INTRODUCTION:

Synthesis of any chemical entities is major bottleneck in the drug discovery. Conventional methods for different chemical synthesis is very well documented and practiced. The methods for synthesis of organic compounds had continuously modified from the last 10 years¹. The application of green chemistry principles and practices renders regulation, control, clean-up, and remediation of the environment². In year 1855 Robert Bunsen invented the burner acts as energy source for heating reaction vessel this was latter superseded by isomental, oil bath but the drawback of the heating though method remains the same³. Microwave Assisted Organic Synthesis had developed in now years which has been considered superior to traditional heating⁴. Microwave assisted organic synthesis has as a new “lead” in the organic synthesis⁵.

The technique offers clean, simple, efficient, fast and economic for the synthesis of a number of organic molecules such reaction has new tool in the organic synthesis. Important advantage of this technology includes highly accelerated rate of the reaction time with an improvement in yield and quality of product⁶. This technique is considered as important approach toward green chemistry because this technique is more environments friendly and this technology is used in the laboratory and has the potential to have a large impact on the fields of combinatorial chemistry, screening, medicinal chemistry and drug development⁷. Conventional method of organic synthesis usually requires longer heating time, tedious apparatus setup which result in higher cost of process and the excessive use of solvents or reagents lead to environmental pollution⁸. Growth of green chemistry holds necessary potential for the reduction of by product, a reduction in the waste production and a lowering of energy costs⁹. Due to its ability to couple directly with reaction molecule and passing thermal conductivity leading to fast rise in the temperature microwave irradiation had used to improve many organic synthesis¹⁰. The Principle behind the heating in microwave oven is because interaction of charged particle of reaction material with electromagnetic wavelength of particular frequency¹¹. The phenomena of the producing heat by electromagnetic irradiation are either by conduction or collision. All the wave energy changes its polarity from +ve to -ve with each cycle of wave this cause rapid orientation and reorientation of molecule which cause heating by collision¹². If any charge particles of material are free to travel in the material for e.g. Electron in a sample of carbon a current will induce which will travel in phase with the field¹³. If charge particle are bound in regions of material the electric field component will cause them to move until opposing force balancing electric force¹⁴.

MATERIAL AND METHODS:

All reagents used were of synthetic grade. Melting point were recorded by open capillary method and are uncorrected. Experimental were performed using microwave synthesizer (catalyst). Comparitivelythe reactions were performed using conventional methods of synthesis using reflux condenser. The reactions were monitored with silica gel G at specific hours of synthesis. The time for the conventional and microwave assisted synthesis were noted.

Synthesis of 2,3-diphenyl quinoxaline¹⁵

A. Microwave assisted reaction:

In 250ml RBF, dissolve 0.108g o-phenylenediamine and 0.21g benzil in 5ml ethanol, then subjected to microwave at 340 W for 10 min, then add water until a slight cloudiness persists and allow to cool. The above mixture was filtered at pump and then filtered solid was washed with cold water. Recrystallized with methanol. M.pt: 125-126^◦C.