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91.
Jingjing Wu Phillip S. Grant Xiabing Li Adam Noble Varinder K. Aggarwal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5753-5757
The use of pyridinium‐activated primary amines as photoactive functional groups for deaminative generation of alkyl radicals under catalyst‐free conditions is described. By taking advantage of the visible light absorptivity of electron donor–acceptor complexes between Katritzky pyridinium salts and either Hantzsch ester or Et3N, photoinduced single‐electron transfer could be initiated in the absence of a photocatalyst. This general reactivity platform has been applied to deaminative alkylation (Giese), allylation, vinylation, alkynylation, thioetherification, and hydrodeamination reactions. The mild conditions are amenable to a diverse range of primary and secondary alkyl pyridiniums and demonstrate broad functional group tolerance. 相似文献
92.
<正>Photoredox catalysis has changed the landscape of modern synthetic organic chemistry by prompting a dramatic increase in research activity into reactions that proceed through free radical intermediates~([1]). Instrumental in this shift in interest from two-electron to single-electron processes was the widespread appreciation of the synthetic utility of pho- 相似文献
93.
94.
Aekta Aggarwal Manas Ranjan Sahoo Abhrojyoti Sen Ganesh Vaidya 《Studies in Applied Mathematics》2020,145(2):247-290
Measure-valued weak solutions for conservation laws with discontinuous flux are proposed and explicit formulae have been derived. We propose convergent discontinuous flux-based numerical schemes for the class of hyperbolic systems that admit nonclassical -shocks, by extending the theory of discontinuous flux for nonlinear conservation laws to scalar transport equation with a discontinuous coefficient. The article also discusses the concentration phenomenon of solutions along the line of discontinuity, for scalar transport equations with a discontinuous coefficient. The existence of the solutions for transport equation is shown using the vanishing viscosity approach and the asymptotic behavior of the solutions is also established. The performance of the numerical schemes for both scalar conservation laws and systems to capture the -shocks effectively is displayed through various numerical experiments. 相似文献
95.
96.
ortho‐Directing Chromium Arene Complexes as Efficient Mediators for Enantiospecific C(sp2)–C(sp3) Cross‐Coupling Reactions 下载免费PDF全文
Dr. Raphael Bigler Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2018,57(4):1082-1086
A new strategy for the coupling of a broad scope of electronically diverse aromatics to boronic esters is reported. The coupling sequence, which relies on the directed ortho‐lithiation of chromium arene complexes followed by boronate formation and oxidation, occurs with complete ortho‐selectivity and enantiospecificity to give the coupling products in excellent yields and with high functional group tolerance. An intermediate chromium arene boronate complex was characterized by X‐ray, NMR, and IR experiments to elucidate the reaction mechanism. 相似文献
97.
P. Hari C. Cheney G. Luepke S. Singh N. Tolk J. S. Sanghera I. D. Aggarwal 《Journal of Non》2000,270(1-3):265-268
In this study we report first measurements of wavelength-selective infrared-induced materials modification of bulk As2S3 and As2Se3. These materials are currently being considered as candidate materials for infrared optical fiber transmission in the range of 1–10 μm. Our study is aimed at modifying oxygen, hydrogen and carbon impurities bound to chalcogenide constituent elements in the materials to reduce absorption. Tunable infrared radiation from the W.M. Keck Free Electron Laser (FEL) at Vanderbilt was used to excite specific vibrational modes, S–O–H and CHx modes in bulk As2S3 and Se–H, CHx and S–H2 modes in bulk As2Se3. Changes in vibrational mode amplitudes are monitored by measuring the intensity of the Fourier transform infrared (FTIR) spectra before and after irradiation at appropriate wavelengths. By tuning wavelengths to hydrogen vibrational modes, we find evidence that hydrogen is released and/or redistributed athermally. In particular, following irradiation at specific resonant wavelengths, vibrational mode amplitudes as monitored by FTIR associated with CHx are significantly reduced in bulk As2S3 and As2Se3 samples. In As2S3, the changes in CHx modes are reversed by heat treatment at 115°C for 35 min in nitrogen atmosphere. 相似文献
98.
Dr. Jingjing Wu Dr. Chao Shu Zhihang Li Dr. Adam Noble Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309684
Decarboxylative halogenation reactions of alkyl carboxylic acids are highly valuable reactions for the synthesis of structurally diverse alkyl halides. However, many reported protocols rely on stoichiometric strong oxidants or highly electrophilic halogenating agents. Herein, we describe visible-light photoredox-catalyzed decarboxylative halogenation reactions of N-hydroxyphthalimide-activated carboxylic acids that avoid stoichiometric oxidants and use inexpensive inorganic halide salts as the halogenating agents. Bromination with lithium bromide proceeds under simple, transition-metal-free conditions using an organic photoredox catalyst and no other additives, whereas dual photoredox-copper catalysis is required for chlorination with lithium chloride. The mild conditions display excellent functional-group tolerance, which is demonstrated through the transformation of a diverse range of structurally complex carboxylic acid containing natural products into the corresponding alkyl bromides and chlorides. In addition, we show the generality of the dual photoredox-copper-catalyzed decarboxylative functionalization with inorganic salts by extension to thiocyanation with potassium thiocyanide, which was applied to the synthesis of complex alkyl thiocyanates. 相似文献
99.
Dr. Trapti Aggarwal Kenshiro Hada Yusuke Murata Dr. Yuji Sumii Kazuhiro Tanagawa Kiyoteru Niina Soichiro Mori Dr. Jorge Escorihuela Prof. Dr. Norio Shibata 《Angewandte Chemie (International ed. in English)》2023,62(33):e202307090
Alkyne hydroamination is an effective approach for the production of enamines and enamine-containing N-heterocycles. However, stereoselectivity control is a considerable challenge in this reaction because of the electronic repulsion between an incoming nitrogen lone pair and the alkyne π-system. Herein, we propose a methodology involving β-regio- and Z-selective alkyne hydroamination by using tetrafluoro-λ6-sulfanyl (SF4) alkynes under superbasic, naked anion conditions. The reaction is compatible with a wide variety of N-heterocycles, including indoles, carbazoles, pyrazoles, and imidazoles, and selectively furnishes SF4-linked Z-vinyl enamines with β-regioselectively. Moreover, the method can be extended to the β- and Z-controlled, base-mediated alkyne hydrophenoxylation with phenols to provide SF4-linked Z-vinyl ethers in high yields. As the SF4 unit has attracted attention as a bioisostere for alkynes, p-benzenes, bicyclo[1.1.1]pentyl (BCP) groups, and cubanes in medicinal chemistry, this chemistry represents an effective approach to creating novel drug candidates incorporating SF4-containing molecules. 相似文献
100.
N.L. Misra Sangita Dhara V.C. Adya S.V. Godbole K.D. Singh Mudher S.K. Aggarwal 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry for the determination of trace metals at concentration of µg/g level in thorium oxide was studied. The TXRF spectrometer was calibrated using a multielement standard solution and the method was validated by analyzing another multielement standard solution. Sample preparation conditions were optimized for the TXRF determinations of trace metals in thorium oxide. The elements K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Ba and Pb present in thorium oxide standards were determined after dissolving them in HNO3/HF mixture and separating the bulk matrix, thorium, by solvent extraction using tri-n-butyl phosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) as extractants. A comparison of TXRF determined concentrations of trace elements Ca, V, Cr, Mn, Fe, Ni and Cu with the certified values shows that TXRF determined concentrations have an RSD of 20% (1 s for n = 4) and are within an agreement of 20% of the certified values in most of the cases. 相似文献