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：Jadhav Amol Maruti; Krishnammagari Suresh Kumar; Kim Jong Tae; Jeong Yeon Tae

来源：Tetrahedron, 2017, 73(34): 5163-5169.

DOI：10.1016/j.tet.2017.07.008

• Pyrano[3,2-c]chromen-5-ones
• Silica-supported tungstic acid
• Heterogeneous catalyst
• Solvent-free condition
• One-pot synthesis

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, imine-enamine tautomerism intramolecular, O-cyclization, elimination of MeSH. The present environmentally benign protocol offers several advantages such as shorter reaction times, a wide range of functional group tolerance, use of an inexpensive heterogeneous catalyst, and high yield of products via a simple experimental and work-up procedure. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields.

• 出版日期2017-8-24