Abstract
Quinoxalinones are fused, aromatic heterocycles which have exhibited interesting biological activities, including antitumor, antibiotic, and antiprotozoal properties. Investigations into the synthesis of these molecules may provide a better understanding of their specific functions and aid in targeted design of new derivatives. The synthesis of 3,4-dihydroquinoxalin-2(1H)-one and 1H-quinoxalin-2-one through the reaction of o-phenylenediamine and ethyl bromoacetate was investigated under various conditions in order to gain an understanding of the overall reaction mechanism and what factors determine the product composition. The reaction was initiated via an SN2 substitution with bromine acting as a good leaving group, then cyclization occured to form 3,4-dihydroquinoxalin-2(1H)-one . These conditions included solvent, temperature, base, and various functional groups as part of the substituted diamines. The type of base that was utilized allowed for some control over the selectivity of the product outcome. Pyridine favored the cyclized products, while not adding a base allowed for an increase in the oxidized quinoxalinone form. Strongly activating (methoxy) and deactivating (benzoyl) groups para to one of the amine groups allowed for a very selective process where only one of the four possible major products was synthesized which included the preference of only one of the two possible quinoxalinone derivative regioisomers.