Lithium Chloride → 5-(3-methylpyrid-2-yl)pyridazin-3(2H)-one

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Reaction Steps

To a mixture of 5-chloropyridazin-3(2H)-one (0.135 g, 1 mmol) and 2-(tri-n-butylstannyl)-3-methylpyridine (0.42 g, 1.1 mmol) in anhydrous 1,4-dioxane (2 ml) was added tetrakis(triphenylphosphine)-palladium (0) (0.06 g, 0.051 mmol), copper(I)iodide (20 mg, 0.1 mmol) and lithium chloride (0.13 g, 3.1 mmol) and the mixture was irradiated in a Smith microwave reactor at 160° C. for 15 minutes. The mixture was allowed to cool to room temperature and poured onto a mixture of ethyl acetate/water (10 ml/5 ml). The phases were separated and the aqueous phase was extracted two times more with ethyl acetate. The combined organic layers were washed with brine, dried over sodium sulfate and adsorbed onto silica gel. Purification by flash chromatography (ethyl acetate) gave 5-(3-methylpyrid-2-yl)pyridazin-3(2H)-one (0.13 g, 69%) as a yellow solid which was suspended in phosphorous oxychloride (5 ml, 54 mmol) and the mixture was heated at 100° C. for 1 hour. After cooling to room temperature the homogeneous dark solution was evaporated under reduced pressure and repartitioned between chloroform and water (50 ml each). The pH was adjusted to 8 by portionwise addition of saturated aqueous sodium carbonate solution and the phases were separated. After two further extractions the combined organic extracts were washed with water and brine and dried over sodium sulfate. After filtration the compound was adsorbed onto silica gel and purified by flash column (50% ethyl acetate-iso-hexane) to yield the title compound (0.38 g, 54%).

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