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991.
992.
The PdCl2-catalyzed allylation of heteroarenes is presented. Various heteroarenes including O-, N-, and S-based ones were allylated efficiently with a rich range of allylic acetates in the presence of only 2 mol % of PdCl2, without the need of bases/acids, additives, and external supporting ligands. In addition, the reactions were carried out under mild and simple conditions just by stirring the two reactants and catalyst in CH2Cl2 at 60 °C. Moreover, the by-product produced was non-toxic acetic acid. Thus, the method presented in this work provides a general, clean, and operationally simple approach for the functionalization of heteroarenes. Finally, a preliminary mechanistic study suggested that the Pd(II) may be reduced in situ by the heteroarenes to Pd(0), which serves as the active metal center to catalyze the following allylations of heteroarenes via a Tsuji–Trost pathway. 相似文献
993.
994.
Jin Liu Xianxue Wang Han Guo Xiaokang Shi Xiaoyu Ren Guosheng Huang 《Tetrahedron》2012,68(5):1560-1565
A novel NH4OAc/CuBr(PPh3)3-induced intermolecular Pummerer-type reaction between free (NH)-indoles and dimethylsulfoxide is first reported, which offers the 3-methylthiomethyl substituted indoles conveniently and efficiently. 相似文献
995.
An efficient synthetic method for the pentasubstituted pyrroles was successfully developed via the one-pot domino reactions of arylamines, acetylenedicarboxylates, and 3-phenacylideneoxindoles. The reaction mechanism involved the sequential Michael addition and ring closure of the in situ generated β-active enamino ester. 相似文献
996.
In a satellite optical communication system, the pointing error is an important factor that strongly influences the system performance. For periscope-type satellite optical communication terminals, installation errors of 45° plane mirrors in the coarse point apparatus (CPA) can lead to pointing errors. In this respect, we classify the installation errors of two 45° plane mirrors in the system and derive the corresponding ??transfer?? matrices to describe them. Furthermore, we establish mathematical models of the pointing error caused by installation errors of 45° plane mirrors. These models allow one to calculate and compensate the pointing errors in periscope-type satellite optical communication terminals. The results of our simulations show that the pointing errors vary with the elevation axis angle but do not depend on the azimuth axis angle. Compared to the side-angle error, the slope-angle error brings a larger pointing error. However, the mathematical model we developed allows one to compensate more than 99.9?% of the overall pointing error. The present work provides a theoretical basis for the design of periscope-type satellite optical communication terminals. 相似文献
997.
998.
999.
We introduced an easy approach to realize the Laplacian first-order and second-order differential of the object wave in transverse direction by use of one in-line digital hologram. It can be used for pinpoint the position of the objects. 相似文献