Acetyl chloride → (8R,9R)-8,10-Diacetyl-2,3-dimethyl-9-phenyl-7,8,9,10-tetrahydroimidazo[1,2-h][1,7]naphthyridin-7-one

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Reaction Steps

50 g of (8R,9R)-2,3-dimethyl-8-hydroxy-9-phenyl-7,8,9,10-tetrahydroimidazo[1,2-h][1,7]naphthyridin-7-one (WO 00/17200, example B1) are dissolved under nitrogen and with exclusion of moisture in 450 ml of dichloromethane. Half of the amount of acetyl chloride (46.6 ml in total) is firstly added dropwise at room temperature. Half the amount of triethylamine (45 ml in total) is then added dropwise with ice cooling in the course of 30 min. After stirring at room temperature for 1 h, the procedure is repeated as described with the second half of the reagents indicated. The mixture is then hydrolyzed using saturated sodium hydrogencarbonate solution and water. The organic phase is separated off and the aqueous phase is extracted with dichloromethane. The combined organic phases are dried over magnesium sulfate and evaporated. The yellow-brown residue is coevaporated a further two times with toluene. 64 g of the title compound are isolated as a brown oil, which is used in the next stage without further purification.

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