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Pechmann Reaction in Non‐Chloroaluminate Acidic Ionic Liquids under Solvent‐Free Conditions
Author(s) -
Gu Yanlong,
Zhang Juan,
Duan Zhiying,
Deng Youquan
Publication year - 2005
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200404316
Subject(s) - chemistry , ionic liquid , resorcinol , catalysis , yield (engineering) , dichloromethane , phenols , trifluoromethanesulfonate , solvent , organic chemistry , ionic bonding , inorganic chemistry , ion , materials science , metallurgy
Abstract Four non‐chloroaluminate acidic ionic liquids have been used as catalysts for Pechmann condensations of phenols under solvent‐free conditions. SO 3 H‐functionalized trifluoromethanesulfonate imidazolium ionic liquid has proved to be the most active catalyst. Ionic liquid loads as low as 5 mol % can be used leading to high yields with activated phenols at an oil bath temperature of 80 °C. The acidities of the four ionic liquids have also been tested using the Hammett method in dichloromethane. The results are consistent with their catalytic activities as observed in the Pechmann reaction of resorcinol. This methodology offers significant improvements for the synthesis of coumarins with regard to yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.