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991.
Yu-Huan Geng Dr. Yuan-Zhao Hua Dr. Shi-Kun Jia Prof. Dr. Min-Can Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5130-5135
The first regio-, diastereo-, and enantioselective direct Mannich reaction of β,γ,-unsaturated ketones with benzoxazinone cyclic imines was enabled by Lewis acid/Brønsted base cooperative catalysis. The dinuclear zinc complex catalyzed the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, leading to corresponding adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–99 % ee range. These products were used as general intermediates in the synthesis of multisubstituted cyclocanalines, tetrahydro pyridazinones, and 4H-furo[2,3-b][1,4]benzoxazine derivatives. 相似文献
992.
以二(苯腈)-二氯化钯为催化剂,在固液相转移条件下,通过芳卤与N,N-二乙基丙烯酰胺发生偶联反应,生成了E式α,β-不饱和酰胺。碘代芳烃的偶联产率较高,从而建立了简便的2E-不饱和酰胺立体选择合成法。 相似文献
993.
The products of base-catalyzed oxidation of secondary aromatic amines were identified by the GC-MS and EPR techniques as nitroxyls, quinone nitrones, quinone imines, and for diarylamines also as the products of C-N bond cleavage-substituted nitrobenzenes, anilines and phenols. It was shown that nitroxyl radicals are the primary paramagnetic products of the reaction and do not form by the interaction of aminyl radicals with dioxygen. A mechanism of the amide ion oxidation through the nonradical addition of dioxygen to the amide ion at the rate-limiting stage is suggested and discussed.The previous report see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1746–1751, October, 1994. 相似文献
994.
The identification of the sex pheromone of the elm spanworm Ennomos subsignaria (Hübner), as the chiral alkenyl epoxide (6Z)-cis-9,10-epoxy-nonadecene has been accomplished. Both enantiomers of (6Z)-cis-9,10-epoxy-nonadecene have been synthesized via two routes. The key steps in the first route were to prepare both threo-epoxy tosylates and then to perform an alkylative rearrangement of these intermediates to obtain the target molecules. An alternative enantioenriched synthesis that took advantage of the Sharpless dihydroxylation reaction was developed so that a common starting material could be used to access both enantiomers. A field study and GC/EAD testing indicated that Z6-cis-9S,10R-epoxy-nonadecene was the sex pheromone of the elm spanworm E. subsignaria (Hübner). 相似文献
995.
Kuniaki Tatsuta Sonoko TokishitaTomohiro Fukuda Takaaki KanoTadaaki Komiya Seijiro Hosokawa 《Tetrahedron letters》2011,52(9):983-986
K1115 B1, isolated from the broth of Streptomyces species, was found to be a mixture of stereoisomers. Authors synthesized all stereoisomers of K1115 B1 by convergent synthesis coupling a rhamnose derivative, an isobenzofuranone, and a chiral tetraol. Comparison of 1H NMR spectra and optical rotations made it clear that the absolute structures of K1115 B1α (the major isomer) and K1115 B1β (the minor isomer) were (1R, 17S)- and (1R, 17R)-configurations, respectively. The optical rotations of the stereoisomers revealed that alnumycin, reported as the identical structure with K1115 B1, might be another mixture of stereoisomers. 相似文献
996.
Sebastian T. Le QuementMette Ishoey Mette T. PetersenPernille M. Simonsen Nanna S. HolckThomas E. Nielsen 《Tetrahedron letters》2011,52(52):7049-7053
An approach for the solid-phase synthesis of apoptosis-inducing Smac peptidomimetics is presented. Using a Rink linker strategy, tetrapeptides mimicking the N-4-terminal residue of the Smac protein [(N-Me)AVPF sequence] were synthesized on PEGA resin in excellent purities and yields. Following two synthetic routes, a known tetrapeptide, incorporating a substituted proline, previously shown to exhibit excellent biological activity in vitro as well as low toxicity, was synthesized effectively on a solid support. 相似文献
997.
Murtaza Hasan Ihsan Ullah Hina Zulfiqar Komal Naeem Arfa Iqbal Huma Gul Muhammad Ashfaq Nasir Mahmood 《Materials Today Chemistry》2018
Synthesis of nanomaterials is being gained extensive attention in the fields of chemistry, applied physics, catalysis, drug delivery and the most important in diagnosis and therapeutic applications. Recently, many reports have been published on physical and chemical synthesis of magnetic as well as metallic nanoparticles (NPs) with viable surface functionalization, but still there is a dire need of such strategies that can combine synthetic methodology with stable surface modification found in nature. Synthesis of NPs via biological methods is the possible way to solve these barriers. However, systematized summary and outlooks of NPs synthesis via biological entities with various influencing factors e.g. temperature, pH, concentration of reactants and reaction time has rarely been reported. This review will present the distinct advantages of biological synthesis of NPs over physical and chemical methods. It will also highlight the recent progress on synthesis of NPs via various biological systems i.e. plant, fungus, bacteria, and yeast. Furthermore, it will explain various factors that control the size, shape, and morphology of these NPs. Finally, it would present the future perspectives of green chemistry for the development of nano-science and -biotechnology. 相似文献
998.
直接甲酸燃料电池Pd阳极催化剂及其电催化稳定性 总被引:1,自引:0,他引:1
直接甲酸燃料电池(DFAFC)中Pd阳极催化剂对甲酸氧化具有很好的电催化活性, 但电催化稳定性较差, 因此, 对Pd催化剂电催化活性和稳定性的影响原因和机理的研究已经成为DFAFC阳极催化剂的研究重点, 本文综述了DFAFC中Pd催化剂和Pd基复合催化剂的研究和发展概况. 主要介绍了Pd催化剂的优缺点、稳定性及提高稳定性的方法和机理等, 为Pd催化剂和Pd基复合催化剂的实际应用奠定基础. 相似文献
999.
本文报道了系列二肽链键联的卟啉-蒽醌及其金属配合物的微波合成,化合物的结构分别经UV-Vis,IR,1H NMR及元素分析确证。探讨了化合物分子内电子转移性质(IETP),并讨论了结构对IETP的影响。 相似文献
1000.