Microwave Assisted Synthesis of Fluoro Substituted Quinoxaline Derivatives for Antimicrobial Studies

S. M. Hipparagi¹, M. Geethavani¹*, V. Suresh Kumar¹ And B. Parikshit²

¹Department of Pharmaceutical Chemistry, K.L.E.S’s College of Pharmacy, ²Block, Rajajinagar, Bangalore - 560 010 (India)

N- (3-chloro-4-fluorophenyl) acetamide was prepared from 3-Chloro-4-fluoro aniline. This was followed by synthesis of N- (3-chloro-4-fluoro-2-nitro Phenyl) acetamide by nitration, which was followed by hydrolysis and carried out in microwave oven at 320 watts for 5 minutes to get 3-chloro-4-fluoro-2-nitroaniline, where as the time required for the same step by conventional method was about 1 hour. This was then subjected for reduction to get 3-chloro-4-fluorobenzene-1,2-diamine. Cyclization of 3-chloro-4-fluorobenzene-1, 2-diamine with benzil was carried out in solvent free condition in microwave by irradiating at 320 watts for 90 seconds to get 5-chloro-6-fluoro-2, 3-diphenyl quinoxaline. The time taken for the same step by conventional method was about 1hour.Various derivatives were prepared by replacing the chlorine atom by different amines from 5-chloro-6-fluoro-2, 3-diphenyl quinoxaline by using modified microwave oven with reflux condenser and thermostat regulator for 1 hour. The time taken for the above step by conventional method was about 14 hours and it was reduced to 1 hour by using modified microwave oven. The synthesized compounds have been characterized by analytical and spectral studies (IR, 1H NMR and Mass) and screened for their antimicrobial activity. The yield of the compounds synthesized by using microwave oven was more when compared to conventional method.

Quinoxaline; benzil; analytical; antimicrobial activity