Synthesis of novel 4, 5-dihydropyridazin - 3 [2H] - one derivatives with benzoxazine and benzoxazole heterocycles at the 6-position as cardiotonic agents

A series of pyridazinone derivatives carrying benzoheterocycles, such as benzoxazole and benzoxazine, was synthesized and tested as inhibitors of cAMP phosphodiesterase enzyme [PDE]. The most promising compound in this series was 6-[2,4-dioxo-3,4-dihydro- l,3[2H]-benzoxazin-6-yl]-4,5 dihydropyridazin-3[2H]-one [3], which showed potent inhibiting activity on cAMP PDE and was ten times more potent than milrinone [a commercially available cardiotonic agent]

Synthesis of 6- [4- [substituted - amino] phenyl] - 4,5 -dihydropyridazin-3 [H] ones as potential positive inotropic agents

A series of 6-[4-[substituted-amino]phenyl] pyridazinones and related compounds were synthesized and evaluated as inhibitors of cardiac cyclic AMP phosphodiesterase. Compounds 2c, 2d, 2h showed potent inhibitory activity and were found more potent than milrinone