Part of the product from (i) (48 g), 6-[4-(3-bromopropionamido)phenyl]-5-methyl-4,5-dihydro-3(2H)-pyridazinone (60 g) and triethylamine (36 g) were stirred under reflux in n-propanol (700 ml) for 18 hours. The reaction mixture was cooled and evaporated under reduced pressure to afford an oil. This oil was subjected to column chromatography on silica using dichloromethane/methanol (gradient elution 100:0 to 100:5). The desired fractions were combined and purified on another silica column (eluting with ethyl acetate/methanol/ammonia 100:20:0.5). The desired fractions were combined and evaporated under reduced pressure to form the title compound (30 g). Part of this was converted to the methanesulphonate salt as in Example 4.
