Methanol → 6-Methoxy-9-fluorobenzo[g]isoquinoline-5,10-dione

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Reaction Steps

A solution of sodium methoxide, freshly prepared under nitrogen atmosphere from anhydrous methanol (97.6 ml) and sodium (2.024 g), is dropped in a time of 2 hours and 35 minutes into a solution of 6,9-difluorobenzo[g]isoquinolin-5,10-dione (19.615 g, preparation 3) in anhydrous THF (883 ml), under stirring and at room temperature. At the end of the addition, the reaction mixture is concentrated to half the starting volume, then is kept at 18° C. for 30 minutes. The separated solid is filtered and washed with 100 ml of THF, then it is suspended in water (80 ml), left overnight under stirring and filtered again to give 9.3 g of crude product, which is suspended in methylene chloride (45 ml) and refluxed for 30 minutes. After cooling at room temperature, the product is filtered and the separated solid is washed with methylene chloride (5×3 ml), then dried under vacuum at 40° C., to obtain 8.65 g of pure product, m.p. 248-250° C.

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