Synthesis of 1H-pyrazino[1,2-a]pyrido[2,3-e]pyrazine and 2H-Pyrano[2,3-b]pyrido[2,3-e]pyrazine Derivatives

With a continuing interest on heteropolycyclic structures which may show biological activities, we synthesized new tricyclic derivatives in which the pyridopyrazine skeleton is fused with pyrazine 7 and 8, B , n = 1. However, the initial design of obtaining also the cyclohomologous structure B (n = 2) produced instead a pyranopyridopyrazine derivative 11 . Thus during the attempt to prepare a pyridodiazepine intermediate, beside a very small amount of the desired product 10 , the pyridopyrazine 9 was obtained. The latter compound reacted with chloroacetyl chloride/chloroketene to give 4-carbethoxy-10-(chloroacetyl)-5,10-dihydro-5-methyl-2H-pyrano2,3-b]pyrido2,3-e]pyrazin-2-one ( 11 ). In studying the behavior of this derivative, compounds 12–14 were obtained. Compounds 4b,c, 5a,b, 7, 8, 9 and 14 have been submitted to preliminary pharmacological screening as CNS depressant agents.