68661-11-0Relevant academic research and scientific papers
Ru-Catalyzed Regioselective CH-Hydroarylation of Alkynes with Benzylthioethers Using Sulfur as Directing Group
Villuendas, Pedro,Urriolabeitia, Esteban P.
supporting information, p. 3178 - 3181 (2015/06/30)
Benzylthioethers react with internal alkynes in the presence of catalytic amounts of [Ru(cymene)Cl2]2 to give the corresponding ortho-alkenylated species, using sulfur as the sole directing group. The reaction is regiospecific, tolerates different substituents at both the sulfur and the aryl ring, and proceeds very efficiently with a large variety of electron-rich alkynes.
Palladium-catalyzed C-H alkenylation of arenes using thioethers as directing groups
Yu, Ming,Xie, Yongju,Xie, Chunsong,Zhang, Yuhong
supporting information; experimental part, p. 2164 - 2167 (2012/07/16)
Thioethers have been proven to be reliable directing groups for palladium catalyzed alkenylation of arenes via C-H activation. Mechanistic investigation reveals that the C-H cleavage of arenes is the turnover-limiting step, and an acetate-bridged dinuclear cyclopalladation intermediate is involved. The alkenylated thioethers can be easily removed and transformed into a variety of useful groups.
Thioethers as directing group for the palladium-catalyzed direct arylation of arenes
Yao, Jinzhong,Yu, Ming,Zhang, Yuhong
supporting information, p. 3205 - 3210 (2013/01/15)
Thioethers have proven to be efficient directing groups for the arylation of arenes under palladium catalysis. The thioether group can be readily removed or converted to other functional groups. Kinetic isotopic effect studies reveal that the C-H cleavage of arenes might be the turnover-limiting step. Copyright
Single-crystal proton ENDOR studies of the [Fe4S4]3+ cluster: Determination of the spin population distribution and proposal of a model to interpret the1H NMR paramagnetic shifts in high-potential ferredoxins
Mouesca,Rius,Lamotte
, p. 4714 - 4731 (2007/10/02)
Proton ENDOR spectroscopy has been used in single crystals of the synthetic compound [N(C2D5)2[Fe4S4-(SCH 2C6D5)4], which is a good biomimetic model of the active sites of many four-iron-four-sulfur proteins. The eight protons of the four thiolate CH2 groups have been used in order to probe in detail the distribution of the unpaired electron spin population in a paramagnetic [Fe4S4]3+ center created by gamma irradiation in the crystals. The thus obtained hyperfine tensors of the eight protons constitute an original, abundant, and precise source of information on this oxidation state. They have been analyzed in two separate parts. From their anisotropic parts, it is possible to deduce the distribution of the unpaired spin population on the different iron and sulfur atoms with the help of a point-dipole model. Within the limitations of the simple and symmetric vectorial spin coupling model which involves two equivalent mixed-valence iron atoms and two equivalent ferric iron atoms, we find that this paramagnetic center is close to the |7/2,3,1/2) state, the first number representing the spin state of the mixed-valence pair, the second one the spin state of the ferric pair, and the last one the resulting spin of the cluster. This attribution is in contrast with recent proposals considering that the [Fe4S4]3+ spin state is |9/2,4,1/2). Finally, the analysis of the isotropic parts of the tensors leads us to propose a new quantitative model establishing the law existing between these isotropic couplings and two different parameters: a magnetic parameter which is the spin population on the adjacent iron and an angular parameter defining the orientation of each CH bond. This model seems indeed able to provide the basis of a quantitative interpretation of 1H paramagnetic shifts in the NMR spectra of high-potential proteins in their oxidized state. Through the variety of results obtained, the interest of the present study is also that it gives the capacity to unify the interpretations of results concerning the [Fe4S4]3+ state in the proteins and in model compounds which have been derived from the EPR, ENDOR, M?ssbauer, and NMR spectroscopies.
Micellar Systems as ''Supercages'' for Reactions of Geminate Radical Pairs. Magnetic Effects
Turro, Nicholas J.,Weed, Gregory C.
, p. 1861 - 1868 (2007/10/02)
The photochemistry of dibenzyl ketone (DBK) and other molecules capable of producing benzyl radicals and substituted benzyl radicals has been investigated in micellar systems.The cage effect (percent of unscavengeable radical pairs produced by photolysis) was measured under a variety of conditions, and the results are compared with those obtained in homogeneous organic solvents.For example, parameters such as mean occupancy of ketone, detergent type and concentration, O2 concentration, additives, temperature, applied magnetic field, and pressure have been varied and investigated as to their influence on the magnitude of cage effect.In addition to modifying its environment, structural modification of the DBK by incorporation of 2H and 13C isotopes, hydrophobic groups, and heavy atoms was performed to investigate the impact of these variations on the cage effect in micellar systems.Isotopic substitution of 2H or 13C leads to results on both the quantum yields for reactions and on the percent cage that were consistent with expectations of magnetic isotope effects.Hydrophobic groups substituted in the 4-position of DBK were found to cause a substantial increase in the cage effect and yet retain the magnetic-field-dependent character found in the parent DBK.Incorporation of Br in the 4-position of DBK was found to enhance the cage effect but at the same time cause the cage effect to become magnetic field independent.Substitution of α-naphthyl for phenyl in DBK also produced magnetic-field-independent behavior, in addition to a dramatic decrease in the efficiency of photolysis.
