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121.
Lukas Fritz Dr. Sebastian Wienhold Sabrina Hackl Prof. Dr. Thorsten Bach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(3):e202104064
A synthetic route to the pulvomycin class of natural products is presented, which culminated in the first synthesis of a pulvomycin, pulvomycin D. Key elements of the strategy include a pivotal aldol reaction which led to bond formation between the C24-C40 and the C8-C23 fragment. The remaining C1-C7 fragment was attached by a Yamaguchi esterification completing the assembly of the 40 carbon atoms within the main skeleton. Ring closure to the 22-membered lactone ring was achieved in the final stages of the synthesis by a Heck reaction. The completion of the synthesis required the removal of six silyl protecting groups in combination with olefin formation at C26-C27 by a Peterson elimination. 相似文献
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A two-component reaction–diffusion system is considered. The question of stabilizing to zero one of the components of the solution via an internal control acting on a small subdomain and preserving nonnegativity of both components is investigated. Our results apply to predator–prey systems. 相似文献
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YbSi2 and the derivatives YbTxSi2–x (T = Cr, Fe, Co) crystallizing in the α‐ThSi2 structure type were obtained as single crystals from reactions run in liquid indium. All silicides were investigated by single‐crystal X‐ray diffraction, I41/amd space group and the lattice constants are: a = 3.9868(6) Å and c = 13.541(3) Å for YbSi2, a = 4.0123(6) Å and c = 13.542(3) Å for YbCr0.27Si1.73, a = 4.0142(6) Å and c = 13.830(3) Å for YbCr0.71Si1.29, a = 4.0080(6) Å and c = 13.751(3) Å for YbFe0.34Si1.66, and a = 4.0036(6) Å, c = 13.707(3) Å for YbCo0.21Si1.79. YbSi2 and YbTxSi2–x compounds are polar intermetallics with three‐dimensional Si and M (T+Si) polyanion sub‐networks, respectively, filled with ytterbium atoms. The degree of substitution of transition metal at the silicon site is signficant and leads to changes in the average bond lengths and bond angles substantially. 相似文献
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Dependence of electrical performance on structural organization in polymer field effect transistors 下载免费PDF全文
Emily G. Bittle Hyun Wook Ro Chad R. Snyder Sebastian Engmann R. Joseph Kline Xinran Zhang Oana D. Jurchescu Dean M. DeLongchamp David J. Gundlach 《Journal of Polymer Science.Polymer Physics》2017,55(14):1063-1074
Organic semiconductors (OSCs) are strong contenders for use in printed, flexible electronics. Although organic electronic materials have been studied for many years, the physics of charge transport is still under investigation. This is in part due to variability resulting from the large variety of molecules that can be synthesized and inconsistency in electrical characterization due to device and processing conditions. Molecular ordering in OSCs is known to alter the charge transport characteristics and attention to long range and short range ordering provides clues as to the nature of transport pathways. Here, we study ordered regioregular poly(3‐hexylthiophene‐2,5‐diyl) films carefully prepared to obtain a set of three samples with incrementally increasing order on identical transistor architectures. Ordering was characterized using a variety of short and long range techniques to probe the coherence and number of crystallites formed during processing, and the correlation between these different measures of order are quantified. We observe three changes in transistor behavior that show a shift from non‐ideal to more textbook‐like characteristics with increasing order: reduction of the contact resistance, shift to field‐independent mobility, and a shift from a diode‐like (S‐shaped) to linear response at low lateral fields. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1063–1074 相似文献
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