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101.
The in situ synthesis and subsequent reactions of macrocylic imine 2 are reported. The imine was trapped with cyanotrimethylsilane to give α-amino nitrile aza-[13]-macrodiolides in a 1:1 ratio of diastereomers. A crystal structure of the syn α-cyano nitrile diastereomer, 7a, provided insights into the lack of selectivity in reactions of 2 relative to macrocyclic alkene 1. Reactions to functionalize the syn diastereomer 7a are also reported. 相似文献
102.
Eve Kozari Dr. Mark Sigalov Dr. Dina Pines Dr. Benjamin P. Fingerhut Prof. Dr. Ehud Pines 《Chemphyschem》2021,22(8):716-725
Infrared (IR) absorption in the 1000–3700 cm−1 range and 1H NMR spectroscopy reveal the existence of an asymmetric protonated water trimer, H7+O3, in acetonitrile. The core H7+O3 motif persists in larger protonated water clusters in acetonitrile up to at least 8 water molecules. Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations reveal irreversible proton transport promoted by propagating the asymmetric H7+O3 structure in solution. The QM/MM calculations allow for the successful simulation of the measured IR absorption spectra of H7+O3 in the OH stretch region, which reaffirms the assignment of the H7+O3 spectra to a hybrid-complex structure: a protonated water dimer strongly hydrogen-bonded to a third water molecule with the proton exchanging between the two possible shared-proton Zundel-like centers. The H7+O3 structure lends itself to promoting irreversible proton transport in presence of even one additional water molecule. We demonstrate how continuously evolving H7+O3 structures may support proton transport within larger water solvates. 相似文献
103.
In this Letter, we demonstrate that electron spin can influence near-field mediated light propagation through a dense ensemble of subwavelength bimetallic ferromagnetic/nonmagnetic microparticles. In particular, we show that ferromagnetic particles coated with nonmagnetic metal nanolayers exhibit an enhanced magnetic field controlled attenuation of the electromagnetic field propagated through the sample. The mechanism is related to dynamic, electromagnetically induced electron spin accumulation in the nonmagnet. The discovery of an electron spin phenomenon in the light interaction with metallic particles opens the door to the marriage of spintronic and plasmonic technologies and could pave the way for the development of light-based devices that exploit the electron spin state. 相似文献
104.
We report on the dynamics of photodegradation and subsequent recovery of two-photon fluorescence in a dye-doped polymer. The energy dependence suggests that photodegradation is a linear process, while recovery is entropic. Such recovery could be useful to high-intensity devices such as two-photon absorbers, which can be used in many applications. 相似文献
105.
Palladium‐Catalyzed Stereoselective Intramolecular Oxidative Amidation of Alkenes in the Synthesis of 1,3‐ and 1,4‐Amino Alcohols and 1,3‐Diamines 下载免费PDF全文
Prof. Dr. Andrei V. Malkov Dr. Darren S. Lee Dr. Maciej Barłóg Dr. Mark R. J. Elsegood Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4901-4905
An efficient and practical Pd‐catalyzed intramolecular oxidative allylic amidation provides facile access to derivatives of 1,3‐ and 1,4‐amino alcohols and 1,3‐diamines. The method operates under mild reaction conditions (RT) with molecular oxygen (1 atm) as the sole reoxidant of Pd. Excellent diastereoselectivities were attained with substrates bearing a secondary stereogenic center 相似文献
106.
Dr. Xinghai Ning Dr. Wonewoo Seo Dr. Seungjun Lee Dr. Kiyoko Takemiya Dr. Mohammad Rafi Dr. Xuli Feng Dr. Daiana Weiss Dr. Xiaojian Wang Larry Williams Vernon M. Camp Malveaux Eugene Prof. W. Robert Taylor Prof. Mark Goodman Prof. Niren Murthy 《Angewandte Chemie (International ed. in English)》2014,53(51):14096-14101
A positron emission tomography (PET) tracer composed of 18F‐labeled maltohexaose (MH18F) can image bacteria in vivo with a sensitivity and specificity that are orders of magnitude higher than those of fluorodeoxyglucose (18FDG). MH18F can detect early‐stage infections composed of as few as 105 E. coli colony‐forming units (CFUs), and can identify drug resistance in bacteria in vivo. MH18F has the potential to improve the diagnosis of bacterial infections given its unique combination of high specificity and sensitivity for bacteria. 相似文献
107.
Multiwavelength light attenuation measurements have been acquired as part of thermal/optical carbon analysis in the U.S.Chemical Speciation Network(CSN)and the ... 相似文献
108.
There have now been a number of experimental studies on the preparation and elastomeric properties of random bimodal networks of polydimethylsiloxane. The mole per cent of the short chains and their molecular masses covered a wide range, thus resulting in various polydisperse chain-length distributions. The networks were studied with regard to their stress-strain isotherms in elongation, and values of their moduli in the large-deformation (phantom) limit were found to depend on the chain-length distribution. This Important result is in disagreement with phantom network theory, which assumes the elastic modulus is dependent only on the mean value of chain lengths such that the cycle rank of the network is preserved. The effective functionality of the long chains was found to depend on the number of short chains present. Better agreement with experiment was obtained when account was taken of the connectivity of the very short chains, in what is essentially a bimodal distribution of both network chain lengths and cross-link functionalities. Relevant here is the fact that as the degree of chemical cross-linking Increases, the shear modulus G moves away from the affine limit, toward the phantom limit. This increase toward phantom behavior is presumably due to the fact that the mutual interspersion of chains is less when the chains are shorter, even in the small-strain region. 相似文献
109.
Navindra Keerthisinghe Matthew S. Christian Anna A. Berseneva Gregory Morrison Vladislav V. Klepov Mark D. Smith Hans-Conrad zur Loye 《Molecules (Basel, Switzerland)》2022,27(1)
The solvothermal synthesis, structure determination and optical characterization of five new metastable halometallate compounds, [1,10-phenH][Pb3.5I8] (1), [1,10-phenH2][Pb5I12]·(H2O) (2), [1,10-phen][Pb2I4] (3), [1,10-phen]2[Pb5Br10] (4) and [1,10-phenH][SbI4]·(H2O) (5), are reported. The materials exhibit rich structural diversity and exhibit structural dimensionalities that include 1D chains, 2D sheets and 3D frameworks. The optical spectra of these materials are consistent with bandgaps ranging from 2.70 to 3.44 eV. We show that the optical behavior depends on the structural dimensionality of the reported materials, which are potential candidates for semiconductor applications. 相似文献
110.
Robert D. Barrows Mark J. Dresel Thomas J. Emge Paul R. Rablen Spencer Knapp 《Molecules (Basel, Switzerland)》2022,27(1)
The amidation reaction of a tetrahydroisoquinolin-1-one-4-carboxylic acid is a key step in the multi-kilogram-scale preparation of the antimalarial drug SJ733, now in phase 2 clinical trials. In the course of investigating THIQ carboxamidations, we found that propanephosphonic acid anhydride (T3P) is an effective reagent, although the yield and byproducts vary with the nature and quantity of the base. As a control, the T3P reaction of a 3-(2-thienyl) THIQ was performed in the absence of the amine, and the products were characterized: among them are three dimeric allenes and two dimeric lactones. A nucleophile-promoted ketene dimerization process subject to subtle steric and stereoelectronic effects accounts for their formation. Two novel monomeric products, a decarboxylated isoquinolone and a purple, fused aryl ketone, were also isolated, and mechanisms for their formation from the ketene intermediate are proposed. 相似文献