The scope of homogeneous Lewis acid-catalyzed benzo[N,N]-heterocyclic condensation was expanded to include the use of various metal salts not reported in the literature and $SnCl_2\cdot}2H_2O$ was finally selected. Among various solid supports activated with $SnCl_2$, heterogeneous $SnCl_2/SiO_2$ proved to be the most effective and significantly higher conversions were achieved compared to $SnCl_2\cdot}2H_2O$ itself. The results of TG-DTA and BET indicated that dispersed $SnCl_2$ coordinates with surface hydroxyl groups of silica leading to formation of stable Lewis acid sites. Low catalyst loading, operational simplicity, practicability and applicability to various substrates render this eco-friendly approach as an interesting alternative to previously applied procedures.
均质
路易斯酸催化的苯并[N,N]-杂环缩合反应的范围扩大到包括使用各种文献中未报道的
金属盐,最终选择了
$SnCl_2\cdot}2H_2O$。在各种用
$SnCl_2$活化的固体载体中,非均质
$SnCl_2/SiO_2$被证明是最有效的,相比于
$SnCl_2\cdot}2H_2O$自身实现了显著更高的转化率。TG-DTA和BET的结果表明,分散的
$SnCl_2$与
硅氧化物表面的羟基配位,导致形成稳定的
路易斯酸位点。低催化剂负载、操作简单、实用性强以及适用于多种底物使得这种环保的方法成为以前应用程序的有趣替代方案。