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Chapter – 5 Synthesis and Characterization…..
O O
Cl
NO 2
R = R' = H, CH 3 , C 2 H 5
Fig. 5.4
O O
16
Bhatt and Thakor prepared 4-anilinocoumarins by direct
condensation of 4-hydroxycoumarins with different amines, thus opening the
single step route of such arylaminocoumarin derivatives.
Joshi 17 and Berghaus 18 have also independently reported the
synthesis of 4-amino [1] benzopyrans as intermediate products during
annelation.
Reddy et. al. 19 carried out condensation reaction of 4-hydroxycoumarin
and 2-aminothiophenol in dimethylsulfoxide. This cyclized product was
desulfurized with Raney-Nickel to give 4-arylaminocoumarin.
Bardan et. al. 20 have prepared 4-aminocoumarin by condensation of
primary and secondary amine with 4-chlorocoumarin under reflux in xylene.
In another different approach, during the study of β-ketoenamino
functionality, the 4-hydroxycoumarins were directly converted to 4-amino / 4arylamino
coumarins by Ivanov et. al. 21
Kirpichenok et. al. 22 reacted 3-iodo-7(dialkylamino) coumarins with
different secondary amines (viz. diethylamine, piperidine, morpholine,
imidazole and benzimidazole) in order to get 4-(substituted amino) coumarin
derivatives in good yield.
Tabaković et. al. 23 also reported the preparation of 3-nitro-4anilinocoumarin
by refluxing 3-nitro-4-coumarinyl-N-phenyldithiocarbamate in
dimethylformamide for 30 minutes.
Department of Chemistry, Saurashtra University, Rajkot – 360 005 280
HN
R
NO 2
COOR'