engleski

Synthesis of [2-Aryl-6-oxo-6H-chromeno[6, 7- d]oxazol-8-yl]-acetic Acid Ethyl Esters

A number of coumarino[6, 7-d]oxazoles (nitrogen analogs of psoralens) have been synthesized from (7-hydroxy-2-oxo-2H-chromen-4-yl) acetic acid ethyl ester 1. The synthetic route began with the nitration of 1 with nitric acid in acetic acid to give (6-nitro-7-hydroxy-2-oxo- 2H-chromen-4-yl) acetic acid ethyl ester 2 ; (3, 6-dinitro-7-hydroxy-2-oxo-2H-chromen-4-yl) acetic acid ethyl ester 3 and (3, 6, 8- trinitro-7-hydroxy-2-oxo-2H-chromen-4-yl) acetic acid ethyl ester 4. The reduction of 2 was accomplished with tin(II) chloride, tin, and concentrated hydrochloric acid in ethanol giving (6-amino-7-hydroxy-2-oxo-2H-chromen-4- yl) acetic acid ethyl ester 5. After the condensation of aminocoumarin 5 with aromatic aldehyde in glacial acetic acid medium, followed the dehydrocyclization to coumarino[6, 7-d]oxazoles 7a-k. The intermediate Schiff's bases 6a-k have been obtained from 5 with aromatic aldehyde in ethanol. Antibacterial and antifungal activities of the compounds have been evaluated.

coumarin hydrazide ; Schiff's bases ; thiosemicarbazide ; oxadiazole ; triazole ; thiazolidine ; antimicrobial activity

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