64071-73-4Relevant academic research and scientific papers
Bifunctional Iminophosphorane-Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α,β-Unsaturated Amides
Dixon, Darren J.,Formica, Michele,Hamlin, Trevor A.,Rozsar, Daniel,Yamazaki, Ken
supporting information, p. 1006 - 1015 (2022/02/03)
The first metal-free catalytic intermolecular enantioselective Michael addition to unactivated α,β-unsaturated amides is described. Consistently high enantiomeric excesses and yields were obtained over a wide range of alkyl thiol pronucleophiles and elect
Coenzyme F430 from Methanogenic Bacteria: Mechanistic Studies on the Reductive Cleavage of Sulfonium Ions Catalyzed by F430 Pentamethyl Ester
Lin, Shu-Kun,Jaun, Bernhard
, p. 1478 - 1490 (2007/10/02)
Mechanistic questions regarding the reductive cleavage of sulfonium ions by the NiI form of coenzyme F430 pentamethylester (F430M) were adressed in a series of kinetic studies and isotope labeling experiments.In neat DMF, methane formation from Dialkyl(methyl)sulfonium ions consistently showed a delay time of ca. 1 h.In the presence of excess propanethiol, no delay was observed and methane formation followed pseudo-first-order kinetics with a logarithmic dependence of the initial rate on the concentration of propanethiol.From the temperature dependence of the reaction rate, an estimate for the activation parameters ΔH(excit.) = 49 kJ mol-1 and (apparent) ΔS(excit.) = -114 J K-1 mol-1 was derived.The observation of deuterium incorporation into methane from (CH3)2CHOD, but not from (CH3)2CDOH, indicates that the fourth H-entity is introduced into CH4 as a proton, and that free CH3 radicals are not involved.In contrast to the reaction with the homogeneous one-electron reductant sodium naphthalide, the F430M-catalyzed reduction of mixed dialkyl(methyl)sulfonium ions showed a pronounced selectivity for the cleavage of Me-S over that of alkyl-S (alkyl Me) bonds.Mechanisms that are consistent with these results, as well as possible explanations for the time delay and the apparent highly negative entropy of activation, are discussed.
Thermoneutral Isotope Exchange Reactions of Cations in the Gas Phase
Ausloos, P.,Lias, S. G.
, p. 3641 - 3647 (2007/10/02)
Rate constants have been measured for reactions of the type AD2+ + MH --> MD + ADH+, where AD2+ is CD3CND+, CD3CDOD+, (CD3COCD3)D+, or (C2D5)2OD+ and the MH molecules are alcohols, acids, mercaptanes, H2S, AsH3, PH3, or aromatic molecules.Rate constants are also presented for the reactions ArHD+ + D2O --> ArDD+ + HDO, where ArHD+ is a deuteronated aromatic molecule and ArDD+ is the same species with a D atom incorporated on the ring.In all but two cases, the competing deuteron transfer is sufficiently endothermic that it cannot be observed under the conditions of the ICR experiments at 320 - 420 K.The efficiencies of the isotope exchange reactions are interpreted in terms of estimated potential surface cross sections for the reactions AD2+ + MH --> 2+*MH> --> +> --> +*MD> --> ADH+ + MD.When the formation of the +> complex is estimated to be thermoneutral or slightly endothermic, the isotope exchange process is inefficient (probability of a reactive collision 2+*MH> --> +> is exothermic.For most of the systems, trends in reaction efficiency appear to be related to factors such as dipole moments of reactant species (or for aromatic compounds, the electron-donating or -withdrawing properties of ring substituents) which influence the relative orientation of the two reactant species in the complex.
