Synthesis of Novel Series of Coumarin Derivatives

Abstract

In a synthetic method similar to Knoevenagel reaction, 3-acetyl coumarin was prepared in the same way through a cyclization condensation reaction between
salicylaldehyde and ethyl acetoacetate under basic condition using piperidine. Hence, 3-acetyl coumarin as a starting material was reacted with bromine in ether using a Lewis acid as a reaction
catalyst to produce the corresponding α–bromoaceyl cromen-2-one derivative. In application of
Hantzsch synthesis, the reaction of α–bromoaceyl cromen-2-one with thioacetamide in ether afforded a
3-methylthiazolyl cromen-2-one derivative also by a cyclization condensation reaction. On the other
hand, the α–bromoaceyl cromen-2-one was also reacted with potassium thiocyanide in ethanol
affording an α–cyanoaceyl cromen-2-one derivative. The latter was then reacted with phenyldiazonium
and 3-methoxyphenyldiazonium salts in sodium acetate solution affording their corresponding
hydrazonyl derivatives as Schiffs’ bases. Purity of the synthesized compounds was checked with thin
layer chromatography techniques and melting point measurements before and after recrystallization. All
the physical and spectral data of the synthesized compounds have been measured