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Chapter – 4 Studies on different types of reactions…..
Preparation of 4-hydroxycoumarin, its 3-acetyl derivative was carried
out by Mohamed et. al. 273 Further this 3-acetyl-4-hydroxycoumarin was
condensed with aryl aldehydes to afford respective α-hydroxychalcones. They
have also reported further cyclization of chalcones into different heterocyclic
moieties.
3-acetyl-4-hydroxylcoumarin was synthesized by acetylation and acyl
chlorination of salicylic acid followed by the cyclocondensation of acetoacetic
ester, then condensation with aldehydes to obtain the three title product by
Ding et. al. 274 The three derivatives have high extinction coefficients in UV-vis
absorption, which were 5.25 x 104 L/(mol-cm), 3.39 x 104 L/(mol-cm), and
3.24 x 104 L/(mol-cm), respectively, and intensive luminescence in both the
THF solution and solid state. Derivatives TM1 and TM2 emit intensive orange
red luminescence with the same absorption peak at 500 nm and the identical
small Stoke shift of 85 nm in the emission spectra in THF. The
photoluminescence peaks of the three derivatives in solid state are at 705,
643, and 660 nm, respectively. Derivative TM3 displays intensive red
luminescence with the peak at 486 nm and a large Stoke shift of 152 nm in
the emission spectrum in THF, which makes it a novel red luminescent
material that may be used in OLEDs.
Title compounds (1) [R 1 = H, OH; R 2 = H, OH, OMe, F, Cl; R 3 = H, OH,
OMe, F, CF3, Cl; R 4 = H, OMe; n = 1, 2] were prepared for use as HIV-1
protease inhibitors by Kulkarni et. al. 275 Thus, 4-hydroxycoumarin was treated
with PhCH=CHCOCl to give (1) [R 1 -R 4 = H, n = 1] which had ki for HIV-1
protease inhibition of 10 µM. (2Z, 4E)-5-phenylpenta-2, 4-dienoic acid was
prepared by treating 3-phenylacrylaldehyde and acetic anhydride which were
treated with 4-hydroxycoumarin to give (1) [R 1 -R 4 = H, n =2]. (Fig. 4.14)
Fig. 4.14
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