Synthesis processes derivatives dihidropiridoftalazinona

A method of making a compound of formula (1): ** ** Formula or a salt thereof, the method comprising: reacting a compound of formula (5) ** ** Formula or a salt thereof, with hydrazine monohydrate; wherein R is C1-C6 alkyl, wherein the compound of formula (5), or salt thereof, is prepared by reacting a compound of formula (4): ** ** Formula or a salt thereof, with 4-fluorobenzaldehyde in the presence of a reducing reagent and an acid or a Lewis acid; wherein R is C1-C6.