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191.
192.
Beatrice Bartolomei Giuseppe Gentile Dr. Cristian Rosso Dr. Giacomo Filippini Prof. Maurizio Prato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16062-16070
Phenols ( I ) are extremely relevant chemical functionalities in natural, synthetic and industrial chemistry. Their corresponding electron-rich anions, namely phenolates ( I ), are characterized by interesting physicochemical properties that can be drastically altered upon light excitation. Specifically, phenolates ( I ) become strong reducing agents in the excited state and are able to generate reactive radicals from suitable precursors via single-electron transfer processes. Thus, these species can photochemically trigger strategic bond-forming reactions, including their direct aromatic C−H functionalization. Moreover, substituted phenolate anions can act as photocatalysts to enable synthetically useful organic transformations. An alternative mechanistic manifold is represented by the ability of phenolate derivatives I to form ground state electron donor-acceptor (EDA) complexes with electron-poor radical sources. These complementary scenarios have paved the way for the development of a wide range of relevant organic reactions. In this Minireview, we present the main examples of this research field, and give insight on emerging trends in phenols photocatalysis towards richer organic synthesis. 相似文献
193.
Dr. Maren A. Chilleck Larissa Hartenstein Prof. Dr. Thomas Braun Prof. Dr. Peter W. Roesky Dr. Beatrice Braun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2594-2602
The cationic zinc triple‐decker complex [Zn2Cp*3]+[BArF4]? (BArF4=B(3,5‐(CF3)2C6H3)4) exhibits catalytic activity in intra‐ and intermolecular hydroamination reactions in the absence of a cocatalyst. These hydroaminations presumably proceed through the activation of the C?C multiple bond of the alkene or alkyne by a highly electrophilic zinc species, which is formed upon elimination of the Cp* ligands. The reaction of [Zn2Cp*3]+[BArF4]? with phenylacetylene gives the hydrocarbonation product (Cp*)(Ph)CCH2, which might be formed via a similar reaction pathway. Additionally, several other structurally well‐defined cationic zinc organyls have been examined as precatalysts for intermolecular hydroamination reactions without the addition of a cocatalyst. These studies reveal that the highest activity is achieved in the absence of any donor ligands. The neutral complex [ZnCp2S2] (Cp2S=C5Me4(CH2)2SMe) shows a remarkably high catalytic activity in the presence of a Brønsted acid. 相似文献
194.
195.
T. Ludlam R. Slansky J. Slaughter F.T. Dao J. Lach E. Malamud J. Schivell R. Poster R. Engelmann T. Kafka M. Pratap 《Physics letters. [Part B]》1974,48(5):449-452
The event-to-event fluctuations of the rapidity distributions are analyzed for semi-inclusive data obtained from 205 GeV/c and 303 GeV/c proton-proton collisions observed at NAL. The results indicate the presence of clustering effects, with cluster sizes approximating those observed in the quasi-elastic events. The average cluster size appears to be independent of the multiplicity of the final state. 相似文献
196.
M. Kopcewicz H. Engelmann S. Stenger G. V. Smirnov U. Gonser H. -G. Wagner 《Applied Physics A: Materials Science & Processing》1987,44(2):131-134
The effect of fast magnetization reversal induced by external radio frequency (rf) fields has been studied in FeBO3 using the Mössbauer technique. The rf collapse and sideband effects were investigated as a function of intensity for two rf field frequencies: 62 and 36 MHz. The switching times estimated for magnetization reversal are of the same order of magnitude as in amorphous metals and Fe-Ni alloys. Because of the relatively short switching times the magnetization reversal must be of rotational character. 相似文献
197.
Mössbauer spectroscopy of cobalt-silicides proved the existence of three stoichiometric phases: CoSi2, CoSi and Co2Si. The values of the hyperfine parameters indicated covalent bonds between Co and Si in all phases and could be understood on the basis of their crystallographic structure and of theoretical predictions for the electronic structure. For CoSi2, anomalous spectra were obtained, the origin of which was not clear. The different spectra of the cobalt-silicides permit the prospective use of Mössbauer spectroscopy for the study of formation and structure of Co/silicide/silicon interfaces. 相似文献
198.
199.
Santagada V Frecentese F Perissutti E Fiorino F Severino B Cirillo D Terracciano S Caliendo G 《Journal of combinatorial chemistry》2005,7(4):618-621
An easy and convenient microwave-assisted synthesis of N-alkylated glycine methyl esters is described. Parallel and nonparallel combinatorial methods are described and compared. The described reactions are reductive alkylations of several aldehydes and glycine methyl ester in the presence of NaBH3CN. Good yields and short reaction times are the main aspects of these procedures. 相似文献
200.
Cordero-Vargas A Perez-Martin I Quiclet-Sire B Zard SZ 《Organic & biomolecular chemistry》2004,2(20):3018-3025
A simple, highly efficient and cheap synthesis of substituted naphthalenes is reported. These aromatic compounds can be easily prepared in acidic or basic conditions from [small alpha]-tetralones, obtained by a xanthate-mediated addition-cyclisation sequence. 相似文献