Design, synthesis and antibacterial activity of new phthalazinedione derivatives

Dibenzobarallene (1) was utilized as the key intermediate for the synthesis of some new 2-substituted 1,4-dioxo-3,4,4a,5,10,10a-hexahydro-1H-5,10-[1',2']-benzenobenzo[g]phthalazine: 2, 5a-d, 8a-c and 10. Condensation of 2 with benzaldehyde or anisaldehyde gave the corresponding acrylonitrile derivatives 3a and b, respectively. Thiophene derivatives 4a and b were obtained via the Gewald reaction of 2 with cyclohexanone or cyclopentanone, respectively. Treatment of 5d with acetyl chloride or p-toluenesulfonyl chloride afforded the corresponding esters 6 and 7, respectively. Cyclization of 8a-c with formalin afforded the corresponding triazine derivatives 9a-c. Ring opening of 10 with sodium hydroxide gave the corresponding triazole derivative 11, which when alkylated with pentyl bromide afforded the pentylthio derivative 12. Representative compounds of the synthesized products were established and evaluated as antibacterial agents.