Halogen salt ionic liquid/O2 catalyzed reaction of aromatic thiophenol and isochroman
1-Substituted thiophenol isochromans were obtained via 1-carboxyethyl-3-methylimidazolium chloride([COOH-EtMIm][Cl])-catalyzed dehydrogenation coupling reaction of subsituted thiophenols and isochroman in the presence of O2.The influencing factors were screened by single factor experiments,and the optimal reaction conditions were obtained as follows:p-toluenethiol(62 mg,0.5 mmol),isochroman(134 mg,1.0 mmol),[COOH-EtMIm][Cl](95 mg,0.5 mmol),O2 pressure 0.10 MPa,reaction temperature 120℃,and reaction time 12 h.Under the optimum reaction conditions,the catalyst could be recycled for 4 times,while the gram-scale synthesis of 1-thiophenol isochroman was accomplished and 12 kinds of 1-substituted thiophenol isochromans with yields ranging from 52%to 96%were obtained.In addition,activation of thiophenol and isochroman by anion and cation ions of[COOH-EtMIm][Cl],respectively,followed by O2 oxidation and final dehydrogenation to form 1-thiophenol isochroman,was proposed as the reaction mechanism.
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