A mixture containing 2-(3-bromophenyl)-1,3-dioxane (136; 2.0 g, 8.23 mmol), 2,6-dimethylmorpholine (122; 1.14 g, 9.88 mmol), Pd2(dba)3 (50 mg), NaOt-Bu (1.39 g, 14.0 mmol) and BINAP (100 mg) in 20 mL of toluene was stirred at reflux for 5 h. Upon cooling to room temperature, enough cold 1N HCl (50 mL) was added to adjust the pH The resulting reaction mixture was stirred at room temperature for 1 h. NaOH(aq) was added to adjust the pH=11. The aqueous mixture was extracted with CH2Cl2 (3×50 mL). The combined organic layers were dried (MgSO4) and concentrated under reduced pressure. Purification by chromatography (petroleum ether:EtOAc=10:1) afforded 3-(2,6-dimethylmorpholino)benzaldehyde 137 as a yellow oil (1.36 g, yield: 72%).
