Hydrochloric Acid → 4-Methyl-6-phenylpyridazin-3(2H)-one

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Reaction Steps

7.0 g (35 mmole) of 2 is placed in a 250 ml single-necked round bottom flask followed by 30 mL of acetonitrile. The mixture is stirred to allow 2 to dissolve. 11.3 g (84 mole, 2.4 equiv.) of anhydrous copper (II) chloride is added to the solution to give a green-yellow suspension. A reflux condenser is connected to the flask and a dry tube filled with anhydrous CaCl2 is fitted to the top of the condenser. To control the HCl gas that forms during the course of the reaction, a NaOH solution is used to absorb the HCl that escapes from dry tube. The reaction mixture is heated to reflux, and the color of the reaction suspension changes to dark green upon heating. When the reaction is complete (after refluxing for 2 h), the flask is removed from the oil bath and cooled to ambient temperature. The reaction is cooled in an ice-water bath and 150 mL of ice-water is added to quench the reaction. The mixture is stirred vigorously for 10 minutes to give a gray precipitate and blue liquid containing copper (I) chloride. The precipitate is collected by filtration (pH of the filtrate is 0-1) and washed with 100 mL of 1N HCl solution, then 100 mL of water 5 times. To remove remaining copper by products that are trapped in the solid, the filter cake is stirred in 150 mL of 1N HCl solution for 0.5 h and filtered. The filter cake is subsequently washed with Milli-Q water until the filtrate is at pH 7 (approximately 7 washes). The solid is dried over a medium frit sintered glass funnel in vacuo to give 3 as a light gray powder in 93.8% yield. [See Eddy, S et al. Synthetic Communications, 2000, 30(1), 1-7.Csende, F et al. Synthesis, 1995, 1240-12420]

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