Efficient TBHP/R4N+X– promoted hydroaroylations of dialkyl azo-1,2-dicarboxylates with methyl arenes, aldehydes, aryl methanols and arylmethyl chlorides are described. These oxidation/oxygenation and hydroaroylation processes were carried out by tert-butyl hydroperoxide as terminal oxidant/oxygen source, and were catalyzed by tetrabutylammonium bromide and tricaprylmethylammonium chloride as the driving force. During this investigation, all these hydroaroylating sources were found to be highly efficient reagents without the need of any transition-metal. 相似文献
In order to find informations on the native structure of the Leu-Enkephalin opiate peptide, the parent peptide and its two thioamide analogs (Thio-Gly2)Leu-Enkephalin and (Thio-Gly3)Leu-Enkephalin were studied by the theoretical method PEPSEA. This comparative conformational analysis showed that the active conformation is a β turn structure centered on Gly3 and Phe4. Moreover, this study showed also that the more active analog (Thio-Gly2)Leu-Enk has a lower tendency to adopt this structure. Consequently, its high activity can only be explained by its long lifetime due to its resistance to enzymatic hydrolysis, following the substitution of the amide linkage by the thioamide one. The weakly active analog (Thio-Gly3)Leu-Enk does not adopt this structure and prefers instead a β turn structure centered on Gly2 and Gly3. This study also confirmed the importance of the distances between the Tyr and Phe residues at positions 1 and 4, and that of the terminal Tyrosine N-H group which must be free of any intramolecular hydrogen bond in order to be available in the molecular recognition process. 相似文献
This paper provides the humanitarian community with an automated tool that can detect a disaster using tweets posted on Twitter, alongside a portal to identify local and regional Non-Governmental Organisations (NGOs) that are best-positioned to provide support to people adversely affected by a disaster. The proposed disaster detection tool uses a linear Support Vector Classifier (SVC) to detect man-made and natural disasters, and a density-based spatial clustering of applications with noise (DBSCAN) algorithm to accurately estimate a disaster’s geographic location. This paper provides two original contributions. The first is combining the automated disaster detection tool with the prototype portal for NGO identification. This unique combination could help reduce the time taken to raise awareness of the disaster detected, improve the coordination of aid, increase the amount of aid delivered as a percentage of initial donations and improve aid effectiveness. The second contribution is a general framework that categorises the different approaches that can be adopted for disaster detection. Furthermore, this paper uses responses obtained from an on-the-ground survey with NGOs in the disaster-hit region of Uttar Pradesh, India, to provide actionable insights into how the portal can be developed further.
MoO3 can react with the gamma phase of bismuth molybdate (Bi2MoO6) in the conditions of propene oxidation to form the alpha phase (Bi2Mo3O12) resulting in a more selective catalyst for propene oxidation to acrolein. Intimate contact between MoO3 and the gamma phase is an important factor favoring the formation of the alpha phase.
This is the first report of the metal-to-ligand charge-transfer (MLCT) emission spectra of the bis-ethylenediamine- and tetraammine-bipyridineruthenium(II) complexes. The emission maxima occur at 800 and 840 nm, respectively, at 77 K in DMSO/H(2)O glasses. The MLCT excited states of these complexes have short lifetimes (less than 50 ns), and as a consequence, the emission intensities are very small. The energies of the emission maxima are very close to those expected on the basis of the difference in reduction potentials of the metal and ligand (DeltaE(1/2)) and the values of the reorganizational free energies (chi(r)) of the vertical transitions estimated from the electron-transfer self-exchange reactions of the complexes (hnu(max)(em) congruent with FDeltaE(1/2) - chi(r), where F is Faraday's constant). The low energy of the emissions is in large part a consequence of the substantial contributions of the reorganizational free energies. 相似文献