A series of 2, 3, 4, 4a-tetrahydro-1H-pyrazino [1, 2-a] quinoxalin-5-(6H) ones and 2, 3, 4, 4a, 5, 6-hexahydro-1H-pyrazino [1, 2-a] quinoxalines was shown to exhibit 5-HT2C agonist binding and functional activity. Compound 21R inhibited food intake over 2 h in fasted, male Sprague–Dawley rats with ED50 values of 2 mg/kg (ip) and 10 mg/kg (po).