A highly efficient and recyclable silica-supported tungstic acid (STA) catalyst for the synthesis of pyrano[3,2- c ]chromen-5-ones under solvent free conditions
作者:Amol Maruti Jadhav、Suresh Kumar Krishnammagari、Jong Tae Kim、Yeon Tae Jeong
DOI:10.1016/j.tet.2017.07.008
日期:2017.8
A simple, efficient, green and solvent-free procedure for the synthesis of pyrano[3,2-c]chromen-5-ones has been developed by multi-component condensation of 4-hydroxycoumarin, aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine in the presence of a catalytic amount of silica-supported tungstic acid (STA). The reaction transformation presumably occurs via Knoevenagel condensation, Michael addition
通过4-羟基香豆素,醛类和(E)-N-甲基的多组分缩合,开发了一种简单,高效,绿色和无溶剂的吡喃并[3,2 - c ]铬n-5-酮合成方法在催化量的二氧化硅负载的钨酸(STA)的存在下,-1-(甲硫基)-2-硝基乙胺。推测反应转化是通过Knoevenagel缩合,Michael加成,亚胺-烯胺互变异构分子内,O-环化,消除MeSH。本发明对环境无害的方案具有几个优点,例如反应时间更短,官能团耐受性范围广,使用便宜的非均相催化剂以及通过简单的实验和后处理程序即可获得高产率的产物。催化剂可以回收并重复使用至少四次,而对产物的收率没有任何重大影响。