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141.
Junhua Tong Liang Zhao Huihui Li Chenglin Wu Xu Han Jiang Wang Hong Liu 《Tetrahedron》2018,74(27):3755-3760
Asymmetric construction of β,β-diaryl substituted glycine bearing two contiguous chiral centers remains a significant challenge. Herein, the application of the para-quinone methides (p-QMs) and Ni(II)- complex of glycine via 1,6-conjugate addition to achieve asymmetric synthesis of β,β-diaryl substituted glycine has been explored successfully. This protocol features operational simplicity, high diastereoselectivity, and recyclable chiral ligand, which provides a versatile approach to the synthesis of highly enantiopure β,β-diaryl substituted glycine. 相似文献
142.
Silver gives a colour reaction with cadion 2B in the presence of the non-ionic surfactant Triton X-100, and the suppression of the colour by competitive complexation of the silver can be used for the spectrophotometric determination of cyanide. Cyanide in waste water can be separated by distillation from other ions that also interfere, and then determined. 相似文献
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For given graphs , , the -color Ramsey number, denoted by , is the smallest integer such that if we arbitrarily color the edges of a complete graph of order with colors, then it always contains a monochromatic copy of colored with , for some . Let be a cycle of length and a star of order . In this paper, firstly we give a general upper bound of . In particular, for the 3-color case, we have and this bound is tight in some sense. Furthermore, we prove that for all and , and if is a prime power, then the equality holds. 相似文献
146.
During the past few years, the construction of fluorescent supramolecular metallocycles has attracted extensive attention due to their diverse applications such as sensing, photoelectric devices, and mimicking complicated natural photo-processes. In this review, we will discuss how we entered the field of fluorescent supramolecular metallacycles and what we investigated in this field. The preparation of various fluorescent supramolecular metallacycles and their applications in monitoring the dynamics of coordination-driven self-assembly, sensing, catalysts, and supramolecular gels will be summarized. 相似文献
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148.
Transition-metal-catalyzed direct C–H bond amination is an attractive strategy in preparation of nitrogen containing molecules which are common in naturally occurring and pharmaceutically important compounds. Comparing to the precious metals commonly used in this reaction, non-precious metals such as iron are abundant in earth, relatively low toxic, and more biocompatible, which meet the increasing demand for environmentally benign and sustainable chemical processes. In this review, we described the development in iron catalyzed C–H bond amination reactions from historical landmarks to recent achievements, and placed emphasis on their applications in organic synthesis, i.e. natural product synthesis and/or modification. 相似文献
149.
In this study, we established a multiphysics coupling model of magnetic fluid hyperthermia (MFH), using complex magnetic permeability to solve the magnetic losses of magnetic nanoparticles (MNPs). The experiments were performed to verify the validity of numerical coupling method. The optimal treatment time (OTT) was regarded as the time required for the lowest temperature point of the tumor to attain the damage criteria. The OTT increased by about 42 s as the tumor radius increased by 1 cm, and decreased by 10 s for the increase in MNP dose per gram of tumor by 1 mg. To achieve cost-effective therapies under moderate treatment conditions, the preferable ranges of external magnetic field intensity H0 and frequency f, MNP radius R and volume fraction are 3–11 kA/m, 200–500 kHz, 8–10 nm, and 5%–10%, respectively. It is greatly encouraged to adopt the combination of higher H0 (8–11 kA/m) and lower f (200–300 kHz), and the conjunction of higher R and . There was a slight thermal damage to normal tissues due to eddy current loss. In conclusion, MFH can provide an excellent therapeutic effect for deep tumors. 相似文献
150.
Xiaotang Gan Zuqi Fu Lixin Liu Yani Yan Chao Chen Yongbo Zhou Jianyu Dong 《Tetrahedron letters》2019,60(32):150906
A metal-free and two-phase protocol for the Meyer-Schuster isomerization of propargyl alcohols to the corresponding α,β-unsaturated carbonyl compounds has been achieved in the presence of stoichiometric phosphorous acid aqueous solution, which produces the desired products in high yields with excellent stereoselectivity. Compared with the traditional methods, the procedure features broad scope of the substrates, mild conditions, and easy separation, providing an appealing alternative to the Meyer-Schuster reaction. 相似文献