Synthesis of Simple Coumarins: Mixed Solvent Recrystallization Approach and Modification

Coumarin compounds have great interest for their wide range of medicinal and
pharmacological properties as well as for their fluorescent properties. Simple coumarins are
being the major precursor for the synthesis of most of the coumarin derivatives. Simple
coumarin (C1) was synthesized by using Perkin condensation reaction whereas 7-hydroxy
coumarin (C2) and 7-hydroxy-4-methyl coumarin (C3) were synthesized by using Pechmann
condensation reaction. Solvent combination which gives higher recovery percentage on
recrystallization was found out. The synthesized simple coumarins were characterized by
using spectroscopic analysis (UV, IR, 1H and 13C NMR). The solvent combination which
gave higher recovery percentage for C1 and C3 were 40 % aqueous methanol and 34 %
aqueous ethanol respectively. Two mixed solvents of 33 % aqueous ethanol and 25 %
aqueous acetic acid were used to obtain pure crystal of 7-hydroxy coumarin (C2) for the
higher recovery percentage.