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

ABSTRACT

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]