Ultrasonic and Microwave Assisted Synthesis of Nitrogen-Containing Derivatives of Juglone as Potential Antibacterial Agents

Ultrasound and microwave assisted expedient synthesis of potential antibacterial compounds, 2-(anilino)-5-hydroxy-1,4-naphthoquinone derivatives 3a-c and 5-hydroxybenzo[f] indole-4,9-dione derivatives 8a-c and 10-hydroxybenzo[b] carbazole-6,11-dione derivatives 9a-c have been developed. For the preparation of 3a-c derivatives the methods Room Temperature Synthesis (RTS), Conventional Heating Synthesis (CHS) and Ultrasound Assisted Synthesis (UAS) were performed. In addition, the Conventional Synthesis (CS) and Microwave Assisted Synthesis (MAS) were used for 8a-c and 9a-c derivatives. UAS and MAS showed the best results and are considered green alternatives of synthesis. In general, the yields obtained were good to excellent (58 to 93%). In addition, antibacterial activity against five bacterial strains was tested, showing bacteriostatic activity at lower concentrations and greater bactericidal against Gram negative strains. The compounds carrying chlorine atoms at 2 and 4 positions on the phenyl ring were the most active. The results obtained indicate that the 1,4-naphthoquinone derivatives presented here have promising use as antibacterial agents. A reaction mechanism is also proposed.