Chemoselective reaction of 3,6-diacetylindole towards hydroxylamine: Synthesis and antimicrobial activity of novel isoxazolo[4,5-f]indole derivatives

The exclusive formation of substituted 6-alpha -oximinoethyl indoles (3a-c) from the reaction of 3,6-diacetylindoles (2a-c) with hydroxy(amine reveale d the chemoselectivity of C-6-acetyl function over C-3-acetyl function towa rds the nucleophilic attack of hydroxylamine. These monooximes (3a-c) were treated with acetic anhydride to produce exclusively substituted indoles (S a-c) which were refluxed in pyridine to yield 5-substituted-7-acetyl-3,6-di methyl-isoxazolo[4,5-]indoles (6a-c) in good yields. The newly synthesised compounds were screened for their antibacterial and antifungal activities.