6-(substituted phenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-ones of medicinal interest. The synthesis of SK&F 94836 and SK&F 95654
Two synthetic routes to the dihydropyridazinone-cyanoguanidine 4 (SK&F 94836) are described, both proceeding via the anilino compound 6. An efficient synthesis of the dihydropyridazinone-pyridone 5 (SK&F 95654) is reported. This synthesis proceeds via the fluoro-keto-acid 24, with subsequent displacement of the fluoro substituent by 4-pyridone. The surprising effectiveness of water as a solvent in this reaction has been highlighted.
