an ice bath then allowed to reach room temperature. The resulting mix-
ture was acidified using dilute HCl (pH 4–5), and the solid product was
collected by filtration and washed two times with water and ethanol.
The crud products were purified by recrystallization from DMF/H2O
for dyes3d–e and column chromatography on silica gel, using ethyl ac-
etate/petroleum (4:3) as eluent for dyes3a–c. The characterization data
of prepared dyes are given below.