Fariba Keshavarzipour1 · Hossein Tavakol1

Department of Chemistry, Isfahan University of Technology,
Isfahan 84156‑83111, Iran

Abstract In this work, choline chloride/zinc chloride was
employed as a deep eutectic solvent (DES) in the green
synthesis of coumarin derivatives using Knoevenagel condensation.
Coumarins are important organic structures
with useful application in various fields. The procedure
consisted of the reaction between salicylaldehyde derivatives
and active methylene compounds (dimethyl malonate,
ethyl cyano acetate and ethyl 3-oxo-3-phenylpropanoate) to
produce various coumarin derivatives. The general procedure
is easy because of simple preparation and isolation of
desired products. Moreover, the method is environmental
friendly because of avoiding use of toxic solvents or hazardous
catalysts. In the presented method, only 10 % of
choline chloride/zinc chloride was employed as a non-toxic
and biologically degradable media. All reactions have been
completed under mild conditions with high yields (61–
96 %). The employed DES plays both roles of solvent and
catalyst in this reaction. Moreover, it has been reused four
times in this procedure without important decreasing in the
yield of reaction.
Keywords Deep eutectic solvent · Coumarin · Choline
chloride · Catalyst