Hydrochloric Acid → 4-Morpholinobenzaldehyde

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A solution of 4-iodobenzaldehyde (1 g, 4.31 mmol) in MeOH (50 mL) was mixed with trimethyl orthoformate (4 mL, 36.10 mmol) and p-toluenesulfonic acid (5 mg). The reaction was stirred at room temperature for 3 h and then quenched by adding excess of sodium bicarbonate solid and stirred for 1 h. The solid was removed by filtration and the filtrate was concentrated to yield 1-dimethoxymethyl-4-iodo-benzene (1.2 g, 100%). A mixture of 1-dimethoxymethyl-4-iodo-benzene (1.2 g, 4.31 mmol), cesium carbonate (1.4 g, 4.31 mmol), morpholine (0.375 g, 4.31 mmol), and palladium tetrakis(triphenyl) phosphine (0.25 g, 0.216 mmol) in toluene (60 mL) and tert-butanol (10 mL) was thoroughly degassed and stirred at 110° C. for 28 h. The reaction was quenched by adding water (50 mL), extracted with DCM (3×100 mL), concentrated to afford a solid residue. Purification by column chromatography left 4-(4-dimethoxymethyl-phenyl)-morpholine (0.61 g, 60%). A solution of 4-(4-dimethoxymethyl-phenyl)-morpholine (0.61 g, 2.58 mmol) in THF (20 mL) was mixed with HCl in ether (10 mL, 10 mmol) and stirred at room temperature for 2 h. The reaction mixture was then neutralized with 1 N sodium bicarbonate aqueous to pH 9 and extracted with DCM (3×100 mL), to afford 4-morpholin-4-yl-benzaldehyde (0.37 g, 75%).

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