A solution of formic acid (0.123 ml, 3.255 mmoles) in dry THF (40 ml), under stirring and dry N2 at room temperature, was added with 1,1′-carbonyldiimidazole (0.53 g, 3.255 mmoles) and the mixture was left to stand for 1 hour. Then 4-(3,5-dichloro-pyridin-4-ylmethyl)-7-methoxy-1,2-dihydro-phthalazine (1 g, 3.1 mmoles), prepared as described in example 22, was portionwise added. After 6.5 hours another portion of a mixture of formic acid/carbonyldiimidazole (about ⅓ of the previous one) was added and the mixture was stirred at room temperature for 1 hour, then left to stand overnight. The mixture was poured into water/ice, THF was evaporated, and the solution was extracted more times with CH2Cl2. The organic phase was washed with KHSO4, then with NaHCO3 and with water, anhydrified and concentrated. The residue was crystallised from acetonitrile (40 ml) to give 1 g of the title compound (yield: 92.6%). m.p.: 165-167° C.
