through palladium catalysis was reported for the first time,and the modified glycals contained stereodefined tetrasubstituted olefins.Using this method,various difunctionalized glycals that were difficult to form by other routes were synthesized in moderate to good yields.Control experiments and density functional theory calculations show that the palladium catalyst played dual roles in this transformation,namely,inducing nucleophilic substitution and catalyzing Suzuki coupling.The reaction intermediate was isolated and confirmed by X-ray crystallographic analysis.Furthermore,the gram-scale synthesis and facile deprotection of the target compound enhances the practicality of this strategy.
基金National Natural Science Foundation of China(Nos.51105247and U1564203)
文摘Hot stamping has been widely used in car industry to produce safety components. Most existing re- searches focused on the stamping and quenching process, but less on the mechanical properties of stamped parts. The fracture behaviors of hot stamped boron steel B1500HS have been studied, and other four commonly used sheet metals with different strengths, including Q235, TRIP780, QP980 and MS1300, were also introduced for comparison. Both uniaxial tests and mechanical trimming tests were performed, and the fracture surfaces under different stress states were observed and discussed. The SEM observations showed that the fracture models are closely related to the stress states, i. e., the tensile surfaces have ductile rupture characters while the trimming surfaces have brittle rupture characters. Compared with other steels, the quenched boron steel has smaller dimple size accompa- nied by shear planes in the tensile surface, and has smaller burnish zone in the trimming surface, and its cutting surface with ＇S＇ like shape is also very different with others. Furthermore, two fitted em pirical models were derived to describe the quantitative correlations between the average dimple diam- eter and the steel strength and between the percentage of burnish zone and the steel strength.
