Synthesis of 2-bromo-7-methyl-3,5-dihydro-imidazo[4,5-d]pyridazin-4-one and 3-alkyl-2-bromo-3,5-dihydro-imidazo[4,5-d]pyridazin-4-one and their selective elaboration

Two synthetic routes to the versatile 3,5-dihydro-imidazo[4,5-d]pyridazin-4-ones 2 and 5 have been developed that allow the production of multigram quantities without the need of any chromatographic purification. Broad and selective elaboration of the heteroaromatic scaffolds has also been accomplished.