Relevant articles and documents
Structure-Reactivity Correlations in the Aminolysis of Ethyl S-Aryl Thiolcarbonates
Castro, Enrique A. Cubillos, Maria Santos, Jose G.
The reactions of secondary alicyclic amines (saa) with ethyl S-4-X-phenyl thiolcarbonates (X = Cl, H, Me, and MeO) are subjected to a kinetic analysis in water, 25.0°C, ionic strength 0.2 (KCl). By following the leaving groups spectrophotometrically (260-270 nm), under amine excess, pseudo-first-order rate coefficients (kobsd) are obtained. Plots of kobsd against free-amine concentration at constant pH are linear, with slope (kN) independent of pH. The Broensted-type plots (log kN against amine pKa) are linear for the aminolysis of the four substrates, with slopes βN = 0.7-0.8. The magnitudes of the slopes are consistent with a stepwise mechanism through a zwitterionic tetrahedral intermediate (T±) whose breakdown to products is rate-determining (k2 step). This mechanism is simpler than that for the same aminolysis of the corresponding ethyl S-aryl dithiocarbonates, which includes proton transfer from T± to the amine (k3 step), due to the fact that for the title reactions k2 > k3[amine]. With the results of the present work and those for the reactions of saa with ethyl S-4-nitrophenyl thiolcarbonate, a dual parametric equation is deduced for kN as a function of amine and leaving group basicity, with both βN and βlg = 0.8. Another dual parametric equation is deduced from literature data for the pyridinolysis of ethyl S-aryl thiolcarbonates. Comparison of both multiparametric expressions shows that pyridines are more reactive than isobasic saa toward thiolcarbonates when breakdown of T± to products is rate-limiting.
Palladium catalyzed synthesis of aryl thiols: Sodium thiosulfate as a cheap and nontoxic mercapto surrogate
Yi, Jun Fu, Yao Xiao, Bin Cui, Wei-Chen Guo, Qing-Xiang
A Pd-catalyzed coupling reaction of ArBr/ArCl/ArOTf with sodium thiosulfate takes place in presence of Cs2CO3 at 80 °C. The reaction mixture is directly treated with Zn/HCl to afford aryl thiols in good to excellent yields.
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