Alumina-Supported Copper(II) Halides as Friedel-Crafts Catalysts

在中性氧化铝上负载氯化铜，可显著提高氯化铜在Friedel-Crafts苄基化反应中的催化活性。游离氯化铜（II）对苯与氯化苄的苄基化反应无活性。氧化铝负载的氯化铜在温和条件下催化苯与氯化苄的Friedel-Crafts苄基化反应。CuCl_2/Al_2O_3催化剂很容易从反应混合物中回收并重复使用，而不降低催化活性。与CuCl_2/Al_2O_3相比，硅胶负载的氯化锌具有更高的活性。ZnCl_2/SiO_2催化多甲基苯的苄基化反应选择性地得到相应的高收率单苯化化合物。以ZnCl_2/SiO_2为催化剂，苯与双（氯甲基）苯反应，得到了相应的高选择性二苯。例如，在二苯甲烷的反应中，高收率地得到了双（4-苄基苯基）-对二甲苯。ZnCl_2/SiO_2可以重复使用，CuCl_2/Al_2O_3也可以重复使用。

Catalytic activity of copper (II) chloride in Friedel-Crafts benzylation was remarkably increased when copper (II) chloride was supported on neutral alumina. Free copper (II) chloride was inactive for the benzylation of benzenes with benzyl chloride. In contrast, alumina-supported copper (II) chloride catalyzed Friedel-Crafts benzylation of benzenes with benzyl chloride under mild conditions. The CuCl_2/Al_2O_3 catalyst is easily recovered from the reaction mixture and reused without a decrease in catalytic activity. Silica gel-supported zinc chloride showed a higher activity compared with CuCl_2/Al_2O_3. Benzylation of polymethylbenzenes catalyzed by ZnCl_2/SiO_2 gave selectively the corresponding monobenzylated compounds in high yields. Reaction of benzenes with bis(chloromethyl)benzene using ZnCl_2/SiO_2 as a catalyst gave the corresponding dibenzylbenzenes in high selectivity. For example, in the reaction of diphenylmethane, bis (4-benzylphenyl) -p-xylene was obtained in high yield. ZnCl_2/SiO_2 can be reused as well as CuCl_2/Al_2O_3.