The catalytic activity of different supported bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well.
不同支撑的双官能硫脲在磺酰基聚苯乙烯树脂上的催化活性已经在不同亲核试剂对反式-β-硝基苯乙烯衍生物的硝基迈克尔加成中进行了研究。催化剂的活性取决于将手性硫脲与聚合物连接的链长度。最佳结果是使用由(L)-缬氨酸和1,6-己二胺衍生的硫脲得到的。催化剂可以在仅2%的负载下使用,并在纯净条件下至少重复使用四个周期。球磨促进的加成也非常有效。